ADIPOR1

Gene Summary

Gene:ADIPOR1; adiponectin receptor 1
Aliases: CGI45, PAQR1, ACDCR1, CGI-45, TESBP1A
Location:1q32.1
Summary:This gene encodes a protein which acts as a receptor for adiponectin, a hormone secreted by adipocytes which regulates fatty acid catabolism and glucose levels. Binding of adiponectin to the encoded protein results in activation of an AMP-activated kinase signaling pathway which affects levels of fatty acid oxidation and insulin sensitivity. A pseudogene of this gene is located on chromosome 14. Multiple alternatively spliced transcript variants have been found for this gene. [provided by RefSeq, Mar 2014]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:adiponectin receptor protein 1
HPRD
Source:NCBIAccessed: 25 June, 2015

Ontology:

What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 25 June 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Case-Control Studies
  • Adipose Tissue
  • Gene Expression
  • Cancer Gene Expression Regulation
  • Oligonucleotide Array Sequence Analysis
  • Obesity
  • Messenger RNA
  • Up-Regulation
  • Smoking
  • Endometrial Cancer
  • Transforming Growth Factor beta
  • Immunoenzyme Techniques
  • Risk Factors
  • Asian Continental Ancestry Group
  • Cell Proliferation
  • Transcription
  • Receptors, Adiponectin
  • Genetic Predisposition
  • Leptin
  • Cell Surface Receptors
  • Adiponectin
  • Body Mass Index
  • Chromosome 1
  • Prostate Cancer
  • Tumor Markers
  • Insulin Resistance
  • Genotype
  • Breast Cancer
  • Receptors, Leptin
  • Stomach Cancer
  • Single Nucleotide Polymorphism
  • Reproductive Techniques, Assisted
  • Base Sequence
  • Polycystic Ovary Syndrome
  • Western Blotting
  • Neoplasm Invasiveness
  • Colorectal Cancer
  • Alleles
  • Apoptosis
  • Signal Transduction
Tag cloud generated 25 June, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (5)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: ADIPOR1 (cancer-related)

Wu S, Zheng C, Chen S, et al.
Adiponectin signals through Adiponectin Receptor 1 to reverse imatinib resistance in K562 human chronic myeloid leukemia cells.
Biochem Biophys Res Commun. 2015; 456(1):367-72 [PubMed] Related Publications
Adiponectin, a member of adipokines, is a functional ligand for Adiponectin Receptor-1 (AdipoR1) and Adiponectin Receptor-2 (AdipoR2), and has been found to be linked to the risk of CML. Imatinib has undoubtedly revolutionised the management and outcome of chronic myeloid leukemia (CML), however imatinib resistance has been recognized as a major problem in CML therapy. In this study, we first established imatinib-resistant K562 CML cells, and then evaluated the effect of Adiponectin in reversing imatinib resistance. The data presented here demonstrated that Adiponectin was able to reverse K562 resistance to imatinib in vitro and in vivo. Additional data with molecular approaches suggested that the reversion of Adiponectin in imatinib resistance signals through AdipoR1 but not AdipoR2 to downregulate Bcr-Abl expression and effect in imatinib-resistant K562 CML cells. Taken together, our data showed that Adiponectin can reverse imatinib resistance in CML, and to a certain extent elucidate the mechanism of Adiponectin reversing imatinib resistance that may provide a new and promising approach in imatinib resistance management in CML therapy.

Huang B, Cheng X, Wang D, et al.
Adiponectin promotes pancreatic cancer progression by inhibiting apoptosis via the activation of AMPK/Sirt1/PGC-1α signaling.
Oncotarget. 2014; 5(13):4732-45 [PubMed] Free Access to Full Article Related Publications
Adiponectin is an adipocyte-secreted adipokine with pleiotropic actions. Clinical evidence has shown that serum adiponectin levels are increased and that adiponectin can protect pancreatic beta cells against apoptosis, which suggests that adiponectin may play an anti-apoptotic role in pancreatic cancer (PC). Here, we investigated the effects of adiponectin on PC development and elucidated the underlying molecular mechanisms. Adiponectin deficiency markedly attenuated pancreatic tumorigenesis in vivo. We found that adiponectin significantly inhibited the apoptosis of both human and mouse pancreatic cancer cells via adipoR1, but not adipoR2. Furthermore, adiponectin can increase AMP-activated protein kinase (AMPK) phosphorylation and NAD-dependent deacetylase sirtuin-1 (Sirt1) of PC cells. Knockdown of AMPK or Sirt1 can increase the apoptosis in PC cells. AMPK up-regulated Sirt1, and Sirt1 can inversely phosphorylate AMPK. Further studies have shown that Sirt1 can deacetylate peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), which can increase the expression levels of mitochondrial genes. Thus, adiponectin exerts potent anti-apoptotic effects on PC cells via the activation of AMPK/Sirt1/PGC1α signaling. Finally, adiponectin can elevate β-catenin levels. Taken together, these novel findings reveal an unconventional role of adiponectin in promoting pancreatic cancers, and suggest that the effects of adiponectin on tumorigenesis are highly tissue-dependent.

Ayyildiz T, Dolar E, Ugras N, et al.
Lack of any prognostic relationship between adiponectin receptor (Adipo R1/R2) expression for early/advanced stage gastric cancer.
Asian Pac J Cancer Prev. 2014; 15(11):4711-6 [PubMed] Related Publications
INTRODUCTION: Adiponectin (ApN) is a complement C1q-related protein, mainly secreted from adipose tissue, that signals through ApN receptor 1 (Adipo-R1) and ApN receptor 2 (Adipo-R2). Low serum ApN concentrations are associated with obesity-related malignancies. However, there are very few studies on any prognostic role of ApN receptors in gastric cancer.
OBJECTIVES: The aim of this study is to investigate the relationship between AdipoR1/R2 expression and early/advanced stage gastric cancer in terms of clinicopathologic characteristics and survival.
MATERIALS AND METHODS: Eighteen patients with early and 39 with advanced stage gastric cancer who underwent surgical gastric resection were included in this study.
RESULTS: Adipo-R1 expression was low in 2 of the 18 patients with early stage gastric cancer (11.1%), while 4 had low Adipo-R2 expression (22.2%). In those with advanced stage gastric cancer, 7 of 39 had low Adipo-R1 expression (17.9%) and 16 had low Adipo-R2 expression (41%). Adipo-R2 expression was significantly higher (p=0.011) in moderately differentiated tumors when compared to well-differentiated tumors. While there was nearly a statistically significant relationship between TNM stage (T, tumor size; N, regional lymph node; M, whether distant metastases exist) and Adipo-R2 expression (p=0.054), there was no relationship between Adipo-R1/-R2 expression with tumor stage and survival.
CONCLUSION: Adipo-R1/-R2 expression has no prognostic significance of in early/advanced stage gastric cancer.

Vetvik KK, Sonerud T, Lindeberg M, et al.
Globular adiponectin and its downstream target genes are up-regulated locally in human colorectal tumors: ex vivo and in vitro studies.
Metabolism. 2014; 63(5):672-81 [PubMed] Related Publications
OBJECTIVE: Low plasma adiponectin levels are linked to obesity, insulin resistance, and the risk of several types of malignancy. Despite the decline in circulating adiponectin concentrations, the increase in the expression of adiponectin receptors AdipoR1 and AdipoR2 is greater in cancerous than in normal colonic tissue. The purpose of this study was to obtain new information regarding local adiponectin signaling in the pathogenesis of colorectal cancer (CRC).
METHODS: We characterized the expressions of adiponectin and several of its downstream targets in paired samples of tumor tissue and adjacent noncancerous mucosa in 60 surgical patients with colorectal adenocarcinomas.
RESULTS: Adiponectin was expressed in both colorectal tumors and the adjacent mucosa. The expressions of adiponectin mRNA and its globular protein variant (gAd), adiponectin receptor type 1 and 5' AMP-activated protein kinase (AMPK) mRNA were significantly higher in colorectal tumors than in the adjacent mucosa. This finding was accompanied by increased mRNA expression of genes encoding proteins involved in fatty-acid trafficking and oxidation. The potential interference between adiponectin stimulation and AMPK activation through AMPK1 was examined in an in vitro model with the aid of silencing-RNA experiments. Furthermore, AMPK mRNA expression on tumors was positively correlated with a more advanced tumor stage in the patients.
CONCLUSION: We propose that the globular adiponectin-AMPK pathway functions in an autocrine manner in colorectal tumors, explaining some of the beneficial changes in cellular oxidative capacity in tumors in favor of tumorigenesis.

Mauro L, Pellegrino M, De Amicis F, et al.
Evidences that estrogen receptor α interferes with adiponectin effects on breast cancer cell growth.
Cell Cycle. 2014; 13(4):553-64 [PubMed] Related Publications
Adiponectin, the most abundant protein secreted by adipose tissue, exhibits insulin-sensitizing, anti-inflammatory, antiatherogenic, and antiproliferative properties. In addition, it appears to play an important role also in the development and progression of several obesity-related malignancies, including breast cancer.   Here, we demonstrated that adiponectin induces a dichotomic effect on breast cancer growth. Indeed, it stimulates growth in ERα+ MCF-7 cells while inhibiting proliferation of ERα- MDA-MB-231 cells. Notably, only in MCF-7 cells adiponectin exposure exerts a rapid activation of MAPK phosphorylation, which is markedly reduced when knockdown of the ERα gene occurred. In addition, adiponectin induces rapid IGF-IR phosphorylation in MCF-7 cells, and the use of ERα siRNA prevents this effect. Moreover, MAPK activation induced by adiponectin was reversed by IGF-IR siRNA. Coimmunoprecipitation studies show the existence of a multiprotein complex involving AdipoR1, APPL1, ERα, IGF-IR, and c-Src that is responsible for MAPK signaling activation in ERα+ positive breast cancer cells. It is well known that in addition to the rapid effects through non-genomic mechanisms, ERα also mediates nuclear genomic actions. In this concern, we demonstrated that adiponectin is able to transactivate ERα in MCF-7 cells. We showed the classical features of ERα transactivation: nuclear localization, downregulation of mRNA and protein levels, and upregulation of estrogen-dependent genes. Thus, our study clarifies the molecular mechanism through which adiponectin modulates breast cancer cell growth, providing evidences on the cell-type dependency of adiponectin action in relationship to ERα status.

Yang Z, Yang X, Xu J, et al.
Association between adiponectin receptor 1 gene polymorphism and insulin resistance in Chinese patients with polycystic ovary syndrome.
Gynecol Obstet Invest. 2014; 77(1):45-9 [PubMed] Related Publications
BACKGROUND/AIMS: Adiponectin receptor 1 (ADIPOR1) is an identified receptor for adiponectin, an adipocytokine with anti-inflammatory and insulin-sensitizing properties. The ADIPOR1 gene is a potential candidate gene in polycystic ovary syndrome (PCOS). The aim of this study is to assess the association between single-nucleotide polymorphism (SNP) rs1539355 in the ADIPOR1 gene and PCOS in Chinese women.
METHODS: 302 patients with PCOS and 312 healthy controls were included in this study. The ADIPOR1 genotype distribution was detected using the polymerase chain reaction melting temperature shift method.
RESULTS: The genotypic distributions of SNP rs1539355 did not differ in patients with PCOS compared to controls. However, the frequency of the G allele in the PCOS group was significantly higher than that in the control group (p = 0.037). Patients with the AG or GG genotype had a higher homeostasis model assessment for insulin resistance (HOMA-IR) (p < 0.05) compared to patients with the AA genotype. The fasting insulin levels in subjects with the GG genotype were significantly higher than those in patients with the AA genotype (p < 0.05).
CONCLUSION: SNP rs1539355 in the ADIPOR1 gene is associated with insulin resistance in Chinese PCOS patients.

Comim FV, Hardy K, Franks S
Adiponectin and its receptors in the ovary: further evidence for a link between obesity and hyperandrogenism in polycystic ovary syndrome.
PLoS One. 2013; 8(11):e80416 [PubMed] Free Access to Full Article Related Publications
Polycystic ovary syndrome (PCOS), characterized by ovarian androgen excess, is the commonest endocrine disorder in women. Obesity increases androgen synthesis, a phenomenon attributed to the accompanying hyperinsulinemia. Our hypothesis was that adipokines, fat cell-derived hormones, play a direct role in modulating ovarian androgen secretion. Therefore, the aims of this study were to explore the effects of adipokines (in particular, adiponectin) on ovarian steroidogenesis and compare the expression of adiponectin receptors in ovaries from women with and without PCO. Sections of archived human ovaries (nine from women with normal ovaries and 16 with PCOS, classified histologically, with reference to menstrual history and ultrasound) were analysed by quantitative morphometry and the proportion of positive-labelling cells compared. In addition, studies of androgen production in relation to adipokine function in primary bovine theca cell culture were also performed. A significantly lower proportion of theca cells expressed adiponectin receptors 1 and 2 (AdipoR1, AdipoR2) in polycystic ovaries than in normal ovaries. In cultured theca cells, adiponectin suppressed androstenedione production and gene expression of LH receptor and key enzymes in the androgen synthesis pathway. Moreover, knockdown of genes for AdipoR1 and AdipoR2 was associated with increased androstenedione secretion by bovine theca cells. These results provide evidence for a direct link between fat cell metabolism and ovarian steroidogenesis, suggesting that disruption of adiponectin and/or its receptors plays a key role in pathogenesis of hyperandrogenism in PCOS.

Dai W, Zeller C, Masrour N, et al.
Promoter CpG island methylation of genes in key cancer pathways associates with clinical outcome in high-grade serous ovarian cancer.
Clin Cancer Res. 2013; 19(20):5788-97 [PubMed] Related Publications
PURPOSE: We aimed to identify DNA methylation biomarkers of progression-free survival (PFS) to platinum-based chemotherapy in high-grade serous ovarian cancer (HGSOC) within biologically relevant ovarian cancer-associated pathways.
EXPERIMENTAL DESIGN: Association with PFS of CpG island (CGI) promoter DNA methylation at genes in the pathways Akt/mTOR, p53, redox, and homologous recombination DNA repair was sought with PFS as the primary objective in a prospectively collected ovarian cancer cohort (n = 150). Significant loci were validated for associations between PFS, methylation, and gene expression in an independent The Cancer Genome Atlas (TCGA) data set of HGSOC (n = 311).
RESULTS: DNA methylation at 29 CGI loci linked to 28 genes was significantly associated with PFS, independent from conventional clinical prognostic factors (adjusted P < 0.05). Of 17 out of the 28 genes represented in the TCGA data set, methylation of VEGFB, VEGFA, HDAC11, FANCA, E2F1, GPX4, PRDX2, RAD54L, and RECQL4 was prognostic in this independent patient cohort (one-sided P < 0.05, false discovery rate < 10%). A multivariate Cox model was constructed, with clinical parameters (age, stage, grade, and histologic type) and significant loci. The final model included NKD1, VEGFB, and PRDX2 as the three best predictors of PFS (P = 6.62 × 10(-6), permutation test P < 0.05). Focussing only on known VEGFs in the TCGA cohort showed that methylation at promoters of VEGFA, VEGFB, and VEGFC was significantly associated with PFS.
CONCLUSIONS: A three loci model of DNA methylation could identify two distinct prognostic groups of patients with ovarian cancer (PFS: HR = 2.29, P = 3.34 × 10(-5); overall survival: HR = 1.87, P = 0.007) and patients more likely to have poor response to chemotherapy (OR = 3.45, P = 0.012).

Reddy SM, Sadim M, Li J, et al.
Clinical and genetic predictors of weight gain in patients diagnosed with breast cancer.
Br J Cancer. 2013; 109(4):872-81 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Post-diagnosis weight gain in breast cancer patients has been associated with increased cancer recurrence and mortality. Our study was designed to identify risk factors for this weight gain and create a predictive model to identify a high-risk population for targeted interventions.
METHODS: Chart review was conducted on 459 breast cancer patients from Northwestern Robert H. Lurie Cancer Centre to obtain weights and body mass indices (BMIs) over an 18-month period from diagnosis. We also recorded tumour characteristics, demographics, clinical factors, and treatment regimens. Blood samples were genotyped for 14 single-nucleotide polymorphisms (SNPs) in fat mass and obesity-associated protein (FTO) and adiponectin pathway genes (ADIPOQ and ADIPOR1).
RESULTS: In all, 56% of patients had >0.5 kg m(-2) increase in BMI from diagnosis to 18 months, with average BMI and weight gain of 1.9 kg m(-2) and 5.1 kg, respectively. Our best predictive model was a primarily SNP-based model incorporating all 14 FTO and adiponectin pathway SNPs studied, their epistatic interactions, and age and BMI at diagnosis, with area under receiver operating characteristic curve of 0.85 for 18-month weight gain.
CONCLUSION: We created a powerful risk prediction model that can identify breast cancer patients at high risk for weight gain.

Ye L, Zhang ZY, Du WD, et al.
Genetic analysis of ADIPOQ variants and gastric cancer risk: a hospital-based case-control study in China.
Med Oncol. 2013; 30(3):658 [PubMed] Related Publications
Single-nucleotide polymorphisms (SNPs) of adiponectin (ADIPOQ), adiponectin receptor 1 (ADIPOR1) and ADIPOR2 genes contribute to the risk and progression of cancers. Here, we investigated the associations between variants of these three genes and the risk of gastric cancer. We genotyped six ADIPOQ SNPs, nine ADIPOR1 SNPs and six ADIPOR2 SNPs using the Sequenom technique in a hospital-based case-control study of patients with gastric cancer and cancer-free controls in the Chinese Han population. We found associations of certain variants with location of gastric cancer. Rs16861205 with the minor allele A in ADIPOQ, rs10773989 with the minor allele C and rs1044471 with the minor allele T in ADIPOR2 presented significant associations with a decreased risk of cardia cancer (P = 0.024, OR 0.605, 95 % CI 0.390-0.938; P = 0.015, OR 0.699, 95 % CI 0.522-0.935; and P = 0.022, OR = 0.703, 95 % CI 0.519-0.951, respectively). ADIPOQ rs16861205 with minor allele A displayed an association with an increased risk of body cancer (P = 0.010, OR 1.821, 95 % CI 1.148-2.890). Further stratified analysis of the patients indicated that there were significant correlations for rs1342387A/G (P = 0.027) and rs16861205A/G (P = 0.000) with tumor location; rs16850799A/G (P = 0.004) and rs2058033C/A (P = 0.003) with invasion depth; rs16850799A/G (P = 0.019) with the tumor-node-metastasis stage; rs16850799A/G (P = 0.016), rs1501299A/C (P = 0.005) and rs1063538C/T (P = 0.017) with alcohol consumption; rs11612414A/G (P = 0.040) and rs12733285T/C (P = 0.005) with salted food; rs1063538C/T (P = 0.043) with family history of gastric cancer; and rs11612414A/G (P = 0.029) with gender. Adiponectin expression significantly correlated with gender (P = 0.014), alcohol consumption (P = 0.037), family history (P = 0.019) and invasion depth of primary tumor (P = 0.024). Our data suggested that variants of ADIPOQ may be genetic markers conferring susceptibility to gastric cancer subtypes. These findings need to be validated in a larger panel of samples from distinct populations.

Bochenek G, Häsler R, El Mokhtari NE, et al.
The large non-coding RNA ANRIL, which is associated with atherosclerosis, periodontitis and several forms of cancer, regulates ADIPOR1, VAMP3 and C11ORF10.
Hum Mol Genet. 2013; 22(22):4516-27 [PubMed] Related Publications
The long non-coding RNA ANRIL is the best replicated genetic risk locus of coronary artery disease (CAD) and periodontitis (PD), and is independently associated with a variety of other immune-mediated and metabolic disorders and several forms of cancer. Recent studies showed a correlation of decreased concentrations of proximal ANRIL transcripts with homozygous carriership of the CAD and PD main risk alleles. To elucidate the relation of these transcripts to disease manifestation, we constructed a short hairpin RNA in a stable inducible knock-down system of T-Rex 293 HEK cell lines, specifically targeting the proximal transcripts EU741058 and DQ485454. By genome-wide expression profiling using Affymetrix HG1.0 ST Arrays, we identified the transcription of ADIPOR1, VAMP3 and C11ORF10 to be correlated with decreased ANRIL expression in a time-dependent manner. We validated these findings on a transcriptional and translational level in different cell types. Exploration of the identified genes for the presence of disease associated variants, using Affymetrix 500K genotyping and Illumina custom genotyping arrays, highlighted a region upstream of VAMP3 within CAMTA1 to be associated with increased risk of CAD [rs10864294 P = 0.015, odds ratio (OR) = 1.30, 95% confidence interval (CI) = 1.1-1.6, 1471 cases, 2737 controls] and aggressive PD (AgP; P = 0.008, OR = 1.31, 95% CI = 1.1-1.6, 864 cases, 3664 controls). In silico replication in a meta-analysis of 14 genome-wide association studies of CAD of the CARDIoGRAM Consortium identified rs2301462, located on the same haplotype block, as associated with P = 0.001 upon adjustment for sex and age. Our results give evidence that specific isoforms of ANRIL regulate key genes of glucose and fatty acid metabolism.

Hwang MS, Yu N, Stinson SY, et al.
miR-221/222 targets adiponectin receptor 1 to promote the epithelial-to-mesenchymal transition in breast cancer.
PLoS One. 2013; 8(6):e66502 [PubMed] Free Access to Full Article Related Publications
The epithelial-to-mesenchymal transition (EMT) is a highly conserved physiological program involved in development and tissue repair; however, its aberrant activation has been implicated in accelerating the progression of a variety of cancers. In breast cancer, the microRNAs (miRNAs) miR-221 and miR-222 (miR-221/222) are differentially expressed in the clinically more aggressive basal-like subtype compared to luminal subtype of breast cancer and upregulation of miR-221/222 induces the EMT by targeting the 3' untranslated region (3'UTR) of the GATA family transcriptional repressor TRPS1 (tricho-rhino-phalangeal syndrome type 1). The complete mechanism through which miR-221/222 promotes the EMT, however, is not fully understood. We identified adiponectin receptor 1 (ADIPOR1), a receptor for the adipocytokine adiponectin, as a direct target of miR-221/222. ADIPOR1 is expressed at higher levels in the luminal compared to the basal-like subtype of breast cancer cell lines, which can be reduced by miR-221/222 targeting of its 3'UTR. In addition, miR-221/222 were negatively correlated with ADIPOR1 expression across breast cancer cell lines and tumors. ADIPOR1 depletion by siRNA in MCF10A cells induced the EMT and increased cell invasion. Depletion of ADIPOR1 by siRNA induced activation of the canonical nuclear factor-kappaB (NF-κB) and subsequent phosphorylation of signal transducer and activator of transcription 3 (STAT3) in an interleukin 6 (IL6)-dependent manner. Finally, overexpression of ADIPOR1 in the basal-like cell line, MDA-MB-231, attenuated cell invasion and promoted the mesenchymal-to-epithelial transition (MET). We conclude that ADIPOR1 negatively regulates EMT in breast cancer and provides an additional node by which miR-221/222 induces the EMT. These results suggest that ADIPOR1 may play an important role in breast cancer progression and metastasis, and could potentially offer an alternative therapeutic strategy for basal-like breast cancer patients.

Mokrowiecka A, Sokolowska M, Luczak E, et al.
Adiponectin and leptin receptors expression in Barrett's esophagus and normal squamous epithelium in relation to central obesity status.
J Physiol Pharmacol. 2013; 64(2):193-9 [PubMed] Related Publications
UNLABELLED: Esophageal adenocarcinoma incidence is rapidly increasing which may be due to the growing incidence of Barrett's esophagus (BE) and obesity. The mechanisms linking obesity and progression of Barrett's carcinogenesis is poorly understood. The aim of the study was to evaluate the expression of adipokines receptors in BE and in normal squamous epithelium in the same patients in correlation with obesity parameters.
METHODS: Expression of adiponectin receptors 1 and 2 protein (AdipoR1, AdipoR2) as well as leptin receptor protein (ObR) in biopsies from 27 BE and normal squamous epithelium (N) in the same patients as well as in obese and normal controls were assessed with Western-blot analysis. These correlations were confirmed with the quantitative RT-PCR (qRT-PCR). AdipoR1 and ObR protein levels were similar in BE mucosa and squamous epithelium in the same patients in Western-blot analysis (2303 vs. 2448 OB units; 106927 vs. 103390, respectively; p>0.05). RT-PCR analysis confirmed this observation for AdipoR1, R2 and ObR genes expression (0.11±0.08 vs. 0.19±0.24, p=0.78; 0.24±0.36 vs. 0.33±0.49, p=0.5375; 0.71±0.8 vs. 1.33±2.95, p=1.0; respectively). Using linear correlation analysis we found the positive correlation between AdipoR1 expression in Barrett's epithelium compared to squamous epithelium in the same patients (N) (r=0.5; p=0.008) and between ObR expression in BE and N (r=0.8; p<0.001). The AdipoR1 and ObR protein levels were significantly higher in BE patients compared to controls and obese controls (2303 vs. 895 vs. 1674 and OD units, p<0.05).
CONCLUSIONS: in opposite to the prior hypothesis adiponectin and leptin receptors activation in BE may be not caused by obesity.

Delort L, Lequeux C, Dubois V, et al.
Reciprocal interactions between breast tumor and its adipose microenvironment based on a 3D adipose equivalent model.
PLoS One. 2013; 8(6):e66284 [PubMed] Free Access to Full Article Related Publications
Breast cancer has become the most common cancer among women in industrialized countries. Obesity is well established as a risk factor, in particular owing to the attendant secretion of the entities called adipokines; there is growing evidence for a role of cells and factors present in the mammary tumor microenvironment such as fibroblasts, preadipocytes, adipocytes and their secretions. To study how the microenvironment influences breast cancer growth, we developed a novel tridimensional adipose model epithelialized with normal human keratinocytes or with breast cancer cell lines. These mimicked a breast tumor in contact with an adipose microenvironment and allowed monitoring of the interactions between the cells. Leptin and adiponectin, two major adipokines, and their respective receptors, ObRt and AdipoR1, were expressed in the model, but not the second adiponectin receptor, AdipoR2. The differentiation of preadipocytes into adipocytes was greater when they were in contact with the breast cancer cell lines. The contact of breast cancer cell lines with the microenvironment completely modified their transcriptional programs by increasing the expression of genes involved in cell proliferation (cyclinD1, MAPK), angiogenesis (MMP9, VEGF) and hormonal pathways (ESR1, IL6). This tridimensional adipose model provides new insights into the interactions between breast cancer cells and their adipose microenvironment, and provides a tool to develop new drugs for the treatment of both cancer and obesity.

Kaklamani VG, Hoffmann TJ, Thornton TA, et al.
Adiponectin pathway polymorphisms and risk of breast cancer in African Americans and Hispanics in the Women's Health Initiative.
Breast Cancer Res Treat. 2013; 139(2):461-8 [PubMed] Free Access to Full Article Related Publications
Adiponectin, a protein secreted by the adipose tissue, is an endogenous insulin sensitizer with circulating levels that are decreased in obese and diabetic subjects. Recently, circulating levels of adiponectin have been correlated with breast cancer risk. Our previous work showed that polymorphisms of the adiponectin pathway are associated with breast cancer risk. We conducted the first study of adiponectin pathways in African Americans and Hispanics in the Women's Health Initiative SNP Health Association Resource cohort of 3,642 self-identified Hispanic women and 8,515 self-identified African American women who provided consent for DNA analysis. Single nucleotide polymorphisms (SNPs) from three genes were included in this analysis: ADIPOQ, ADIPOR1, and ADIPOR2. The genome-wide human SNP array 6.0 (909,622 SNPs) ( www.affymetrix.com ) was used. We found that rs1501299, a functional SNP of ADIPOQ that we previously reported was associated with breast cancer risk in a mostly Caucasian population, was also significantly associated with breast cancer incidence (HR for the GG/TG genotype: 1.23; 95 % CI 1.059-1.43) in African American women. We did not find any other SNPs in these genes to be associated with breast cancer incidence. This is the first study assessing the role of adiponectin pathway SNPs in breast cancer risk in African Americans and Hispanics. RS1501299 is significantly associated with breast cancer risk in African American women. As the rates of obesity and diabetes increase in African Americans and Hispanics, adiponectin and its functional SNPs may aid in breast cancer risk assessment.

Palin MF, Bordignon VV, Murphy BD
Adiponectin and the control of female reproductive functions.
Vitam Horm. 2012; 90:239-87 [PubMed] Related Publications
Adiponectin is the most abundant protein secreted by the white adipose tissue. It circulates at high levels in the bloodstream and its serum concentration is inversely correlated with body fat mass. The wide distribution of adiponectin receptors (AdipoR1, AdipoR2, and T-cadherin) in peripheral tissues and organs allows adiponectin to exert pleiotropic effects on whole-body metabolism. Besides its well-known antidiabetic, antiatherogenic, and anti-inflammatory properties, accumulating evidence suggests a direct role for adiponectin in reproductive tissues. The mammalian ovary and the ovarian follicle express AdipoR1 and AdipoR2, and treating pig granulosa cells with adiponectin induces changes characteristic of the periovulatory period. Moreover, additive effects are observed between adiponectin and insulin in induction of granulosa cell gene expression, thus suggesting that adiponectin actions on the ovary may be mediated through its insulin-sensitizing effects. Adiponectin receptors are also detected in the uterus. In women, higher AdipoR1 and AdipoR2 gene expression was observed during the mid-secretory phase of the menstrual cycle, suggesting that adiponectin is implicated in the endometrial changes in preparation for embryo implantation. Adiponectin receptors are found in oocytes and early developing pig, rabbit, and mice embryos, and it has been demonstrated that adiponectin can increase the success of porcine embryo development to the blastocyst stage in vitro. Moreover, adiponectin concentration is two to three times greater in human fetal circulation and in umbilical cord blood, compared to adult plasma. This further indicates a role for adiponectin in fetal growth. It has been further suggested that adipose-derived and locally produced adiponectin may act as a key neuromodulator of reproductive functions. For example, the inhibition of LH and GnRH release from rat pituitary and hypothalamic cells following treatment with adiponectin provides evidence that adiponectin may also act on the release of gonadotropins. Adipose tissue is now recognized as an important factor in the complex equation by which the nutritional status regulates female reproductive functions. For example, underweight women have delayed puberty and higher risk of premature delivery, whereas overweight and obese women have early puberty and are prone to develop polycystic ovary syndrome (PCOS), gestational diabetes mellitus (GDM), and preeclampsia. Because hypoadiponectinemia is often associated with the abovementioned disorders, it has been suggested that this adipokine might play a role in the development of these pregnancy-related complications. Moreover, as these reproductive disorders often come with metabolic complications such as insulin and glucose resistance, the insulin-sensitizing effects of adiponectin may explain the observed association of this adipokine with PCOS, GDM, and preeclampsia. This review summarizes current knowledge on the role of adiponectin in female reproductive tissues and highlights mechanisms where information is available. We also discuss about the known and potential roles of adiponectin in the development of reproductive disorders.

Faryna M, Konermann C, Aulmann S, et al.
Genome-wide methylation screen in low-grade breast cancer identifies novel epigenetically altered genes as potential biomarkers for tumor diagnosis.
FASEB J. 2012; 26(12):4937-50 [PubMed] Related Publications
Aberrant DNA methylation constitutes a well-established epigenetic marker for breast cancer. Changes in methylation early in cancer development may be clinically relevant for cancer detection and prognosis-based therapeutic decisions. In the present study, a combination of methyl-CpG immunoprecipitation (MCIp) and human CpG island (CGI) arrays was applied to compare genome-wide DNA methylation profiles in 10 low-grade in situ and invasive breast cancers against 10 normal breast samples. In total, 214 CGIs were found to be hypermethylated in ≥6 of 10 tumors. Functional term enrichment analyses revealed an overrepresentation of homeobox genes and genes involved in transcription and regulation of transcription. Significant hypermethylation of 11 selected genes in tumor vs. normal tissue was validated in two independent sample sets (45 tumors and 11 controls, 43 tumors and 8 controls) using quantitative EpiTyper technology. In tumors, median methylation levels of BCAN, HOXD1, KCTD8, KLF11, NXPH1, POU4F1, SIM1, and TCF7L1 were ≥30% higher than in normal samples, representing potential biomarkers for tumor diagnosis. Using the 90th percentile of methylation levels in normal tissue as cutoff value, 62-92% of in situ samples (n=13), 72-97% of invasive samples from the first validation set (n=32), and 86-100% of invasive samples from the second validation set (n=43) were classified as hypermethylated. Hypermethylation of KLF11 and SIM1 might also be associated with increased risk of developing metastases. In summary, early methylation changes are frequent in the low-grade pathway of breast cancer and may be useful in the development of differential diagnostic and possibly also prognostic markers.

Yamauchi N, Takazawa Y, Maeda D, et al.
Expression levels of adiponectin receptors are decreased in human endometrial adenocarcinoma tissues.
Int J Gynecol Pathol. 2012; 31(4):352-7 [PubMed] Related Publications
Adiponectin is a cytokine secreted by adipocytes, whose plasma levels are decreased in obesity. Adiponectin has insulin-sensitizing, antiatherogenic, and antidiabetogenic effects. It has been shown that adiponectin may also exert antineoplastic activity through suppression of tumor proliferation and neoangiogenesis and through induction of apoptosis. Recently, low adiponectin serum concentration has been found in obesity-related malignancies, including endometrial cancer. In addition, the expression of adiponectin receptors (AdipoR1 and AdipoR2) has been documented in several human cancer tissues, but the expression has previously not been assessed in human endometrial cancer tissues. In this study, we analyzed the immunohistochemical expression of AdipoR1 and AdipoR2 in a series of surgically resected human endometrioid adenocarcinoma tissues from a total of 141 cases. Decreased AdipoR1 or AdipoR2 expression was significantly associated with histological higher grade (P=0.0026 and 0.0004, respectively). Decreased expression of AdipoR1 was associated with myometrial invasion and lymph node metastasis of endometrioid adenocarcinoma (P=0.0039 and P=0.0069, respectively). AdipoR1 and AdipoR2 immunoexpression was significantly associated with the expression of the progesterone receptor, although it was not significantly correlated with the expression of the estrogen receptor, Ki-67 or p53. Our present study raises the possibility that decreased expression of adiponectin receptors is implicated in the development, invasion, and metastasis of human endometrioid adenocarcinoma. Our findings, moreover, indicate that adiponectin receptors could be considered as therapeutic targets for endometrioid adenocarcinoma. In adiponectin receptor-positive endometrioid adenocarcinoma, we think adiponectin-based anticancer therapy is useful; however, in histological high-grade endometrioid adenocarcinoma, in which the expression levels of adiponectin receptors are relatively low, adiponectin therapy supported by adiponectin receptor induction is needed.

Lu JP, Hou ZF, Duivenvoorden WC, et al.
Adiponectin inhibits oxidative stress in human prostate carcinoma cells.
Prostate Cancer Prostatic Dis. 2012; 15(1):28-35 [PubMed] Related Publications
BACKGROUND: Emerging data suggest that obesity increases the risk of aggressive prostate cancer (PC), but the mechanisms underlying this relationship remain to be fully elucidated. Oxidative stress (OS) is a key process in the development and progression of PC. Adiponectin, an adipocyte-specific hormone, circulates at relatively high levels in healthy humans, but at reduced levels in obese subjects. Moreover, case-control studies also document lower levels of serum adiponectin in PC patients compared with healthy individuals.
METHODS: Human 22Rv1 and DU-145 PC cell lines were examined for the generation of OS and detoxification of reactive oxygen species after treatment with adiponectin. Normality was confirmed using the Shapiro-Wilk test and results were analyzed using a one-way analysis of variance.
RESULTS: We demonstrate that adiponectin increased cellular anti-oxidative defense mechanisms and inhibited OS in a significant and dose-dependent manner. We show that adiponectin treatment decreased the generation of superoxide anion in both cell lines, whereas the transcript levels of NADPH oxidase (NOX)2 and NOX4 increased. We also found indications of an overall anti-oxidative effect, as the total anti-oxidative potential, catalase activity and protein levels, and manganese superoxide dismutase protein levels increased significantly (P<0.05) in both cell lines after treatment with adiponectin.
CONCLUSION: Lower levels of adiponectin in obese individuals may result in higher levels of prostatic OS, which may explain the clinical association between obesity, hypoadiponectinemia and PC.

Niu K, Asada M, Okazaki T, et al.
Adiponectin pathway attenuates malignant mesothelioma cell growth.
Am J Respir Cell Mol Biol. 2012; 46(4):515-23 [PubMed] Related Publications
Malignant mesothelioma (MM) is caused by exposure to asbestos. Because MM has a latency period, short survival time, and has a poor response to current therapeutic regimes, long-term preventive strategies are required to suppress the advance of pathological states after asbestos exposure. Accumulating evidence suggests that adiponectin plays a crucial role in the regulation of energy metabolism by increasing AMP-activated protein kinase (AMPK) activation. Several studies have indicated that the activation of AMPK decreases cyclooxygenase (COX)-2 expression. Because high COX-2 levels correlated with a worse prognosis and survival rate in MM, we examined whether the adiponectin pathway suppresses MM cell growth through the AMPK/COX-2 pathway. In vivo, dietary fish oil (a potential promoter of adiponectin) decreased the growth rate of MM, which was accompanied by an increase in adiponectin and phospho-AMPK levels, and a decrease in COX-2 level. In vitro, adiponectin significantly impaired the cell proliferation rate of MM cell lines. These effects partly involved induction of growth arrest and apoptosis to MM cells. MM cells expressed both adiponectin receptors 1 and 2 (AdipoR1 and -R2) at mRNA and proteins levels. These receptors were functional, because adiponectin activated AMPK. Adiponectin treatment also significantly down-regulated protein levels of COX-2 and its downstream prostaglandin E(2). Finally, inhibitory analysis of AdipoR1/R2 by small interfering RNA knockdown suggests that adiponectin enhances AMPK activity and impairs the cell proliferation rate of MM cells, mainly via AdipoR1. These findings suggest that the induction or supplementation of adiponectin is an important tactic for developing therapeutic strategies against MM.

Liu L, Zhong R, Wei S, et al.
Interactions between genetic variants in the adiponectin, adiponectin receptor 1 and environmental factors on the risk of colorectal cancer.
PLoS One. 2011; 6(11):e27301 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Metabolic syndrome traits play an important role in the development of colorectal cancer. Adipokines, key metabolic syndrome cellular mediators, when abnormal, may induce carcinogenesis.
METHODOLOGY/PRINCIPAL FINDINGS: To investigate whether polymorphisms of important adipokines, adiponectin (ADIPOQ) and its receptors, either alone or in combination with environmental factors, are implicated in colorectal cancer, a two-stage case-control study was conducted. In the first stage, we evaluated 24 tag single nucleotide polymorphisms (tag SNPs) across ADIPOQ ligand and two ADIPOQ receptors (ADIPOR1 and ADIPOR2) among 470 cases and 458 controls. One SNP with promising association was then analyzed in stage 2 among 314 cases and 355 controls. In our study, ADIPOQ rs1063538 was consistently associated with increased colorectal cancer risk, with an odds ratio (OR) of 1.94 (95%CI: 1.48-2.54) for CC genotype compared with TT genotype. In two-factor gene-environment interaction analyses, rs1063538 presented significant interactions with smoking status, family history of cancer and alcohol use, with ORs of 4.52 (95%CI: 2.78-7.34), 3.18 (95%CI: 1.73-5.82) and 1.97 (95%CI: 1.27-3.04) for smokers, individuals with family history of cancer or drinkers with CC genotype compared with non-smokers, individuals without family history of cancer or non-drinkers with TT genotype, respectively. Multifactor gene-environment interactions analysis revealed significant interactions between ADIPOQ rs1063538, ADIPOR1 rs1539355, smoking status and BMI. Individuals carrying one, two and at least three risk factors presented 1.18-fold (95%CI:0.89-fold to 1.58-fold), 1.87-fold (95%CI: 1.38-fold to 2.54-fold) and 4.39-fold (95%CI: 2.75-fold to 7.01-fold) increased colorectal cancer risk compared with those who without risk factor, respectively (P(trend) <0.0001).
CONCLUSIONS/SIGNIFICANCE: Our results suggest that variants in ADIPOQ may contribute to increased colorectal cancer risk in Chinese and this contribution may be modified by environmental factors, such as smoking status, family history of cancer and BMI.

Ozturk K, Avcu F, Ural AU
Aberrant expressions of leptin and adiponectin receptor isoforms in chronic myeloid leukemia patients.
Cytokine. 2012; 57(1):61-7 [PubMed] Related Publications
BACKGROUND: Leptin and adiponectin receptors mediate the role of leptin in stimulating the growth of leukemic cells and the protective function of adiponectin undertaken in several malignancies such as leukemia. In this study, we investigated the involvement of the expression of leptin and adiponectin receptors in chronic myeloid leukemia (CML) pathogenesis.
METHODS: The expression of leptin receptor isoforms, OB-Rt, OB-Ra, and OB-Rb, and the expression of adiponectin receptors, AdipoR1 and AdipoR2, were measured as mRNA levels in two CML cell lines (K562 and Meg-01) and 20 CML patients and 24 healthy controls by using RT-PCR.
RESULTS: OB-Rt and OB-Ra isoforms expression of the leptin receptors were found to be significantly lower in Meg-01 cell lines than K562 cells. All leptin receptors were downregulated in CML patients and more particularly OB-Rb level was found to be undetectably low in normal PBMC as well as in CML patients. AdipoR1 expression level was higher in Meg-01 than in K562, whereas AdipoR2 level was found to be unchanged in both cell lines. Interestingly, while AdipoR1 expression increased in CML patients, AdipoR2 decreased. Moreover, imatinib therapy did not affect both leptin and adiponectin isoform expressions.
CONCLUSION: While the decrease in leptin receptor levels in CML patients was confirmed, the increase in AdipoR1 levels and relevant decrease in AdipoR2 levels depicted their possible involvement in CML pathogenesis. This suggests different functions of adiponectin receptors in CML development.

Chen X, Xiang YB, Long JR, et al.
Genetic polymorphisms in obesity-related genes and endometrial cancer risk.
Cancer. 2012; 118(13):3356-64 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Obesity is associated with circulating levels of adiponectin and leptin and endometrial cancer risk. Little is known about whether single nucleotide polymorphisms (SNPs) in the genes that encode adiponectin (ADIPOQ), leptin (LEP), adiponectin receptor 1 (ADIPOR1), adiponectin receptor 2 (ADIPOR2), and leptin receptor (LEPR) are associated with endometrial cancer.
METHODS: The authors selected 87 tagging SNPs to capture common genetic variants in these 5 genes. These SNPs were evaluated in 1028 endometrial cancer cases and 1932 community controls recruited from Chinese women. Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs).
RESULTS: Three of the 10 SNPs evaluated in the ADIPOQ gene were significantly associated with reduced cancer risk. The OR for women homozygous for the minor allele (A/A) for rs3774262 was 0.68 (95% CI, 0.48-0.97) compared with women homozygous for the major allele (G/G). Similar results were found for SNPs rs1063539 and rs12629945 in ADIPOQ, which were in linkage disequilibrium with rs3774262. These associations became nonsignificant after Bonferroni correction was applied. Controls with the minor allele A at rs3774262 had lower weight, smaller waist and hip circumferences, and lower body mass index than controls with the major allele G (all P < .05). Women homozygous for the minor allele (T/T) of rs2071045 in the LEP gene also had significantly lower risk (OR, 0.70; 95% CI, 0.54-0.90) than women homozygous for the major allele (C/C). No other SNPs in the LEP, ADIPOR1, ADIPOR2, or LEPR genes were found to be associated with cancer risk.
CONCLUSIONS: Although a chance finding cannot be ruled out, the consistency of findings for gene-endometrial cancer risk and gene-obesity measurements suggests that genetic polymorphisms in the ADIPOQ gene may play a role in endometrial cancer development.

Moon HS, Chamberland JP, Aronis K, et al.
Direct role of adiponectin and adiponectin receptors in endometrial cancer: in vitro and ex vivo studies in humans.
Mol Cancer Ther. 2011; 10(12):2234-43 [PubMed] Free Access to Full Article Related Publications
Low adiponectin levels are an independent risk factor for and mediate the effect of obesity on endometrial cancer in epidemiology studies. The direct or indirect mechanisms underlying these findings remain to be elucidated. We first examined the expression of adiponectin receptor 1 (AdipoR1) and 2 (AdipoR2) in normal human endometrium and in endometrial cancer tissues ex vivo. We then used KLE and RL95-2 human endometrial cancer cell lines in vitro to study relative expression of AdipoRs, to investigate the effect of adiponectin on activating intracellular signaling pathways, and to assess its potential to alter malignant properties. We report for the first time that the relative expression level of AdipoR1 is higher than AdipoR2 in human endometrial cancer tissue, but the expression of AdipoRs is not statistically different from nonneoplastic tissues. We also show for the first time in endometrial cancer cell lines in vitro that adiponectin suppresses endometrial cancer proliferation acting through AdipoRs. Adiponectin also increases the expression of the adaptor molecule LKB1, which is required for adiponectin-mediated activation of AMPK/S6 axis and modulation of cell proliferation, colony formation, adhesion, and invasion of KLE and RL95-2 cell lines. These novel mechanistic studies provide for the first time in vitro and ex vivo evidence for a causal role of adiponectin in endometrial cancer.

Dhillon PK, Penney KL, Schumacher F, et al.
Common polymorphisms in the adiponectin and its receptor genes, adiponectin levels and the risk of prostate cancer.
Cancer Epidemiol Biomarkers Prev. 2011; 20(12):2618-27 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Adiponectin, an insulin-sensitizing adipokine, is inversely associated with adiposity and prostate cancer risk and progression. However, the role of genetic variation in the adiponectin (ADIPOQ) and receptor genes (ADIPOR1/R2) in prostate cancer is largely unknown.
METHODS: In a nested case-control study of 1,286 cases and 1,267 controls within the Physicians' Health Study, we evaluated 29 common single-nucleotide polymorphisms (SNP) in ADIPOQ (n = 13), ADIPOR1 (n = 5), and ADIPOR2 (n = 11) in relation to the risk of prostate cancer. In subgroups, we also evaluated the association of genotype and circulating adiponectin levels (n = 951) and prostate tumor expression of insulin receptor (IR) and insulin-like growth factor 1 (IGF-IR) receptor (n = 181).
RESULTS: Among the 12 tagging polymorphisms in ADIPOQ, four (rs266729, rs182052, rs822391, and rs2082940) were significantly associated (P < 0.05) with overall prostate cancer risk, with no significant difference by tumor grade or clinical stage. Two of the risk SNPs (rs266729 and rs182052) plus four other SNPs (rs16861209, rs17366568, rs3774261, and rs7639352) were also associated with plasma adiponectin levels, and three of these (rs1686109, rs17366568, and rs3774261) were also significantly associated with IR expression in prostate tumor tissue. One additional SNP was associated with IGFI-R tumor tissue expression (rs16861205). None of the 16 variants in ADIPOR1/R2 were related to cancer risk or circulating adiponectin levels.
CONCLUSIONS: Common variants in the adiponectin gene were associated with prostate cancer risk, plasma adiponectin levels, and IR or IGF-IR expression in the prostate tumor.
IMPACT: These genotype-phenotype associations support the biological relevance of adiponectin for prostate carcinogenesis, particularly in earlier stages of development.

He B, Pan Y, Zhang Y, et al.
Effects of genetic variations in the adiponectin pathway genes on the risk of colorectal cancer in the Chinese population.
BMC Med Genet. 2011; 12:94 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Decreased expression of adiponectin (ADIPOQ) is associated with an increased risk for developing colorectal cancer (CRC) in humans. This study was designed to determine whether polymorphisms present in the ADIPOQ and its type 1 receptor (ADIPOR1) could affect the risk of CRC.
METHODS: We measured five polymorphisms in the ADIPOQ and two polymorphisms in ADIPOR1, and analyzed their associations with CRC risk in 420 CRC patients and 555 age- and gender-matched healthy individuals.
RESULTS: Multivariate logistic regression analyses revealed that the CRC risks (adjusted odds ratio and 95% confidence interval) associated with the ADIPOR1 genotypes were 0.53 (95% CI, 0.35-0.81) for rs12733285C/T, 0.59 (95% CI, 0.45-0.78) for rs1342387A/G, and 0.59 (95% CI, 0.39-0.89) for rs1342387A/A, respectively. Furthermore, the risks were more significant in carriers of the allele A of rs1342387A/G (adjusted OR, 0.59; 95% CI, 0.46-0.77) than noncarriers (G/G). In a further subgroup analysis, we observed that rs266729G/C was associated with an increased risk for colon cancer (adjusted OR, 1.50; 95% CI, 1.05-2.14) but not for rectal cancer (adjusted OR, 0.88; 95% CI, 0.63-1.22), and that carriers of the G allele had an increased risk for developing colon cancer (adjusted OR, 1.45; 95% CI, 1.03-2.05).
CONCLUSIONS: We conclude that the rs12733285C/T genotype and the carriage of the A allele of rs1342387 (A/G or A/A) in ADIPOR1 are the protective factors for CRC, while that rs266729G/C and G allele of ADIPOQ are the risk factors for colon cancer after excluding rectal cancer cases.

Carroll PA, Healy L, Lysaght J, et al.
Influence of the metabolic syndrome on leptin and leptin receptor in breast cancer.
Mol Carcinog. 2011; 50(8):643-51 [PubMed] Related Publications
Obesity and its associated metabolic syndrome (MetS) are recognized risk factors for breast cancer. The molecular basis for this association remains largely unknown. Adipokines, in particular leptin and adiponectin, are thought to form part of the mechanism linking obesity with cancer through their altered expression/production either systemically (endocrine pathway) or locally (paracrine/autocrine pathway). Using quantitative PCR, mRNA expression of adiponectin (AdipoQ) and leptin (Ob) in mammary adipose tissue (MAT), intratumoral leptin and associated ligand receptors (ObR, AdipoR1, and AdipoR2) was examined in 77 patients with complete anthropomorphic and serological data. Expression of Ob in MAT, and ObR in matched tumor tissue was significantly higher in patients with MetS compared to obese only or normal weight cancer patients (P < 0.005). There was no difference in intratumoral leptin adiponectin or its ligand receptors in the same groups. Individual features of MetS correlated with Ob and ObR expression, but not obesity markers (BMI, waist circumference). mRNA expression of leptin (Ob) and ObR, in adipose tissue and matched tumor samples, respectively, appear to be associated with obesity status in breast cancer. Increasing insulin resistance is a predominant feature of this higher Ob/ObR expression observed. These novel data indicate that the MetS may be an amenable risk factor for breast cancer.

Byeon JS, Jeong JY, Kim MJ, et al.
Adiponectin and adiponectin receptor in relation to colorectal cancer progression.
Int J Cancer. 2010; 127(12):2758-67 [PubMed] Related Publications
Although obesity is a risk factor for colorectal cancer, the underlying mechanism is not clear. Adiponectin is an adipokine that binds to 2 types of receptors, AdipoR1 and AdipoR2. The plasma concentrations of adiponectin are reduced in obese individuals and adiponectin has been reported to have anticarcinogenic properties. Furthermore, AdipoR1 and AdipoR2 have been reported to be expressed in several malignancies. However, little is known about the expression of AdipoR1 and AdipoR2 in colorectal cancer and its clinicopathological implications. In addition, the relationship between adiponectin and colorectal cancer has not yet been determined. Here, we sought to investigate adiponectin and adiponectin receptors in relation to colorectal cancer. AdipoR1 and AdipoR2 immunostaining was detected in 72 and 68% of human colorectal cancer tissue, respectively. AdipoR1 and AdipoR2 expression levels were inversely related to T stage. The lowest AdipoR1 and AdipoR2 expression were detected in poorly differentiated adenocarcinoma. RT-PCR also showed the expression of AdipoR1 and AdipoR2 in HCT116 and SW620. MTT assay and TUNEL assay demonstrated the tendency of growth inhibition and apoptosis induction in both cell lines after full-length adiponectin treatment although statistically insignificant. Microarray analysis revealed several gene responses to full-length adiponectin, including upregulation of ENDOGL1 and MT1G. In conclusion, AdipoR1 and AdipoR2 may be intimately related to the progression of colorectal cancer. Further studies may be warranted to assess adiponectin and its receptors as a novel target for inhibition of colorectal cancer growth.

Beebe-Dimmer JL, Zuhlke KA, Ray AM, et al.
Genetic variation in adiponectin (ADIPOQ) and the type 1 receptor (ADIPOR1), obesity and prostate cancer in African Americans.
Prostate Cancer Prostatic Dis. 2010; 13(4):362-8 [PubMed] Free Access to Full Article Related Publications
Adiponectin is a protein derived from adipose tissue suspected to have an important role in prostate carcinogenesis. Variants in the adiponectin gene (ADIPOQ) and its type 1 receptor (ADIPOR1) have been recently linked to risk of both breast and colorectal cancer. Therefore, we set out to examine the relationship between polymorphisms in these genes, obesity and prostate cancer in study of African-American men. Ten single-nucleotide polymorphisms (SNPs) in ADIPOQ and ADIPOR1 were genotyped in DNA samples from 131 African-American prostate cancer cases and 344 controls participating in the Flint Men's Health Study. Logistic regression was then used to estimate their association with prostate cancer and obesity. While no significant associations were detected between any of the tested SNPs and prostate cancer, the rs1501299 SNP in ADIPOQ was significantly associated with body mass (P=0.03). Genetic variation in ADIPOQ and ADIPOR1 did not predict risk of prostate cancer in this study of African-American men. However, the rs1501299 SNP in ADIPOQ was associated with obesity. Further investigation is warranted to determine if racial differences exist in the influence of the adiponectin pathway on prostate cancer risk.

Möllerström E, Kovács A, Lövgren K, et al.
Up-regulation of cell cycle arrest protein BTG2 correlates with increased overall survival in breast cancer, as detected by immunohistochemistry using tissue microarray.
BMC Cancer. 2010; 10:296 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Previous studies have shown that the ADIPOR1, ADORA1, BTG2 and CD46 genes differ significantly between long-term survivors of breast cancer and deceased patients, both in levels of gene expression and DNA copy numbers. The aim of this study was to characterize the expression of the corresponding proteins in breast carcinoma and to determine their correlation with clinical outcome.
METHODS: Protein expression was evaluated using immunohistochemistry in an independent breast cancer cohort of 144 samples represented on tissue microarrays. Fisher's exact test was used to analyze the differences in protein expression between dead and alive patients. We used Cox-regression multivariate analysis to assess whether the new markers predict the survival status of the patients better than the currently used markers.
RESULTS: BTG2 expression was demonstrated in a significantly lower proportion of samples from dead patients compared to alive patients, both in overall expression (P = 0.026) and cell membrane specific expression (P = 0.013), whereas neither ADIPOR1, ADORA1 nor CD46 showed differential expression in the two survival groups. Furthermore, a multivariate analysis showed that a model containing BTG2 expression in combination with HER2 and Ki67 expression along with patient age performed better than a model containing the currently used prognostic markers (tumour size, nodal status, HER2 expression, hormone receptor status, histological grade, and patient age). Interestingly, BTG2 has previously been described as a tumour suppressor gene involved in cell cycle arrest and p53 signalling.
CONCLUSIONS: We conclude that high-level BTG2 protein expression correlates with prolonged survival in patients with breast carcinoma.

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