Gene Summary

Gene:CRY2; cryptochrome circadian clock 2
Aliases: HCRY2, PHLL2
Summary:This gene encodes a flavin adenine dinucleotide-binding protein that is a key component of the circadian core oscillator complex, which regulates the circadian clock. This gene is upregulated by CLOCK/ARNTL heterodimers but then represses this upregulation in a feedback loop using PER/CRY heterodimers to interact with CLOCK/ARNTL. Polymorphisms in this gene have been associated with altered sleep patterns. The encoded protein is widely conserved across plants and animals. Two transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Feb 2014]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Source:NCBIAccessed: 09 March, 2017


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 (1992-2017)
Graph generated 10 March 2017 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.

  • China
  • Colorectal Cancer
  • Cryptochromes
  • Adenocarcinoma
  • Translocation
  • Cell Cycle Proteins
  • Nuclear Proteins
  • Staging
  • RT-PCR
  • Young Adult
  • Genotype
  • Flavoproteins
  • Hepatocellular Carcinoma
  • Risk Factors
  • Breast Cancer
  • Liver Cancer
  • Transfection
  • Circadian Clocks
  • Biomarkers, Tumor
  • CLOCK Proteins
  • Up-Regulation
  • Transcription
  • Apoptosis
  • Basic Helix-Loop-Helix Transcription Factors
  • Cancer Gene Expression Regulation
  • Stomach Cancer
  • Genetic Predisposition
  • Transcription Factors
  • Chromosome 11
  • Cell Cycle
  • Case-Control Studies
  • Mutagens
  • Circadian Rhythm
  • Alleles
  • Sirtuin 1
  • Prostate Cancer
  • Period Circadian Proteins
  • Gene Silencing
  • Messenger RNA
Tag cloud generated 09 March, 2017 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: CRY2 (cancer-related)

Huisman SA, Ahmadi AR, IJzermans JN, et al.
Disruption of clock gene expression in human colorectal liver metastases.
Tumour Biol. 2016; 37(10):13973-13981 [PubMed] Free Access to Full Article Related Publications
The circadian timing system controls about 40 % of the transcriptome and is important in the regulation of a wide variety of biological processes including metabolic and proliferative functions. Disruption of the circadian clock could have significant effect on human health and has an important role in the development of cancer. Here, we compared the expression levels of core clock genes in primary colorectal cancer (CRC), colorectal liver metastases (CRLM), and liver tissue within the same patient. Surgical specimens of 15 untreated patients with primary CRC and metachronous CRLM were studied. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to measure the expression of 10 clock genes: CLOCK, BMAL1, PER1, PER2, PER3, CRY1, CRY2, CSNK1E, TIM, TIPIN, and 2 clock-controlled genes: Cyclin-D1, and WEE1. Expression levels of 7 core clock genes were downregulated in CRLM: CLOCK (p = 0.006), BMAL1 (p = 0.003), PER1 (p = 0.003), PER2 (p = 0.002), PER3 (p < 0.001), CRY1 (p = 0.002), and CRY2 (p < 0.001). In CRC, 5 genes were downregulated: BMAL1 (p = 0.02), PER1 (p = 0.004), PER2 (p = 0.008), PER3 (p < 0.001), and CRY2 (p < 0.001). CSNK1E was upregulated in CRC (p = 0.02). Cyclin-D1 and WEE1 were both downregulated in CRLM and CRC. Related to clinicopathological factors, a significant correlation was found between low expression of CRY1 and female gender, and low PER3 expression and the number of CRLM. Our data demonstrate that the core clock is disrupted in CRLM and CRC tissue from the same patient. This disruption may be linked to altered cell-cycle dynamics and carcinogenesis.

Mazzoccoli G, Colangelo T, Panza A, et al.
Deregulated expression of cryptochrome genes in human colorectal cancer.
Mol Cancer. 2016; 15:6 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Circadian disruption and deranged molecular clockworks are involved in carcinogenesis. The cryptochrome genes (CRY1 and CRY2) encode circadian proteins important for the functioning of biological oscillators. Their expression in human colorectal cancer (CRC) and in colon cancer cell lines has not been evaluated so far.
METHODS: We investigated CRY1 and CRY2 expression in fifty CRCs and in the CaCo2, HCT116, HT29, SW480 cell lines.
RESULTS: CRY1 (p = 0.01) and CRY2 (p < 0.0001) expression was significantly changed in tumour tissue, as confirmed in a large independent CRC dataset. In addition, lower CRY1 mRNA levels were observed in patients in the age range of 62-74 years (p = 0.018), in female patients (p = 0.003) and in cancers located at the transverse colon (p = 0.008). Lower CRY2 levels were also associated with cancer location at the transverse colon (p = 0.007). CRC patients displaying CRY1 (p = 0.042) and CRY2 (p = 0.043) expression levels over the median were hallmarked by a poorer survival rate. Survey of selected colon cancer cell lines evidenced variable levels of cryptochrome genes expression and time-dependent changes in their mRNA levels. Moreover, they showed reduced apoptosis, increased proliferation and different response to 5-fluorouracil and oxaliplatin upon CRY1 and CRY2 ectopic expression. The relationship with p53 status came out as an additional layer of regulation: higher CRY1 and CRY2 protein levels coincided with a wild type p53 as in HCT116 cells and this condition only marginally affected the apoptotic and cell proliferation characteristics of the cells upon CRY ectopic expression. Conversely, lower CRY and CRY2 levels as in HT29 and SW480 cells coincided with a mutated p53 and a more robust apoptosis and proliferation upon CRY transfection. Besides, an heterogeneous pattern of ARNTL, WEE and c-MYC expression hallmarked the chosen colon cancer cell lines and likely influenced their phenotypic changes.
CONCLUSION: Cryptochrome gene expression is altered in CRC, particularly in elderly subjects, female patients and cancers located at the transverse colon, affecting overall survival. Altered CRY1 and CRY2 expression patterns and the interplay with the genetic landscape in colon cancer cells may underlie phenotypic divergence that could influence disease behavior as well as CRC patients survival and response to chemotherapy.

Yang MY, Lin PM, Hsiao HH, et al.
Up-regulation of PER3 Expression Is Correlated with Better Clinical Outcome in Acute Leukemia.
Anticancer Res. 2015; 35(12):6615-22 [PubMed] Related Publications
BACKGROUND: Altered expression of circadian clock genes has been linked to various types of cancer. This study aimed to investigate whether these genes are also altered in acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL).
MATERIALS AND METHODS: The expression profiles of nine circadian clock genes of peripheral blood (PB) leukocytes from patients with newly-diagnosed AML (n=41), ALL (n=23) and healthy individuals (n=51) were investigated.
RESULTS: In AML, the expression of period 1 (PER1), period 2 (PER2), period 3 (PER3), cryptochrome 1 (CRY1), cryptochrome 2 (CRY2), brain and muscle aryl hydrocarbon receptor nuclear translocator (ARNT)-like 1 (BMAL1), and timeless (TIM) was significantly down-regulated, while that of CK1ε was significantly up-regulated. In ALL, the expression of PER3 and CRY1 was significantly down-regulated, whereas those of CK1ε and TIM were significantly up-regulated. Recovery of PER3 expression was observed in both patients with AML and those with ALL who achieved remission but not in patients who relapsed after treatment.
CONCLUSION: Circadian clock genes are altered in patients with acute leukemia and up-regulation of PER3 is correlated with a better clinical outcome.

Lu H, Chu Q, Xie G, et al.
Circadian gene expression predicts patient response to neoadjuvant chemoradiation therapy for rectal cancer.
Int J Clin Exp Pathol. 2015; 8(9):10985-94 [PubMed] Free Access to Full Article Related Publications
Preoperative neoadjuvant chemoradiation therapy may be useful in patients with operable rectal cancer, but treatment responses are variable. We examined whether expression levels of circadian clock genes could be used as biomarkers to predict treatment response. We retrospectively analyzed clinical data from 250 patients with rectal cancer, treated with neoadjuvant chemoradiation therapy in a single institute between 2011 and 2013. Gene expression analysis (RT-PCR) was performed in tissue samples from 20 patients showing pathological complete regression (pCR) and 20 showing non-pCR. The genes analyzed included six core clock genes (Clock, Per1, Per2, Cry1, Cry2 and Bmal1) and three downstream target genes (Wee1, Chk2 and c-Myc). Patient responses were analyzed through contrast-enhanced pelvic MRI and endorectal ultrasound, and verified by histological assessment. pCR was defined histologically as an absence of tumor cells. Among the 250 included patients, 70.8% showed regression of tumor size, and 18% showed pCR. Clock, Cry2 and Per2 expressions were significantly higher in the pCR group than in the non-pCR group (P<0.05), whereas Per1, Cry1 and Bmal1 expressions did not differ significantly between groups. Among the downstream genes involved in cell cycle regulation, c-Myc showed significantly higher expression in the pCR group (P<0.05), whereas Wee1 and Chk2 expression did not differ significantly between groups. Circadian genes are potential biomarkers for predicting whether a patient with rectal cancer would benefit from neoadjuvant chemoradiation therapy.

Gutiérrez-Monreal MA, Villela L, Baltazar S, et al.
A PER3 polymorphism is associated with better overall survival in diffuse large B-cell lymphoma in Mexican population.
Cancer Biomark. 2015; 15(5):699-705 [PubMed] Related Publications
BACKGROUND: Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of malignant lymphoma. Presently, one of the most important clinical predictors of survival in DLBCL patients is the International Prognostic Index (IPI). Circadian rhythms are the approximate 24 hour biological rhythms with more than 10 genes making up the molecular clock.
OBJECTIVE: Determine if functional single nucleotide polymorphism in circadian genes may contribute to survival status in patients diagnosed with diffuse large B-cell lymphoma.
METHODS: Sixteen high-risk non-synonymous polymorphisms in circadian genes (CLOCK, CRY2, CSNK1E, CSNK2A1, NPAS2, PER1, PER2, PER3, PPP2CA, and TIM) were genotyped by screening PCR. Results were visualized by agarose gel electrophoresis and confirmed by two-direction sequencing. Clinical variables were compared between mutated and non-mutated groups. LogRank survival analysis and Kaplan-Meier method were used to calculate the overall survival.
RESULTS: PER3 rs10462020 variant showed significant difference in overall survival between patients containing mutated genotypes and those with non-mutated genotypes (p = 0.047). LDH levels (p = 0.021) and IPI score (p < 0.001) also showed differences in overall survival. No clinical differences were observed in mutated vs. non-mutated patients.
CONCLUSIONS: This work suggests a role of PER3 rs10462020 in predicting a prognosis in DLBCL overall survival of patients.

Labonne JD, Vogt J, Reali L, et al.
A microdeletion encompassing PHF21A in an individual with global developmental delay and craniofacial anomalies.
Am J Med Genet A. 2015; 167A(12):3011-8 [PubMed] Related Publications
In Potocki-Shaffer syndrome (PSS), the full phenotypic spectrum is manifested when deletions are at least 2.1 Mb in size at 11p11.2. The PSS-associated genes EXT2 and ALX4, together with PHF21A, all map to this region flanked by markers D11S1393 and D11S1319. Being proximal to EXT2 and ALX4, a 1.1 Mb region containing 12 annotated genes had been identified by deletion mapping to explain PSS phenotypes except multiple exostoses and parietal foramina. Here, we report a male patient with partial PSS phenotypes including global developmental delay, craniofacial anomalies, minor limb anomalies, and micropenis. Using microarray, qPCR, RT-qPCR, and Western blot analyses, we refined the candidate gene region, which harbors five genes, by excluding two genes, SLC35C1 and CRY2, which resulted in a corroborating role of PHF21A in developmental delay and craniofacial anomalies. This microdeletion contains the least number of genes at 11p11.2 reported to date. Additionally, we also discuss the phenotypes observed in our patient with respect to those of published cases of microdeletions across the Potocki-Shaffer interval.

Fang L, Yang Z, Zhou J, et al.
Circadian Clock Gene CRY2 Degradation Is Involved in Chemoresistance of Colorectal Cancer.
Mol Cancer Ther. 2015; 14(6):1476-87 [PubMed] Free Access to Full Article Related Publications
Biomarkers for predicting chemotherapy response are important to the treatment of colorectal cancer patients. Cryptochrome 2 (CRY2) is a circadian clock protein involved in cell cycle, but the biologic consequences of this activity in cancer are poorly understood. We set up biochemical and cell biology analyses to analyze CRY2 expression and chemoresistance. Here, we report that CRY2 is overexpressed in chemoresistant colorectal cancer samples, and CRY2 overexpression is correlated with poor patient survival. Knockdown of CRY2 increased colorectal cancer sensitivity to oxaliplatin in colorectal cancer cells. We also identify FBXW7 as a novel E3 ubiquitin ligase for targeting CRY2 through proteasomal degradation. Mechanistic studies show that CRY2 is regulated by FBXW7, in which FBXW7 binds directly to phosphorylated Thr300 of CRY2. Furthermore, FBXW7 expression leads to degradation of CRY2 through enhancing CRY2 ubiquitination and accelerating the CRY2's turnover rate. High FBXW7 expression downregulates CRY2 and increases colorectal cancer cells' sensitivity to chemotherapy. Low FBXW7 expression is correlated with high CRY2 expression in colorectal cancer patient samples. Also, low FBXW7 expression is correlated with poor patient survival. Taken together, our findings indicate that the upregulation of CRY2 caused by downregulation of FBXW7 may be a novel prognostic biomarker and may represent a new therapeutic target in colorectal cancer.

Tavano F, Pazienza V, Fontana A, et al.
SIRT1 and circadian gene expression in pancreatic ductal adenocarcinoma: Effect of starvation.
Chronobiol Int. 2015; 32(4):497-512 [PubMed] Related Publications
Pancreatic cancer (PC), the fourth leading cause of cancer-related deaths, is characterized by high aggressiveness and resistance to chemotherapy. Pancreatic carcinogenesis is kept going by derangement of essential cell processes, such as proliferation, apoptosis, metabolism and autophagy, characterized by rhythmic variations with 24-h periodicity driven by the biological clock. We assessed the expression of the circadian genes ARNLT, ARNLT2, CLOCK, PER1, PER2, PER3, CRY1, CRY2 and the starvation-activated histone/protein deacetylase SIRT1 in 34 matched tumor and non-tumor tissue specimens of PC patients, and evaluated in PC derived cell lines if the modulation of SIRT1 expression through starvation could influence the temporal pattern of expression of the circadian genes. We found a significant down-regulation of ARNLT (p = 0.015), CRY1 (p = 0.013), CRY2 (p = 0.001), PER1 (p < 0.0001), PER2 (p < 0.001), PER3 (p = 0.001) and SIRT1 (p = 0.017) in PC specimens. PER3 and CRY2 expression levels were lower in patients with jaundice at diagnosis ( < 0.05). Having adjusted for age, adjuvant therapy and tumor stage, we evidenced that patients with higher PER2 and lower SIRT1 expression levels showed lower mortality (p = 0.028). Levels and temporal patterns of expression of many circadian genes and SIRT1 significantly changed upon serum starvation in vitro, with differences among four different PC cell lines examined (BXPC3, CFPAC, MIA-PaCa-2 and PANC-1). Serum deprivation induced changes of the overall mean level of the wave and amplitude, lengthened or shortened the cycle time and phase-advanced or phase-delayed the rhythmic oscillation depending on the gene and the PC cell line examined. In conclusion, a severe deregulation of expression of SIRT1 and circadian genes was evidenced in the cancer specimens of PC patients, and starvation influenced gene expression in PC cell lines, suggesting that the altered interplay between SIRT1 and the core circadian proteins could represent a crucial player in the process of pancreatic carcinogenesis.

Mao Y, Fu A, Hoffman AE, et al.
The circadian gene CRY2 is associated with breast cancer aggressiveness possibly via epigenomic modifications.
Tumour Biol. 2015; 36(5):3533-9 [PubMed] Related Publications
Although the role of core circadian gene cryptochrome 2 (CRY2) in breast tumorigenesis has been demonstrated, the correlations of CRY2 with clinical parameters in breast cancer patients and its involvement in epigenetic processes such as DNA methylation remain relatively unexplored. In the current study, we first queried the Oncomine database and the Gene Expression-Based Outcome for Breast Cancer Online (GOBO) database to identify associations between CRY2 expression levels and clinical parameters in breast cancer patients. We then silenced CRY2 in vitro and performed a genome-wide methylation array to determine the epigenetic impact of CRY2 silencing. The Ingenuity Pathway Analysis software was used to further explore the genes exhibiting altered methylation identified using the array. We found that CRY2 was frequently down-regulated in breast cancer tissue compared to adjacent normal tissue or breast tissue from healthy controls. Lower CRY2 expression was associated with estrogen receptor (ER)-negativity (P < 0.0001), higher tumor grade (P < 0.0001), and shorter overall survival time in breast cancer patients (HR = 1.44, 95 % confidence interval (CI) 1.09-1.91). Genome-wide methylation analysis showed that a total of 515 CpG sites were hypermethylated following CRY2 knockdown, while 730 sites were hypomethylated. The pathway analysis revealed several cancer-relevant networks with genes exhibiting significantly altered methylation following CRY2 silencing. These findings suggest that the core circadian gene CRY2 is associated with breast cancer progression and prognosis, and that knockdown of CRY2 causes the epigenetic dysregulation of genes involved in cancer-relevant pathways, which provide further evidence supporting a role of the circadian system in breast tumorigenesis.

Yu C, Yang SL, Fang X, et al.
Hypoxia disrupts the expression levels of circadian rhythm genes in hepatocellular carcinoma.
Mol Med Rep. 2015; 11(5):4002-8 [PubMed] Related Publications
Disturbance in the expression of circadian rhythm genes is a common feature in certain types of cancer, however the mechanisms mediating this disturbance remain to be elucidated. The present study aimed to investigate the effect of hypoxia on the expression of circadian rhythm genes in liver cancer cells and to identify the mechanisms underlying this effect in hepatocellular carcinoma (HCC). The HCC cell line, PLC/PRF/5. was treated with either a vehicle control or CoCl2 at 50, 100 or 200 µΜ for 24 h. Following treatment, the protein expression levels of hypoxia‑inducible factor (HIF)‑1α and HIF‑2α were detected by western blotting and the mRNA expression levels of circadian rhythm genes, including circadian locomotor output cycles kaput (Clock), brain and muscle Arnt‑like 1 (Bmal1), period (Per)1, Per2, Per3, cryptochrome (Cry)1, Cry2 and casein kinase Iε (CKIε), were detected by reverse transcription quantitative polymerase chain reaction (RT‑qPCR). Expression plasmids containing HIF‑1α or HIF‑2α were transfected into the PLC/PRF/5 cells using liposomes and RT‑qPCR was used to determine the effects of the transfections on the expression levels of circadian rhythm genes. Following treatment with CoCl2, the protein expression levels of HIF‑1α and HIF‑2α were upregulated in a CoCl2 concentration‑dependent manner. The mRNA expression levels of Clock, Bmal1 and Cry2 were increased, and the mRNA expression levels of Per1, Per2, Per3, Cry1 and CKIε were decreased following CoCl2 treatment (P<0.05). In the PLC/PRF/5 cells transfected with the plasmid containing HIF‑1α, the mRNA expression levels of Clock, Bmal1 and Cry2 were increased, and the mRNA expression levels of Per1, Per2, Per3, Cry1 and CKIε were decreased. In the PLC/PRF/5 cells transfected with the plasmid containing HIF‑2α, the mRNA expression levels of Clock, Bmal1, Per1, Cry1, Cry2 and CKIε were upregulated, and the mRNA expression levels of Per2 and Per3 were downregulated (P<0.05). A hypoxic microenvironment may contribute to the disturbance in the expression of circadian genes in HCC. HIF‑1α and HIF‑2α are involved in this process and have redundant, but not identical effects.

Cadenas C, van de Sandt L, Edlund K, et al.
Loss of circadian clock gene expression is associated with tumor progression in breast cancer.
Cell Cycle. 2014; 13(20):3282-91 [PubMed] Free Access to Full Article Related Publications
Several studies suggest a link between circadian rhythm disturbances and tumorigenesis. However, the association between circadian clock genes and prognosis in breast cancer has not been systematically studied. Therefore, we examined the expression of 17 clock components in tumors from 766 node-negative breast cancer patients that were untreated in both neoadjuvant and adjuvant settings. In addition, their association with metastasis-free survival (MFS) and correlation to clinicopathological parameters were investigated. Aiming to estimate functionality of the clockwork, we studied clock gene expression relationships by correlation analysis. Higher expression of several clock genes (e.g., CLOCK, PER1, PER2, PER3, CRY2, NPAS2 and RORC) was found to be associated with longer MFS in univariate Cox regression analyses (HR<1 and FDR-adjusted P < 0.05). Stratification according to molecular subtype revealed prognostic relevance for PER1, PER3, CRY2 and NFIL3 in the ER+/HER2- subgroup, CLOCK and NPAS2 in the ER-/HER2- subtype, and ARNTL2 in HER2+ breast cancer. In the multivariate Cox model, only PER3 (HR = 0.66; P = 0.016) and RORC (HR = 0.42; P = 0.003) were found to be associated with survival outcome independent of established clinicopathological parameters. Pairwise correlations between functionally-related clock genes (e.g., PER2-PER3 and CRY2-PER3) were stronger in ER+, HER2- and low-grade carcinomas; whereas, weaker correlation coefficients were observed in ER- and HER2+ tumors, high-grade tumors and tumors that progressed to metastatic disease. In conclusion, loss of clock genes is associated with worse prognosis in breast cancer. Coordinated co-expression of clock genes, indicative of a functional circadian clock, is maintained in ER+, HER2-, low grade and non-metastasizing tumors but is compromised in more aggressive carcinomas.

Rabstein S, Harth V, Justenhoven C, et al.
Polymorphisms in circadian genes, night work and breast cancer: results from the GENICA study.
Chronobiol Int. 2014; 31(10):1115-22 [PubMed] Related Publications
OBJECTIVES: The role of genetic variants and environmental factors in breast cancer etiology has been intensively studied in the last decades. Gene-environment interactions are now increasingly being investigated to gain more insights into the development of breast cancer, specific subtypes, and therapeutics. Recently, night shift work that involves circadian disruption has gained rising interest as a potential non-genetic breast cancer risk factor. Here, we analyzed genetic polymorphisms in genes of cellular clocks, melatonin biosynthesis and signaling and their association with breast cancer as well as gene-gene and gene-night work interactions in a German case-control study on breast cancer.
METHODS: GENICA is a population-based case-control study on breast cancer conducted in the Greater Region of Bonn. Associations between seven polymorphisms in circadian genes (CLOCK, NPAS2, ARTNL, PER2 and CRY2), genes of melatonin biosynthesis and signaling (AANAT and MTNR1B) and breast cancer were analyzed with conditional logistic regression models, adjusted for potential confounders for 1022 cases and 1014 controls. Detailed shift-work information was documented for 857 breast cancer cases and 892 controls. Gene-gene and gene-shiftwork interactions were analyzed using model-based multifactor dimensionality reduction (mbMDR).
RESULTS: For combined heterozygotes and rare homozygotes a slightly elevated breast cancer risk was found for rs8150 in gene AANAT (OR 1.17; 95% CI 1.01-1.36), and a reduced risk for rs3816358 in gene ARNTL (OR 0.82; 95% CI 0.69-0.97) in the complete study population. In the subgroup of shift workers, rare homozygotes for rs10462028 in the CLOCK gene had an elevated risk of breast cancer (OR for AA vs. GG: 3.53; 95% CI 1.09-11.42). Shift work and CLOCK gene interactions were observed in the two-way interaction analysis. In addition, gene-shiftwork interactions were detected for MTNR1B with NPAS2 and ARNTL.
CONCLUSIONS: In conclusion, the results of our population-based case-control study support a putative role of the CLOCK gene in the development of breast cancer in shift workers. In addition, higher order interaction analyses suggest a potential relevance of MTNR1B with the key transcriptional factor NPAS2 with ARNTL. Hence, in the context of circadian disruption, multivariable models should be preferred that consider a wide range of polymorphisms, e.g. that may influence chronotype or light sensitivity. The investigation of these interactions in larger studies is needed.

Mo W, Liu Y, Bartlett PF, He R
Transcriptome profile of human neuroblastoma cells in the hypomagnetic field.
Sci China Life Sci. 2014; 57(4):448-61 [PubMed] Related Publications
Research has shown that the hypomagnetic field (HMF) can affect embryo development, cell proliferation, learning and memory, and in vitro tubulin assembly. In the present study, we aimed to elucidate the molecular mechanism by which the HMF exerts its effect, by comparing the transcriptome profiles of human neuroblastoma cells exposed to either the HMF or the geomagnetic field. A total of 2464 differentially expressed genes (DEGs) were identified, 216 of which were up-regulated and 2248 of which were down-regulated after exposure to the HMF. These DEGs were found to be significantly clustered into several key processes, namely macromolecule localization, protein transport, RNA processing, and brain function. Seventeen DEGs were verified by real-time quantitative PCR, and the expression levels of nine of these DEGs were measured every 6 h. Most notably, MAPK1 and CRY2, showed significant up- and down-regulation, respectively, during the first 6 h of HMF exposure, which suggests involvement of the MAPK pathway and cryptochrome in the early bio-HMF response. Our results provide insights into the molecular mechanisms underlying the observed biological effects of the HMF.

Hu ML, Yeh KT, Lin PM, et al.
Deregulated expression of circadian clock genes in gastric cancer.
BMC Gastroenterol. 2014; 14:67 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Gastric cancer (GC), an aggressive malignant tumor of the alimentary tract, is a leading cause of cancer-related death. Circadian rhythm exhibits a 24-hour variation in physiological processes and behavior, such as hormone levels, metabolism, gene expression, sleep and wakefulness, and appetite. Disruption of circadian rhythm has been associated with various cancers, including chronic myeloid leukemia, head and neck squamous cell carcinoma, hepatocellular carcinoma, endometrial carcinoma, and breast cancer. However, the expression of circadian clock genes in GC remains unexplored.
METHODS: In this study, the expression profiles of eight circadian clock genes (PER1, PER2, PER3, CRY1, CRY2, CKIϵ, CLOCK, and BMAL1) of cancerous and noncancerous tissues from 29 GC patients were investigated using real-time quantitative reverse-transcriptase polymerase chain reaction and validated through immunohistochemical analysis.
RESULTS: We found that PER2 was significantly up-regulated in cancer tissues (p < 0.005). Up-regulated CRY1 expression was significantly correlated with more advanced stages (stage III and IV) (p < 0.05).
CONCLUSIONS: Our results suggest deregulated expressions of circadian clock genes exist in GC and circadian rhythm disturbance may be associated with the development of GC.

Madden MH, Anic GM, Thompson RC, et al.
Circadian pathway genes in relation to glioma risk and outcome.
Cancer Causes Control. 2014; 25(1):25-32 [PubMed] Free Access to Full Article Related Publications
PURPOSE: There is growing evidence that circadian disruption may alter risk and aggressiveness of cancer. We evaluated common genetic variants in the circadian gene pathway for associations with glioma risk and patient outcome in a US clinic-based case-control study.
METHODS: Subjects were genotyped for 17 candidate single nucleotide polymorphisms in ARNTL, CRY1, CRY2, CSNK1E, KLHL30, NPAS2, PER1, PER3, CLOCK, and MYRIP. Unconditional logistic regression was used to estimate age and gender-adjusted odds ratios (OR) and 95 % confidence intervals (CI) for glioma risk under three inheritance models (additive, dominant, and recessive). Proportional hazards regression was used to estimate hazard ratios for glioma-related death among 441 patients with high-grade tumors. Survival associations were validated using The Cancer Genome Atlas (TCGA) dataset.
RESULTS: A variant in PER1 (rs2289591) was significantly associated with overall glioma risk (per variant allele OR 0.80; 95 % CI 0.66-0.97; p trend = 0.027). The variant allele for CLOCK rs11133391 under a recessive model increased risk of oligodendroglioma (OR 2.41; 95 % CI 1.31-4.42; p = 0.005), though not other glioma subtypes (p for heterogeneity = 0.0033). The association remained significant after false discovery rate adjustment (p = 0.008). Differential associations by gender were observed for MYRIP rs6599077 and CSNK1E rs1534891 though differences were not significant after adjustment for multiple testing. No consistent mortality associations were identified. Several of the examined genes exhibited differential expression in glioblastoma multiforme versus normal brain in TCGA data (MYRIP, ARNTL, CRY1, KLHL30, PER1, CLOCK, and PER3), and expression of NPAS2 was significantly associated with a poor patient outcome in TCGA patients.
CONCLUSION: This exploratory analysis provides some evidence supporting a role for circadian genes in the onset of glioma and possibly the outcome of glioma.

Kelleher FC, Rao A, Maguire A
Circadian molecular clocks and cancer.
Cancer Lett. 2014; 342(1):9-18 [PubMed] Related Publications
Physiological processes such as the sleep-wake cycle, metabolism and hormone secretion are controlled by a circadian rhythm adapted to 24h day-night periodicity. This circadian synchronisation is in part controlled by ambient light decreasing melatonin secretion by the pineal gland and co-ordinated by the suprachiasmatic nucleus of the hypothalamus. Peripheral cell autonomous circadian clocks controlled by the suprachiasmatic nucleus, the master regulator, exist within every cell of the body and are comprised of at least twelve genes. These include the basic helix-loop-helix/PAS domain containing transcription factors; Clock, BMal1 and Npas2 which activate transcription of the periodic genes (Per1 and Per2) and cryptochrome genes (Cry1 and Cry2). Points of coupling exist between the cellular clock and the cell cycle. Cell cycle genes which are affected by the molecular circadian clock include c-Myc, Wee1, cyclin D and p21. Therefore the rhythm of the circadian clock and cancer are interlinked. Molecular examples exist including activation of Per2 leads to c-myc overexpression and an increased tumor incidence. Mice with mutations in Cryptochrome 1 and 2 are arrhythmic (lack a circadian rhythm) and arrhythmic mice have a faster rate of growth of implanted tumors. Epidemiological finding of relevance include 'The Nurses' Health Study' where it was established that women working rotational night shifts have an increased incidence of breast cancer. Compounds that affect circadian rhythm exist with attendant future therapeutic possibilities. These include casein kinase I inhibitors and a candidate small molecule KL001 that affects the degradation of cryptochrome. Theoretically the cell cycle and malignant disease may be targeted vicariously by selective alteration of the cellular molecular clock.

Mannic T, Meyer P, Triponez F, et al.
Circadian clock characteristics are altered in human thyroid malignant nodules.
J Clin Endocrinol Metab. 2013; 98(11):4446-56 [PubMed] Related Publications
CONTEXT: The circadian clock represents the body's molecular time-keeping system. Recent findings revealed strong changes of clock gene expression in various types of human cancers.
OBJECTIVE: Due to emerging evidence on the connection between the circadian oscillator, cell cycle, and oncogenic transformation, we aimed to characterize the circadian clockwork in human benign and malignant thyroid nodules.
DESIGN: Clock transcript levels were assessed by quantitative RT-PCR in thyroid tissues. To provide molecular characteristics of human thyroid clockwork, primary thyrocytes established from normal or nodular thyroid tissue biopsies were subjected to in vitro synchronization with subsequent clock gene expression analysis by circadian bioluminescence reporter assay and by quantitative RT-PCR.
RESULTS: The expression levels of the Bmal1 were up-regulated in tissue samples of follicular thyroid carcinoma (FTC), and in papillary thyroid carcinoma (PTC), as compared with normal thyroid and benign nodules, whereas Cry2 was down-regulated in FTC and PTC. Human thyrocytes derived from normal thyroid tissue exhibited high-amplitude circadian oscillations of Bmal1-luciferase reporter expression and endogenous clock transcripts. Thyrocytes established from FTC and PTC exhibited clock transcript oscillations similar to those of normal thyroid tissue and benign nodules (except for Per2 altered in PTC), whereas cells derived from poorly differentiated thyroid carcinoma exhibited altered circadian oscillations.
CONCLUSIONS: This is the first study demonstrating a molecular makeup of the human thyroid circadian clock. Characterization of the thyroid clock machinery alterations upon thyroid nodule malignant transformation contributes to understanding the connections between circadian clocks and oncogenic transformation. Moreover, it might help in improving the thyroid nodule preoperative diagnostics.

Grundy A, Schuetz JM, Lai AS, et al.
Shift work, circadian gene variants and risk of breast cancer.
Cancer Epidemiol. 2013; 37(5):606-12 [PubMed] Related Publications
Circadian (clock) genes have been linked with several functions relevant to cancer, and epidemiologic research has suggested relationships with breast cancer risk for variants in NPAS2, CLOCK, CRY2 and TIMELESS. Increased breast cancer risk has also been observed among shift workers, suggesting potential interactions in relationships of circadian genes with breast cancer. Relationships with breast cancer of 100 SNPs in 14 clock-related genes, as well as potential interactions with shift work history, were investigated in a case-control study (1042 cases, 1051 controls). Odds ratios in an additive genetic model for European-ancestry participants (645 cases, 806 controls) were calculated, using a two-step correction for multiple testing: within each gene through permutation testing (10,000 permutations), and correcting for the false discovery rate across genes. Interactions of genotypes with ethnicity and shift work (<2 years vs ≥2 years) were evaluated individually. Following permutation analysis, two SNPs (rs3816360 in ARNTL and rs11113179 in CRY1) displayed significant associations with breast cancer and one SNP (rs3027188 in PER1) was marginally significant; however, none were significant following adjustment for the false discovery rate. No significant interaction with shift work history was detected. If shift work causes circadian disruption, this was not reflected in associations between clock gene variants and breast cancer risk in this study. Larger studies are needed to assess interactions with longer durations (>30 years) of shift work that have been associated with breast cancer.

Luo Y, Wang F, Chen LA, et al.
Deregulated expression of cry1 and cry2 in human gliomas.
Asian Pac J Cancer Prev. 2012; 13(11):5725-8 [PubMed] Related Publications
Growing evidence shows that deregulation of the circadian clock plays an important role in the development of malignant tumors, including gliomas. However, the molecular mechanisms of gene chnages controlling circadian rhythm in glioma cells have not been explored. Using real time polymerase chain reaction and immunohistochemistry techniques, we examined the expression of two important clock genes, cry1 and cry2, in 69 gliomas. In this study, out of 69 gliomas, 38 were cry1-positive, and 51 were cry2-positive. The expression levels of cry1 and cry2 in glioma cells were significantly different from the surrounding non-glioma cells (P<0.01). The difference in the expression rate of cry1 and cry 2 in high-grade (grade III and IV) and low-grade (grade 1 and II) gliomas was non-significant (P>0.05) but there was a difference in the intensity of immunoactivity for cry 2 between high-grade gliomas and low-grade gliomas (r=-0.384, P=0.021). In this study, we found that the expression of cry1 and cry2 in glioma cells was much lower than in the surrounding non-glioma cells. Therefore, we suggest that disturbances in cry1 and cry2 expression may result in the disruption of the control of normal circadian rhythm, thus benefiting the survival of glioma cells. Differential expression of circadian clock genes in glioma and non-glioma cells may provide a molecular basis for the chemotherapy of gliomas.

Relles D, Sendecki J, Chipitsyna G, et al.
Circadian gene expression and clinicopathologic correlates in pancreatic cancer.
J Gastrointest Surg. 2013; 17(3):443-50 [PubMed] Related Publications
INTRODUCTION: The circadian rhythm is responsible for physiologic homeostasis, behavior, and components of multiple metabolic processes. Disruption of the circadian rhythm is associated with cancer development, and several circadian clock genes have been implicated in loss of cell cycle control, impaired DNA damage repair, and subsequent tumor formation. Here, we investigated the expression profiles of several circadian clock genes in pancreatic ductal adenocarcinoma (PDA).
METHODS: Quantitative real-time polymerase chain reaction was used to examine the circadian clock genes (brain-muscle-like (Bmal)-ARNTL, circadian locomotor output cycles kaput (Clock), cryptochrome 1 (Cry1), cryptochrome 2 (Cry2), casein kinase 1ε (CK1ε), period 1 (Per1), period 2 (Per2), period 3 (Per3), timeless (Tim), and timeless-interacting protein (Tipin)) in PDA, as well as matching adjacent and benign tissue. Logistic regression models with robust variance were used to analyze the gene expression levels, and Kaplan-Meier survival curves were generated based on gene expression.
RESULTS: In the tumor tissue of PDA patients, compared to their matched adjacent tissue, expression levels of all circadian genes were lower, with statistical significance for Per1, Per2, Per3, Cry1, Cry2, Tipin, Tim, CK1ε, Bmal-ARNTL, and Clock (p < 0.025). PDA tumors also expressed significantly lower levels of the circadian genes when compared to benign lesions for Per1, Per2, Per3, Cry2, Tipin, and CK1ε. A significant association between low levels of expression in the tumors and reduced survival was found with Per1, Per2, Per3, Cry2, Tipin, CK1ε, Clock, and Bmal-ARNTL.
CONCLUSIONS: Our results reveal for the first time a dysregulated transcription of several circadian genes in PDA. Elevation of the gene levels in the benign and matched adjacent tissues may be indicative of their role during the process of tumorigenesis. The potential of using circadian genes as predictive markers of the outcomes and survival and distinguishing PDA from benign pancreas must be studied in larger populations to validate and demonstrate their eventual clinical utility.

Montgomery ND, Turcott CM, Tepperberg JH, et al.
A 137-kb deletion within the Potocki-Shaffer syndrome interval on chromosome 11p11.2 associated with developmental delay and hypotonia.
Am J Med Genet A. 2013; 161A(1):198-202 [PubMed] Related Publications
Potocki-Shaffer syndrome (PSS) is a rare disorder caused by haploinsufficiency of genes located on the proximal short arm of chromosome 11 (11p11.2p12). Classic features include biparietal foramina, multiple exostoses, profound hypotonia, dysmorphic features, and developmental delay/intellectual disability. Fewer than 40 individuals with PSS have been reported, with variable clinical presentations due in part to disparity in deletion sizes. We report on a boy who presented for initial evaluation at age 13 months because of a history of developmental delay, hypotonia, subtle dysmorphic features, and neurobehavioral abnormalities. SNP microarray analysis identified a 137 kb deletion at 11p11.2, which maps within the classically defined PSS interval. This deletion results in haploinsufficiency for all or portions of six OMIM genes: SLC35C1, CRY2, MAPK8IP1, PEX16, GYLTL1B, and PHF21A. Recently, translocations interrupting PHF21A have been associated with intellectual disability and craniofacial anomalies similar to those seen in PSS. The identification of this small deletion in a child with developmental delay and hypotonia provides further evidence for the genetic basis of developmental disability and identifies a critical region sufficient to cause hypotonia in this syndrome. Additionally, this case illustrates the utility of high resolution genomic approaches in correlating clinical phenotypes with specific genes in contiguous gene deletion syndromes.

Doi M
Circadian clock-deficient mice as a tool for exploring disease etiology.
Biol Pharm Bull. 2012; 35(9):1385-91 [PubMed] Related Publications
One of the most significant conceptual changes brought about by the analysis of circadian clock-deficient mice is that abnormalities in the circadian clock are linked not only to sleep arousal disorder but also to a wide variety of common diseases, including hypertension, diabetes, obesity, and cancer. It has recently been shown that the disruption of the two cryptochrome genes Cry1 and Cry2-core elements of the circadian clock-induces salt-dependent hypertension due to abnormally high synthesis of the mineralocorticoid aldosterone by the adrenal gland. This adrenal disorder occurs as a result of increased expression of Hsd3b6, a newly identified steroidogenic enzyme that regulates aldosterone production within the adrenal zona glomerular cells. Importantly, this enzyme is functionally conserved in humans, and the pathophysiologic condition of human idiopathic hyperaldosteronism resembles that of Cry1/2-deficient mice. This review highlights the potential utility of circadian clock-deficient mice as a tool for exploring hitherto unknown disease etiology linked to the circadian clock.

Zhao B, Lu J, Yin J, et al.
A functional polymorphism in PER3 gene is associated with prognosis in hepatocellular carcinoma.
Liver Int. 2012; 32(9):1451-9 [PubMed] Related Publications
BACKGROUND: Previous studies have revealed that circadian genes play important roles in cell proliferation, apoptosis, cell cycle control, DNA damage response and treatment response of chemotherapy agents in cancers.
AIMS: We hypothesized that the polymorphisms in circadian genes may be associated with prognosis of hepatocellular carcinoma (HCC) patients treated with transcatheter arterial chemoembolization (TACE).
METHODS: Twelve functional single nucleotide polymorphisms (SNPs) in circadian negative feedback regulation genes (including CRY1, CRY2, PER1, PER2 and PER3) were genotyped using Sequenom iPLEX genotyping method in 337 HCC patients treated with TACE and analysed for associations with overall survival.
RESULTS: Our data showed that one SNP rs2640908 in PER3 gene was significantly associated with overall survival of HCC patients (P = 0.027). Patients carrying at least one variant allele of rs2640908 (WV + VV) had a significantly decreased risk of death (hazard ratio, 0.71; 95% confidence interval, 0.53-0.90), when compared with those carrying homozygous wild-type alleles (WW). Kaplan-Meier analyses showed a significantly longer median survival time in patients with WV + VV genotypes of SNP rs2640908 than those with WW genotype (11.6 months vs. 8.1 months; log rank P = 0.030). In addition, we also observed a significant difference on the genotype distribution of SNP rs2640908 in patients with and without portal vein thrombus (P = 0.041).
CONCLUSIONS: Our study provides the first evidence that a single functional polymorphism of PER3 gene is significantly associated with overall survival in HCC patients treated with TACE.

Mazzoccoli G, Piepoli A, Carella M, et al.
Altered expression of the clock gene machinery in kidney cancer patients.
Biomed Pharmacother. 2012; 66(3):175-9 [PubMed] Related Publications
BACKGROUND AND AIM: Kidney cancer is associated with alteration in the pathways regulated by von Hippel-Lindau protein and hypoxia inducible factor α. Tight interrelationships have been evidenced between hypoxia response pathways and circadian pathways. The dysregulation of the circadian clock circuitry is involved in carcinogenesis. The aim of our study was to evaluate the clock gene machinery in kidney cancer.
METHODS: mRNA expression levels of the clock genes ARNTL1, ARNTL2, CLOCK, PER1, PER2, PER3, CRY1, CRY2, TIMELESS, TIPIN and CSNK1E and of the clock controlled gene SERPINE1 were evaluated by DNA microarray assays and by qRT-PCR in primary tumor and matched nontumorous tissue collected from a cohort of 11 consecutive kidney cancer patients.
RESULTS: In kidney tumor tissue, we found down-regulation of PER2 (median=0.658, Q1-Q3=0.562-0.744, P<0.01), TIMELESS (median=0.705, Q1-Q3=0.299-1.330, P=0.04) and TIPIN (median=0.556, Q1-Q3=0.385-1.945, P=0.01), up-regulation of SERPINE1 (median=1.628, Q1-Q3=0.339-4.071, P=0.04), whereas the expression of ARNTL2 (median=0.605, Q1-Q3=0.318-1.738, P=0.74) and CSNK1E (median=0.927, Q1-Q3=0.612-2.321, P=0.33) did not differ. A statistically significant correlation was evidenced between mRNA levels of PER2 and CSNKIE (r=0.791, P<0.01), PER2 and TIPIN (r=0.729, P=0.01), PER2 and SERPINE1 (r=0.704, P=0.01), TIMELESS and TIPIN (r=0.605, P=0.04), TIMELESS and CSNKIE (r=0.637, P=0.03), TIPIN and CSNKIE (r=0.940, P<0.01).
CONCLUSION: In kidney cancer, the circadian clock circuitry is deregulated and the altered expression of the clock genes might be involved in disease onset and progression.

Hsu CM, Lin SF, Lu CT, et al.
Altered expression of circadian clock genes in head and neck squamous cell carcinoma.
Tumour Biol. 2012; 33(1):149-55 [PubMed] Related Publications
Head and neck squamous cell carcinoma (HNSCC) means a group of cancers developed from the upper aerodigestive tract, and 90% of them are squamous cell carcinomas. HNSCC is the tenth most commonly diagnosed form of cancer in males worldwide, but it is the seventh most common cause of cancer-related death. The circadian clock regulates daily rhythmic variations in various physiologic processes including sleep and activity, appetite, hormone levels, metabolism, and gene expression. Many recent studies have demonstrated that the disruption of circadian rhythm is associated with cancer development and tumor progression, such as chronic myeloid leukemia, hepatocellular carcinoma, endometrial carcinoma, and breast cancer. However the direct links between aberrant circadian clock gene expression and human malignancies, including HNSCC, remain largely unknown. In this study, the expression profiles of nine circadian clock genes of cancer tissue and noncancerous part from 40 patients of HNSCC were investigated. The expression of PER1, PER2, PER3, CRY1, CRY2, CKIε, and BMAL1 showed significant downregulation in the cancer tissues (p < 0.005). Downregulated PER3, CRY2, and BMAL1 expression was correlated with more advanced cancer stages (p < 0.05). Downregulated PER3 and upregulated TIM expression correlated with larger tumor size (p < 0.05), and lower expression of PER3 correlated with deeper tumor invasion (p < 0.05). Poor survival was related to lower expression of PER1 (p < 0.05) and PER3 (p < 0.01). These results indicate a possible association of circadian clock gene, especially PER3, expression with the pathogenesis of HNSCC.

Mazzoccoli G, Panza A, Valvano MR, et al.
Clock gene expression levels and relationship with clinical and pathological features in colorectal cancer patients.
Chronobiol Int. 2011; 28(10):841-51 [PubMed] Related Publications
The clock gene machinery controls cellular metabolism, proliferation, and key functions, such as DNA damage recognition and repair. Dysfunction of the circadian clock is involved in tumorigenesis, and altered expression of some clock genes has been found in cancer patients. The aim of this study was to evaluate the expression levels of core clock genes in colorectal cancer (CRC). Quantitative real-time polymerase chain reaction (qPCR) was used to examine ARNTL1, CLOCK, PER1, PER2, PER3, CRY1, CRY2, Timeless (TIM), TIPIN, and CSNK1? expression levels in the tumor tissue and matched apparently healthy mucosa of CRC patients. In the tumor tissue of CRC patients, compared to their matched healthy mucosa, expression levels of ARNTL1 (p=.002), PER1 (p=.002), PER2 (p=.011), PER3 (p=.003), and CRY2 (p=.012) were lower, whereas the expression level of TIM (p=.044) was higher. No significant difference was observed in the expression levels of CLOCK (p=.778), CRY1 (p=.600), CSNK1 (p=.903), and TIPIN (p=.136). As to the clinical and pathological features, a significant association was found between low CRY1 expression levels in tumor mucosa and age (p=.026), and female sex (p=.005), whereas high CRY1 expression levels in tumor mucosa were associated with cancer location in the distal colon (p?=?.015). Moreover, high TIM mRNA levels in the tumor mucosa were prevalent whenever proximal lymph nodes were involved (p= .013) and associated with TNM stages III-IV (p=.005) and microsatellite instability (p=.015). Significantly poorer survival rates were evidenced for CRC patients with lower expression in the tumor tissue of PER1 (p=.010), PER3 (p= .010), and CSNKIE (p=.024). In conclusion, abnormal expression levels of core clock genes in CRC tissue may be related to the process of tumorigenesis and exert an influence on host/tumor interactions.

Lee JH, Sancar A
Circadian clock disruption improves the efficacy of chemotherapy through p73-mediated apoptosis.
Proc Natl Acad Sci U S A. 2011; 108(26):10668-72 [PubMed] Free Access to Full Article Related Publications
The circadian clock in mammalian organisms is generated by a transcription-translation feedback loop that controls many biochemical pathways at the cellular level and physiology and behavior at the organismal level. Cryptochrome (Cry) is a key protein in the negative arm of the transcription-translation feedback loop. It has been found that Cry mutation in cells with p53-null genotype increased their sensitivity to apoptosis by genotoxic agents. Here we show that this increased sensitivity is due to up-regulation of the p53 gene family member p73 in response to DNA damage. As a consequence, when tumors arising from oncogenic Ras-transformed p53(-/-) and p53(-/-)Cry1(-/-)Cry2(-/-) cells are treated with the anticancer drug oxaliplatin, p53(-/-) tumors continue to grow whereas p53(-/-)Cry1(-/-)Cry2(-/-) tumors exhibit extensive apoptosis and stop growing. This finding provides a mechanistic foundation for overcoming the resistance of p53-deficient tumor cells to apoptosis induced by DNA-damaging agents and suggests that disruption of cryptochrome function may increase the sensitivity of tumors with p53 mutation to chemotherapy.

Yang MY, Yang WC, Lin PM, et al.
Altered expression of circadian clock genes in human chronic myeloid leukemia.
J Biol Rhythms. 2011; 26(2):136-48 [PubMed] Related Publications
Circadian clock genes use transcriptional-translational feedback loops to control circadian rhythms. Recent studies have demonstrated that expression of some circadian clock genes displays daily oscillation in peripheral tissues including peripheral blood and bone marrow. Circadian rhythms regulate various functions of human body, and the disruption of circadian rhythm has been associated with cancer development and tumor progression. However, the direct links between aberrant circadian clock gene expression and human disorders remain largely unknown. In this study, comparisons were made between the expression profiles of 9 circadian clock genes from peripheral blood mononuclear cells (PBMCs) and polymorphonuclear cells (PMNs) from 18 healthy volunteers. Peripheral blood (PB) total leukocytes from 54 healthy volunteers and 95 patients with chronic myeloid leukemia (CML) were also investigated. Similar expression profiles of all 9 circadian clock genes were observed in PBMCs and PMNs of healthy individuals. In PB total leukocytes of healthy individuals, the daily pattern of PER1, PER2, PER3, CRY1, CRY2, and CKIε expression level peaked at 0800 h, and BMAL1 peaked at 2000 h. Daily pattern expression of these 7 genes was disrupted in newly diagnosed pre-imatinib mesylate-treated and blast crisis-phase patients with CML. Partial daily pattern gene expression recoveries were observed in patients with CML with complete cytogenetic response and major molecular response. The expression of CLOCK and TIM did not show a time-dependent variation among the healthy and patients with CML. These results indicate a possible association of the disrupted daily patterns of circadian clock gene expression with the pathogenesis of CML.

Oshima T, Takenoshita S, Akaike M, et al.
Expression of circadian genes correlates with liver metastasis and outcomes in colorectal cancer.
Oncol Rep. 2011; 25(5):1439-46 [PubMed] Related Publications
Circadian rhythms are daily oscillations in various biological processes, generated by the feedback loops of eight core circadian genes: Period1 (Per1), Period2 (Per2), Period3 (Per3), Cryptochrome1 (Cry1), Cryptochrome2 (Cry2), Clock, Bmal1 and Casein Kinase I ε (CKIε). Recent studies have suggested that circadian genes participate in the growth and development of various cancers. This study examined the relations of circadian gene expression to clinicopathological factors and outcomes in patients with colorectal cancer. We studied surgical specimens of cancer tissue and adjacent normal mucosa obtained from 202 patients with untreated colorectal cancer. The relative expression levels of the circadian genes in the specimens were measured by quantitative real-time, reverse-transcription polymerase chain reaction. Expression of the Clock gene and the CKIε gene in cancer tissue were significantly higher compared to that in adjacent normal mucosa. Expression of the Per1 and Per3 genes in cancer tissue was significantly lower compared to that in adjacent normal mucosa. Analysis of the relations between clinicopathological features and expression of the eight circadian genes in cancer tissue showed that high expression of the Bmal1 gene and low expression of the Per1 gene correlated with liver metastasis. On analysis of the relations between outcomes and gene expression, high expression of the Per2 gene was associated with significantly better outcomes than low expression of the Per2 gene. Overexpression of the Bmal1 gene and reduced expression of the Per1 gene may thus be useful predictors of liver metastasis. Moreover, reduced expression of the Per2 gene may be a predictor of outcomes in patients with colorectal cancer.

Dai H, Zhang L, Cao M, et al.
The role of polymorphisms in circadian pathway genes in breast tumorigenesis.
Breast Cancer Res Treat. 2011; 127(2):531-40 [PubMed] Related Publications
Disruption of the circadian rhythm or biological clock, which is regulated by a number of clock genes, including circadian locomotor output cycles kaput (CLOCK), period genes (PERs), and cryptochrome genes (CRYs), is a risk factor for breast cancer. We hypothesized that genetic variation in these clock genes may influence breast cancer risk. To test this hypothesis, we designed a hospital-based study that included 1,538 breast cancer patients and 1,605 healthy controls. We genotyped subjects for five single nucleotide polymorphisms (SNPs) and a length variant of the circadian clock genes and evaluated their associations with breast cancer risk. These polymorphisms were determined by TaqMan allelic discrimination assays and the polymerase chain reaction-restriction fragment length polymorphism method. Univariate logistic regression analysis showed that polymorphisms of the CLOCK and CRY1 genes were associated with breast cancer risk. We found that carriers of the CLOCK CT and combined CT+TT genotypes had a significantly higher risk of breast cancer than carriers of the CC genotype (aOR = 1.35, 95% CI = 1.12-1.63 and aOR = 1.30, 95% CI = 1.09-1.56, respectively). Carriers of the CRY1 GT genotype had a decreased risk of breast cancer (aOR = 0.84, 95% CI = 0.71-0.99). We also observed a lower risk of breast cancer in carriers of the CRY2 CC genotype who were ER-positive than in those who were ER-negative (OR = 0.15, 95% CI = 0.04-0.67). When stratified by the CLOCK genotype, patients with the CLOCK CT/ CRY2 CC genotypes had significantly lower cancer risk than those with the GG genotype (aOR = 0.36, 95% CI = 0.14-0.95). Individuals carrying both the CLOCK CC and PER2 AA genotypes had an increased cancer risk (aOR = 2.28, 95% CI = 1.22-4.26). Our study suggests that genetic variants of the circadian rhythm regulatory pathway genes contribute to the differential risk of developing breast cancer in Chinese populations.

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