HOXB7

Gene Summary

Gene:HOXB7; homeobox B7
Aliases: HOX2, HOX2C, HHO.C1, Hox-2.3
Location:17q21.32
Summary:This gene is a member of the Antp homeobox family and encodes a protein with a homeobox DNA-binding domain. It is included in a cluster of homeobox B genes located on chromosome 17. The encoded nuclear protein functions as a sequence-specific transcription factor that is involved in cell proliferation and differentiation. Increased expression of this gene is associated with some cases of melanoma and ovarian carcinoma. [provided by RefSeq, Jul 2008]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:homeobox protein Hox-B7
Source:NCBIAccessed: 11 March, 2017

Ontology:

What does this gene/protein do?
Show (13)

Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 11 March 2017 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 11 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: HOXB7 (cancer-related)

Kim TH, Chang JH, Lee HJ, et al.
mRNA expression of CDH3, IGF2BP3, and BIRC5 in biliary brush cytology specimens is a useful adjunctive tool of cytology for the diagnosis of malignant biliary stricture.
Medicine (Baltimore). 2016; 95(27):e4132 [PubMed] Free Access to Full Article Related Publications
Although advances have been made in diagnostic tools, the distinction between malignant and benign biliary strictures still remains challenging. Intraductal brush cytology is a convenient and safe method that is used for the diagnosis of biliary stricture, but, low sensitivity limits its usefulness. This study aimed to demonstrate the usefulness of mRNA expression levels of target genes in brush cytology specimens combined with cytology for the diagnosis of malignant biliary stricture. Immunohistochemistry for cadherin 3 (CDH3), p53, insulin-like growth factor II mRNA-binding protein 3 (IGF2BP3), homeobox B7 (HOXB7), and baculoviral inhibitor of apoptosis repeat containing 5 (BIRC5) was performed in 4 benign and 4 malignant bile duct tissues. Through endoscopic or interventional radiologic procedures, brush cytology specimens were prospectively obtained in 21 and 35 paitents with biliary strictures. In the brush cytology specimens, the mRNA expressions levels of 5 genes were determined by real-time polymerase chain reaction. Immunohistochemistry for CDH3, p53, IGF2BP3, HOXB7, and BIRC5 all showed positive staining in malignant tissues in contrast to benign tissues, which were negative. In the brush cytology specimens, the mRNA expression levels of CDH3, IGF2BP3, HOXB7, and BIRC5 were significantly higher in cases of malignant biliary stricture compared with cases of benign stricture (P = 0.006, P < 0.001, P < 0.001, and P = 0.001). The receiver-operating characteristic curves of these 4 mRNAs demonstrated that mRNA expression levels are useful for the prediction of malignant biliary stricture (P = 0.006, P < 0.001, P < 0.001, and P = 0.002). The sensitivity and specificity, respectively, for malignant biliary stricture were 57.1% and 100% for cytology, 57.1% and 64.3% for CDH3, 76.2% and 100% for IGF2BP3, 71.4% and 57.1% for HOXB7, and 76.2% and 64.3% for BIRC5. When cytology was combined with the mRNA levels of CDH3, IGF2BP3, or BIRC5, the sensitivity for malignant biliary stricture improved to 90.5%. The measurement of the mRNA expression levels of CDH3, IGF2BP3, and BIRC5 by real-time polymerase chain reaction combined with cytology was useful for the differentiation of malignant and benign biliary strictures in brush cytology specimens.

Komatsu H, Iguchi T, Masuda T, et al.
HOXB7 Expression is a Novel Biomarker for Long-term Prognosis After Resection of Hepatocellular Carcinoma.
Anticancer Res. 2016; 36(6):2767-73 [PubMed] Related Publications
BACKGROUND/AIM: Homeobox B7 (HOXB7) gene is involved in various cellular functions. We investigated the clinical significance of HOXB7 expression in hepatocellular carcinoma (HCC).
MATERIALS AND METHODS: HOXB7 mRNA expression in 103 HCC samples and 58 matched non-cancerous liver tissues were examined by quantitative real-time polymerase chain reaction (qRT-PCR). HOXB7 protein expression was also examined by immunohistochemistry. Gene set enrichment analysis (GSEA) was performed using a public dataset.
RESULTS: HOXB7 expression was significantly higher in HCC tissues than in liver parenchyma. Ten-year overall survival (OS) and 5-year recurrence-free survival (RFS) of cases with higher HOXB7 expression were significantly poorer than those with lower HOXB7 expression. HOXB7 expression was significantly associated with larger tumor size and higher rate of biliary invasion and constituted an independent prognostic factor for OS by multivariate analysis. These results were supported by GSEA.
CONCLUSION: HOXB7 expression in HCC could be a novel biomarker for long-term prognosis after tumor resection.

Zhang E, He X, Yin D, et al.
Increased expression of long noncoding RNA TUG1 predicts a poor prognosis of gastric cancer and regulates cell proliferation by epigenetically silencing of p57.
Cell Death Dis. 2016; 7:e2109 [PubMed] Free Access to Full Article Related Publications
Recent evidence highlights long noncoding RNAs (lncRNAs) as crucial regulators of cancer biology that contribute to tumorigenesis. LncRNA TUG1 was initially detected in a genomic screen for genes upregulated in response to taurine treatment in developing mouse retinal cells. Our previous study showed that TUG1 could affect cell proliferation through epigenetically regulating HOXB7 in human non-small cell lung cancer. However, the clinical significance and potential role of TUG1 in GC remains unclear. In this study, we found that TUG1 is significantly increased and is correlated with outcomes in gastric cancer (GC). Further experiments revealed that knockdown of TUG1 repressed GC proliferation both in vitro and in vivo. Mechanistic investigations showed that TUG1 has a key role in G0/G1 arrest. We further demonstrated that TUG1 was associated with PRC2 and that this association was required for epigenetic repression of cyclin-dependent protein kinase inhibitors, including p15, p16, p21, p27 and p57, thus contributing to the regulation of GC cell cycle and proliferation. Together, our results suggest that TUG1, as a regulator of proliferation, may serve as a candidate prognostic biomarker and target for new therapies in human GC.

Soret C, Martin E, Duluc I, et al.
Distinct mechanisms for opposite functions of homeoproteins Cdx2 and HoxB7 in double-strand break DNA repair in colon cancer cells.
Cancer Lett. 2016; 374(2):208-15 [PubMed] Related Publications
Homeobox genes, involved in embryonic development and tissues homeostasis in adults, are often deregulated in cancer, but their relevance in pathology is far from being fully elucidated. In colon cancers, we report that the homeoproteins HoxB7 and Cdx2 exhibit different heterogeneous patterns, Cdx2 being localized in moderately altered neoplasic glands in contrast to HoxB7 which predominates in poorly-differentiated areas; they are coexpressed in few cancer cells. In human colon cancer cells, both homeoproteins interact with the DNA repair factor KU70/80, but functional studies reveal opposite effects: HoxB7 stimulates DNA repair and cell survival upon etoposide treatment, whereas Cdx2 inhibits both processes. The stimulatory effect of HoxB7 on DNA repair requires the transactivation domain linked to the homeodomain involved in the interaction with KU70/80, whereas the transactivation domain of Cdx2 is dispensable for its inhibitory function, which instead needs the homeodomain to interact with KU70/80 and the C-terminal domain. Thus, HoxB7 and Cdx2 respectively use transcription-dependent and -independent mechanisms to stimulate and inhibit DNA repair. In addition, in cells co-expressing both homeoproteins, Cdx2 lessens DNA repair activity through a novel mechanism of inhibition of the transcriptional function of HoxB7, whereby Cdx2 forms a molecular complex with HoxB7 and prevents it to recognize its target in the chromatin. These results point out the complex interplay between the DSB DNA repair activity and the homeoproteins HoxB7 and Cdx2 in colon cancer cells, making the balance between these factors a determinant and a potential indicator of the efficacy of genotoxic drugs.

Milanovic D, Sticht C, Röhrich M, et al.
Inhibition of 13-cis retinoic acid-induced gene expression of reactive-resistance genes by thalidomide in glioblastoma tumours in vivo.
Oncotarget. 2015; 6(30):28938-48 [PubMed] Free Access to Full Article Related Publications
The cell differentiation potential of 13-cis retinoic acid (RA) has not succeeded in the clinical treatment of glioblastoma (GBM) so far. However, RA may also induce the expression of resistance genes such as HOXB7 which can be suppressed by Thalidomide (THAL). Therefore, we tested if combined treatment with RA+THAL may inhibit growth of glioblastoma in vivo. Treatment with RA+THAL but not RA or THAL alone significantly inhibited tumour growth. The synergistic effect of RA and THAL was corroborated by the effect on proliferation of glioblastoma cell lines in vitro. HOXB7 was not upregulated but microarray analysis validated by real-time PCR identified four potential resistance genes (IL-8, HILDPA, IGFBPA, and ANGPTL4) whose upregulation by RA was suppressed by THAL. Furthermore, genes coding for small nucleolar RNAs (snoRNA) were identified as a target for RA for the first time, and their upregulation was maintained after combined treatment. Pathway analysis showed upregulation of the Ribosome pathway and downregulation of pathways associated with proliferation and inflammation. In conclusion, combined treatment with RA + THAL delayed growth of GBM xenografts and suppressed putative resistance genes associated with hypoxia and angiogenesis. This encourages further pre-clinical and clinical studies of this drug combination in GBM.

Cai JQ, Xu XW, Mou YP, et al.
Upregulation of HOXB7 promotes the tumorigenesis and progression of gastric cancer and correlates with clinical characteristics.
Tumour Biol. 2016; 37(2):1641-50 [PubMed] Related Publications
Several examples of aberrant homeobox gene expression have been found across a range of cancers, and it is also confirmed that homeobox genes play a critical roles in tumorigenesis and progression. Notwithstanding homeobox B7 (HOXB7) has been documented that its deregulation promotes carcinogenesis and development in gastrointestinal tract, its function in gastric cancer has not been investigated. In this study, HOXB7 expression was examined to be distinctly upregulated in gastric carcinoma GC cell lines and in the tumor relative to normal gastric tissue. High HOXB7 expression was correlated with tumor differentiation (P = 0.025) and TNM stage (P = 0.008). HOXB7 knockdown in BGC-823 and SGC-7901 resulted in decreased migration and invasion with alteration of epithelial-mesenchymal transition (EMT) proteins and influenced proliferation, apoptosis, and cell cycle. Furthermore, complementary DNA (cDNA) microarray, qPCR, and Western blotting were performed to explore potential downstream target genes of HOXB7. HOXB7 is generally overexpressed in GC, associated with patient clinical characteristics, and specifically promotes GC cell malignant biological properties through PIK3R3/AKT signaling pathways, indicating HOXB7 as a causal factor in promoting tumor progression.

Kar SP, Tyrer JP, Li Q, et al.
Network-Based Integration of GWAS and Gene Expression Identifies a HOX-Centric Network Associated with Serous Ovarian Cancer Risk.
Cancer Epidemiol Biomarkers Prev. 2015; 24(10):1574-84 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Genome-wide association studies (GWAS) have so far reported 12 loci associated with serous epithelial ovarian cancer (EOC) risk. We hypothesized that some of these loci function through nearby transcription factor (TF) genes and that putative target genes of these TFs as identified by coexpression may also be enriched for additional EOC risk associations.
METHODS: We selected TF genes within 1 Mb of the top signal at the 12 genome-wide significant risk loci. Mutual information, a form of correlation, was used to build networks of genes strongly coexpressed with each selected TF gene in the unified microarray dataset of 489 serous EOC tumors from The Cancer Genome Atlas. Genes represented in this dataset were subsequently ranked using a gene-level test based on results for germline SNPs from a serous EOC GWAS meta-analysis (2,196 cases/4,396 controls).
RESULTS: Gene set enrichment analysis identified six networks centered on TF genes (HOXB2, HOXB5, HOXB6, HOXB7 at 17q21.32 and HOXD1, HOXD3 at 2q31) that were significantly enriched for genes from the risk-associated end of the ranked list (P < 0.05 and FDR < 0.05). These results were replicated (P < 0.05) using an independent association study (7,035 cases/21,693 controls). Genes underlying enrichment in the six networks were pooled into a combined network.
CONCLUSION: We identified a HOX-centric network associated with serous EOC risk containing several genes with known or emerging roles in serous EOC development.
IMPACT: Network analysis integrating large, context-specific datasets has the potential to offer mechanistic insights into cancer susceptibility and prioritize genes for experimental characterization.

Jin K, Park S, Teo WW, et al.
HOXB7 Is an ERα Cofactor in the Activation of HER2 and Multiple ER Target Genes Leading to Endocrine Resistance.
Cancer Discov. 2015; 5(9):944-59 [PubMed] Free Access to Full Article Related Publications
UNLABELLED: Why breast cancers become resistant to tamoxifen despite continued expression of the estrogen receptor-α (ERα) and what factors are responsible for high HER2 expression in these tumors remains an enigma. HOXB7 chromatin immunoprecipitation analysis followed by validation showed that HOXB7 physically interacts with ERα, and that the HOXB7-ERα complex enhances transcription of many ERα target genes, including HER2. Investigating strategies for controlling HOXB7, our studies revealed that MYC, stabilized via phosphorylation mediated by EGFR-HER2 signaling, inhibits transcription of miR-196a, a HOXB7 repressor. This leads to increased expression of HOXB7, ER target genes, and HER2. Repressing MYC using small-molecule inhibitors reverses these events and causes regression of breast cancer xenografts. The MYC-HOXB7-HER2 signaling pathway is eminently targetable in endocrine-resistant breast cancer.
SIGNIFICANCE: HOXB7 acts as an ERα cofactor regulating a myriad of ER target genes, including HER2, in tamoxifen-resistant breast cancer. HOXB7 expression is controlled by MYC via transcriptional regulation of the HOXB7 repressor miR-196a; consequently, antagonists of MYC cause reversal of selective ER modulator resistance both in vitro and in vivo.

Ma R, Zhang D, Hu PC, et al.
HOXB7-S3 inhibits the proliferation and invasion of MCF-7 human breast cancer cells.
Mol Med Rep. 2015; 12(4):4901-8 [PubMed] Free Access to Full Article Related Publications
Homeobox B7 (HOXB7) has been found to be overexpressed in numerous types of human cancer. However, the role of HOXB7 in breast cancer remains to be elucidated. The aim of the present study was to investigate the effects of HOXB7 on the proliferation and invasion of breast cancer cells. Initially, reverse transcription quantitative polymerase chain reaction and western blotting were respectively employed to detect the mRNA and protein expression levels of the HOXB7 gene in the MDA‑MB‑231 and MCF‑7 human breast cancer cell lines. Subsequently, small interfering RNAs designed to interfere with the expression of HOXB7 were used to knockdown the expression of HOXB7 in the MCF‑7 cell line, the effects of which on cell proliferation, the apoptotic rate and invasion capacity were measured using a Cell Counting kit‑8 assay, flow cytometry and transwell chambers, respectively. The results demonstrated that HOXB7 mRNA and protein were all overexpressed in MDA‑MB‑231 and MCF‑7 breast cancer cell lines. Furthermore, HOXB7‑S3 effectively inhibited the proliferation and invasion of MCF‑7 breast cancer cells. In conclusion, these results demonstrated that HOXB7 may be a potential therapeutic target in human breast cancer.

Li SC, Shi H, Khan M, et al.
Roles of miR-196a on gene regulation of neuroendocrine tumor cells.
Mol Cell Endocrinol. 2015; 412:131-9 [PubMed] Related Publications
This study aims at investigating miR-196a roles using in vitro models. miR-196a was detected in small intestinal neuroendocrine tumors (SI-NETs) and lung NETs. miR-196a target prediction analysis suggested HOXA9, HOXB7, LRP4 and RSPO2 genes for further investigation. The level of these four genes is detectable in SI-NET tissue specimens at different disease stages and serum samples of untreated and somatostatin analogs treated patients with liver metastases. A miR-196a inhibitor was used to silence its effects in NET cells. We show that the four target genes were significantly upregulated at transcriptional level in silenced NET cells. HOXA9, HOXB7, LRP4 and RSPO2 encoded proteins are also upregulated at translational level in miR-196a silenced NET cells. miR-196a downstream genes BMP4, ETS1, CTNNB1, FZD5, LRP5 and LRP6 were significantly upregulated at transcriptional level in miR-196a silenced CNDT2.5 and NCI-H727 cells. In addition, miR-196a clearly does not play a role in NET cell growth control.

Heinonen H, Lepikhova T, Sahu B, et al.
Identification of several potential chromatin binding sites of HOXB7 and its downstream target genes in breast cancer.
Int J Cancer. 2015; 137(10):2374-83 [PubMed] Free Access to Full Article Related Publications
HOXB7 encodes a transcription factor that is overexpressed in a number of cancers and encompasses many oncogenic functions. Previous results have shown it to promote cell proliferation, angiogenesis, epithelial-mesenchymal transition, DNA repair and cell survival. Because of its role in many cancers and tumorigenic processes, HOXB7 has been suggested to be a potential drug target. However, HOXB7 binding sites on chromatin and its targets are poorly known. The aim of our study was to identify HOXB7 binding sites on breast cancer cell chromatin and to delineate direct target genes located nearby these binding sites. We found 1,504 HOXB7 chromatin binding sites in BT-474 breast cancer cell line that overexpresses HOXB7. Seventeen selected binding sites were validated by ChIP-qPCR in several breast cancer cell lines. Furthermore, we analyzed expression of a large number of genes located nearby HOXB7 binding sites and found several new direct targets, such as CTNND2 and SCGB1D2. Identification of HOXB7 chromatin binding sites and target genes is essential to understand better the role of HOXB7 in breast cancer and mechanisms by which it regulates tumorigenic processes.

Liu S, Jin K, Hui Y, et al.
HOXB7 promotes malignant progression by activating the TGFβ signaling pathway.
Cancer Res. 2015; 75(4):709-19 [PubMed] Free Access to Full Article Related Publications
Overexpression of HOXB7 in breast cancer cells induces an epithelial-mesenchymal transition and promotes tumor progression and lung metastasis. However, the underlying mechanisms for HOXB7-induced aggressive phenotypes in breast cancer remain largely unknown. Here, we report that phosphorylation of SMAD3 was detected in a higher percentage in primary mammary tumor tissues from double-transgenic MMTV-Hoxb7/Her2 mice than tumors from single-transgenic Her2/neu mice, suggesting activation of TGFβ/SMAD3 signaling by HOXB7 in breast tumor tissues. As predicted, TGFβ2 was high in four MMTV-Hoxb7/Her2 transgenic mouse tumor cell lines and two breast cancer cell lines transfected with HOXB7, whereas TGFβ2 was low in HOXB7-depleted cells. HOXB7 directly bound to and activated the TGFβ2 promoter in luciferase and chromatin immunoprecipitation assays. Increased migration and invasion as a result of HOXB7 overexpression in breast cancer cells were reversed by knockdown of TGFβ2 or pharmacologic inhibition of TGFβ signaling. Furthermore, knockdown of TGFβ2 in HOXB7-overexpressing MDA-MB-231 breast cancer cells dramatically inhibited metastasis to the lung. Interestingly, HOXB7 overexpression also induced tumor-associated macrophage (TAM) recruitment and acquisition of an M2 tumor-promoting phenotype. TGFβ2 mediated HOXB7-induced activation of macrophages, suggesting that TAMs may contribute to HOXB7-promoted tumor metastasis. Providing clinical relevance to these findings, by real-time PCR analysis, there was a strong correlation between HOXB7 and TGFβ2 expression in primary breast carcinomas. Taken together, our results suggest that HOXB7 promotes tumor progression in a cell-autonomous and non-cell-autonomous manner through activation of the TGFβ signaling pathway.

Rivera C, González-Arriagada WA, Loyola-Brambilla M, et al.
Clinicopathological and immunohistochemical evaluation of oral and oropharyngeal squamous cell carcinoma in Chilean population.
Int J Clin Exp Pathol. 2014; 7(9):5968-77 [PubMed] Free Access to Full Article Related Publications
In oral and oropharyngeal squamous cell carcinoma (OCSCC and OPSCC) exist an association between clinical and histopathological parameters with cell proliferation, basal lamina, connective tissue degradation and surrounding stroma markers. We evaluated these associations in Chilean patients. A convenience sample of 37 cases of OCSCC (n=16) and OPSCC (n=21) was analyzed clinically (TNM, clinical stage) and histologically (WHO grade of differentiation, pattern of tumor invasion). We assessed the expression of p53, Ki67, HOXA1, HOXB7, type IV collagen (ColIV) and carcinoma-associated fibroblast (α-SMA-positive cells). Additionally we conducted a univariate/bivariate analysis to assess the relationship of these variables with survival rates. Males were mostly affected (56.2% OCSCC, 76.2% OPSCC). Patients were mainly diagnosed at III/IV clinical stages (68.8% OCSCC, 90.5% OPSCC) with a predominantly infiltrative pattern invasion (62.9% OCSCC, 57.1% OPSCC). Significant association between regional lymph nodes (N) and clinical stage with OCSCC-HOXB7 expression (Chi-Square test P < 0.05) was observed. In OPSCC a statistically significant association exists between p53, Ki67 with gender (Chi-Square test P < 0.05). In OCSCC and OPSCC was statistically significant association between ki67 with HOXA1, HOXB7, and between these last two antigens (Pearson's Correlation test P < 0.05). Furthermore OPSCC-p53 showed significant correlation when it was compared with α-SMA (Kendall's Tau-c test P < 0.05). Only OCSCC-pattern invasion and OPSCC-primary tumor (T) pattern resulted associated with survival at the end of the follow up period (Chi-Square Likelihood Ratio, P < 0.05). Clinical, histological and immunohistochemical features are similar to seen in other countries. Cancer proliferation markers were associated strongly from each other. Our sample highlights prognostic value of T and pattern of invasion, but the conclusions may be limited and should be considered with caution (small sample). Many cases were diagnosed in the advanced stages of the disease, which suggests that the diagnosis of OCSCC and OPSCC is made late.

Zhang R, Leng H, Huang J, et al.
miR-337 regulates the proliferation and invasion in pancreatic ductal adenocarcinoma by targeting HOXB7.
Diagn Pathol. 2014; 9:171 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: miRNAs are involved in coordinating a variety of cellular processes by regulating their target genes. Aberrant expression of miRNAs is correlated with various cancers. Previous studies have shown that miR-337 is significantly down-regulated in pancreatic ductal adenocarcinoma (PDAC) and that its expression is negatively correlated to the expression of HOXB7. Both miR-337 and HOXB7 are associated with the prognosis of PDAC patients. The purpose of this study was to identify the molecular mechanisms by which miR-337 acts as a tumor suppressor in PDAC.
METHODS: Synthetic miR-337 mimics were transfected into PANC-1 and As-PC-1 cells using Lipofectamine™ 2000. The expression of HOXB7 protein was analyzed by Western blot. Luciferase reporter plasmids were constructed to confirm that HOXB7 3'UTR was the target of miR-337. The effect of miR-337 on cell proliferation was evaluated by CCK8 assay and colony formation assay, and cell invasion was evaluated by wound healing assay and transwell assay.
RESULTS: Western blot and luciferase activity assays identified HOXB7 as the target of miR-337. A CCK-8 assay showed the absorbance of cells transfected with miR-337 mimics to be less than that of control cells, and that the number of cell clones was significantly decreased by miR-337 expression. A wound healing assay showed the invasion rate of cells transfected with miR-337 mimics at 36 h to be markedly lower than in controls. The average number of cells penetrating the Matrigel was significantly lower than the controls.
CONCLUSION: These findings suggest that miR-337 targets HOXB7 and effects significant suppression of PDAC cell proliferation and invasion.
VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_171.

Pritchett TL, Bader HL, Henderson J, Hsu T
Conditional inactivation of the mouse von Hippel-Lindau tumor suppressor gene results in wide-spread hyperplastic, inflammatory and fibrotic lesions in the kidney.
Oncogene. 2015; 34(20):2631-9 [PubMed] Related Publications
Mutations of the tumor suppressor gene von Hippel-Lindau (VHL) can lead to benign and malignant tumors, including clear-cell renal cell carcinoma (ccRCC). To understand the progression of ccRCC, we generated a novel mouse Vhlh conditional knockout, using Hoxb7-driven Cre that is specific for the collecting ducts and a subset of distal tubules. These mice exhibited wide-spread epithelial disruption and interstitial inflammation as early as 2 months of age with high penetrance. Lesions are cystic, show severe fibrosis and display significant hyperplasia. An abundance of infiltrating macrophages and lymphocytes was detected. Interestingly, the Vhlh mutant lesions could be rescued when Hif-1α, but not Hif-2α, was also knocked out. In addition, administration of a JAK1/2 kinase inhibitor alleviated the Vhlh knockout phenotypes. Taken together, these results suggest that HIF-1α-dependent inflammation and fibrosis may be an early event in the development of ccRCC.

Zhang EB, Yin DD, Sun M, et al.
P53-regulated long non-coding RNA TUG1 affects cell proliferation in human non-small cell lung cancer, partly through epigenetically regulating HOXB7 expression.
Cell Death Dis. 2014; 5:e1243 [PubMed] Free Access to Full Article Related Publications
Recently, a novel class of transcripts, long non-coding RNAs (lncRNAs), is being identified at a rapid pace. These RNAs have critical roles in diverse biological processes, including tumorigenesis. Here we report that taurine-upregulated gene 1 (TUG1), a 7.1-kb lncRNA, recruiting and binding to polycomb repressive complex 2 (PRC2), is generally downregulated in non-small cell lung carcinoma (NSCLC) tissues. In a cohort of 192 NSCLC patients, the lower expression of TUG1 was associated with a higher TNM stage and tumor size, as well as poorer overall survival (P<0.001). Univariate and multivariate analyses revealed that TUG1 expression serves as an independent predictor for overall survival (P<0.001). Further experiments revealed that TUG1 expression was induced by p53, and luciferase and chromatin immunoprecipitation (ChIP) assays confirmed that TUG1 was a direct transcriptional target of p53. TUG1 knockdown significantly promoted the proliferation in vitro and in vivo. Moreover, the lncRNA-mediated regulation of the expression of HOX genes in tumorigenesis and development has been recently receiving increased attention. Interestingly, inhibition of TUG1 could upregulate homeobox B7 (HOXB7) expression; ChIP assays demonstrated that the promoter of HOXB7 locus was bound by EZH2 (enhancer of zeste homolog 2), a key component of PRC2, and was H3K27 trimethylated. This TUG1-mediated growth regulation is in part due to specific modulation of HOXB7, thus participating in AKT and MAPK pathways. Together, these results suggest that p53-regulated TUG1 is a growth regulator, which acts in part through control of HOXB7. The p53/TUG1/PRC2/HOXB7 interaction might serve as targets for NSCLC diagnosis and therapy.

Kraiklang R, Pairojkul C, Khuntikeo N, et al.
A novel predictive equation for potential diagnosis of cholangiocarcinoma.
PLoS One. 2014; 9(2):e89337 [PubMed] Free Access to Full Article Related Publications
Cholangiocarcinoma (CCA) is the second most common-primary liver cancer. The difficulties in diagnosis limit successful treatment of CCA. At present, histological investigation is the standard diagnosis for CCA. However, there are some poor-defined tumor tissues which cannot be definitively diagnosed by general histopathology. As molecular signatures can define molecular phenotypes related to diagnosis, prognosis, or treatment outcome, and CCA is the second most common cancer found after hepatocellularcarcinoma (HCC), the aim of this study was to develop a predictive model which differentiates CCA from HCC and normal liver tissues. An in-house PCR array containing 176 putative CCA marker genes was tested with the training set tissues of 20 CCA and 10 HCC cases. The molecular signature of CCA revealed the prominent expression of genes involved in cell adhesion and cell movement, whereas HCC showed elevated expression of genes related to cell proliferation/differentiation and metabolisms. A total of 69 genes differentially expressed in CCA and HCC were optimized statistically to formulate a diagnostic equation which distinguished CCA cases from HCC cases. Finally, a four-gene diagnostic equation (CLDN4, HOXB7, TMSB4 and TTR) was formulated and then successfully validated using real-time PCR in an independent testing set of 68 CCA samples and 77 non-CCA controls. Discrimination analysis showed that a combination of these genes could be used as a diagnostic marker for CCA with better diagnostic parameters with high sensitivity and specificity than using a single gene marker or the usual serum markers (CA19-9 and CEA). This new combination marker may help physicians to identify CCA in liver tissues when the histopathology is uncertain.

Marcinkiewicz KM, Gudas LJ
Altered histone mark deposition and DNA methylation at homeobox genes in human oral squamous cell carcinoma.
J Cell Physiol. 2014; 229(10):1405-16 [PubMed] Free Access to Full Article Related Publications
We recently reported a role of polycomb repressive complex 2 (PRC2) and PRC2 trimethylation of histone 3 lysine 27 (H3K27me3) in the regulation of homeobox (HOX) (Marcinkiewicz and Gudas, 2013, Exp Cell Res) gene transcript levels in human oral keratinocytes (OKF6-TERT1R) and tongue squamous cell carcinoma (SCC) cells. Here, we assessed both the levels of various histone modifications at a subset of homeobox genes and genome wide DNA methylation patterns in OKF6-TERT1R and SCC-9 cells by using ERRBS (enhanced reduced representation bisulfite sequencing). We detected the H3K9me3 mark at HOXB7, HOXC10, HOXC13, and HOXD8 at levels higher in OKF6-TERT1R than in SCC-9 cells; at IRX1 and SIX2 the H3K9me3 levels were conversely higher in SCC-9 than in OKF6-TERT1R. The H3K79me3 mark was detectable only at IRX1 in OKF6-TERT1R and at IRX4 in SCC-9 cells. The levels of H3K4me3 and H3K36me3 marks correlate with the transcript levels of the assessed homeobox genes in both OKF6-TERT1R and SCC-9. We detected generally lower CpG methylation levels on DNA in SCC-9 cells at annotated genomic regions which were differentially methylated between OKF6-TERT1R and SCC-9 cells; however, some genomic regions, including the HOX gene clusters, showed DNA methylation at higher levels in SCC-9 than OKF6-TERT1R. Thus, both altered histone modification patterns and changes in DNA methylation are associated with dysregulation of homeobox gene expression in human oral cavity SCC cells, and this dysregulation potentially plays a role in the neoplastic phenotype of oral keratinocytes.

Kraemer A, Chen IP, Henning S, et al.
UVA and UVB irradiation differentially regulate microRNA expression in human primary keratinocytes.
PLoS One. 2013; 8(12):e83392 [PubMed] Free Access to Full Article Related Publications
MicroRNA (miRNA)-mediated regulation of the cellular transcriptome is an important epigenetic mechanism for fine-tuning regulatory pathways. These include processes related to skin cancer development, progression and metastasis. However, little is known about the role of microRNA as an intermediary in the carcinogenic processes following exposure to UV-radiation. We now show that UV irradiation of human primary keratinocytes modulates the expression of several cellular miRNAs. A common set of miRNAs was influenced by exposure to both UVA and UVB. However, each wavelength band also activated a distinct subset of miRNAs. Common sets of UVA- and UVB-regulated miRNAs harbor the regulatory elements GLYCA-nTRE, GATA-1-undefined-site-13 or Hox-2.3-undefined-site-2 in their promoters. In silico analysis indicates that the differentially expressed miRNAs responding to UV have potential functions in the cellular pathways of cell growth and proliferation. Interestingly, the expression of miR-23b, which is a differentiation marker of human keratinocytes, is remarkably up-regulated after UVA irradiation. Studying the interaction between miR-23b and its putative skin-relevant targets using a Luciferase reporter assay revealed that RRAS2 (related RAS viral oncogene homolog 2), which is strongly expressed in highly aggressive malignant skin cancer, to be a direct target of miR-23b. This study demonstrates for the first time a differential miRNA response to UVA and UVB in human primary keratinocytes. This suggests that selective regulation of signaling pathways occurs in response to different UV energies. This may shed new light on miRNA-regulated carcinogenic processes involved in UV-induced skin carcinogenesis.

Zhu M, Xu Z, Wang K, et al.
MicroRNA and gene networks in human Hodgkin's lymphoma.
Mol Med Rep. 2013; 8(6):1747-54 [PubMed] Related Publications
There has been significant progress in gene and microRNA (miRNA) research with regard to the morbidity of Hodgkin's lymphoma (HL). However, the regulatory mechanisms of genes and miRNAs have yet to be determined. In the current study, the regulatory association between genes, miRNAs and transcription factors (TFs) was investigated to gain an understanding of the mechanisms and key pathways of HL. The association between TFs and miRNAs, miRNAs and target genes and miRNA and its host gene was examined. To show the regulatory correlation clearly, three regulatory networks were hierarchically constructed: Differentially expressed, associated and global networks. Following comparison and analysis of the similarities and differences among the three networks, a number of key pathways, which showed self-adaptation associations were identified. This included NFκB1 and hsa-miR-9, hsa-miR-196a-1 and its host gene HOXB7, which separately forms a self-adaptation association. The differentially expressed network illuminated the pathogenesis of HL. In addition, the associated network further described the regulatory mechanism associated with HL, including prevention, diagnosis, development and therapy. The current study systematically explains the regulatory mechanisms of HL and supplies comprehensive data associated with HL for further studies. With increasing knowledge of the occurrence, mechanism, improvement, metastasis and treatment, an increased understanding of HL may be achieved.

Chile T, Fortes MA, Corrêa-Giannella ML, et al.
HOXB7 mRNA is overexpressed in pancreatic ductal adenocarcinomas and its knockdown induces cell cycle arrest and apoptosis.
BMC Cancer. 2013; 13:451 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Human homeobox genes encode nuclear proteins that act as transcription factors involved in the control of differentiation and proliferation. Currently, the role of these genes in development and tumor progression has been extensively studied. Recently, increased expression of HOXB7 homeobox gene (HOXB7) in pancreatic ductal adenocarcinomas (PDAC) was shown to correlate with an invasive phenotype, lymph node metastasis and worse survival outcomes, but no influence on cell proliferation or viability was detected. In the present study, the effects arising from the knockdown of HOXB7 in PDAC cell lines was investigated.
METHODS: Real time quantitative PCR (qRT-PCR) (Taqman) was employed to assess HOXB7 mRNA expression in 29 PDAC, 6 metastatic tissues, 24 peritumoral tissues and two PDAC cell lines. siRNA was used to knockdown HOXB7 mRNA in the cell lines and its consequences on apoptosis rate and cell proliferation were measured by flow cytometry and MTT assay respectively.
RESULTS: Overexpression of HOXB7 mRNA was observed in the tumoral tissues and in the cell lines MIA PaCa-2 and Capan-1. HOXB7 knockdown elicited (1) an increase in the expression of the pro-apoptotic proteins BAX and BAD in both cell lines; (2) a decrease in the expression of the anti-apoptotic protein BCL-2 and in cyclin D1 and an increase in the number of apoptotic cells in the MIA PaCa-2 cell line; (3) accumulation of cell in sub-G1 phase in both cell lines; (4) the modulation of several biological processes, especially in MIA PaCa-2, such as proteasomal ubiquitin-dependent catabolic process and cell cycle.
CONCLUSION: The present study confirms the overexpression of HOXB7 mRNA expression in PDAC and demonstrates that decreasing its protein level by siRNA could significantly increase apoptosis and modulate several biological processes. HOXB7 might be a promising target for future therapies.

Marcinkiewicz KM, Gudas LJ
Altered epigenetic regulation of homeobox genes in human oral squamous cell carcinoma cells.
Exp Cell Res. 2014; 320(1):128-43 [PubMed] Free Access to Full Article Related Publications
To gain insight into oral squamous cell carcinogenesis, we performed deep sequencing (RNAseq) of non-tumorigenic human OKF6-TERT1R and tumorigenic SCC-9 cells. Numerous homeobox genes are differentially expressed between OKF6-TERT1R and SCC-9 cells. Data from Oncomine, a cancer microarray database, also show that homeobox (HOX) genes are dysregulated in oral SCC patients. The activity of Polycomb repressive complexes (PRC), which causes epigenetic modifications, and retinoic acid (RA) signaling can control HOX gene transcription. HOXB7, HOXC10, HOXC13, and HOXD8 transcripts are higher in SCC-9 than in OKF6-TERT1R cells; using ChIP (chromatin immunoprecipitation) we detected PRC2 protein SUZ12 and the epigenetic H3K27me3 mark on histone H3 at these genes in OKF6-TERT1R, but not in SCC-9 cells. In contrast, IRX1, IRX4, SIX2 and TSHZ3 transcripts are lower in SCC-9 than in OKF6-TERT1R cells. We detected SUZ12 and the H3K27me3 mark at these genes in SCC-9, but not in OKF6-TERT1R cells. SUZ12 depletion increased HOXB7, HOXC10, HOXC13, and HOXD8 transcript levels and decreased the proliferation of OKF6-TERT1R cells. Transcriptional responses to RA are attenuated in SCC-9 versus OKF6-TERT1R cells. SUZ12 and H3K27me3 levels were not altered by RA at these HOX genes in SCC-9 and OKF6-TERT1R cells. We conclude that altered activity of PRC2 is associated with dysregulation of homeobox gene expression in human SCC cells, and that this dysregulation potentially plays a role in the neoplastic transformation of oral keratinocytes.

How C, Hui AB, Alajez NM, et al.
MicroRNA-196b regulates the homeobox B7-vascular endothelial growth factor axis in cervical cancer.
PLoS One. 2013; 8(7):e67846 [PubMed] Free Access to Full Article Related Publications
The down-regulation of microRNA-196b (miR-196b) has been reported, but its contribution to cervical cancer progression remains to be investigated. In this study, we first demonstrated that miR-196b down-regulation was significantly associated with worse disease-free survival (DFS) for cervical cancer patients treated with combined chemo-radiation. Secondly, using a tri-modal approach for target identification, we determined that homeobox-B7 (HOXB7) was a bona fide target for miR-196b, and in turn, vascular endothelial growth factor (VEGF) was a downstream transcript regulated by HOXB7. Reconstitution of miR-196b expression by transient transfection resulted in reduced cell growth, clonogenicity, migration and invasion in vitro, as well as reduced tumor angiogenesis and tumor cell proliferation in vivo. Concordantly, siRNA knockdown of HOXB7 or VEGF phenocopied the biological effects of miR-196b over-expression. Our findings have demonstrated that the miR-196b/HOXB7/VEGF pathway plays an important role in cervical cancer progression; hence targeting this pathway could be a promising therapeutic strategy for the future management of this disease.

Mihály Z, Kormos M, Lánczky A, et al.
A meta-analysis of gene expression-based biomarkers predicting outcome after tamoxifen treatment in breast cancer.
Breast Cancer Res Treat. 2013; 140(2):219-32 [PubMed] Related Publications
To date, three molecular markers (ER, PR, and CYP2D6) have been used in clinical setting to predict the benefit of the anti-estrogen tamoxifen therapy. Our aim was to validate new biomarker candidates predicting response to tamoxifen treatment in breast cancer by evaluating these in a meta-analysis of available transcriptomic datasets with known treatment and follow-up. Biomarker candidates were identified in Pubmed and in the 2007-2012 ASCO and 2011-2012 SABCS abstracts. Breast cancer microarray datasets of endocrine therapy-treated patients were downloaded from GEO and EGA and RNAseq datasets from TCGA. Of the biomarker candidates, only those identified or already validated in a clinical cohort were included. Relapse-free survival (RFS) up to 5 years was used as endpoint in a ROC analysis in the GEO and RNAseq datasets. In the EGA dataset, Kaplan-Meier analysis was performed for overall survival. Statistical significance was set at p < 0.005. The transcriptomic datasets included 665 GEO-based and 1,208 EGA-based patient samples. All together 68 biomarker candidates were identified. Of these, the best performing genes were PGR (AUC = 0.64, p = 2.3E-07), MAPT (AUC = 0.62, p = 7.8E-05), and SLC7A5 (AUC = 0.62, p = 9.2E-05). Further genes significantly correlated to RFS include FOS, TP53, BTG2, HOXB7, DRG1, CXCL10, and TPM4. In the RNAseq dataset, only ERBB2, EDF1, and MAPK1 reached statistical significance. We evaluated tamoxifen-resistance genes in three independent platforms and identified PGR, MAPT, and SLC7A5 as the most promising prognostic biomarkers in tamoxifen treated patients.

Nguyen Kovochich A, Arensman M, Lay AR, et al.
HOXB7 promotes invasion and predicts survival in pancreatic adenocarcinoma.
Cancer. 2013; 119(3):529-39 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The homeobox gene HOXB7 is overexpressed across a range of cancers and promotes tumorigenesis through varying effects on proliferation, survival, invasion, and angiogenesis. Although published microarray data suggest HOXB7 is overexpressed in pancreatic ductal adenocarcinoma (PDAC), its function in pancreatic cancer has not been studied.
METHODS: HOXB7 message and protein levels were examined in PDAC cell lines and patient samples, as well as in normal pancreas. HOXB7 protein expression in patient tumors was determined by immunohistochemistry and correlated with clinicopathologic factors and survival. The impact of HOXB7 on cell proliferation, growth, and invasion was assessed by knockdown and overexpression in PDAC cell lines. Candidate genes whose expression levels were altered following HOXB7 knockdown were determined by microarray analysis.
RESULTS: HOXB7 message and protein levels were significantly elevated in PDAC cell lines and patient tumor samples relative to normal pancreas. Evaluation of a tissue microarray of 145 resected PDACs found high HOXB7 protein expression was correlated with lymph node metastasis (P = .034) and an independent predictor of worse overall survival in multivariate analysis (hazard ratio = 1.56, 95% confidence interval = 1.02-2.39). HOXB7 knockdown or overexpression in PDAC cell lines resulted in decreased or increased invasion, respectively, without influencing proliferation or cell viability.
CONCLUSIONS: HOXB7 is frequently overexpressed in PDAC, specifically promotes invasive phenotype, and is associated with lymph node metastasis and worse survival outcome. HOXB7 and its downstream targets may represent novel clinical biomarkers or targets of therapy for inhibiting the invasive and metastatic capacity of PDAC.

Yuan W, Zhang X, Xu Y, et al.
Role of HOXB7 in regulation of progression and metastasis of human lung adenocarcinoma.
Mol Carcinog. 2014; 53(1):49-57 [PubMed] Related Publications
Dysregulation of homeobox B7 (HOXB7), a member of the homeobox genes family, was suggested to play a role in regulation of tumorigenesis and metastases of some cancers. However, the functions of HOXB7 in association with lung adenocarcinoma (LAC) have not been investigated. The correlation between the level of HOXB7 expression and cancer progression in patients is not known. In this study, through analysis of 75 LAC samples and their corresponding normal lung epithelium tissues immunohistochemistry (IHC), we demonstrate that HOXB7 was overexpressed in LAC specimens compared to their paired normal lung epithelium tissues. Increased expression of HOXB7 was associated with poor clinical outcomes, correlating significantly with a short survival time in patients who had LAC. Moreover, HOXB7 expression level was correlated with the tumor status (P = 0.028), nodal status (P = 0.012) and tumor stage (P = 0.029) in lung adenocarcinoma. Silencing HOXB7 inhibited cell growth and metastases in vitro and in vivo. In conclusion, our results suggest that HOXB7 promotes LAC progression by enhancing proliferation and metastasis. The increased expression of HOXB7 in LAC is a potential prognostic indicator for patients, and HOXB7 could be a novel target for treatment of LAC patients.

Nischalke HD, Schmitz V, Luda C, et al.
Detection of IGF2BP3, HOXB7, and NEK2 mRNA expression in brush cytology specimens as a new diagnostic tool in patients with biliary strictures.
PLoS One. 2012; 7(8):e42141 [PubMed] Free Access to Full Article Related Publications
INTRODUCTION: It is a challenging task to distinguish between benign and malignant lesions in patients with biliary strictures. Here we analyze whether determination of target gene mRNA levels in intraductal brush cytology specimens may be used to improve the diagnosis of bile duct carcinoma.
MATERIALS AND METHODS: Brush cytology specimens from 119 patients with biliary strictures (malignant: n = 72; benign: n = 47) were analyzed in a retrospective cohort study. mRNA of IGF-II mRNA-binding protein 3 (IGF2BP3), homeobox B7 (HOXB7), Forkhead box M1 (FOXM1), kinesin family member 2C (KIF2C) and serine/threonine kinase NEK2 was determined by semi-quantitative RT-PCR using the ΔCt method.
RESULTS: IGF2BP3 (p<0.0001), HOXB7 (p<0.0001), and NEK2 (p<0.0001) mRNA expression levels were significantly increased in patients with cholangiocarcinoma or pancreatic cancer. Median ΔCt values differed by 3.5 cycles (IGF2BP3), 2.8 cycles (HOXB7) and 1.3 cycles (NEK2) corresponding to 11-fold, 7-fold and 2.5-fold increased mRNA levels in malignant versus benign samples. Sensitivity to detect biliary cancer was 76.4% for IGF2BP3 (80.9% specificity); 72.2% for HOXB7 (78.7% specificity) and 65.3% for NEK2 (72.3% specificity), whereas routine cytology reached only 43.1% sensitivity (85.4% specificity). Diagnostic precision was further improved, when all three molecular markers were assessed in combination (77.8% sensitivity, 87.2% specificity) and achieved 87.5% sensitivity and 87.2% specificity when molecular markers were combined with routine cytology.
CONCLUSIONS: Our data suggest that measuring IGF2BP3, HOXB7 and NEK2 mRNA levels by RT-PCR in addition to cytology has the potential to improve detection of malignant biliary disorders from brush cytology specimens.

di Pietro M, Lao-Sirieix P, Boyle S, et al.
Evidence for a functional role of epigenetically regulated midcluster HOXB genes in the development of Barrett esophagus.
Proc Natl Acad Sci U S A. 2012; 109(23):9077-82 [PubMed] Free Access to Full Article Related Publications
Barrett esophagus (BE) is a human metaplastic condition that is the only known precursor to esophageal adenocarcinoma. BE is characterized by a posterior intestinal-like phenotype in an anterior organ and therefore it is reminiscent of homeotic transformations, which can occur in transgenic animal models during embryonic development as a consequence of mutations in HOX genes. In humans, acquired deregulation of HOX genes during adulthood has been linked to carcinogenesis; however, little is known about their role in the pathogenesis of premalignant conditions. We hypothesized that HOX genes may be implicated in the development of BE. We demonstrated that three midcluster HOXB genes (HOXB5, HOXB6, and HOXB7) are overexpressed in BE, compared with the anatomically adjacent normal esophagus and gastric cardia. The midcluster HOXB gene signature in BE is identical to that seen in normal colonic epithelium. Ectopic expression of these three genes in normal squamous esophageal cells in vitro induces markers of intestinal differentiation, such as KRT20, MUC2, and VILLIN. In BE-associated adenocarcinoma, the activation midcluster HOXB gene is associated with loss of H3K27me3 and gain of AcH3, compared with normal esophagus. These changes in histone posttranslational modifications correlate with specific chromatin decompaction at the HOXB locus. We suggest that epigenetically regulated alterations of HOX gene expression can trigger changes in the transcriptional program of adult esophageal cells, with implications for the early stages of carcinogenesis.

Agnelli L, Storti P, Todoerti K, et al.
Overexpression of HOXB7 and homeobox genes characterizes multiple myeloma patients lacking the major primary immunoglobulin heavy chain locus translocations.
Am J Hematol. 2011; 86(12):E64-6 [PubMed] Related Publications
Homeobox (HOX) gene transcription factors are frequently deregulated in hematologic malignancies and involved in leukemogenic transformation [1]. Moreover, their overexpression has been associated with tumoral-induced neoangiogenesis in solid cancer [2]. The expression and the role of these genes have not yet been completely elucidated in multiple myeloma (MM). Recently, we reported that a small fraction of MM patients shows a HOXB7 overexpression as compared with normal samples and that HOXB7 expression correlates with bone marrow angiogenesis and the production of the proangiogenic factors by MM cells [3]. Other authors previously reported that HOXA cluster genes are expressed in a small fraction of MM patients [4]. Herein, we extended our previous evidences with the evaluation of the expression level of HOXB7 and the other gene family members in a large number of primary MM cells in relationship with the different molecular subgroups of MM and the presence of specific chromosome translocations. We found that HOXB7 and other genes of HOX family have a preferential distribution based on the characteristics of molecular MM subtypes based on the translocations/cyclins (TC) classification, suggesting a potential relationship between HOX genes expression, angiogenesis, and molecular features of MM patients.

Jin K, Kong X, Shah T, et al.
The HOXB7 protein renders breast cancer cells resistant to tamoxifen through activation of the EGFR pathway.
Proc Natl Acad Sci U S A. 2012; 109(8):2736-41 [PubMed] Free Access to Full Article Related Publications
Multiple factors including long-term treatment with tamoxifen are involved in the development of selective estrogen receptor (ER) modulator resistance in ERα-positive breast cancer. Many underlying molecular events that confer resistance are known but a unifying theme is yet to be revealed. In this report, we provide evidence that HOXB7 overexpression renders MCF-7 cells resistant to tamoxifen via cross-talk between receptor tyrosine kinases and ERα signaling. HOXB7 is an ERα-responsive gene. Extended treatment of MCF-7 cells with tamoxifen resulted in progressively increasing levels of HOXB7 expression, along with EGFR and EGFR ligands. Up-regulation of EGFR occurs through direct binding of HOXB7 to the EGFR promoter, enhancing transcriptional activity. Finally, higher expression levels of HOXB7 in the tumor significantly correlated with poorer disease-free survival in ERα-positive patients with breast cancer on adjuvant tamoxifen monotherapy. These studies suggest that HOXB7 acts as a key regulator, orchestrating a major group of target molecules in the oncogenic hierarchy. Functional antagonism of HOXB7 could circumvent tamoxifen resistance.

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