HOXB13 homeodomain protein suppresses the growth of prostate cancer cells by the negative regulation of T-cell factor 4

AR coactivators, CBP/p300, are critical mediators of DNA repair in prostate cancer

Castration resistant prostate cancer (CRPC) remains an incurable disease stage with ineffective treatments options. Here, the androgen receptor (AR) coactivators CBP/p300, which are histone acetyltransferases, were identified as critical mediators of DNA damage repair (DDR) to potentially enhance therapeutic targeting of CRPC. Key findings demonstrate that CBP/p300 expression increases with disease progression and selects for poor prognosis in metastatic disease. CBP/p300 bromodomain inhibition enhances response to standard of care therapeutics. Functional studies, CBP/p300 cistrome mapping, and transcriptome in CRPC revealed that CBP/p300 regulates DDR. Further mechanistic investigation showed that CBP/p300 attenuation via therapeutic targeting and genomic knockdown decreases homologous recombination (HR) factors in vitro, in vivo, and in human prostate cancer (PCa) tumors ex vivo. Similarly, CBP/p300 expression in human prostate tissue correlates with HR factors. Lastly, targeting CBP/p300 impacts HR-mediate repair and patient outcome. Collectively, these studies identify CBP/p300 as drivers of PCa tumorigenesis and lay the groundwork to optimize therapeutic strategies for advanced PCa via CBP/p300 inhibition, potentially in combination with AR-directed and DDR therapies.

MNX1 Promotes Anti-HER2 Therapy Sensitivity via Transcriptional Regulation of CD-M6PR in HER2-Positive Breast Cancer

Although targeted therapy for human epidermal growth factor receptor 2 (HER2)-positive breast cancer has significantly prolonged survival time and improved patients' quality of life, drug resistance has gradually emerged. This study explored the mechanisms underlying the effect of the motor neuron and pancreatic homeobox 1 (MNX1) genes on drug sensitivity in HER2-positive breast cancer. From July 2017 to 2018, core needle biopsies of HER2-positive breast cancer were collected from patients who received paclitaxel, carboplatin, and trastuzumab neoadjuvant therapy at our center. Based on treatment efficacy, 81 patients were divided into pathological complete response (pCR) and non-pCR groups. High-throughput RNA sequencing results were analyzed along with the GSE181574 dataset. MNX1 was significantly upregulated in the pCR group compared with the non-pCR group in both sequencing datasets, suggesting that MNX1 might be correlated with drug sensitivity in HER2-positive breast cancer. Meanwhile, tissue array results revealed that high MNX1 expression corresponded to a good prognosis. In vitro functional tests showed that upregulation of MNX1 significantly increased the sensitivity of HER2-positive breast cancer cells to lapatinib and pyrotinib. In conclusion, MNX1 may serve as a prognostic marker for patients with HER2-positive breast cancer, and its expression may facilitate clinical screening of patients sensitive to anti-HER2-targeted therapy.

Hierarchical Phosphorylation of HOXB13 by mTOR Dictates Its Activity and Oncogenic Function in Prostate Cancer

Dysregulation of mTOR signaling plays a critical role in promoting prostate cancer growth. HOXB13, a homeodomain transcription factor, is known to influence the androgen response and prostate cancer development. Recently, HOXB13 was found to complex with mTOR on chromatin. However, the functional crosstalk between HOXB13 and mTOR remains elusive. We now report that mTOR directly interacts with and hierarchically phosphorylates HOXB13 at threonine 8 and 41 then serine 31 to promote its interaction with the E3 ligase SKP2 while enhancing its oncogenic properties. Expression of HOXB13 harboring phosphomimetic mutations at the mTOR-targeted sites stimulates prostate cancer cellular growth both in vitro and in murine xenografts. Transcriptional profiling studies revealed a phospho-HOXB13-dependent gene signature capable of robustly discriminating between normal prostate tissues, primary and metastatic prostate cancer samples. This work uncovers a previously unanticipated molecular cascade by which mTOR directly phosphorylates HOXB13 to dictate a specific gene program with oncogenic implications in prostate cancer.

IMPLICATIONS

Control of HOXB13 transcriptional activity via its direct phosphorylation by the mTOR kinase is a potential therapeutic avenue for the management of advanced prostate cancer.

Differential Protein Expression Patterns of HOXA13 and HOXB13 Are Associated with Bladder Cancer Progression

Bladder cancer is a common urological cancer and has the highest recurrence rate of any cancer. The aim of our study was to profile and characterize the protein expression of homeobox A13 (HOXA13) and homeobox B13 (HOXB13) genes in Malaysian bladder cancer patients. The protein expression of HOXA13 and HOXB13 in formalin-fixed paraffin-embedded (FFPE) bladder cancer tissues was determined by immunohistochemistry (IHC) analysis. The association between HOXA13/HOXB13 protein expression and demographic/clinicopathological characteristics of the bladder cancer patients was determined by chi-square analysis. Approximately 63.6% of the bladder cancer tissues harbored high HOXA13 expression. High HOXA13 expression was significantly associated with non-muscle invasive bladder cancer, lower tumor grade, higher number of lymph node metastases, and recurrence risk. In contrast, low HOXB13 expression (including those with negative expression) was observed in 71.6% of the bladder cancer tissues analyzed. Low HOXB13 expression was significantly associated with muscle-invasive bladder cancer, higher tumor stage, tumor grade, and metastatic risk. Both HOXA13 and HOXB13 protein expression were found to be associated with bladder tumorigenesis. The putative oncogenic and tumor suppressive roles of HOXA13 and HOXB13, respectively, suggest their potential utility as biomarkers in bladder cancer.

A transcriptional network of cell cycle dysregulation in noninvasive papillary urothelial carcinoma

Human cancers display a restricted set of expression profiles, despite diverse mutational drivers. This has led to the hypothesis that select sets of transcription factors act on similar target genes as an integrated network, buffering a tumor’s transcriptional state. Noninvasive papillary urothelial carcinoma (NIPUC) with higher cell cycle activity has higher risk of recurrence and progression. In this paper, we describe a transcriptional network of cell cycle dysregulation in NIPUC, which was delineated using the ARACNe algorithm applied to expression data from a new cohort (n = 81, RNA sequencing), and two previously published cohorts. The transcriptional network comprised 121 transcription factors, including the pluripotency factors SOX2 and SALL4, the sex hormone binding receptors ESR1 and PGR, and multiple homeobox factors. Of these 121 transcription factors, 65 and 56 were more active in tumors with greater and less cell cycle activity, respectively. When clustered by activity of these transcription factors, tumors divided into High Cell Cycle versus Low Cell Cycle groups. Tumors in the High Cell Cycle group demonstrated greater mutational burden and copy number instability. A putative mutational driver of cell cycle dysregulation, such as homozygous loss of CDKN2A, was found in only 50% of High Cell Cycle NIPUC, suggesting a prominent role of transcription factor activity in driving cell cycle dysregulation. Activity of the 121 transcription factors strongly associated with expression of EZH2 and other members of the PRC2 complex, suggesting regulation by this complex influences expression of the transcription factors in this network. Activity of transcription factors in this network also associated with signatures of pluripotency and epithelial-to-mesenchymal transition (EMT), suggesting they play a role in driving evolution to invasive carcinoma. Consistent with this, these transcription factors differed in activity between NIPUC and invasive urothelial carcinoma.

Expression profile and prognostic significance of HOXB13 in rectal cancer

BACKGROUND

This study aimed to investigate the expression pattern and prognostic significance of HOXB13 in rectal cancer.

METHODS

HOXB13 expression in rectal cancer and normal adjacent tissues was detected by reverse transcriptase-polymerase chain reaction and immunohistochemistry, and its clinicopathological characteristics and prognosis were statistically tested. Furthermore, we evaluated the association between tumor immune infiltrating cells and HOXB13 using the tumor immune estimation resource (TIMER) database. The potential biological mechanism associated with HOXB13 overexpression was investigated by gene set enrichment analysis (GSEA).

RESULTS

The expression of HOXB13 messenger RNA and protein in human rectal cancer tissues were significantly higher than those in the normal adjacent tissues (P < 0.05). HOXB13 expression was significantly correlated with depth of invasion, lymphatic invasion, lymph node metastasis, distant metastasis, and pathological tumor node metastasis stage (P < 0.05). Kaplan-Meier survival curves confirmed that HOXB13 overexpression was correlated negatively with overall survival and disease-free survival in rectal cancer (P < 0.05). Also, multivariate Cox regression analysis demonstrated that HOXB13 expression, age, and lymphatic invasion were independent prognostic factors in rectal cancer (P < 0.05). Plus, the results from the TIMER database indicated that HOXB13 expression has a significant association with several immune cell infiltrates. Finally, the GSEA results indicated that HOXB13 participated in the various immune-associated processes, including natural killer cell-mediated cytotoxicity and the T-cell receptor signaling pathway.

CONCLUSION

Our study showed an essential role of HOXB13 in rectal cancer immunity and prognosis. Significantly, the overexpression of HOXB13 leads to the worse prognosis for patients with rectal cancer, which will contribute to understanding molecular mechanisms associated with tumor pathogenesis and prognosis in this disease.

Comprehensive Network Analysis of Dysregulated Genes Revealed MNX1‐AS1/ hsa‐miR‐4697‐3p/ HOXB13 Axis in OC Chemotherapy Response

Poor chemotherapy response is the main obstacle of ovarian cancer (OC) treatment. Platinum‐refractory and ‐resistant patients are associated with a worse outcome than platinum‐sensitive and partially sensitive patients, but the comprehensive similarities and differences among them are not yet clear. In this study, we analyzed the data of patients with different chemotherapy response in The Cancer Genome Atlas. We found a minority of altered genes were overlapped in refractory and resistant groups, as did the enriched pathways and Gene Ontology terms. We noticed that the neural signaling and drug metabolism enzymes were more significantly enriched and the protein–protein interaction supported these results. The transcription analysis highlighted PDX1 as the common and central transcription factor in both refractory and resistant groups. The competing endogenous RNA (ceRNA) network shared no common ceRNA pairs, indicating a major difference in noncoding RNA post‐transcriptional regulation. In the end, we validated the expression, regulation, binding, and effect on chemotherapy response for selected MNX1‐AS1/hsa‐miR‐4697‐3p/HOXB13 in OC cell lines. Our study offered a novel and comprehensive insight into chemotherapy response, and potential targets for improving chemotherapy response in OC.

Downstream of the HOX genes: explaining conflicting tumour suppressor and oncogenic functions in cancer

The HOX genes are a highly conserved group of transcription factors that have key roles in early development, but which are also highly expressed in most cancers. Many studies have found strong associative relationships between the expression of individual HOX genes in tumours and clinical parameters including survival. For the majority of HOX genes, high tumour expression levels seem to be associated with a worse outcome for patients, and in some cases this has been shown to result from the activation of pro-oncogenic genes and pathways. However, there are also many studies that indicate a tumour suppressor role for some HOX genes, sometimes with conclusions that contradict earlier work. In this review, we have attempted to clarify the role of HOX genes in cancer by focusing on their downstream targets as identified in studies that provide experimental evidence for their activation or repression. On this basis, the majority of HOX genes would appear to have a pro-oncogenic function, with the notable exception of HOXD10, which acts exclusively as a tumour suppressor. HOX proteins regulate a wide range of target genes involved in metastasis, cell death, proliferation, and angiogenesis, and activate key cell signalling pathways. Furthermore, for some functionally related targets, this regulation is achieved by a relatively small subgroup of HOX genes.

Molecular implications of HOX genes targeting multiple signaling pathways in cancer

Homeobox (HOX) genes encode highly conserved homeotic transcription factors that play a crucial role in organogenesis and tissue homeostasis. Their deregulation impacts the function of several regulatory molecules contributing to tumor initiation and progression. A functional bridge exists between altered gene expression of individual HOX genes and tumorigenesis. This review focuses on how deregulation in the HOX-associated signaling pathways contributes to the metastatic progression in cancer. We discuss their functional significance, clinical implications and ascertain their role as a diagnostic and prognostic biomarker in the various cancer types. Besides, the mechanism of understanding the theoretical underpinning that affects HOX-mediated therapy resistance in cancers has been outlined. The knowledge gained shall pave the way for newer insights into the treatment of cancer.

Wnt/β-catenin signaling in cancers and targeted therapies

Wnt/β-catenin signaling has been broadly implicated in human cancers and experimental cancer models of animals. Aberrant activation of Wnt/β-catenin signaling is tightly linked with the increment of prevalence, advancement of malignant progression, development of poor prognostics, and even ascendence of the cancer-associated mortality. Early experimental investigations have proposed the theoretical potential that efficient repression of this signaling might provide promising therapeutic choices in managing various types of cancers. Up to date, many therapies targeting Wnt/β-catenin signaling in cancers have been developed, which is assumed to endow clinicians with new opportunities of developing more satisfactory and precise remedies for cancer patients with aberrant Wnt/β-catenin signaling. However, current facts indicate that the clinical translations of Wnt/β-catenin signaling-dependent targeted therapies have faced un-neglectable crises and challenges. Therefore, in this study, we systematically reviewed the most updated knowledge of Wnt/β-catenin signaling in cancers and relatively targeted therapies to generate a clearer and more accurate awareness of both the developmental stage and underlying limitations of Wnt/β-catenin-targeted therapies in cancers. Insights of this study will help readers better understand the roles of Wnt/β-catenin signaling in cancers and provide insights to acknowledge the current opportunities and challenges of targeting this signaling in cancers.

Homeobox-A13 acts as a functional prognostic and diagnostic biomarker via regulating P53 and Wnt signaling pathways in lung cancer

BACKGROUND

The prognosis of lung cancer patients is poor without useful prognostic and diagnostic biomarker. To search for novel prognostic and diagnostic markers, we previously found homeobox-A13 (HOXA13) as a promising candidate in lung cancer.

OBJECTIVE

To determine the precisely clinical feature, prognostic and diagnostic value, possible role and mechanism of HOXA13.

METHODS

Gene-expression was explored by real-time quantitative-PCR, western-blot and tissue-microarray. The associations were analyzed by Chi-square test, Kaplan-Meier and Cox-regression. The roles and mechanisms were evaluated by MTS, EdU, transwell, xenograft tumor and luciferase-reporter assays.

RESULTS

HOXA13 expression is increased in tumors, and correlated with age of patients. HOXA13 expression is associated with unfavorable overall survival and relapse-free survival of patients in four cohorts. Interestingly, HOXA13 has different prognostic significance in adenocarcinoma (ADC) and squamous-cell carcinoma (SCC), and is a sex- and smoke-related prognostic factor only in ADC. Importantly, HOXA13 can serve as a diagnostic biomarker for lung cancer, especially for SCC. HOXA13 can promote cancer-cell proliferation, migration and invasion in vitro, and facilitate tumorigenicity and tumor metastasis in vivo. HOXA13 acts the oncogenic roles on tumor growth and metastasis by regulating P53 and Wnt/β-catenin signaling activities in lung cancer.

CONCLUSIONS

HOXA13 is a new prognostic and diagnostic biomarker associated with P53 and Wnt/β-catenin signaling pathways.

Homeobox B5 promotes metastasis and poor prognosis in Hepatocellular Carcinoma, via FGFR4 and CXCL1 upregulation

Background: Since metastasis remains the main reason for HCC-associated death, a better understanding of molecular mechanism underlying HCC metastasis is urgently needed. Here, we elucidated the role of Homeobox B5 (HOXB5), a member of the HOX transcriptional factor family, in promoting HCC metastasis.

Method: The expression of HOXB5 and its functional targets fibroblast growth factor receptor 4 (FGFR4) and C-X-C motif chemokine ligand 1 (CXCL1) were detected by immunohistochemistry. Luciferase reporter and chromatin immunoprecipitation assays were performed to measure the transcriptional regulation of target genes by HOXB5. The effects of FGFR4 and CXCL1 on HOXB5-mediated metastasis were analyzed by an orthotopic metastasis model.

Results: Elevated expression of HOXB5 had a positive correlation with poor tumour differentiation, higher TNM stage, and indicated unfavorable prognosis. Overexpression of HOXB5 promoted HCC metastasis through transactivating FGFR4 and CXCL1 expression, whereas knockdown of FGFR4 and CXCL1 decreased HOXB5-enhanced HCC metastasis. Moreover, HOXB5 overexpression in HCC cells promoted myeloid derived suppressor cells (MDSCs) infiltration through CXCL1/CXCR2 axis. Either depletion of MDSCs by anti-Gr1 or blocking CXCL1-CXCR2 axis by CXCR2 inhibitor impaired HOXB5-mediated HCC metastasis. In addition, fibroblast growth factor 19 (FGF19) contributed to the HOXB5 upregulation through PI3K/AKT/HIF1α pathway. Overexpression of FGF15 (an analog of FGF19 in mouse) promoted HCC metastasis, whereas knockdown of HOXB5 significantly inhibited FGF15-enhanced HCC metastasis in immunocompetent mice. HOXB5 expression was positively associated with CXCL1 expression and intratumoral MDSCs accumulation in human HCC tissues. Patients who co-expressed HOXB5/CXCL1 or HOXB5/CD11b exhibited the worst prognosis. Furthermore, the combination of FGFR4 inhibitor BLU-554 and CXCR2 inhibitor SB265610 dramatically decreased HOXB5-mediated HCC metastasis.

Conclusion: HOXB5 was a potential prognostic biomarker in HCC patients and targeting this loop may provide a promising treatment strategy for the inhibition of HOXB5-mediated HCC metastasis.

Induction of HOX Genes by Hepatitis C Virus Infection via Impairment of Histone H2A Monoubiquitination

Hepatitis C virus (HCV) infection causes liver pathologies, including hepatocellular carcinoma (HCC). Homeobox (HOX) gene products regulate embryonic development and are associated with tumorigenesis, although the regulation of HOX genes by HCV infection has not been clarified in detail. We examined the effect of HCV infection on HOX gene expression. In this study, HCV infection induced more than half of the HOX genes and reduced the level of histone H2A monoubiquitination on lysine 119 (K119) (H2Aub), which represses HOX gene promoter activity. HCV infection also promoted proteasome-dependent degradation of RNF2, which is an E3 ligase mediating H2A monoubiquitination as a component of polycomb repressive complex 1. Since full-genomic replicon cells but not subgenomic replicon cells exhibited reduced RNF2 and H2Aub levels and induction of HOX genes, we focused on the core protein. Expression of the core protein reduced the amounts of RNF2 and H2Aub and induced HOX genes. Treatment with LY-411575, which can reduce HCV core protein expression via signal peptide peptidase (SPP) inhibition without affecting other viral proteins, dose-dependently restored the amounts of RNF2 and H2Aub in HCV-infected cells and impaired the induction of HOX genes and production of viral particles but not viral replication. The chromatin immunoprecipitation assay results also indicated infection- and proteasome-dependent reductions in H2Aub located in HOX gene promoters. These results suggest that HCV infection or core protein induces HOX genes by impairing histone H2A monoubiquitination via a reduction in the RNF2 level.IMPORTANCE Recently sustained virologic response can be achieved by direct-acting antiviral (DAA) therapy in most hepatitis C patients. Unfortunately, DAA therapy does not completely eliminate a risk of hepatocellular carcinoma (HCC). Several epigenetic factors, including histone modifications, are well known to contribute to hepatitis C virus (HCV)-associated HCC. However, the regulation of histone modifications by HCV infection has not been clarified in detail. In this study, our data suggest that HCV infection or HCV core protein expression impairs monoubiquitination of histone H2A K119 in the homeobox (HOX) gene promoter via destabilization of RNF2 and then induces HOX genes. Several lines of evidence suggest that the expression of several HOX genes is dysregulated in certain types of tumors. These findings reveal a novel mechanism of HCV-related histone modification and may provide information about new targets for diagnosis and prevention of HCC occurrence.

Identification of Tumor Tissue of Origin with RNA-Seq Data and Using Gradient Boosting Strategy

BACKGROUND

Cancer of unknown primary (CUP) is a type of malignant tumor, which is histologically diagnosed as a metastatic carcinoma while the tissue-of-origin cannot be identified. CUP accounts for roughly 5% of all cancers. Traditional treatment for CUP is primarily broad-spectrum chemotherapy; however, the prognosis is relatively poor. Thus, it is of clinical importance to accurately infer the tissue-of-origin of CUP.

METHODS

We developed a gradient boosting framework to trace tissue-of-origin of 20 types of solid tumors. Specifically, we downloaded the expression profiles of 20,501 genes for 7713 samples from The Cancer Genome Atlas (TCGA), which were used as the training data set. The RNA-seq data of 79 tumor samples from 6 cancer types with known origins were also downloaded from the Gene Expression Omnibus (GEO) for an independent data set.

RESULTS

400 genes were selected to train a gradient boosting model for identification of the primary site of the tumor. The overall 10-fold cross-validation accuracy of our method was 96.1% across 20 types of cancer, while the accuracy for the independent data set reached 83.5%.

CONCLUSION

Our gradient boosting framework was proven to be accurate in identifying tumor tissue-of-origin on both training data and independent testing data, which might be of practical usage.

HOXB4 inhibits the proliferation and tumorigenesis of cervical cancer cells by downregulating the activity of Wnt/β-catenin signaling pathway

Homeobox B4 (HOXB4), which belongs to the homeobox (HOX) family, possesses transcription factor activity and has a crucial role in stem cell self-renewal and tumorigenesis. However, its biological function and exact mechanism in cervical cancer remain unknown. Here, we found that HOXB4 was markedly downregulated in cervical cancer. We demonstrated that HOXB4 obviously suppressed cervical cancer cell proliferation and tumorigenic potential in nude mice. Additionally, HOXB4-induced cell cycle arrest at the transition from the G0/G1 phase to the S phase. Conversely, loss of HOXB4 promoted cervical cancer cell growth both in vitro and in vivo. Bioinformatics analyses and mechanistic studies revealed that HOXB4 inhibited the activity of the Wnt/β-catenin signaling pathway by direct transcriptional repression of β-catenin. Furthermore, β-catenin re-expression rescued HOXB4-induced cervical cancer cell defects. Taken together, these findings suggested that HOXB4 directly transcriptional repressed β-catenin and subsequently inactivated the Wnt/β-catenin signaling pathway, leading to significant inhibition of cervical cancer cell growth and tumor formation.

MEIS-mediated suppression of human prostate cancer growth and metastasis through HOXB13-dependent regulation of proteoglycans

The molecular roles of HOX transcriptional activity in human prostate epithelial cells remain unclear, impeding the implementation of new treatment strategies for cancer prevention and therapy. MEIS proteins are transcription factors that bind and direct HOX protein activity. MEIS proteins are putative tumor suppressors that are frequently silenced in aggressive forms of prostate cancer. Here we show that MEIS1 expression is sufficient to decrease proliferation and metastasis of prostate cancer cells in vitro and in vivo murine xenograft models. HOXB13 deletion demonstrates that the tumor-suppressive activity of MEIS1 is dependent on HOXB13. Integration of ChIP-seq and RNA-seq data revealed direct and HOXB13-dependent regulation of proteoglycans including decorin (DCN) as a mechanism of MEIS1-driven tumor suppression. These results define and underscore the importance of MEIS1-HOXB13 transcriptional regulation in suppressing prostate cancer progression and provide a mechanistic framework for the investigation of HOXB13 mutants and oncogenic cofactors when MEIS1/2 are silenced.

Contributions of HOX genes to cancer hallmarks: Enrichment pathway analysis and review

Homeobox genes function as master regulatory transcription factors during development, and their expression is often altered in cancer. The HOX gene family was initially studied intensively to understand how the expression of each gene was involved in forming axial patterns and shaping the body plan during embryogenesis. More recent investigations have discovered that HOX genes can also play an important role in cancer. The literature has shown that the expression of HOX genes may be increased or decreased in different tumors and that these alterations may differ depending on the specific HOX gene involved and the type of cancer being investigated. New studies are also emerging, showing the critical role of some members of the HOX gene family in tumor progression and variation in clinical response. However, there has been limited systematic evaluation of the various contributions of each member of the HOX gene family in the pathways that drive the common phenotypic changes (or "hallmarks") and that underlie the transformation of normal cells to cancer cells. In this review, we investigate the context of the engagement of HOX gene targets and their downstream pathways in the acquisition of competence of tumor cells to undergo malignant transformation and tumor progression. We also summarize published findings on the involvement of HOX genes in carcinogenesis and use bioinformatics methods to examine how their downstream targets and pathways are involved in each hallmark of the cancer phenotype.

HOX genes function in Breast Cancer development

Breast cancer develops in the mammary glands during mammalian adulthood and is considered the second most common type of human carcinoma and the most incident and mortal in the female population. In contrast to other human structures, the female mammary glands continue to develop after birth, undergoing various modifications during pregnancy, lactation and involution under the regulation of hormones and transcription factors, including those encoded by the HOX clusters (A, B, C, and D). Interestingly, HOX gene deregulation is often associated to breast cancer development. Within the HOXB cluster, 8 out of the 10 genes present altered expression levels in breast cancer with an impact in its aggressiveness and resistance to hormone therapy, which highlights the importance of HOXB genes as potential therapeutic targets used to overcome the limitations of tamoxifen-resistant cancer treatments. Here, we review the current state of knowledge on the role of HOX genes in breast cancer, specially focus on HOXB, discussing the causes and consequences of HOXB gene deregulation and their relevance as prognostic factors and therapeutic targets.

Shaping Chromatin States in Prostate Cancer by Pioneer Transcription Factors

The androgen receptor (AR) is a critical therapeutic target in prostate cancer that responds to antagonists in primary disease, but inevitably becomes reactivated, signaling onset of the lethal castration-resistant prostate cancer (CRPC) stage. Epigenomic investigation of the chromatin environment and interacting partners required for AR transcriptional activity has uncovered three pioneer factors that open up chromatin and facilitate AR-driven transcriptional programs. FOXA1, HOXB13, and GATA2 are required for normal AR transcription in prostate epithelial development and for oncogenic AR transcription during prostate carcinogenesis. AR signaling is dependent upon these three pioneer factors both before and after the clinical transition from treatable androgen-dependent disease to untreatable CRPC. Agents targeting their respective DNA binding or downstream chromatin-remodeling events have shown promise in preclinical studies of CRPC. AR-independent functions of FOXA1, HOXB13, and GATA2 are emerging as well. While all three pioneer factors exert effects that promote carcinogenesis, some of their functions may inhibit certain stages of prostate cancer progression. In all, these pioneer factors represent some of the most promising potential therapeutic targets to emerge thus far from the study of the prostate cancer epigenome.

Circular RNA ITCH suppressed prostate cancer progression by increasing HOXB13 expression via spongy miR-17-5p

BACKGROUND

Circular RNA Itchy E3 ubiquitin protein ligase (Circ-ITCH) is significantly down-regulated in various kinds of tumors, however, the mechanisms of action and functions of circITCH gene in prostate cancer (PC) are still under investigation. The mail goal of this research was to study the functional role of Circ-ITCH gene in prostate cancer and to illuminate the function role of circ-ITCH gene in prostate cancer by targeting miR-17-5p/HOXB13.

METHODS

RT-qPCR was applied to measure the expression level of circ-ITCH and miR-17-5p in PC cell lines and tissues. CCK-8, colony formation, Brdu incorporation labeling and flow cytometry assays were applied to detect the effects of circ-ITCH and miR-17-5p on proliferation and cell apoptosis. Target gene prediction and screening, luciferase reporter gene assays were utilized to assess downstream target genes of miR-17-5p and Circ-ITCH. The protein and expression of HOXB13 gene were measured by Western blotting and RT-qPCR.

RESULTS

CircITCH was significantly reduced in PC cell lines and tissues. Low circITCH expression level was highly related with preoperative PSA, tumor stage and Gleason score. Overexpression of circITCH can inhibit the malignant phenotype of prostate cancer. There was a high negative relationship between the expression level of microRNA-17-5p and circITCH in PC tissues, however, there existed a positive relationship between the expression of HOXB13 and circITCH. CircITCH acted as a sponge of miR-17-5p to increase HOXB13 gene expression. In addition, miR-17-5p overexpression or HOXB13 silencing can reduce the carcinogenic effects of circICCH in prostate cancer.

CONCLUSION

CircITCH promoted prostate cancer progression by regulating the HOXB13/miR-17-5p axis, and circITCH have a potential usage as therapeutic target for PC tumors.

HOX family transcription factors: Related signaling pathways and post-translational modifications in cancer

HOX family transcription factors belong to a highly conserved subgroup of the homeobox superfamily that determines cellular fates in embryonic morphogenesis and the maintenance of adult tissue architecture. HOX family transcription factors play key roles in numerous cellular processes including cell growth, differentiation, apoptosis, motility, and angiogenesis. As tumor promoters or suppressors HOX family members have been reported to be closely related with a variety of cancers. They closely regulate tumor initiation and growth, invasion and metastasis, angiogenesis, anti-cancer drug resistance and stem cell origin. Here, we firstly described the pivotal roles of HOX transcription factors in tumorigenesis. Then, we summarized the main signaling pathways regulated by HOX transcription factors, including Wnt/β-catenin, transforming growth factor β, mitogen-activated protein kinase, phosphoinositide 3-kinase/Akt, and nuclear factor-κB signalings. Finally, we outlined the important post-translational modifications of HOX transcription factors and their regulation in cancers. Future research directions on the HOX transcription factors are also discussed.

Analysis of lncRNA-miRNA-mRNA Interactions in Hyper-proliferative Human Pulmonary Arterial Smooth Muscle Cells

We previously reported enhanced proliferation of smooth muscle cells on the combined exposure of HIV proteins and cocaine leading to the development of HIV-pulmonary arterial hypertension. Here, we attempt to comprehensively understand the interactions between long noncoding RNAs (lncRNAs), mRNAs and micro-RNAs (miRNAs) to determine their role in smooth muscle hyperplasia. Differential expression of lncRNAs, mRNAs and miRNAs were obtained by microarray and small-RNA sequencing from HPASMCs treated with and without cocaine and/or HIV-Tat. LncRNA to mRNA associations were conjectured by analyzing their genomic proximity and by interrogating their association to vascular diseases and cancer co-expression patterns reported in the relevant databases. Neuro-active ligand receptor signaling, Ras signaling and PI3-Akt pathway were among the top pathways enriched in either differentially expressed mRNAs or mRNAs associated to lncRNAs. HPASMC with combined exposure to cocaine and Tat (C + T) vs control identified the following top lncRNA-mRNA pairs, ENST00000495536-HOXB13, T216482-CBL, ENST00000602736-GDF7, and, TCONS_00020413-RND1. Many of the down-regulated miRNAs in the HPASMCs treated with C + T were found to be anti-proliferative and targets of up-regulated lncRNAs targeting up-regulated mRNAs, including down-regulation of miR-185, -491 and up-regulation of corresponding ENST00000585387. Specific knock down of the selected lncRNAs highlighted the importance of non-coding RNAs in smooth muscle hyperplasia.

Paralogous HOX13 Genes in Human Cancers

Hox genes (HOX in humans), an evolutionary preserved gene family, are key determinants of embryonic development and cell memory gene program. Hox genes are organized in four clusters on four chromosomal loci aligned in 13 paralogous groups based on sequence homology (Hox gene network). During development Hox genes are transcribed, according to the rule of “spatio-temporal collinearity”, with early regulators of anterior body regions located at the 3’ end of each Hox cluster and the later regulators of posterior body regions placed at the distal 5’ end. The onset of 3’ Hox gene activation is determined by Wingless-type MMTV integration site family (Wnt) signaling, whereas 5’ Hox activation is due to paralogous group 13 genes, which act as posterior-inhibitors of more anterior Hox proteins (posterior prevalence). Deregulation of HOX genes is associated with developmental abnormalities and different human diseases. Paralogous HOX13 genes (HOX A13, HOX B13, HOX C13 and HOX D13) also play a relevant role in tumor development and progression. In this review, we will discuss the role of paralogous HOX13 genes regarding their regulatory mechanisms during carcinogenesis and tumor progression and their use as biomarkers for cancer diagnosis and treatment.

HOXB13 expression and promoter methylation as a candidate biomarker in gastric cancer

Homeobox b13 (HOXB13) is considered to be a tumor suppressor gene in multiple types of human cancer. The present study aimed to identify the difference in expression of HOXB13 mRNA between gastric cancer (GC) tissues and corresponding non-malignant gastric tissues. The clinical significance of HOXB13 mRNA expression was also assessed in GC and a potential association between HOXB13 mRNA expression and DNA promoter methylation was observed. The expression of HOXB13 mRNA was assessed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and HOXB13 methylation status was assessed by methylation-specific PCR (MSP) in 5 GC cell lines and 85 paired GC and normal gastric tissues. Kaplan-Meier survival curves were used to assess the survival of patients with GC. HOXB13 mRNA expression was significantly lower in primary GC tissues than in corresponding nonmalignant gastric tissues, and decreased HOXB13 expression was associated with poorer differentiation, lymph node metastasis, invasion depth and Tumor-Node-Metastasis (TNM) stage. Kaplan-Meier survival analysis demonstrated that HOXB13 mRNA expression was a significant prognostic indicator of GC patient survival. Furthermore, MSP revealed that the proportion of GC samples with hypermethylated HOXB13 (60.0%, 51/85) was increased compared with the corresponding nonmalignant gastric tissues (11.8%, 10/85). Decreased HOXB13 mRNA expression was due to DNA hypermethylation as following treatment with the DNA methyltransferase inhibitor 5-Aza-dC, HOXB13 expression in the GC MKN-45 cell line was upregulated. The results of the present study indicate that decreased expression of HOXB13 mRNA was associated with tumor differentiation, depth of invasion, lymph node metastases and TNM stage in GC, and it was a significant poor prognostic factor for patients with GC. Aberrant DNA promoter methylation was a crucial reason for the downregulation of HOXB13 mRNA expression.

Morphoregulatory pathways in prostate ductal development

The mouse prostate is a male sex-accessory gland comprised of a branched ductal network arranged into three separate bilateral lobes: the anterior, dorsolateral, and ventral lobes. Prostate ductal development is the primary morphogenetic event in prostate development and requires a complex regulation of spatiotemporal factors. This review provides an overview of prostate development and the major genetic regulators and signaling pathways involved. To identify new areas for further study, we briefly highlight the likely important, but relatively understudied, role of the extracellular matrix (ECM). Finally, we point out the potential importance of the ECM in influencing the behavior and prognosis of prostate cancer. Developmental Dynamics 246:89-99, 2017. © 2016 Wiley Periodicals, Inc.

HOXA13 is associated with unfavorable survival and acts as a novel oncogene in prostate carcinoma

AIM

To investigate the clinical relevance and functional role of HOXA13 in prostate cancer Methods: PCR, western blot and immunohistochemistry were performed to determine the expression. Kaplan-Meier and Cox regression survival analyses investigated the clinical relevance. Cell viability, flow cytometry and transwell assays were used to determine the functional roles.

RESULTS

HOXA13 expression is sharply increased in carcinoma tissues and is significantly associated with poor prognosis of prostate cancer patients. Interestingly, nucleus not cytoplasm HOXA13 expression is associated with unfavorable survival of the patients. Furthermore, nucleus HOXA13 expression represents an unfavorable and independent prognosis factor of histological grade 2 or Gleason grade <8 patients. Functionally, forced expression of HOXA13 obviously promotes tumor cell proliferation, migration and invasion, whereas inhibits tumor cell apoptosis.

CONCLUSION

HOXA13 is an unfavorable prognostic factor and a novel oncogene for prostate cancer.

HOXB9 Expression Correlates with Histological Grade and Prognosis in LSCC

The purpose of this study was to investigate the HOX gene expression profile in laryngeal squamous cell carcinoma (LSCC) and assess whether some genes are associated with the clinicopathological features and prognosis in LSCC patients. The HOX gene levels were tested by microarray and validated by qRT-PCR in paired cancerous and adjacent noncancerous LSCC tissue samples. The microarray testing data of 39 HOX genes revealed 15 HOX genes that were at least 2-fold upregulated and 2 that were downregulated. After qRT-PCR evaluation, the three most upregulated genes (HOXB9, HOXB13, and HOXD13) were selected for tissue microarray (TMA) analysis. The correlations between the HOXB9, HOXB13, and HOXD13 expression levels and both clinicopathological features and prognosis were analyzed. Three HOX gene expression levels were markedly increased in LSCC tissues compared with adjacent noncancerous tissues (P < 0.001). HOXB9 was found to correlate with histological grade (P < 0.01) and prognosis (P < 0.01) in LSCC. In conclusion, this study revealed that HOXB9, HOXB13, and HOXD13 were upregulated and may play important roles in LSCC. Moreover, HOXB9 may serve as a novel marker of poor prognosis and a potential therapeutic target in LSCC patients.

Exploration of the molecular mechanism of prostate cancer based on mRNA and miRNA expression profiles

Prostate cancer, the second most common cancer in men, has been rarely explored by integrating mRNA and miRNA expression profiles. In this study, we combined two mRNA expression datasets and six documented miRNAs to uncover the comprehensive molecular mechanism of prostate cancer. Results showed that a total of 30 genes were significantly differentially expressed in 49 tumor samples by comparing with 22 normal samples. Importantly, all samples from the two datasets can be clearly classified into two groups, tumor group and normal group, based on the selected differentially expressed genes (DEGs). The miRNA–mRNA regulation network indicated that 4 out of 30 DEGs can be regulated by three miRNAs. In addition, prognostic performance validation using in silico databases showed that the DEGs can significantly differentiate between low-risk and high-risk prostate cancer. In summary, multiple biological processes are probably involved in the development and progression of prostate cancer. First, dysregulation of SV2 can regulate transporter and transmembrane transporter activity and then provide the necessary nutrients for tumor cell proliferation. Second, HOXD10 can induce cell proliferation via TCF-4. Finally, dysregulation of CACNA1D can further suppress tumor apoptosis in prostate cancer. The identification of critical genes and valuable biological processes can be useful for the understanding of the molecular mechanism of prostate cancer.

Oncogenic mechanisms of HOXB13 missense mutations in prostate carcinogenesis

The recurrent germline mutation HOXB13 p.(Gly84Glu) (G84E) has recently been identified as a risk factor for prostate cancer. In a recent study, we have performed full sequencing of the HOXB13 gene in 462 Portuguese prostate cancer patients with early-onset and/or familial/hereditary disease, and identified two novel missense mutations, p.(Ala128Asp) (A128D) and p.(Phe240Leu) (F240L), that were predicted to be damaging to protein function. In the present work we aimed to investigate the potential oncogenic role of these mutations, comparing to that of the recurrent G84E mutation and wild-type HOXB13. We induced site-directed mutagenesis in a HOXB13 expression vector and established in vitro cell models of prostate carcinogenesis with stable overexpression of either the wild-type or the mutated HOXB13 variants. By performing in vitro assays we observed that, while the wild-type promotes proliferation, also observed with the F240L variant along with a decrease in apoptosis, the A128D mutation decreases apoptosis and promotes anchorage independent growth. No phenotypic impact was observed for the G84E mutation in the cell line model used. Our data show that specific HOXB13 mutations are involved in the acquisition of different cancer-associated capabilities and further support an oncogenic role for HOXB13 in prostate carcinogenesis.

HOXB9 induction of mesenchymal-to-epithelial transition in gastric carcinoma is negatively regulated by its hexapeptide motif

HOXB9, a transcription factor, plays an important role in development. While HOXB9 has been implicated in tumorigenesis and metastasis, its mechanisms are variable and its role in gastric carcinoma (GC) remains unclear. In the present study, we demonstrated that the expression of HOXB9 decreased in gastric carcinoma and was associated with malignancy and metastasis. Re-expression of HOXB9 in gastric cell lines resulted in the suppression of cell proliferation, migration, and invasion, which was accompanied by the induction of mesenchymal-to-epithelial transition (MET). Comparative sequence analysis and examination of a HOXB9 structural model indicated that three sites might possibly be involved in MET regulation. The in vitro study of HOXB9 mutants showed that these were unable to inhibit MET induction. However, when overexpressing a HOXB9 mutant lacking the hexapeptide motif, a more potent MET induction and tumor suppression was observed compared to that of the wild-type, indicating that the presence of the hexapeptide motif reduced HOXB9 MET induction and tumor suppression activity. Therefore, the results of the present study suggested that HOXB9 is a tumor suppressor in gastric carcinoma, and its activity was controlled by different regulatory mechanisms such as the hexapeptide motif as a "brake" in this case. The results of these regulatory effects could lead to either oncogenic or tumor suppressive roles of HOXB9, depending on the context of the particular type of cancer involved.

The roles of HOXB7 in promoting migration, invasion, and anti-apoptosis in gastric cancer

BACKGROUND AND AIM

The aim of this study was to compare HOXB7 expression level between gastric cancer and non-cancerous gastric tissues. Additionally, the functional effects of HOXB7, including its pro-migration or invasion and anti-apoptosis roles, were evaluated in gastric cancer cells.

METHODS

Both gene and protein expression levels of HOXB7 were examined in gastric cancer cell lines, and HOXB7 expression was compared between primary or metastatic gastric cancer tissues and chronic gastritis or intestinal metaplasia tissues. Functional studies included a wound healing assay, a Matrigel invasion assay, and an Annexin-V assay were performed, and Akt/PTEN activity was measured by western blotting.

RESULTS

Both gene and protein expression levels of HOXB7 could be clearly detected in various gastric cancer cell lines except MKN-28 cell. HOXB7 expression was significantly higher in primary or metastatic gastric cancer tissues than in chronic gastritis or intestinal metaplasia tissues. HOXB7 knockdown led to inhibition of cell invasion and migration, had an apoptotic effect, downregulated phosphor-Akt, and upregulated PTEN in AGS and SNU-638 cells. Reinforced expression of HOXB7 caused the opposite effects in MKN-28 and MKN-45 cells.

CONCLUSION

Our study suggests that HOXB7 has an oncogenic role in gastric cancer, which might be related to the modulation of Akt/PTEN activity to induce cell migration/invasion and anti-apoptotic effects.

Engrailed-2 might play an anti-oncogenic role in clear-cell renal cell carcinoma

Our preliminary study indicated that Engrailed-2 (EN2) is downregulated but also ectopically expressed in clear-cell renal cell carcinoma (CCRCC), and the absence of EN2 expression was associated with poor histological grade. However, the specific roles of EN2 in CCRCC have yet to be elucidated. In the present study, we examined the effects of inhibiting EN2 expression by human renal tubular epithelial cells (HK-2) and overexpressing EN2 by human clear-cell renal cells (786-O). Results showed that EN2 inhibition accelerated HK-2 cell proliferation, shortened the cell cycle, reduced apoptosis, and acted more invasively. By contrast, EN2 overexpression in 786-O cells decelerated the proliferative ability of 786-O, increased the percentage of cell apoptosis, and weakened the invasive ability. Overall, the results demonstrated that EN2 might play an anti-oncogenic role in oncogenesis and development of CCRCC, thereby maintaining the normal growth of human renal tubular epithelial cells.

Moving Beyond the Androgen Receptor (AR): Targeting AR-Interacting Proteins to Treat Prostate Cancer

Medical or surgical castration serves as the backbone of systemic therapy for advanced and metastatic prostate cancer, taking advantage of the importance of androgen signaling in this disease. Unfortunately, resistance to castration emerges almost universally. Despite the development and approval of new and more potent androgen synthesis inhibitors and androgen receptor (AR) antagonists, prostate cancers continue to develop resistance to these therapeutics, while often maintaining their dependence on the AR signaling axis. This highlights the need for innovative therapeutic approaches that aim to continue disrupting AR downstream signaling but are orthogonal to directly targeting the AR itself. In this review, we discuss the preclinical research that has been done, as well as clinical trials for prostate cancer, on inhibiting several important families of AR-interacting proteins, including chaperones (such as heat shock protein 90 (HSP90) and FKBP52), pioneer factors (including forkhead box protein A1 (FOXA1) and GATA-2), and AR transcriptional coregulators such as the p160 steroid receptor coactivators (SRCs) SRC-1, SRC-2, SRC-3, as well as lysine deacetylases (KDACs) and lysine acetyltransferases (KATs). Researching the effect of-and developing new therapeutic agents that target-the AR signaling axis is critical to advancing our understanding of prostate cancer biology, to continue to improve treatments for prostate cancer and for overcoming castration resistance.

Polycomb Complex PRC1 Preserves Intestinal Stem Cell Identity by Sustaining Wnt/β-Catenin Transcriptional Activity

Polycomb repressive complexes (PRCs) are among the most important gatekeepers of establishing and maintaining cell identity in metazoans. PRC1, which plays a dominant role in this context, executes its functions via multiple subcomplexes, which all contribute to H2AK119 mono-ubiquitination (H2Aubq). Despite our comprehensive knowledge of PRC1-dependent H2Aubq in embryonic stem cells and during early development, its role in adult stem cells still remains poorly characterized. Here we show that PRC1 activity is required for the integrity of the intestinal epithelium, regulating stem cell self-renewal via a cell-autonomous mechanism that is independent from Cdkn2a expression. By dissecting the PRC1-dependent transcription program in intestinal stem cells, we demonstrate that PRC1 represses a large number of non-lineage-specific transcription factors that directly affect β-catenin/Tcf transcriptional activity. Our data reveal that PRC1 preserves Wnt/β-catenin activity in adult stem cells to maintain intestinal homeostasis and supports tumor formation induced by the constitutive activation of this pathway.

EN2 in Prostate Cancer

Despite extensive efforts to identify a clinically useful diagnostic biomarker in prostate cancer, no new test has been approved by regulatory authorities. As a result, this unmet need has shifted to biomarkers that additionally indicate presence or absence of "significant" disease. EN2 is a homeodomain-containing transcription factor secreted by prostate cancer into the urine and can be detected by enzyme-linked immunoassay. EN2 may be an ideal biomarker because normal prostate tissue and benign prostatic hypertrophic cells do not secrete EN2. This review discusses the enormous potential of EN2 to address this unmet need and provide the urologist with a simple, inexpensive, and reliable prostate cancer biomarker.

Identification of Two Novel HOXB13 Germline Mutations in Portuguese Prostate Cancer Patients

The HOXB13 germline variant G84E (rs138213197) was recently described in men of European descent, with the highest prevalence in Northern Europe. The G84E mutation has not been found in patients of African or Asian ancestry, which may carry other HOXB13 variants, indicating allelic heterogeneity depending on the population. In order to gain insight into the full scope of coding HOXB13 mutations in Portuguese prostate cancer patients, we decided to sequence the entire coding region of the HOXB13 gene in 462 early-onset or familial/hereditary cases. Additionally, we searched for somatic HOXB13 mutations in 178 prostate carcinomas to evaluate their prevalence in prostate carcinogenesis. Three different patients were found to carry in their germline DNA two novel missense variants, which were not identified in 132 control subjects. Both variants are predicted to be deleterious by different in silico tools. No somatic mutations were found. These findings further support the hypothesis that different rare HOXB13 mutations may be found in different ethnic groups. Detection of mutations predisposing to prostate cancer may require re-sequencing rather than genotyping, as appropriate to the population under investigation.

Overexpression of HOXA13 as a potential marker for diagnosis and poor prognosis of hepatocellular carcinoma

HOXA13 is a member of homeobox genes that encode transcription factors regulating embryonic development and cell fate. Abnormal HOXA13 expression was reported in hepatocellular carcinoma (HCC), but its correlation with tumor angiogenesis and prognosis still remain unclear. This study was aimed to uncover the expression, diagnostic and prognostic significance of HOXA13 in HCC. Immunohistochemistry was performed to detect HOXA13 expression in HCC and corresponding paracarcinomatous tissues from 90 patients. Enzyme-linked immunosorbent assay was used to detect serum HOXA13 in 90 HCC patients and 20 healthy volunteers. Receiver operating characteristics was analyzed to calculate diagnostic accuracy of serum HOXA13, alpha-fetoprotein (AFP) and their combination. Immunoreactivity of HOXA13 was detected in 72.2% of HCC, and 12.2% of adjacent non-cancerous samples. HOXA13 expression was significantly associated with tumor size, microvascular invasion, pathological grade, tumor capsula status, AFP level, tumor-node-metastasis stage and positively correlated with VEGF (p < 0.001) and microvessel density (p < 0.001). The combination of serum HOXA13 and AFP had a markedly higher area under the curve than HOXA13 alone. HOXA13 expression was associated with unfavorable overall survival (OS) (p < 0.001) and disease-free survival (DFS) (p < 0.001). Multivariate analysis indicated that patients with HOXA13-expressing tumors had a significantly shorter OS (p = 0.030) and DFS (p = 0.005) than those with HOXA13-negative tumors. Thus, HOXA13 expression possibly plays an important role in tumor angiogenesis, progression and prognosis of HCC. Moreover, we demonstrate that serum HOXA13 may serve as a biomarker for early HCC diagnosing and predicting outcome.

Dysregulation of the homeobox transcription factor gene HOXB13: role in prostate cancer

Prostate cancer (PC) is the most common noncutaneous cancer in men, and epidemiological studies suggest that about 40% of PC risk is heritable. Linkage analyses in hereditary PC families have identified multiple putative loci. However, until recently, identification of specific risk alleles has proven elusive. Cooney et al used linkage mapping and segregation analysis to identify a putative risk locus on chromosome 17q21-22. In search of causative variant(s) in genes from the candidate region, a novel, potentially deleterious G84E substitution in homeobox transcription factor gene HOXB13 was observed in multiple hereditary PC families. In follow-up testing, the G84E allele was enriched in cases, especially those with an early diagnosis or positive family history of disease. This finding was replicated by others, confirming HOXB13 as a PC risk gene. The HOXB13 protein plays diverse biological roles in embryonic development and terminally differentiated tissue. In tumor cell lines, HOXB13 participates in a number of biological functions, including coactivation and localization of the androgen receptor and FOXA1. However, no consensus role has emerged and many questions remain. All HOXB13 variants with a proposed role in PC risk are predicted to damage the protein and lie in domains that are highly conserved across species. The G84E variant has the strongest epidemiological support and lies in a highly conserved MEIS protein-binding domain, which binds cofactors required for activation. On the basis of epidemiological and biological data, the G84E variant likely modulates the interaction between the HOXB13 protein and the androgen receptor, as well as affecting FOXA1-mediated transcriptional programming. However, further studies of the mutated protein are required to clarify the mechanisms by which this translates into PC risk.

HOXB13 regulates the prostate-derived Ets factor: implications for prostate cancer cell invasion

HOXB13 has been shown to enhance the invasive potential of breast and endometrial tumors. HOXB13 is also abundant in castration-resistant prostate tumors. To determine the invasive potential of HOXB13 in prostate tumors, highly metastatic PC3 prostate cancer cells were manipulated to express HOXB13 and/or the prostate-derived Ets factor (PDEF). The PDEF is believed to reduce the invasive potential of various tumors, including prostate tumors. To further demonstrate the functional correlation between HOXB13 and PDEF, transwell invasion and gelatin zymography assays were performed. In addition, the western blot analysis was used to demonstrate the expression of PDEF target proteins involved in cancer cell migration and invasion, MMP-9 and survivin. According to the results, HOXB13 promoted PC3 cell migration and invasion. The DNA microarray analysis demonstrated that HOXB13 significantly suppressed the expression of the PDEF. Accordingly, the expression of MMP-9 and survivin was regulated by HOXB13. In addition, HOXB13 promoted the invasive potential of PC3 cells while inhibiting the PDEF. The coexpression of HOXB13 and the PDEF led to moderate retardation of the number of invasive cells, indicating that HOXB13 functionally counteracted cell invasion by reducing PDEF expression. The western blot analysis demonstrated that HOXB13 counteracted the PDEF-mediated inhibition of the expression of PDEF target proteins such as MMP-9 and survivin. The results suggest that the HOXB13-mediated promotion of tumor cell invasion is accomplished mainly through the downregulation of PDEF expression.

HOXB13 G84E-related familial prostate cancers: a clinical, histologic, and molecular survey

Recent genetic epidemiologic studies identified a germline mutation in the homeobox transcription factor, HOXB13 G84E, which is associated with markedly increased risk for prostate cancer, particularly early-onset hereditary prostate cancer. The histomorphologic and molecular features of cancers arising in such carriers have not been studied. Here, we reviewed prostatectomy specimens from 23 HOXB13 G84E mutation carriers, mapping the total cancer burden by anatomically distinct cancer focus and evaluating morphologic features. We also assessed basic molecular subtypes for all cancer foci (ERG/SPINK1 status) by dual immunohistochemistry staining on full sections. The cohort showed a median age of 58 years, a median serum PSA level of 5.7 ng/mL, and a median of 6 cancer foci (range, 1 to 14) per case. Of evaluable cases, dominant foci were Gleason score 6 in 23%, 3+4=7 in 41%, 4+3=7 in 23%, and ≥8 in 14%; biochemical recurrence was observed in 1 case over a median of 36 months follow-up. Histologic review found a high prevalence of cases showing cancers with a spectrum of features previously described with pseudohyperplastic carcinomas, with 45% of cases showing a dominant focus with such features. Molecular subtyping revealed a strikingly low prevalence of ERG cancer with increased prevalence of SPINK1 cancer (dominant focus ERG 17%, SPINK1 26%, ERG/SPINK1 52%, single ERG/SPINK1 focus 4%). One ERG/SPINK1 dominant focus showed aberrant p63 immunophenotype. In summary, HOXB13 G84E variant-related prostate cancers show frequent pseudohyperplastic-type features and markedly low prevalence of ERG cancers relative to unselected cases and, especially, to early-onset cohorts. These findings suggest that novel molecular pathways may drive disease in HOXB13 G84E carriers.

HOXB13 contributes to G1/S and G2/M checkpoint controls in prostate

HOXB13 is a homeobox protein that is expressed in normal adult prostate and colon tissues; however, its deregulated expression was evidenced in various malignancies. To characterize the putative role of HOXB13 in cell cycle progression, we performed overexpression and siRNA-mediated knockdown studies in PC-3 and LNCaP cells. Immunohistochemistry (IHC) analyses were also performed using formalin-fixed, paraffin-embedded tissues containing normal, H-PIN and PCa sections from 20 radical prostatectomy specimens. Furthermore, when the role of HOXB13 during cell cycle progression, association with cyclins, cell growth and colony formation using real-time cell proliferation were assessed, we observed that ectopic expression of HOXB13 accumulated cells at G1 through decreasing the cyclin D1 level by promoting its ubiquitination and degradation. This loss slowed S phase entry in both cell lines examined, with an associated decrease in pRb((S780) and (S795)) phosphorylations. Contrary, siRNA-mediated depletion of HOXB13 expression noticeably increased cyclin levels, stabilized E2F1 and CDC25C, subsequent to increased pRb phosphorylations. This increase in Cyclin B1 and CDC25C both together facilitated activation of cyclin B complex via dephosphorylating CDK1((T14Y15)), and resumed the G2/M transition after nocodazole synchronization. Despite an increase in the total expression level and cytoplasmic retention of HOXB13 in H-PIN and PCa samples that were observed via IHC evaluation of prostate tissues, HOXB13 depletion facilitated to an increase in PC-3 and LNCaP cell proliferation. Thus, we suggest that HOXB13 expression is required for cell cycle regulation, and increases by an unknown mechanism consequent to its functional loss in cancer.

Comprehensive functional annotation of 77 prostate cancer risk loci

Genome-wide association studies (GWAS) have revolutionized the field of cancer genetics, but the causal links between increased genetic risk and onset/progression of disease processes remain to be identified. Here we report the first step in such an endeavor for prostate cancer. We provide a comprehensive annotation of the 77 known risk loci, based upon highly correlated variants in biologically relevant chromatin annotations--we identified 727 such potentially functional SNPs. We also provide a detailed account of possible protein disruption, microRNA target sequence disruption and regulatory response element disruption of all correlated SNPs at r(2) ≥ 0.88%. 88% of the 727 SNPs fall within putative enhancers, and many alter critical residues in the response elements of transcription factors known to be involved in prostate biology. We define as risk enhancers those regions with enhancer chromatin biofeatures in prostate-derived cell lines with prostate-cancer correlated SNPs. To aid the identification of these enhancers, we performed genomewide ChIP-seq for H3K27-acetylation, a mark of actively engaged enhancers, as well as the transcription factor TCF7L2. We analyzed in depth three variants in risk enhancers, two of which show significantly altered androgen sensitivity in LNCaP cells. This includes rs4907792, that is in linkage disequilibrium (r(2) = 0.91) with an eQTL for NUDT11 (on the X chromosome) in prostate tissue, and rs10486567, the index SNP in intron 3 of the JAZF1 gene on chromosome 7. Rs4907792 is within a critical residue of a strong consensus androgen response element that is interrupted in the protective allele, resulting in a 56% decrease in its androgen sensitivity, whereas rs10486567 affects both NKX3-1 and FOXA-AR motifs where the risk allele results in a 39% increase in basal activity and a 28% fold-increase in androgen stimulated enhancer activity. Identification of such enhancer variants and their potential target genes represents a preliminary step in connecting risk to disease process.

Importance of HOX genes in normal prostate gland formation, prostate cancer development and its early detection

The aims of this paper were to review the published literature on the role of HOX genes in the development of the normal prostate gland and in prostate cancer and to discuss the potential role of the HOX family member, Engrailed-2 (EN2), as a diagnostic test of PCa. Hox genes were first described in the fruit fly Drosphila melanogaster, where they specify the body plan and control the formation of body segments. They belong to a family of homeodomain-containing transcription factors that determine cell and tissue identity during normal embryonic development. They have been shown to be re-expressed by several different types of cancers. Studies have shown that different Hox genes are responsible for the development of the separate lobes of the prostate gland, the seminal vesicles and the epididymis. All HOX13 paralogues are expressed in the adult human prostate, suggesting the possibility of similarities between the function and expression of HOX genes within urological structures at similar anterior-posterior positions. The oncogenic and tumour suppressor signalling pathways associated with PCa converge on the HOX gene network, which ultimately controls gene expression, affecting tumour formation and metastatic progression. The Engrailed genes (EN1 and EN2) from the HOX gene family show a very high degree of functional conservation during embryonic development. Urinary EN2 is being investigated as a potential diagnostic marker of early PCa. It is secreted into the urine by PCa cells but not by normal prostatic tissue. A recent study has shown an association between urinary EN2 levels and cancer volume in radical prostatectomy specimens. The ability to predict tumour volume could inform the treatment decision-making process for patients with localized PCa choosing between active surveillance and radical treatment options.

Regulation of DU145 prostate cancer cell growth by Scm-like with four mbt domains 2

Mammalian SFMBTs have been considered to be polycomb group repressors. However, molecular mechanisms underlying mammalian SFMBTs-mediated gene regulation and their biological function have not been characterized. In the present study, we identified YY1 and methylated histones as interacting proteins of human SFMBT2. We also found that human SFMBT2 binds preferentially to methylated histone H3 and H4 that are associated with transcriptional repression. Using DU145 prostate cancer cells as a model, we showed that SFMBT2 has a transcriptional repression activity on HOXB13 gene expression. In addition, occupancy of SFMBT2 coincided with enrichment of diand tri-methylated H3K9 and H4K20 as well as tri-methylated H3K27 at the HOXB13 gene promoter. When SFMBT2 was depleted by siRNA in DU145 prostate cancer cells, significant up-regulation of HOXB13 gene expression and decreased cell growth were observed. Collectively, our findings indicate that human SFMBT2 may regulate cell growth via epigenetic regulation of HOXB13 gene expression in DU145 prostate cancer cells.

HOXB13 mutation and prostate cancer: studies of siblings and aggressive disease

BACKGROUND

Recent work detected for the first time a high-risk prostate cancer mutation, in homeobox B13 (HOXB13) among European-Americans.

METHODS

We further evaluated this G84E missense mutation (rs138213197) in two genetic association studies of prostate cancer: a family-based study of brothers and a case-control study of more aggressive disease (N = 2,665 total). We then calculated overall impact of this mutation by pooling all published studies of European-Americans.

RESULTS

In our studies, the mutation was found exclusively among men with prostate cancer (carrier frequency = 1.48%) or unaffected brothers of cases carrying the mutation (frequency = 0.34%), and carrying the mutation gave an OR for disease = 4.79 (P = 0.01). The G84E mutation was more common among men with an earlier age of onset (≤55 years) or a family history of prostate cancer. We also observed for the first time an African-American case carrying the G84E mutation, although at HOXB13 both of his chromosomes were of European-American ancestry. The pooled analysis also indicated that carrying the G84E mutation results in an almost five-fold increase in risk of prostate cancer (P = 3.5 × 10(-17)), and this risk is even higher among cases with an early age of prostate cancer onset (≤55 years) or a family history of disease: a test of heterogeneity across these strata gives P < 1 × 10(-5).

CONCLUSIONS

The HOXB13 mutation substantially increases risk of early onset, familial prostate cancer in European-American men.

IMPACT

Testing for the G84E mutation in men with a positive family history may help distinguish those who merit more regular screening for prostate cancer.