Epigenetic inactivation of inhibitor of differentiation 4 (Id4) correlates with prostate cancer

Cryptotanshinone Protects against PCOS-Induced Damage of Ovarian Tissue via Regulating Oxidative Stress, Mitochondrial Membrane Potential, Inflammation, and Apoptosis via Regulating Ferroptosis

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women of childbearing age. Cryptotanshinone (CRY) has been shown to be effective in reversing reproductive disorders, but whether it can be used in the treatment of polycystic ovary syndrome remains unclear. We aimed to explore whether the mechanism of cryptotanshinone (CRY) in the treatment of polycystic ovary syndrome (PCOS) can be driven via regulating ferroptosis. A rat model of PCOS was established by daily injection of human chorionic gonadotropin and insulin for 22 days. An in vitro model of ischemia-reperfusion (IR) of granulosa cells was established. The in vitro and rat models of PCOS were subjected to different treatments including ferroptosis activators and inhibitors, CRY, and MAPK inhibitor. Oxidative stress was evaluated by measuring the activities of SOD, MDA, and GSH-PX. Total body weight and ovarian weight, as well as the levels of LH and the LH to FSH ratio, significantly increased in rats with PCOS, compared with controls. The expression of Bax was increased in PCOS tissues while PGC1α, NFR1, GPX4, catalase p-ERK, and Bcl-2 were all downregulated. Ferroptosis activator, erastin, had effects similar to those of PCOS while the contrary was found with CRY and ferroptosis inhibitor treatment groups. In vitro, CRY inhibited oxidative stress, MMP, and NF-κB and activated MAPK/ERK signaling by regulating ferroptosis. Overall, this study indicated that CRY protects against PCOS-induced damage of the ovarian tissue, via regulating oxidative stress, MMP, inflammation, and apoptosis via regulating ferroptosis.

The helix-loop-helix transcriptional regulator Id4 is required for terminal differentiation of luminal epithelial cells in the prostate

Inhibitor of differentiation 4 (Id4), a member of the helix-loop-helix family of transcriptional regulators has emerged as a tumor suppressor in prostate cancer. In this study we investigated the effect of loss of Id4 (Id4-/-) on mouse prostate development. Histological analysis was performed on prostates from 25 days, 3 months and 6 months old Id4-/- mice. Expression of Amacr, Ck8, Ck18, Fkbp51, Fkbp52, androgen receptor, Pten, sca-1 and Nkx3.1 was investigated by immunohistochemistry. Results were compared to the prostates from Nkx3.1-/- mice. Id4-/- mice had smaller prostates with fewer and smaller tubules. Subtle PIN like lesions were observed at 6mo. Decreased Nkx3.1 and Pten and increased stem cell marker sca-1, PIN marker Amacr and basal cell marker p63 was observed at all ages. Persistent Ck8 and Ck18 expression suggested that loss of Id4 results in epithelial commitment but not terminal differentiation in spite of active Ar. Loss of Id4 attenuates normal prostate development and promotes hyperplasia/ dysplasia with PIN like lesions. The results suggest that loss of Id4 maintains stem cell phenotype of "luminal committed basal cells", identifying a unique prostate developmental pathway regulated by Id4.

Identification of potential and novel target genes in pituitary prolactinoma by bioinformatics analysis

Pituitary prolactinoma is one of the most complicated and fatally pathogenic pituitary adenomas. Therefore, there is an urgent need to improve our understanding of the underlying molecular mechanism that drives the initiation, progression, and metastasis of pituitary prolactinoma. The aim of the present study was to identify the key genes and signaling pathways associated with pituitary prolactinoma using bioinformatics analysis. Transcriptome microarray dataset GSE119063 was downloaded from Gene Expression Omnibus (GEO) database. Limma package in R software was used to screen DEGs. Pathway and Gene ontology (GO) enrichment analysis were conducted to identify the biological role of DEGs. A protein-protein interaction (PPI) network was constructed and analyzed by using HIPPIE database and Cytoscape software. Module analyses was performed. In addition, a target gene-miRNA regulatory network and target gene-TF regulatory network were constructed by using NetworkAnalyst and Cytoscape software. Finally, validation of hub genes by receiver operating characteristic (ROC) curve analysis. A total of 989 DEGs were identified, including 461 up regulated genes and 528 down regulated genes. Pathway enrichment analysis showed that the DEGs were significantly enriched in the retinoate biosynthesis II, signaling pathways regulating pluripotency of stem cells, ALK2 signaling events, vitamin D3 biosynthesis, cell cycle and aurora B signaling. Gene Ontology (GO) enrichment analysis showed that the DEGs were significantly enriched in the sensory organ morphogenesis, extracellular matrix, hormone activity, nuclear division, condensed chromosome and microtubule binding. In the PPI network and modules, SOX2, PRSS45, CLTC, PLK1, B4GALT6, RUNX1 and GTSE1 were considered as hub genes. In the target gene-miRNA regulatory network and target gene-TF regulatory network, LINC00598, SOX4, IRX1 and UNC13A were considered as hub genes. Using integrated bioinformatics analysis, we identified candidate genes in pituitary prolactinoma, which might improve our understanding of the molecular mechanisms of pituitary prolactinoma.

ID1 and ID4 Are Biomarkers of Tumor Aggressiveness and Poor Outcome in Immunophenotypes of Breast Cancer

Simple Summary

Inhibitor of differentiation (ID) proteins are essential to promote proliferation during embryonic development, but they are silenced in most adult tissues. Evidence to date shows ID1 expression in many tumor types, including breast cancer. However, the role of the remaining ID family members, especially ID4, in breast cancer remains unclear. In this work, we aimed to assess the four ID genes expression in breast cancer cell lines and a long series of breast cancer samples and correlate them with clinicopathological features and patients’ survival. We observed a significantly higher expression of ID4 in tumor cell lines than the healthy breast epithelium cell line. We confirmed that the overexpression of ID1 and ID4 correlated with more aggressive phenotypes and poor survival in breast cancer patients’ samples. Our results support the importance of ID proteins as targets for the development of anti-cancer drugs.

Abstract

Inhibitor of differentiation (ID) proteins are a family of transcription factors that contribute to maintaining proliferation during embryogenesis as they avoid cell differentiation. Afterward, their expression is mainly silenced, but their reactivation and contribution to tumor development have been suggested. In breast cancer (BC), the overexpression of ID1 has been previously described. However, whether the remaining ID genes have a specific role in this neoplasia is still unclear. We studied the mRNA expression of all ID genes by q RT-PCR in BC cell lines and 307 breast carcinomas, including all BC subtypes. Our results showed that ID genes are highly expressed in all cell lines tested. However, ID4 presented higher expression in BC cell lines compared to a healthy breast epithelium cell line. In accordance, ID1 and ID4 were predominantly overexpressed in Triple-Negative and HER2-enriched samples. Moreover, high levels of both genes were associated with larger tumor size, histological grade 3, necrosis and vascular invasion, and poorer patients’ outcomes. In conclusion, ID1 and ID4 may act as biomarkers of tumor aggressiveness and worse prognosis in breast cancer, and they could be used as potential targets for new treatments discover.

UVB induces cutaneous squamous cell carcinoma progression by de novo ID4 methylation via methylation regulating enzymes

BACKGROUND

Little is known about whether UVB can directly influence epigenetic regulatory pathways to induce cutaneous squamous cell carcinoma (CSCC). This study aimed to identify epigenetic-regulated signalling pathways through global methylation and gene expression profiling and to elucidate their function in CSCC development.

METHODS

Global DNA methylation profiling by reduced representation bisulfite sequencing (RRBS) and genome-wide gene expression analysis by RNA sequencing (RNA-seq) in eight pairs of matched CSCC and adjacent normal skin tissues were used to investigate the potential candidate gene(s). Clinical samples, animal models, cell lines, and UVB irradiation were applied to validate the mechanism and function of the genes of interest.

FINDINGS

We identified the downregulation of the TGF-β/BMP-SMAD-ID4 signalling pathway in CSCC and increased methylation of inhibitor of DNA binding/differentiation 4 (ID4). In normal human and mouse skin tissues and cutaneous cell lines, UVB exposure induced ID4 DNA methylation, upregulated DNMT1 and downregulated ten-eleven translocation (TETs). Similarly, we detected the upregulation of DNMT1 and downregulation of TETs accompanying ID4 DNA methylation in CSCC tissues. Silencing of DNMT1 and overexpression of TET1 and TET2 in A431 and Colo16 cells led to increased ID4 expression. Finally, we showed that overexpression of ID4 reduced cell proliferation, migration, and invasion, and increased apoptosis in CSCC cell lines and reduced tumourigenesis in mouse models.

INTERPRETATION

The results indicate that ID4 is downregulated by UVB irradiation via DNA methylation. ID4 acts as a tumour suppressor gene in CSCC development.

FUNDING

CAMS Innovation Fund for Medical Sciences (CIFMS) (2016-I2M-3-021, 2017-I2M-1-017), the Natural Science Foundation of Jiangsu Province (BK20191136), and the Fundamental Research Funds for the Central Universities (3332019104).

Expression and Prognostic Value of Id-4 in Patients with Esophageal Squamous Cell Carcinoma

Background

Our previous study demonstrated that Id-1 may promote the tumorigenicity of esophageal squamous cell carcinoma (ESCC). Id-4 is another member of Id family, which is rare to be studied in ESCC. In this study, we investigated the expression of Id-4 in human ESCC specimens and determined whether Id-4 expression was associated with the clinicopathologic characteristic and the prognosis of ESCC patients.

Methods

We examined Id-4 expression using immunohistochemistry in 92 ESCC tissues and adjacent normal tissues. The association between Id-4 expression and clinical parameters and survival was evaluated by statistical analysis. Cox regression analyses were conducted to identify prognostic factors associated with overall survival (OS). In addition, we explored the functional mechanism of Id-4 in ESCC.

Results

Id-4 expression was significantly downregulated in ESCC tissues compared with adjacent normal tissues. The expression of Id-4 was associated negatively with pT stage (p=0.002), AJCC stage (p=0.008) and histologic differentiation (p<0.001). OS was more unfavorable in patients with low expression of Id-4 than those with high expression of ESCC patients (p=0.007). In subgroup analysis, low expression of Id-4 could reveal unfavorable OS of patients with pT1b/T2 stage (p=0.024) or with pN0/N1 stage (p=0.004). By univariate analysis, pT stage and Id-4 expression showed statistically significant associations with OS (p=0.025, p=0.01, respectively). By multivariate analysis, Id-4 expression was an independent prognostic factor in ESCC (p =0.038). In addition, we observed that Id-4 could decrease the levels of the p-Smad2, p-Smad3 and TGF-β1 in both Eca109 and TE1 cells, indicating Id-4 may inactivate the TGF-β signaling pathway.

Conclusion

Low expression of Id-4 suggested unfavorable prognosis for ESCC patients and could identify the prognosis in patients of early-stage tumors. The potential mechanism for Id-4’s tumor suppressor role in ESCC may be related to its inhibitory effect on TGF-β signaling pathway. Thus, we believe that Id-4 may be a promising prognostic marker and a therapeutic target in ESCC.

LncRNA SNHG7 promotes pancreatic cancer proliferation through ID4 by sponging miR-342-3p

BACKGROUND

Small nucleolar RNA host gene 7 (SNHG7) is a novel identified oncogenic gene in tumorigenesis. However, the role that SNHG7 plays in pancreatic cancer (PC) remains unclear. In this study, we aimed to investigate the functional effects of SNHG7 on PC and the possible mechanism.

METHODS

The expression levels of SNHG7 in tissues and cell lines were measured by RT-qPCR. Cell viability, apoptosis, migration and invasion were examined to explore the function of SNHG7 on PC. Bioinformatics methods were used to predict the target genes. The mechanism was further investigated by transfection with specific si-RNA, miRNA mimics or miRNA inhibitor. Tumor xenograft was carried out to verify the effects of SNHG7 in vivo.

RESULTS

We found that SNHG7 was overexpressed in both PC tissues and cell lines. High expression level of SNHG7 was correlated with the poor prognosis. SNHG7 knockdown inhibited the proliferation, migration and invasion of PC cells. Moreover, SNHG7 was found to regulate the expression of ID4 via sponging miR-342-3p. Additionally, this finding was supported by in vivo experiments.

CONCLUSIONS

LncRNA SNHG7 was overexpressed in PC tissues, and knockdown of SNHG7 suppressed PC cell proliferation, migration and invasion via miR-342-3p/ID4 axis. The results indicated that SNHG7 as a potential target for clinical treatment of PC.

HCRP1, ID4 and Glypican-3: an optimal panel of biomarkers for diagnosis of hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide with high morbidity and mortality. The aim of this study was to assess the diagnostic role of HCC related protein 1 (HCRP1) and inhibitor of DNA Binding 4 (ID4) as novel reliable markers for HCC diagnosis.

METHODS

Immunohistochemistry for HCRP1, ID4 and Glypican-3 (GPC-3) was performed in 98 cases of HCCs, 15 large regenerative nodules arising in cirrhotic livers, 12 hepatocellular adenomas (HCA), 10 focal nodular hyperplasias (FNH), and 20 specimens of normal liver tissues (NL).

RESULTS

HCRP1 immunoactivity was decreased in 64 of 98 (65.3%) HCC cases but present in almost all of the benign liver nodules (56/57, 98.2%, P < 0.001). 68 of 98 (69.4%) and 70 of 98 (71.4%) HCC cases were positive for ID4 and GPC-3, respectively, which were much higher than in benign lesions. Even though HCRP1 is highly specific (98.25%) in differentiating well differentiated HCC (WDHCC) from benign liver nodules, it has only a limited value because of its low sensitivity (37.5%), neither for the ID4, GPC-3 alone or combination (P > 0.05). The expression of HCRP1 alone could efficiently distinguish WDHCC from moderate-poorly differentiated HCC (M-PHCC), and the combination of using either two or three markers could notably increase the diagnosis accuracy (P < 0.05).

CONCLUSION

HCRP1 and ID4 represent potentially novel valuable biomarkers for distinguishing HCC from benign liver nodules, and it is recommended to use the combination of HCRP1, ID4 and GPC-3 as a panel in HCC differentiation estimation.

Intra-tumoral delivery of functional ID4 protein via PCL/maltodextrin nano-particle inhibits prostate cancer growth

ID4, a helix loop helix transcriptional regulator has emerged as a tumor suppressor in prostate cancer. Epigenetic silencing of ID4 promotes prostate cancer whereas ectopic expression in prostate cancer cell lines blocks cancer phenotype. To directly investigate the anti-tumor property, full length human recombinant ID4 encapsulated in biodegradable Polycaprolactone/Maltodextrin (PCL-MD) nano-carrier was delivered to LNCaP cells in which the native ID4 was stably silenced (LNCaP(-)ID4). The cellular uptake of ID4 resulted in increased apoptosis, decreased proliferation and colony formation. Intratumoral delivery of PCL-MD ID4 into growing LNCaP(-)ID4 tumors in SCID mice significantly reduced the tumor volume compared to the tumors treated with chemotherapeutic Docetaxel. The study supports the feasibility of using nano-carrier encapsulated ID4 protein as a therapeutic. Mechanistically, ID4 may assimilate multiple regulatory pathways for example epigenetic re-programming, integration of multiple AR co-regulators or signaling pathways resulting in tumor suppressor activity of ID4.

Inactivation of ID4 promotes a CRPC phenotype with constitutive AR activation through FKBP52

Castration-resistant prostate cancer (CRPC) is the emergence of prostate cancer cells that have adapted to the androgen-depleted environment of the prostate. In recent years, targeting multiple chaperones and co-chaperones (e.g., Hsp27, FKBP52) that promote androgen receptor (AR) signaling and/or novel AR regulatory mechanisms have emerged as promising alternative treatments for CRPC. We have shown that inactivation of inhibitor of differentiation 4 (ID4), a dominant-negative helix loop helix protein, promotes de novo steroidogenesis and CRPC with a gene expression signature that resembles constitutive AR activity in castrated mice. In this study, we investigated the underlying mechanism through which loss of ID4 potentiates AR signaling. Proteomic analysis between prostate cancer cell line LNCaP (L+ns) and LNCaP lacking ID4 (L(-)ID4) revealed elevated levels of Hsp27 and FKBP52, suggesting a role for these AR-associated co-chaperones in promoting constitutively active AR signaling in L(-)ID4 cells. Interestingly, protein interaction studies demonstrated a direct interaction between ID4 and the 52-kDa FK506-binding protein (FKBP52) in vitro, but not with AR. An increase in FKBP52-dependent AR transcriptional activity was observed in L(-)ID4 cells. Moreover, pharmacological inhibition of FKBP52-AR signaling, by treatment with MJC13, attenuated the tumor growth, weight, and volume in L(-)ID4 xenografts. Together, our results demonstrate that ID4 selectively regulates AR activity through direct interaction with FKBP52, and its loss, promotes CRPC through FKBP52-mediated AR signaling.

Id4 promotes cell proliferation in hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is a common malignant tumor in the world, especially in China. As a member of the inhibitor of differentiation (Id) family, Id4 has been reported to function in many cancer types, but relatively little is known about its role in HCC. The purpose of this study was to investigate the potential relationship between Id4 and HCC development and the underlying mechanism involving the function of Id4 in HCC.

Methods

We used quantitative real-time polymerase chain reaction and Western blotting to examine the RNA and protein expression of Id4. In addition, we used Cell Counting Kit-8 assay and colony formation assay to identify the function of Id4 in the regulation of cell proliferation in human HCC.

Results

We found that the expression of Id4 protein was up-regulated in tumor tissues from HCC patients. Overexpression of Id4 promoted HCC cell proliferation, clonogenicity in vitro, and tumorigenicity in vivo. Id4 knockdown experiments showed that silencing Id4 blocked the proliferation and colony formation ability of HCC cells in vitro. Furthermore, overexpression of CCAAT/enhancer-binding protein β inhibited Id4 expression in HCC cells.

Conclusion

Id4 may be developed as a potent therapeutic agent for the treatment of HCC, but more details about the underlying mechanisms of action are needed.

ID4 promotes AR expression and blocks tumorigenicity of PC3 prostate cancer cells

Deregulation of tumor suppressor genes is associated with tumorigenesis and the development of cancer. In prostate cancer, ID4 is epigenetically silenced and acts as a tumor suppressor. In normal prostate epithelial cells, ID4 collaborates with androgen receptor (AR) and p53 to exert its tumor suppressor activity. Previous studies have shown that ID4 promotes tumor suppressive function of AR whereas loss of ID4 results in tumor promoter activity of AR. Previous study from our lab showed that ectopic ID4 expression in DU145 attenuates proliferation and promotes AR expression suggesting that ID4 dependent AR activity is tumor suppressive. In this study, we examined the effect of ectopic expression of ID4 on highly malignant prostate cancer cell, PC3. Here we show that stable overexpression of ID4 in PC3 cells leads to increased apoptosis and decreased cell proliferation and migration. In addition, in vivo studies showed a decrease in tumor size and volume of ID4 overexpressing PC3 cells, in nude mice. At the molecular level, these changes were associated with increased androgen receptor (AR), p21, and AR dependent FKBP51 expression. At the mechanistic level, ID4 may regulate the expression or function of AR through specific but yet unknown AR co-regulators that may determine the final outcome of AR function.

ID4 controls luminal lineage commitment in normal mammary epithelium and inhibits BRCA1 function in basal-like breast cancer

Inhibitor of differentiation (ID) proteins are key regulators of development and tumorigenesis. One member of this family, ID4, controls lineage commitment during mammary gland development by acting upstream of key developmental pathways. Recent evidence suggests an emerging role for ID4 as a lineage-dependent proto-oncogene that is overexpressed and amplified in a subset of basal-like breast cancers (BLBCs), conferring poor prognosis. Several lines of evidence suggest ID4 may suppress BRCA1 function in BLBC and in doing so, define a subset of BLBC patients who may respond to therapies traditionally used in BRCA1-mutant cancers. This review highlights recent advances in our understanding of the requirement for ID4 in mammary lineage commitment and the role for ID4 in BLBC. We address current shortfalls in this field and identify important areas of future research.

EZH2 dependent H3K27me3 is involved in epigenetic silencing of ID4 in prostate cancer

Inhibitor of DNA binding/differentiation protein 4 (ID4) is dominant negative helix loop helix transcriptional regulator is epigenetically silenced due to promoter hyper-methylation in many cancers including prostate. However, the underlying mechanism involved in epigenetic silencing of ID4 is not known. Here, we demonstrate that ID4 promoter methylation is initiated by EZH2 dependent tri-methylation of histone 3 at lysine 27 (H3K27me3). ID4 expressing (LNCaP) and non-expressing (DU145 and C81) prostate cancer cell lines were used to investigate EZH2, H3K27me3 and DNMT1 enrichment on ID4 promoter by Chromatin immuno-precipitation (ChIP). Enrichment of EZH2, H3K27Me3 and DNMT1 in DU145 and C81 cell lines compared to ID4 expressing LNCaP cell line. Knockdown of EZH2 in DU145 cell line led to re-expression of ID4 and decrease in enrichment of EZH2, H3K27Me3 and DNMT1 demonstrating that ID4 is regulated in an EZH2 dependent manner. ChIP data on prostate cancer tissue specimens and cell lines suggested EZH2 occupancy and H3K27Me3 marks on the ID4 promoter. Collectively, our data indicate a PRC2 dependent mechanism in ID4 promoter silencing in prostate cancer through recruitment of EZH2 and a corresponding increase in H3K27Me3. Increased EZH2 but decreased ID4 expression in prostate cancer strongly supports this model.

Inhibitor of differentiation 4 (ID4) acts as an inhibitor of ID-1, -2 and -3 and promotes basic helix loop helix (bHLH) E47 DNA binding and transcriptional activity

The four known ID proteins (ID1-4, Inhibitor of Differentiation) share a homologous helix loop helix (HLH) domain and act as dominant negative regulators of basic-HLH transcription factors. ID proteins also interact with many non-bHLH proteins in complex networks. The expression of ID proteins is increasingly observed in many cancers. Whereas ID-1, ID-2 and ID-3, are generally considered as tumor promoters, ID4 on the contrary has emerged as a tumor suppressor. In this study we demonstrate that ID4 heterodimerizes with ID-1, -2 and -3 and promote bHLH DNA binding, essentially acting as an inhibitor of inhibitors of differentiation proteins. Interaction of ID4 was observed with ID1, ID2 and ID3 that was dependent on intact HLH domain of ID4. Interaction with bHLH protein E47 required almost 3 fold higher concentration of ID4 as compared to ID1. Furthermore, inhibition of E47 DNA binding by ID1 was restored by ID4 in an EMSA binding assay. ID4 and ID1 were also colocalized in prostate cancer cell line LNCaP. The alpha helix forming alanine stretch N-terminal, unique to HLH ID4 domain was required for optimum interaction. Ectopic expression of ID4 in DU145 prostate cancer line promoted E47 dependent expression of CDKNI p21. Thus counteracting the biological activities of ID-1, -2 and -3 by forming inactive heterodimers appears to be a novel mechanism of action of ID4. These results could have far reaching consequences in developing strategies to target ID proteins for cancer therapy and understanding biologically relevant ID-interactions.

Interferon inducible antiviral MxA is inversely associated with prostate cancer and regulates cell cycle, invasion and Docetaxel induced apoptosis

BACKGROUND

The interferon inducible Myxovirus (influenza virus) resistance A (MxA) is considered as a key mediator of the interferon-induced antiviral response. Mx proteins contain the typical GTP-binding motif and show significant homology to dynamin family of GTPases. Strong interaction of MxA with tubulin suggests that Mx proteins could be involved in mitosis. Studies have shown that MxA inhibit tumor motility/metastasis and virus induced apoptosis. However, the clear association between MxA expression and cancer remains unknown. Meta-analysis suggested that MxA expression was inversely correlated with prostate cancer (PCa). In this study, we demonstrate the expression MxA in PCa and its functional significance on the cancer phenotype.

METHODS

The expression of MxA protein in prostate cancer was examined by immuno-histochemistry. MxA was knocked down (shMxA) or over-expressed (pMxA) in DU145 or LNCaP PCa cell lines respectively. These cell lines were used to study proliferation, apoptosis, invasion, migration, and anchorage independent growth. Co-localization of MxA with tubulin was performed by immuno-cytochemistry following Docetaxel treatment.

RESULTS

The expression of MxA protein was significantly decreased in PCa as compared to the normal tissues. DU145 cells lacking MxA (DU145 + chMxA) showed significant increase in proliferation, associated with decreased expression of CDKN1A and B. Increased migration, anchorage independent growth in DU145 + shMxA cells was associated with increased MMP13 expression. Tubulin organization was also dependent on MxA expression. Tubulin polymerizing agents such as Docetaxel was less effective in promoting apoptosis in cells lacking MxA due to altered tubulin organization. Gain of MxA expression in LNCaP cells (LNCaP + pMxA) resulted in cell cycle arrest that was associated with increased expression of CDKN1A. MxA expression was also down-regulated by dihydrotestosterone in LNCaP cells.

CONCLUSIONS

MxA expression is inversely correlated with prostate cancer. Down-regulation of MxA in LNCaP cells by DHT suggests that MxA could play a significant role in disease progression. Loss of MxA expression results in increased metastasis and decreased sensitivity to Docetaxel suggesting that MxA expression could determine the outcome of chemo-therapeutic treatment. Additional studies will be required to fully establish the cross-talk between androgen receptor-IFN pathway in regulating MxA expression in the normal prostate and prostate cancer. Prostate 75:266-279, 2015. © 2014 Wiley Periodicals, Inc.

Prostate cancer epigenome

Prostate cancer is a major health burden within the ever-increasingly aging US population. The molecular mechanisms involved in prostate cancer are diverse and heterogeneous. In this context, epigenetic changes, both global and gene specific, are now an emerging alternate mechanism in disease initiation and progression. The three major risk factors in prostate cancer: age, geographic ancestry, and environment are all influenced by epigenetics and additional significant insight is required to gain an understanding of the underlying mechanisms. The androgen receptor and its downstream effector pathways, central to prostate cancer initiation and progression, are subject to a multitude of epigenetic alterations. In this review we focus on the global perspective of epigenetics and the use of recent next-generation sequencing platforms to interrogate epigenetic changes in the prostate cancer genome.

Inhibitor of differentiation 4 (ID4): From development to cancer

Highly conserved Inhibitors of DNA-Binding (ID1-ID4) genes encode multi-functional proteins whose transcriptional activity is based on dominant negative inhibition of basic helix-loop-helix (bHLH) transcription factors. Initial animal models indicated a degree of compensatory overlap between ID genes such that deletion of multiple ID genes was required to generate easily recognizable phenotypes. More recently, new model systems have revealed alterations in mice harboring deletions in single ID genes suggesting complex gene and tissue specific functions for members of the ID gene family. Because ID genes are highly expressed during development and their function is associated with a primitive, proliferative cellular phenotype there has been significant interest in understanding their potential roles in neoplasia. Indeed, numerous studies indicate an oncogenic function for ID1, ID2 and ID3. In contrast, the inhibitor of differentiation 4 (ID4) presents a paradigm shift in context of well-established role of ID1, ID2 and ID3 in development and cancer. Apart from some degree of functional redundancy such as HLH dependent interactions with bHLH protein E2A, many of the functions of ID4 are distinct from ID1, ID2 and ID3: ID4 proteins a) regulate distinct developmental processes and tissue expression in the adult, b) promote stem cell survival, differentiation and/or timing of differentiation, c) epigenetic inactivation/loss of expression in several advanced stage cancers and d) increased expression in some cancers such as those arising in the breast and ovary. Thus, in spite of sharing the conserved HLH domain, ID4 defies the established model of ID protein function and expression. The underlying molecular mechanism responsible for the unique role of ID4 as compared to other ID proteins still remains largely un-explored. This review will focus on the current understanding of ID4 in context of development and cancer.

Inhibitor of differentiation 4 (ID4) inactivation promotes de novo steroidogenesis and castration-resistant prostate cancer

Prostate cancer (PCa) is the most commonly diagnosed cancer in men in the Western world. The transition of androgen-dependent PCa to castration-resistant (CRPC) is a major clinical manifestation during disease progression and presents a therapeutic challenge. Our studies have shown that genetic ablation of inhibitor of differentiation 4 (Id4), a dominant-negative helix loop helix protein, in mice results in prostatic intraepithelial neoplasia lesions and decreased Nkx3.1 expression without the loss of androgen receptor (Ar) expression. ID4 is also epigenetically silenced in the majority of PCa. However, the clinical relevance and molecular pathways altered by ID4 inactivation in PCa are not known. This study investigates the effect of loss of ID4 in PCa cell lines on tumorigenicity and addresses the underlying mechanism. Stable silencing of ID4 in LNCaP cells (L-ID4) resulted in increased proliferation, migration, invasion, and anchorage-independent growth. An increase in the rate of tumor growth, weight, and volume was observed in L-ID4 xenografts compared with that in the LNCaP cells transfected with nonspecific short hairpin RNA (L+ns) in noncastrated mice. Interestingly, tumors were also observed in castrated mice, suggesting that loss of ID4 promotes CRPC. RNA sequence analysis revealed a gene signature mimicking that of constitutively active AR in L-ID4, which was consistent with gain of de novo steroidogenesis. Prostate-specific antigen expression as a result of persistent AR activation was observed in L-ID4 cells but not in L+ns cells. The results demonstrate that ID4 acts as a tumor suppressor in PCa, and its loss, frequently observed in PCa, promotes CRPC through constitutive AR activation.

Evaluation of candidate spermatogonial markers ID4 and GPR125 in testes of adult human cadaveric organ donors

The optimal markers for human spermatogonial stem cells (SSCs) are not known. Among the genes recently linked to SSCs in mice and other animals are the basic helix-loop-helix transcription factor ID4 and the orphan G-protein-coupled receptor GPR125. While ID4 and GPR125 are considered putative markers for SSCs, they have not been evaluated for coexpression in human tissue. Furthermore, neither the size nor the character of the human spermatogonial populations that express ID4 and GPR125, respectively, are known. A major barrier to addressing these questions is the availability of healthy adult testis tissue from donors with no known reproductive health problems. To overcome this obstacle, we have employed healthy testicular tissue from a novel set of organ donors (n = 16; aged 17-68 years) who were undergoing post-mortem clinical organ procurement. Using immunolabelling, we found that ID4 and GPR125 are expressed on partially overlapping spermatogonial populations and are more broadly expressed in the normal adult human testis. In addition, we found that expression of ID4 remained stable during ageing. These findings suggest that ID4 and GPR125 could be efficacious for identifying previously unrecognized human spermatogonial subpopulations in conjunction with other putative human stem cell markers, both in younger and older donors.

Distinct phenotypes of human prostate cancer cells associate with different adaptation to hypoxia and pro-inflammatory gene expression

Hypoxia and inflammation are strictly interconnected both concurring to prostate cancer progression. Numerous reports highlight the role of tumor cells in the synthesis of pro-inflammatory molecules and show that hypoxia can modulate a number of these genes contributing substantially to the increase of cancer aggressiveness. However, little is known about the importance of the tumor phenotype in this process. The present study explores how different features, including differentiation and aggressiveness, of prostate tumor cell lines impact on the hypoxic remodeling of pro-inflammatory gene expression and malignancy. We performed our studies on three cell lines with increasing metastatic potential: the well differentiated androgen-dependent LNCaP and the less differentiated and androgen-independent DU145 and PC3. We analyzed the effect that hypoxic treatment has on modulating pro-inflammatory gene expression and evaluated the role HIF isoforms and NF-kB play in sustaining this process. DU145 and PC3 cells evidenced a higher normoxic expression and a more complete hypoxic induction of pro-inflammatory molecules compared to the well differentiated LNCaP cell line. The role of HIF1α and NF-kB, the master regulators of hypoxia and inflammation respectively, in sustaining the hypoxic pro-inflammatory phenotype was different according to cell type. NF-kB was observed to play a main role in DU145 and PC3 cells in which treatment with the NF-kB inhibitor parthenolide was able to counteract both the hypoxic pro-inflammatory shift and HIF1α activation but not in LNCaP cells. Our data highlight that tumor prostate cell phenotype contributes at a different degree and with different mechanisms to the hypoxic pro-inflammatory gene expression related to tumor progression.

Id4 dependent acetylation restores mutant-p53 transcriptional activity

Background

The mechanisms that can restore biological activity of mutant p53 are an area of high interest given that mutant p53 expression is observed in one third of prostate cancer. Here we demonstrate that Id4, an HLH transcriptional regulator and a tumor suppressor, can restore the mutant p53 transcriptional activity in prostate cancer cells.

Methods

Id4 was over-expressed in prostate cancer cell line DU145 harboring mutant p53 (P223L and V274F) and silenced in LNCaP cells with wild type p53. The cells were used to quantitate apoptosis, p53 localization, p53 DNA binding and transcriptional activity. Immuno-precipitation/-blot studies were performed to demonstrate interactions between Id4, p53 and CBP/p300 and acetylation of specific lysine residues within p53.

Results

Ectopic expression of Id4 in DU145 cells resulted in increased apoptosis and expression of BAX, PUMA and p21, the transcriptional targets of p53. Mutant p53 gained DNA binding and transcriptional activity in the presence of Id4 in DU145 cells. Conversely, loss of Id4 in LNCaP cells abrogated wild type p53 DNA binding and transactivation potential. Gain of Id4 resulted in increased acetylation of mutant p53 whereas loss of Id4 lead to decreased acetylation in DU145 and LNCaP cells respectively. Id4 dependent acetylation of p53 was in part due to a physical interaction between Id4, p53 and acetyl-transferase CBP/p300.

Conclusions

Taken together, our results suggest that Id4 regulates the activity of wild type and mutant p53. Id4 promoted the assembly of a macromolecular complex involving CBP/P300 that resulted in acetylation of p53 at K373, a critical post-translational modification required for its biological activity.

Id4 promotes senescence and sensitivity to doxorubicin-induced apoptosis in DU145 prostate cancer cells

Inhibitor of differentiation proteins (Id1, 2, 3 and 4) are dominant negative regulators of basic helix loop helix transcription factors and play dominant roles in cancer cells, spanning several molecular pathways including senescence, invasion, metastasis, proliferation and apoptosis. In contrast to high Id1, Id2 and Id3 expression, the expression of Id4 is epigenetically silenced in prostate cancer. In the present study we demonstrated a novel role of Id4, that of promotion of cellular senescence in prostate cancer cells.

MATERIALS AND METHODS

Id4 was ectopically expressed in DU145 cells (DU145+Id4). The cells treated with Doxorubicin (0-500 nm) or vehicle control were analyzed for apoptosis, senescence (SA-beta Galactosidase), and expression of CDKN1A (p21), CDKN1B(p27), CDKN2A (p16), E2F1, vimentin and E-cadherin by immuno-histochemistry and/or Western blot.

RESULTS

In the present study we demonstrated that Id4 promotes cellular senescence in prostate cancer cell line DU145. Ectopic overexpression of Id4 in androgen receptor-negative DU145 prostate cancer cells resulted in increased expression of p16, p21, p27, E-cadherin and vimentin but down-regulated E2F1 expression. Id4 also potentiated the effect of doxorubicin induced senescence and apoptosis.

CONCLUSION

The absence of functional p16, pRB and p53 in DU145 suggests that Id4 could alter additional molecular pathways such as those involving E2F1 to promote senescence and increased sensitivity to doxorubicin-induced apoptosis. The results of the present study support the role of Id4 as a tumor suppressor in prostate cancer.

Id4 deficiency attenuates prostate development and promotes PIN-like lesions by regulating androgen receptor activity and expression of NKX3.1 and PTEN

Background

Inhibitor of differentiation 4 (Id4), a member of the helix-loop-helix family of transcriptional regulators has emerged as a tumor suppressor in prostate cancer. Id4 is expressed in the normal prostate where its expression is also regulated by androgens. In this study we investigated the effect of loss of Id4 (Id4-/-) on adult prostate morphology.

Methods

Histological analysis was performed on prostates from 6-8 weeks old Id4-/-, Id4+/- and Id4+/+ mice. Expression of Id1, Sox9, Myc, androgen receptor, Akt, p-Akt, Pten and Nkx3.1 was investigated by immunohistochemistry. Androgen receptor binding on NKX3.1 promoter was studied by chromatin immuno-precipitation. Id4 was either over-expressed or silenced in prostate cancer cell lines DU145 and LNCaP respectively followed by analysis of PTEN, NKX3.1 and Sox9 expression.

Results

Id4-/- mice had smaller prostates with fewer tubules, smaller tubule diameters and subtle mPIN like lesions. Levels of androgen receptor were similar between wild type and Id4-/- prostate. Decreased NKX3.1 expression was in part due to decreased androgen receptor binding on NKX3.1 promoter in Id4-/- mice. The increase in the expression of Myc, Sox9, Id1, Ki67 and decrease in the expression of PTEN, Akt and phospho-AKT was associated with subtle mPIN like lesions in Id4-/- prostates. Finally, prostate cancer cell line models in which Id4 was either silenced or over-expressed confirmed that Id4 regulates NKX3.1, Sox9 and PTEN.

Conclusions

Our results suggest that loss of Id4 attenuates normal prostate development and promotes hyperplasia/dysplasia with subtle mPIN like lesions characterized by gain of Myc and Id1 and loss of Nkx3.1 and Pten expression. One of the mechanisms by which Id4 may regulate normal prostate development is through regulating androgen receptor binding to respective response elements such as those on NKX3.1 promoter. In spite of these complex alterations, large neoplastic lesions in Id4-/- prostates were not observed suggesting the possibility of mechanisms/pathways such as loss of Akt that could restrain the formation of significant pre-cancerous lesions.