Attenuation of TGFBR2 expression and tumour progression in prostate cancer involve diverse hypoxia-regulated pathways

Abstract

BackgroundDysregulation of transforming growth factor β (TGF-β) signaling and hypoxic microenvironment have respectively been reported to be involved in disease progression in malignancies of prostate. Emerging evidence indicates that downregulation of TGFBR2, a pivotal regulator of TGF-β signaling, may contribute to carcinogenesis and progression of prostate cancer (PCa). However, the biological function and regulatory mechanism of TGFBR2 in PCa remain poorly understood. In this study, we propose to investigate the crosstalk of hypoxia and TGF-β signaling and provide insight into the molecular mechanism underlying the regulatory pathways in PCa.MethodsProstate cancer cell lines were cultured in hypoxia or normoxia to evaluate the effect of hypoxia on TGFBR2 expression. Methylation specific polymerase chain reaction (MSP) and demethylation agents was used to evaluate the methylation regulation of TGFBR2 promoter. Besides, silencing of EZH2 via specific siRNAs or chemical inhibitor was used to validate the regulatory effect of EZH2 on TGFBR2. Moreover, we conducted PCR, western blot, and luciferase assays which studied the relationship of miR-93 and TGFBR2 in PCa cell lines and specimens. We also detected the impacts of hypoxia on EZH2 and miR-93, and further examined the tumorigenic functions of miR-93 on proliferation and epithelial-mesenchymal transition via a series of experiments.ResultsTGFBR2 expression was attenuated under hypoxia. Hypoxia-induced EZH2 promoted H3K27me3 which caused TGFBR2 promoter hypermethylation and contributed to its epigenetic silencing in PCa. Besides, miR-93 was significantly upregulated in PCa tissues and cell lines, and negatively correlated with the expression of TGFBR2. Ectopic expression of miR-93 promoted cell proliferation, migration and invasion in PCa, and its expression could also be induced by hypoxia. In addition, TGFBR2 was identified as a bona fide target of miR-93.ConclusionsOur findings elucidate diverse hypoxia-regulated pathways including EZH2-mediated hypermethylation and miR-93-induced silencing contribute to attenuation of TGFBR2 expression and promote cancer progression in prostate cancer.Electronic supplementary materialThe online version of this article (10.1186/s13046-018-0764-9) contains supplementary material, which is available to authorized users.

miR‐210 is induced by hypoxia and regulates neural cell adhesion molecule in prostate cells

“…To further evidence that the increased expression of miR‐210 is associated with hypoxia in clinical samples, we examined expression of various hypoxia‐related genes in a well‐characterized TCGA dataset ( n = 330). This showed that EZH2 , another marker of prostate tumour hypoxia (Zhou et al, 2018), has a strong positive correlation with miR‐210 expression in these samples (Figure 3f). Likewise, the hypoxia‐induced genes SPP1 and DLGAP5 , which code for ostepontin and HURP proteins respectively, also show significant positive correlation with clinic‐pathological parameters of prostate cancer progression (Figure S2).…”

Effects of metformin and phenformin on apoptosis and epithelial‐mesenchymal transition in chemoresistant rectal cancer

“…Therefore, other modulators may regulate TGFBR2 at the mRNA level. For example, the H3K27 methyltransferase enzyme EZH2 contributes to TGFBR2 silencing by promoter hypermethylation in prostate cancer . Moreover, miR‐93 and miR‐204 , which are aberrantly expressed in various malignant tumors, including prostate and breast cancers, respectively, regulate cancer progression by targeting TGFBR2 .…”

TGF-β and microRNA Interplay in Genitourinary Cancers

“…The resistance of prostate cancer cells to TGF-β-mediated growth inhibition is thus possibly a result of decreased expression of TGFBR2, which acts as a tumor suppressor gene [237,238]. Downregulation of TGFBR2 in PCa cells might result from hypoxic activation of DNA methyltransferases, which leads to the hypermethylation of the promoter region of TGFBR2 [239]. Contrarily, earlier research reported a lack of promoter methylation and mutations in the TGFBR2 gene [240].…”

“…The expression of miR-93 is increased in prostate tumors compared with non-tumorous control samples and correlates with cancer progression. Transfection of prostate cancer cell lines with miR-93 mimics stimulates their proliferation, migration, and invasion [239]. Complex regulation of the TGF-β signaling pathway is exerted by miR-34b, which modulates expressions of TGF-β, TGFBR1, and pSMAD4, p53.…”