Methylation of thePMEPA1gene, a negative regulator of the androgen receptor in prostate cancer

Abstract

The prostate transmembrane protein androgen induced 1 (PMEPA1) gene is highly expressed in prostate epithelial cells and is a direct transcriptional target for the androgen receptor (AR). AR protein levels are controlled by the AR-PMEPA1 negative feedback loop through NEDD4-E3 ligase. Reduced expression of PMEPA1 observed in prostate tumors, suggests that loss of PMEPA1 may play critical roles in prostate tumorigenesis. This study focuses on epigenetic mechanisms of reduced PMEPA1 expression in the cancer of the prostate (CaP). Benign (n = 77) and matched malignant (n = 77) prostate epithelial cells were laser capture micro-dissected from optimum cutting temperature embedded frozen prostate sections from 42 Caucasian American (CA) and 35 African American (AA) cases. Purified DNA specimens were analyzed for CpG methylation of the PMEPA1 gene. PMEPA1 mRNA expression levels were evaluated by qRT-PCR. Analysis of PMEPA1 methylation and mRNA expression in the same tumor cell populations indicated a significant inverse correlation between mRNA expression and methylation in CaP (P = 0.0115). We noted higher frequency of CpG methylation within the evaluated first intronic region of the PMEPA1 gene in prostate tumors of CA men as compared with AA. In CaP cell lines, PMEPA1 expression was induced and AR protein levels were diminished in response to treatment with the DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine (decitabine). Cell culture-based studies demonstrated that decitabine restores PMEPA1 expression in AR-positive CaP cell lines. This report reveals the potential role of PMEPA1 gene methylation in the regulation of AR stability. Thus, downregulation of PMEPA1 may result in increased AR protein levels and function in CaP cells, contributing to prostate tumorigenesis.

The TGF-β Signaling Regulator PMEPA1 Suppresses Prostate Cancer Metastases to Bone

“…Even though Pmepa1 levels are increased in the primary tumor, we also found that expression of PMEPA1 was decreased in distant metastases of PCa patients when compared to the primary tumor. This result is consistent with observation from Xu et al (2003) and report of loss of expression of Pmepa1 due to accumulated methylation in PMEPA1 promoter (Sharad et al, 2014). Methyltransferase inhibitors restored TGFβ-inducible expression of PMEPA1 in HepG2 cells suggesting that TGFβ response elements in PMEPA1 promoter can also be inactivated by methylation.…”

“…Despite activation of TGFβ signaling as shown by phosphorylated Smad3, HepG2 cells did not express detectable amount of any PMEPA1 isoform (Fig 2C). DNA methylation can prevent induction of PMEPA1 gene by androgens (Sharad et al, 2014). Thus we cultured HepG2 with the methyltransferase inhibitors 5-azacytidine or 5-aza-2-deoxycytidine which restored expression of PMEPA1a and c in the presence of TGFβ (Fig 2D).…”

Characterization of unique PMEPA1 gene splice variants (isoforms d and e) from RNA Seq profiling provides novel insights into prognostic evaluation of prostate cancer

“…5′-GGATGAATTCGCTCTGGTCTAG-3′ (forward), 5′-ACCACCATCACCATCATCAC-3′(reverse); PMEPA1-d: 5′-ACAGGCGAAAAGTCAAAATGC-3′ (forward), 5′-ACCACCATCACCATCATCAC-3′ (reverse); PMEPA1-e: 5′-CTTCCCCGTGTGCAAGAG-3′ (forward), 5′-CTGGATCCTCAGCCACTG-3′ (reverse). The PCR primers for COL1A1, NEDD9, and THBS1 [2] and AR, PSA (KLK3) and GAPDH [15] were described previously.…”

“…Quantitative-PCR (Q-PCR) analysis in matched prostate normal/tumor tissues showed that decreased expression of PMEPA1 in approximately 65% of prostate tumors, which also strongly associated with higher pathologic stage and serum prostate-specific antigen (PSA) [13]. It was shown that the methylation of PMEPA1 gene promoter accounted for the silencing of PMEPA1 in prostate cancer cells in vitro and in vivo [14,15]. The PMEPA1 silencing conferred the development of resistance to AR inhibitors in vitro, as well as promoted the androgen independent xenograft growth of prostate tumor in nude mice [16].…”

Analysis of PMEPA1 Isoforms (a and b) as Selective Inhibitors of Androgen and TGF-β Signaling Reveals Distinct Biological and Prognostic Features in Prostate Cancer

“…We further showed that PMEPA1 gene expression was reduced or absent in about 65% of prostate tumors and methylation of the PMEPA1 gene promoter was one of the major mechanisms of silencing PMEPA1 in prostate cancer [16][17][18]. Furthermore, depletion of PMEPA1 in androgen responsive prostate cancer cells facilitated the development of resistance to AR inhibitors (enzalutamide and bicalutamide) in vitro.…”