MicroRNA profiling of novel African American and Caucasian Prostate Cancer cell lines reveals a reciprocal regulatory relationship ofmiR-152and DNA methyltranferase 1

Abstract

miRNA expression in African American compared to Caucasian PCa patients has not been widely explored. Herein, we probed the miRNA expression profile of novel AA and CA derived prostate cancer cell lines. We found a unique miRNA signature associated with AA cell lines, independent of tumor status. Evaluation of the most differentially expressed miRNAs showed that miR-132, miR-367b, miR-410, and miR-152 were decreased in more aggressive cells, and this was reversed after treatment of the cells with 5-aza-2′-deoxycytidine. Sequencing of the miR-152 promoter confirmed that it was highly methylated. Ectopic expression of miR-152 resulted in decreased growth, migration, and invasion. Informatics analysis of a large patient cohort showed that decreased miR-152 expression correlated with increased metastasis and a decrease in biochemical recurrence free survival. Analysis of 39 prostate cancer tissues with matched controls (20 AA and 19 CA), showed that 50% of AA patients had statistically significant lower miR-152 expression compared to only 35% of CA patients. Ectopic expression of miR-152 in LNCaP, PC-3, and MDA-PCa-2b cells down-regulated DNA (cytosine-5)-methyltransferase 1 (DNMT1) through direct binding in the DNMT1 3'UTR. There appeared to be a reciprocal regulatory relationship of miR-152/DNMT1 expression, as cells treated with siRNA DNMT1 caused miR-152 to be re-expressed in all cell lines. In summary, these results demonstrate that epigenetic regulation of miR-152/DNMT1 may play an important role in multiple events that contribute to the aggressiveness of PCa tumors, with an emphasis on AA PCa patients.

miR-152 as a tumor suppressor microRNA: Target recognition and regulation in cancer

“…Braconi et al (14) first described that the DNA methyltransferase 1 (DNMT1) gene is a direct target of miR-148a and miR-152 by using luciferase reporter constructs, which revealed that miR-152 could target the 3'-UTR of DNMT1, resulting in a significant reduction of DNMT1 at both mRNA and protein levels. This finding was further confirmed in subsequent studies on ovarian cancer (15), endometrial cancer (9), nickel sulphide (NiS)-induced cell malignant transformation (16), breast cancer (17), hepatitis B virus-related hepatocellular carcinoma (18), pancreatic cancer (19) and prostate cancer (20). In addition, E2F transcription factor 3, mesenchymal to epithelial transition (MET), rapamycin-insensitive companion of mechanistic target of rapamycin (9), insulin-like growth factor 1 receptor (IGF-1R), insulin receptor substrate 1 (IRS1) (17), a disintegrin and metalloproteinase metallopeptidase domain 17 (ADAM17) (21,22), Kruppel-like factor 4 (KLF4) (23), fibroblast growth factor 2 (FGF2) (24), winglessrelated integration site (Wnt1) (25), cluster of differentiation (CD) 151 (26), matrix metalloproteinase 3 (MMP3) (27) and transforming growth factor alpha (28) have been identified as targets of miR-152 in a wide array of human malignancies.…”

“…These results suggest that the hypermethylation of the CpG island of miR-152 may downregulate its expression, and may be involved in endometrial cancer. Due to the hypermethylation of its CpG island, silencing of miR-152 expression and overexpression of DNMT1 were also observed in NiS-transformed cells (16), breast cancer (17) and prostate cancer (20). Notably, there may be a crucial functional crosstalk between miR-152 and DNMT1 via a double-negative feedback regulatory loop, as speculated by Ji et al (16) regarding the classic 'chicken and egg' argument.…”

“…Once increased expression of DNMT1 ('egg') occurs, DNMT1 is recruited to the miR-152 CpG island promoter, where it increases DNA methylation, contributing to reduced miR-152 expression ('chicken') (16). Furthermore, downregulated expression of miR-152 further increases DNMT1 expression by reduced targeting on DNMT1 3'-UTR (14)(15)(16)(17)(18)(19)(20). Therefore, epigenetic regulation of miR-152/DNMT1 may be important in tumorigenesis.…”

“…In previous studies, several miRNAs have been demonstrated to affect target genes that are involved in the control of cell proliferation and apoptosis (14)(15)(16)(17)(18)(19)(20). It has been well established that phosphatidylinositol-3 kinase (PI3K)/AKT and mitogen-activated protein kinase (MAPK)-mediated signaling pathways are two of the most predominant signaling pathways in human cancer, since they are involved in cell proliferation, survival and metabolism (38,39).…”

Racial disparities in prostate cancer a molecular perspective

“…miR-1b-1, miR-26a, miR-30c-1, miR-219 and miR-301 were shown to be differentially-expressed in prostate tumors of AA and EA racial backgrounds (37). Later, Theodore et al examined the expression of miR-26a in prostate cancer cell lines of AA (RC77N/E, RC77T/E and MDA-2PCa-2b) and EA (PrEC, RC-92a and PC-3) origin, representing non-malignant, malignant, and metastatic prostate cancer tumors, respectively (38,39). They observed increased (2.2. to 13.3. folds) expression of miR-26a in AA prostate cancer cells of all three stages and grades, when compared with EA cell lines of similar clinical stage and pathological-grade.…”