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Updated: Jun 4, 2026
miRNA Expression Analyses in Prostate Cancer Clinical Tissues
Published on: September 8, 2015
MicroRNA-145 is regulated by DNA methylation and p53 gene mutation in prostate cancer
Seong O Suh1, Yi Chen, Mohd Saif Zaman
1Department of Urology, Veterans Affairs Medical Center and University of California at San Francisco, 4150 Clement Street, San Francisco, CA 94121, USA.
Abstract:
MiR-145 is downregulated in various cancers including prostate cancer. However, the underlying mechanisms of miR-145 downregulation are not fully understood. Here, we reported that miR-145 was silenced through DNA hypermethylation and p53 mutation status in laser capture microdissected (LCM) prostate cancer and matched adjacent normal tissues. In 22 of 27 (81%) prostate tissues, miR-145 was significantly downregulated in the cancer compared with the normal tissues. Further studies on miR-145 downregulation mechanism showed that miR-145 is methylated at the promoter region in both prostate cancer tissues and 50 different types of cancer cell lines. In seven cancer cell lines with miR-145 hypermethylation, 5-aza-2'-deoxycytidine treatment dramatically induced miR-145 expression. Interestingly, we also found a significant correlation between miR-145 expression and the status of p53 gene in both LCM prostate tissues and 47 cancer cell lines. In 29 cell lines with mutant p53, miR-145 levels were downregulated in 28 lines (97%), whereas in 18 cell lines with wild-type p53 (WT p53), miR-145 levels were downregulated in only 6 lines (33%, P < 0.001). Electrophoretic mobility shift assay showed that p53 binds to the p53 response element upstream of miR-145, but the binding was inhibited by hypermethylation. To further confirm that p53 binding to miR-145 could regulate miR-145 expression, we transfected WT p53 and MUT p53 into PC-3 cells and found that miR-145 is upregulated by WT p53 but not with MUTp53. The apoptotic cells are increased after WT p53 transfection. In summary, this is the first report documenting that downregulation of miR-145 is through DNA methylation and p53 mutation pathways in prostate cancer.
Insights
MicroRNA-145 (miR-145) is downregulated in prostate cancer due to DNA hypermethylation and p53 mutations. Restoring wild-type p53 and demethylating DNA reactivates miR-145, inducing apoptosis.
Area of Science:
- Molecular Biology
- Oncology
- Epigenetics
Background:
- MicroRNA-145 (miR-145) is frequently downregulated in various cancers, including prostate cancer.
- The precise mechanisms driving miR-145 downregulation remain incompletely elucidated.
Purpose of the Study:
- To investigate the molecular mechanisms responsible for miR-145 downregulation in prostate cancer.
- To explore the roles of DNA methylation and p53 gene status in regulating miR-145 expression.
Main Methods:
- Analysis of miR-145 expression in laser capture microdissected (LCM) prostate cancer tissues and matched normal tissues.
- Assessment of miR-145 promoter methylation status in cancer tissues and cell lines.
- Treatment of cancer cell lines with 5-aza-2'-deoxycytidine to evaluate the effect of demethylation on miR-145 expression.
- Correlation analysis between miR-145 expression and p53 gene mutation status.
- Electrophoretic mobility shift assay (EMSA) to study p53 binding to the miR-145 promoter.
- Transfection of wild-type (WT) and mutant (MUT) p53 into prostate cancer cells (PC-3) to assess functional impact on miR-145 and apoptosis.
Main Results:
- miR-145 was significantly downregulated in 81% of prostate cancer tissues compared to adjacent normal tissues.
- miR-145 promoter hypermethylation was observed in prostate cancer tissues and 50 cancer cell lines.
- Demethylation treatment (5-aza-2'-deoxycytidine) significantly induced miR-145 expression in hypermethylated cell lines.
- A strong correlation was found between miR-145 downregulation and mutant p53 status (97% of cell lines with mutant p53 showed downregulation).
- Wild-type p53 was shown to bind to the miR-145 promoter, regulating its expression, while this binding was inhibited by hypermethylation.
- Transfection of WT p53 upregulated miR-145 and increased apoptosis in PC-3 cells, whereas MUT p53 had no significant effect.
Conclusions:
- This study identifies DNA hypermethylation and p53 gene mutations as key mechanisms for miR-145 silencing in prostate cancer.
- Restoration of wild-type p53 function and reversal of DNA methylation can reactivate miR-145 expression and promote apoptosis.
- These findings provide novel insights into the epigenetic and genetic regulation of miR-145 in cancer development.
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