A new molecular marker for carcinoma in the urinary bladder is needed as a diagnostic tool or therapeutic target. Candidate markers include microRNAs (miRNAs), which are short, low-molecular-weight RNAs 19-24 nt in length, that regulate genes associated with cell proliferation, differentiation, and development in various cancers. In this study, we investigated the molecular mechanisms by which miR-145 promotes the survival of urothelial carcinoma cells and their differentiation into multiple lineages.
Cell proliferation in the human urothelial carcinoma cell lines T24 and KU7 was assessed by MTS assay. Cellular senescence and apoptosis were measured by senescence-associated b-galactosidase (SA-b-gal) and a TUNEL assay, respectively. Quantitative RT-PCR was used to measure the mRNA expression levels of various genes, including syndecan-1, stem cell factors, and markers of squamous, glandular, or neuroendocrine differentiation. The expression of miR-145 in urothelial carcinoma tissues from patients that were not undergoing chemotherapy or Bacillus Calmette-Guerin treatment was detected by quantitative RT-PCR.
Overexpression of miR-145 induced cell senescence, and thus significantly inhibited cell proliferation in T24 and KU7 cells. Syndecan-1, a heparin sulfate proteoglycan, expression decreased, whereas the levels of stem cell markers such as SOX2, NANOG, OCT4, and E2F3 increased. miR-145 also up-regulated the markers of squamous (p63, TP63, and CK5), glandular (MUC-1, MUC-2, and MUC-5AC), and neuroendocrine (NSE and UCHL-1) differentiation. Finally, miR-145 expression was down-regulated in high-grade urothelial carcinomas, but not in low-grade tumors.
The results indicate that miR-145 suppresses syndecan-1 and consequently up-regulates stem cell factors to induce cell senescence and differentiation. Our data provide a new mechanism of urothelial carcinogenesis via miR-145, and show that the related molecules could contribute to the development of new diagnostic or prognostic markers, as well as potential therapeutic targets.
Clinical trial identification
Legal entity responsible for the study
Nara Medical University School of Medicine, Nara, Japan
Grant-in-Aid from the Ministry of Education, Culture, Sports, Science and Technology, Japan (26462424)
All authors have declared no conflicts of interest.