The role and clinical value of POLR2A, RUNX2, and micro-RNA378 in sarcomatoid renal cell carcinoma

Kai-Jie Yu^{1, 2, 3}, Ju-Wen Jhan¹, See-Tong Pang^{2, 3}, Wen-Hui Weng¹

Abstract

Background Sarcomatoid renal cell carcinoma (sRCC) constitutes a highly metastatic and aggressive subtype of renal cell carcinoma, and predisposes to a drug-resistant status with a median survival of less than one year. It is known that the expression of different microRNAs (miRNAs) in cancer can be used as biomarkers to predict drug response and prognosis at various stages. Based on our previous studies, we demonstrated that miR-378a-3p over-expression could significantly inhibit ERK2 protein expression, which may further hinder cell cycle progression and lead to apoptosis. Interestingly, we observed lower miR-378a-3p expression levels in ccRCC and sRCC. Therefore, we hypothesized that overexpression of miR-378a-3p promotes apoptosis of RCC cells. Methods The current study enrolled five RCC cell lines and thirteen clinical samples of sarcomatoid RCC and bladder cancer. First, by using the KEGG pathway, Pathway Commons and Ingenuity Pathway Analysis systems, we found two candidate genes (Pol II and Runx2) by cross-matching the signaling pathways of RCC. Second, real-time polymerase chain reaction and western blot analysis were performed in all cell lines to evaluate the expression levels of mRNA and protein of Pol II and Runx 2 before and after transfection of miR-378a-3p. Finally, clinical samples were testified to verify the expression levels observed in cell lines and then apoptosis was analyzed by flow cytometry. Result The results showed that both mRNA and protein expression level of Pol II and Runx2 in sRCC cell lines were significantly increased, and similar results were identified as well in clinical samples (p < 0.01). Second, after overexpression of miR-378a-3p, it was observed that expression level of mRNA and protein of Pol II and Runx2 were significantly reduced in sRCC cell lines (p < 0.01), and apoptosis in sRCC cell lines was significantly increased (p < 0.05). However, there are inconsistent expression level of mRNA and protein in the ccRCC cell lines. Conclusions The results of this study demonstrated that miR-378a-3p, as an inhibitor of sRCC, inhibits the mRNA and protein expression of Pol II and Runx2 via regulation of the ERK2 and PI3K/AKT pathway, and thereby promoted apoptosis of sRCC cell lines. On the other hand, we speculate that the difference in cell site mutation will lead to inconsistent expression of mRNA and protein in ccRCC cell lines. If it could be verified in the future, when the miR-378a-3p base is only partially matched with the 3’UTR of the target protein, the ability to regulate the target gene can also be achieved.

Key words: Sarcomatoid renal cell carcinoma, POLR2A, RUNX2, micro-RNA378, ERK2 (MAPK1)

¹Department of Chemical Engineering and Biotechnology and Graduate Institute of Biochemical and Biomedical Engineering, National Taipei University of Technology, Taipei City 106, Taiwan, R.O.C

²Graduate Institute of Clinical Medical Sciences, Chang Gung University, Taoyuan, Taiwan, R. O. C.

³Department of Urology, Chang Gung Memorial Hospital, Taiwan, R.O.C.