p63 is a regulator of microRNA expression in hepatocellular carcinoma

Question:

Transcription factors of the p53 family (p53, p63, p73) respond to cellular stress signals by inducing a defined set of target genes, thereby exerting cancerogenic or tumorsuppressive functions in tumors such as hepatocellular carcinoma (HCC). p63 is known as a tumor suppressor gene which is of importance in the development of epithelia and in epithelial mesenchymal transition, a process that results in metastasis of primary cancer. microRNAs (miRNAs) are small non coding RNA molecules that are alsocapable to influence gene expression. p53-family members have been shown to play a role in the regulation of miRNA expression. Previous work identified a set of p53-regulated miRNAs in HCC. p63 influences miRNA levels in squamous cell carcinoma (SCC) and a number of other epithelial carcinomas. However, little is known about the role of p63 in miRNA regulation in HCC. The aim of this study was therefore to evaluate whether miRNA profiles in HCC cells are influenced by p63.

Methods:

Hep3B cells were transfected with rAd-p63 and rAd-GFP. Expression of miR34a, mir145, miR149, miR192 and miR194 was determined by qPCR. To analyze effects of HCC-relevant therapeutics on p63-dependent microRNA regulation transfected Hep3B cells were treated with HCC-relevant therapeutics with doxorubicin, bleomycin, regorafenib, sorafenib or tivantinib for up to 72 hours.

Results:

24h after transfection overexpression of p63 induced an induction of miR34a by 1.9-fold, miR149 by 1.96-fold, miR192 by 3.85-fold and miR194 by 5.25 fold. 72h in vitro incubation with doxorubicin resulted in an increase of p63-dependent expression of miR34a (2.64-fold), miR145 (4.88-fold), miR149 (2.63-fold), miR192 (2.11-fold) and miR194 (1.91-fold). Bleomycin increased p63-dependent miR34a expression by 4.29-fold. Sorafenib had a moderate increasing effect on p63-dependent miR34a expression (2.44-fold) and strongly enhanced p63-dependent expression of miR145 by 40.55-fold.

Conclusion:

We demonstrate for the first time a p63-dependent induction of tumorsuppressive miRNAs in HCC. Furthermore, synergistic effects of p63 overexpression and HCC-relevant therapeutics on miRNA levels were observed and may provide further understanding of mechanisms by which p53 family members exert their tumorsuppressive functions in HCC.