Characterization of a stemness-related gene RALYL in the development and progression of hepatocellular carcinoma

Abstract

Recent discovery of tumor biology postulates that tumor development is driven by a small population of stem-like cells. Poorly differentiated tumors which usually preserving phenotype of their ancestral precursor cells, are commonly associated with high recurrence and poor prognosis. Here, we identified a gene, named as RALY RNA binding protein-like (RALYL), specifically expressed in liver progenitor and progenitor-like cells, which were acquired in a vitro hepatic differentiation model from embryonic stem (ES) cells. Interestingly, RALYL was rarely expressed in mature liver and the expression of RALYL was associated with poor differentiation in hepatocellular carcinoma (HCC) clinical samples. Functional assays showed that RALYL could promote tumor cell proliferation, foci formation, colony formation in soft agar and sphere formation and tumor formation in nude mice. Furthermore, higher RALYL expression was observed in CD133+ HCC cells. RALYL overexpression could increase the population of CD133+ cells, which was decreased when RALYL was silenced with short hairpin RNA (shRNA). qRT-PCR results indicated that RALYL could promote stemness related gene expression such as CD133, CD44 and lgr5 in human immortalized liver cell line as well as HCC cell lines. Mechanically, RALYL is a RNA binding protein and expected to function in RNA splicing. RNP Immunoprecipitation (RIP) sequencing demonstrated that RNA splicing involved in stemness related pathways were regulated by RALYL. In conclusion, our study has identified and characterized RALYL as a novel stemness-related gene in HCC which might facilitate the treatment of HCC.