MTREX and hepatocellular carcinoma: While the overexpression of MTR4 induced the splicing of pre-mRNA transcribed from PKM minigene to PKM2 isoform in HCC cells, the silence of PTBP1 in HCC cells inhibits the AS of the pre-mRNA transcribed from PKM minigene to PKM2, suggesting that PTBP1 is involved in MTR4-dependent splicing events (Fig. 5c).