CHEK1 and hepatocellular carcinoma: To investigate the biological functions of different CHK1 transcripts in HCC, we stably overexpressed CHK1-L or CHK1-S in HepG2 cells by transfecting CHK1-L expression vector (pLVX-CHK1-L) or CHK1-S expression vector (pLVX-CHK1-S) (as showed Fig. 2A).