BID and hepatocellular carcinoma: To examine how sorafenib induces apoptosis in HCC cell lines, we monitored the proteins involved in the intrinsic and mitochondrial apoptosis pathways, including pro-apoptotic proteins (Bad, Bax, Bim, Bid, and PUMA) and anti-apoptotic proteins (survivin, Mcl-1, Bcl-XL, Bcl-2, and PTMA).