FAS and hepatocellular carcinoma: HCC cells or tissues become unresponsive to Fas by downregulating Fas expression resulting in reduced expression of FADD or FLICE or increased expression of cellular FLICE/caspase-8-inhibitory protein (cFLIP), or by upregulation of nuclear factor-kappa B (NF-κB), Bcl-2 or Bcl-XL and Mcl-1 [38-40].