FAS and neoplasm: First, increased expression of various antiapoptotic proteins (BCL-2, BCL-xL, and MCL-1) in tumor cells can enhance the apoptotic resistance of tumor cells.30–32 Second, inhibition of the expression of apoptosis-related receptors (FAS, DR4, and DR5) and ligands (FASL and TRAIL) can also enable tumor cells to escape apoptotic pathway-induced cell death.33,34 Third, tumor cells can escape cytotoxic T lymphocyte (CTL)- and NK cell-mediated death by blocking the perforin/granzyme pathway in immune cells.