BAK1 and metastatic melanoma: In this study, we therefore assessed the expression of nine apoptosis regulators (Bax, Bak, Bcl-2, Bcl-xL, Smac, Procaspase-9, Apaf-1, Procaspase-3 and XIAP) in metastatic melanoma tissues by immunohistochemistry (IHC), using antibodies that passed rigorous validation.