Combined treatment downregulates the expression of anti-apoptotic proteins and enhances the expression of pro-apoptotic proteins. Western blot analysis results of (A) anti-apoptotic and (B) pro-apoptotic protein expression 24 h following cis, bor and cis plus bortezomib combination treatment. C, control; cis, cisplatin; bor, bortezomib; Bcl-2, B-cell lymphoma-2; Bcl-xL, B-cell lyphoma-extra large; Bim, B-cell lyphoma-2-like 11; Bik, Bcl-2-interacting killer.