XIAP and renal cell carcinoma: We previously demonstrated that GSK-3β positively regulates the proliferation, survival, and anti-apoptosis mechanisms of cancer cells through decreased expression of the nuclear factor-kappa B target genes BCL-2 and X-linked inhibitor of apoptosis protein (XIAP) [18, 20], and that nuclear accumulation of GSK-3β could be a novel biomarker of bladder cancer [18] and RCC [20].