Background:X-linked inhibitor of apoptosis (XIAP) is a vital factor in the anti-apoptosis mechanism of tumors and is highly expressed in renal cell carcinoma (RCC).However,the mechanism through which XIAP regulates DNA damage repair is unknown.This study investigated the regulatory mechanism of XIAP in etoposide-induced apoptosis in two Caki-1 cell lines with high or low XIAP expression.Methods:The two cell lines were established using RNA interference technology.The differentially expressed proteins in the two cell lines were globally analyzed through an isobaric tags for relative and absolute quantitation-based quantitative proteomics approach.Proteomic analysis revealed 255,375,362,and 5 differentially expressed proteins after 0,0.5,3,and 12 h of drug stimulation,respectively,between the two cell lines.The identified differentially expressed proteins were involved in numerous biological processes.In addition,the expression of histone proteins (H1.4,H2AX,H3.1,H3.2,and H3.3) was drastically altered,and the effects of XIAP silencing were accompanied by the marked downregulation of H2AX.Protein-protein interactions were assessed and confirmed through immunofluorescence and West blot analyses.Results:The results suggested that XIAP may act as a vital cell signal regulator that regulates the expression of DNA repair-related proteins,such as H2AX,and influences the DNA repair process.Conclusions:Given these functions,XIAP may be the decisive factor in determining the sensitivity of RCC cell apoptosis induction in response to chemotherapeutic agents.