Decreased expression of Bax-interacting factor-1 (Bif-1) in invasive urinary bladder and gallbladder cancers

Abstract

Mounting evidence indicates that deregulation of apoptosis is involved in the mechanisms of cancer development. Bax-interacting factor-1 (Bif-1) interacts with both Bax and Bak that are crucial for the intrinsic apoptosis signalling. Functionally, loss of Bif-1 expression has been proven to enhance tumorigenesis. The aim of this study was to explore whether loss of Bif-1 expression occurs in urinary bladder (UB) and gallbladder (GB) cancer tissues. We analysed Bif-1 protein expression in 41 transitional cell carcinomas of UB and 26 GB adenocarcinomas by immunohistochemistry. In both UB and GB, normal mucosal epithelial cells strongly expressed Bif-1 protein. In the UB cancers, Bif-1 expression was strongly positive in 25 cases (61.0%), but the remaining 16 cases showed no (14.6%) or markedly decreased (24.4%) Bif-1 immunostaining compared with the normal mucosal epithelial cells. Similarly, in the GB cancers, Bif-1 immunostaining was strong in 17 cases (65.4%), while the remaining nine cases showed no (15.4%) or markedly decreased (19.2%) Bif-1 immunostaining compared with the normal mucosal epithelial cells. The decreased expression of Bif-1 in large fractions of both UB and GB cancers (39.0% and 34.6%, respectively) compared with their normal mucosal cells suggested that loss of Bif-1 expression might play a role in tumorigenesis in both UB and GB cancers, possibly by inhibiting apoptosis mediated by Bif-1.