Abstract
Recent studies have indicated that using statins to inhibit the mevalonate pathway induces mutant p53 degradation by impairing the interaction of mutant p53 with DnaJ subfamily A member 1 (DNAJA1). However, the role of the C-terminus of DNAJA1 with a CAAX box for farnesylation in the binding, folding, and translocation of client proteins such as mutant p53 is not known. In the present study, we used a genetically engineered mouse model of pancreatic carcinoma and showed that atorvastatin significantly increased animal survival and inhibited pancreatic carcinogenesis. There was a dramatic decrease in mutant p53 protein accumulation in the pancreatic acini, pancreas intraepithelial neoplasia lesions, and adenocarcinoma. Supplementation with farnesyl pyrophosphate, a substrate for protein farnesylation, rescued atorvastatin-induced mutant p53 degradation in pancreatic cancer cells. Tipifarnib, a farnesyltransferase inhibitor, mirrored atorvastatin's effects on mutant p53, degraded mutant p53 in a dose-dependent manner, and converted farnesylated DNAJA1 into unfarnesylated DNAJA1. Farnesyltransferase gene knockdown also significantly promoted mutant p53 degradation. Coimmunoprecipitation either by an anti-DNAJA1 or p53 antibody confirmed the direct interaction of mutant p53 and DNAJA1 and higher doses of atorvastatin treatments converted more farnesylated DNAJA1 into unfarnesylated DNAJA1 with much less mutant p53 pulled down by DNAJA1. Strikingly, C394S mutant DNAJA1, in which the cysteine of the CAAX box was mutated to serine, was no longer able to be farnesylated and lost the ability to maintain mutant p53 stabilization. Our results show that farnesylated DNAJA1 is a crucial chaperone in maintaining mutant p53 stabilization and targeting farnesylated DNAJA1 by atorvastatin will be critical for inhibiting p53 mutant cancer.