Folliculin deficient renal cancer cells exhibit BRCA1 A complex expression impairment and sensitivity to PARP1 inhibitor olaparib.

Background: Deficiency of folliculin (FLCN) may lead to renal cell carcinoma (RCC) in patients with Birt-Hogg-Dubé (BHD) disease. In this study, we investigated the cytotoxicity induced by PARP inhibitor olaparib in FLCN deficient RCC cells, and the interaction between FLCN and BRCA1 A complex-regulated DNA repair pathway.

Methods And Materials: FLCN expressing (ACHN and UOK257-F) and FLCN deficient (ACHN-2 and UOK257) cell lines were used in this research. Cell viability was detected by clonogenic assay and MTT assay. Flow cytometry and TUNEL assay were used to detect apoptosis. Autophagy in cells was measured by MDC assay, western blot, and transmission electron microscopy. Co-immunoprecipitation, immunofluorescence and western blot experiments were performed to determine the interaction between FLCN protein and BRCA1 A complex. The in vivo experiments were performed in a xenograft model by inoculating UOK 257 in nude mice.

Results: RCC cells with FLCN protein deficiency were more sensitive to olaparib treatment than the cells with FLCN expression. Olaparib treatment led to more severe autophagy and apoptosis in FLCN deficient ACHN-2 and UOK257 cells compared to the FLCN expressing ACHN and UOK257-F cells. Decreased BRCA1 A complex expression and disruption of DNA repair ability were detected in FLCN-deficient cells, suggesting that FLCN deficiency impaired BRCA1 A complex expression and sensitized cells to PARP inhibitor olaparib.

Conclusions: RCC cells deficient in FLCN are sensitive to olaparib treatment due to the impairment of BRCA1 A complex associated DNA repair ability. The results suggest that PARP inhibitor, such as olaparib, may be a potentially effective therapeutic approach for kidney tumors with deficiency of FLCN protein.