Targeting BRCA1/2-deficient cancers with folate and vitamin C

Project Summary BRCA1 and BRCA2 are tumor suppressor genes frequently inactivated in cancer, particularly in ovarian and breast cancers. Despite recent advances in therapy, many patients with BRCA1/2-deficient cancers eventually die of the disease and, therefore, new treatment options are needed. The goal of this proposal is to develop a novel targeted therapy against BRCA1/2-deficient cancers that combines high doses of tetrahydrofolate (THF) and vitamin C (VC) to generate metabolic genotoxins in cancer cells. The rationale of the proposed strategy stems from the recent discovery that high doses of THF, the active form of folate, oxidize generating the potent crosslinker formaldehyde (FA), which kills cells deficient in DNA crosslink repair such as BRCA1/2-mutant cells. In addition, preliminary data show that vitamin C (VC) promotes the selective killing of BRCA1/2-deficient cells by THF. VC and THF synergize at generating reactive oxygen species (ROS), suggesting formaldehyde and ROS generation might drive the cytotoxic effects in BRCA-mutant cells. In contrast, VC reduces THF toxicity in normal tissues in mice, which allows the administration of higher doses of THF. Furthermore, treatment with THF and VC in combination prolongs the survival of mice with BRCA1-mutant tumors. Based on these findings, this proposal aims to: (1) Understand the mechanism of selectivity of the vitamin combination against BRCA1/2- deficient cells, by using isogenic cell lines, metabolic tools, DNA damage assays and molecular and cell biology techniques. (2) Characterize the interaction between THF and VC in mice, by employing metabolomics, ultrasensitive mass-spectrometry analysis of DNA adducts, immunohistochemistry and infrared microscopy. (3) Assess the efficacy of THF/VC therapy against BRCA-mutant tumors in mice, by using orthotopic syngeneic models of ovarian and breast cancer and measuring the impact of THF/VC in tumor growth and overall survival. By using state-of-the-art tools and cancer models, this project could provide the foundations of a novel therapeutic strategy for the treatment of BRCA1/2-mutant cancers. In addition, it could support an unconventional approach of harnessing metabolism for cancer therapy that manipulates metabolism to generate metabolic genotoxins in cancer cells.