Combined epigenetic and metabolic inhibition blocks platinum-induced ovarian cancer stem cell enrichment

High grade serous ovarian cancer (HGSOC) is the most common and aggressive type of ovarian cancer. Platinum resistance is a common occurrence in HGSOC and a main cause of tumor relapse resulting in high patient mortality rates. Recurrent OC is enriched in aldehyde dehydrogenase (ALDH)+ ovarian cancer stem cells (OCSCs), which are resistant to platinum agents. We demonstrated that acute platinum treatment induced a DNA damage-dependent decrease in BRCA1 levels. In a parallel response associated with G2/M arrest, platinum treatment also induced an increase in expression of NAMPT, the rate limiting regulator of NAD+ production from the salvage pathway, and levels of NAD+, the cofactor required for ALDH activity. Concurrent inhibition of DNA methyltransferases (DNMTs) and NAMPT synergistically abrogated the platinum-induced increase in OCSCs. Combining pharmacological inhibitors of DNMT and NAMPT with carboplatin reduced tumorigenesis and OCSC percentage in vivo. We conclude that both epigenetic and metabolic alterations lead to platinum induced OCSC enrichment, providing preclinical evidence that in the neoadjuvant setting, combining DNMT and NAMPT inhibitors with platinum has the potential to reduce OC recurrence and avert the development of platinum resistance.