Dual-inhibition of NAMPT and PAK4 induces anti-tumor effects in 3D-spheroids model of platinum-resistant ovarian cancer

Abstract Ovarian cancer follows a characteristic progression pattern, forming multiple tumor masses enriched with cancer stem cells (CSCs) within the abdomen. Most patients develop resistance to standard platinum-based drugs, necessitating better treatment approaches. To target CSCs, inhibition of nicotinamide phosphoribosyltransferase (NAMPT), which is the rate-limiting enzyme in the salvage pathway for NAD+ synthesis, has been explored in ovarian cancer. KPT-9274 is an innovative drug targeting both NAMPT and PAK4. However, its effectiveness against ovarian cancer has not been validated. Here, we show the efficacy and mechanisms of KPT-9274 in treating 3D-cultured spheroids that are resistant to platinum-based drugs. In these spheroids, KPT-9274 not only inhibited NAD+ production in NAMPT-dependent cell lines, but also suppressed NADPH and ATP production, indicating reduced mitochondrial function. It also downregulated expression of genes involved with inflammation and DNA repair. Moreover, KPT-9274 impaired the kinase activity of PAK4 by altering the localization from cytoplasmic to nucleus, leading to decreased phosphorylation of S6 Ribosomal protein, AKT, and β-Catenin in the cytoplasm in a NAD+- dependent manner. These findings suggest that KPT-9274 is a promising treatment for ovarian cancer patients resistant to platinum drugs. Our study also indicates that the identification of specific NAD+-producing pathway is required for stratification of patients who can benefit from a KPT-9274 therapy.