Effect of RBN-2397, paclitaxel and their combination on ovarian cancer cell biology.

PARP7 (TiPARP), a mono (ADP-ribosyl) transferase (MART) was found to target α-tubulin proteins in ovarian cancer cells, enhancing their growth and migration. RBN-2397 is a potent inhibitor that selectively acts on PARP7. Here, we show that RBN-2397 treatment leads to the stabilization of microtubules in ovarian cancer cells, namely α-tubulin, mimicking what was previously observed with PARP7 knockdown. When treated with RBN-2397, we observe a decrease in growth and migration of ovarian cancer cells and, interestingly, the effect is intensified upon adding the microtubule stabilizing chemotherapeutic agent, paclitaxel. Mutating the site of α-tubulin MARylation by PARP7 similarly results in α-tubulin stabilization and decreased cell migration in the presence of paclitaxel when the tubulin network is further stabilized. In sum, we demonstrate that PARP7 inhibition decreases α-tubulin MARylation resulting in its stabilization, and ultimately leading to decreased ovarian cancer cell proliferation and migration. Finally, we show that combining PARP7 inhibitor and paclitaxel results in a more robust inhibition of aggressive ovarian cancer phenotypes. Collectively, this study highlights the potential of targeting PARP7 in combination with established chemotherapeutic agents to enhance treatment efficacy for ovarian cancer.