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. RNA seq of OVCAR4 and OVCAR3 cell lines treated with DMSO, PARP7 inhibitor, taxol and combination.