PARP Inhibitor Talazoparib Drives Cancer Cell Senescence in Lung Tumors

Cellular senescence — a state of irreversible proliferation arrest — is increasingly recognized as both a consequence of anticancer therapy and a driver of tumor biology. While PARP inhibitors (PARPi) are established treatments in BRCA-mutated cancers, their capacity to induce senescence in lung cancer cells remained poorly characterized. This study systematically evaluated five clinically relevant PARPi — Veliparib, Rucaparib, Olaparib, Niraparib, and Talazoparib — in three NSCLC cell lines (A549, Calu-1, and H460), with a focus on mapping which drug most potently triggers therapy-induced senescence (TIS).

Across all three cell lines, Talazoparib stood out as the strongest inducer of senescence. Treated cells displayed the full senescence phenotype: enlarged cell shape, elevated senescence-associated beta-galactosidase (SA-β-Gal) activity, and reduced Lamin B1 expression. Critically, the senescence phenotype was not simply a function of catalytic PARP inhibition — the level of pADPr (poly-ADP-ribose) suppression did not correlate directly with senescence induction across the five drugs. This suggests the mechanism involves PARP trapping on DNA rather than mere enzymatic blockade, consistent with Talazoparib's known status as the most potent PARP-trapping agent.

To directly test PARP1's role, the researchers used PARP1 knockout cells. In the absence of PARP1, Talazoparib failed to induce any measurable senescence phenotype, firmly establishing that PARP1 is a necessary mediator of this effect — not just a bystander. This mechanistic insight distinguishes the senescence-inducing pathway from simple catalytic inhibition.

Recognizing that senescent cancer cells upregulate anti-apoptotic proteins such as Bcl-2 and Bcl-XL to evade death, the team then tested whether the senolytic drug Navitoclax (ABT-263) — which inhibits these survival proteins — could eliminate the Talazoparib-induced senescent cells. The combination of Talazoparib followed by Navitoclax produced significantly greater cell death than either agent alone, and this additive effect was PARP1-dependent: it was absent in PARP1 knockout cells, confirming that the senolytic effect specifically targeted the PARP1-driven senescent population.

These findings carry direct implications for lung cancer treatment. Several ongoing clinical trials are exploring PARPi in NSCLC, yet the possibility that these agents generate senescent, treatment-resistant tumor cells has received limited attention. By identifying senescence as a measurable and mechanistically explicable outcome of PARPi treatment — and by demonstrating that senolytics can eliminate these cells — this study charts a rational path toward combination regimens that could prevent therapy failure driven by TIS.