The Potent and Paradoxical Biology of Cellular Senescence in Cancer

Cellular senescence is a tumor-suppressive program that promotes tissue homeostasis by identifying damaged cells for immune-mediated clearance. Thus, the ability to evade senescence and the ensuing immune surveillance is a hallmark of cancer. Reactivation of senescence programs can result in profound immune-mediated tumor regressions or sensitize tumors to immunotherapy, although the aberrant persistence of senescent cells can promote tissue decline and contribute to the side effects of some cancer therapies. In this review, we first briefly describe the discovery of senescence as a tumor-suppressive program. Next, we highlight the dueling good and bad effects of the senescence-associated secretory program (SASP) in cancer, including SASP-dependent immune effects. We then summarize the beneficial and deleterious effects of senescence induction by cancer therapies and strategies in development to leverage senescence therapeutically. Finally, we highlight challenges and unmet needs in understanding senescence in cancer and developing senescence-modulating therapies.