Paracrine Effects of the Senescence-Associated Secretory Phenotype Decrease Cancer Cell Adhesion

ABSTRACT High grade serous ovarian cancer (HGSOC) is the most lethal gynecological cancer. Platinumbased therapies such as cisplatin are standard-of-care for HGSOC patients; however, the majority of HGSOCs initially treated with cisplatin will recur with widespread disseminated disease. Cisplatin induces cellular senescence, a stable cell cycle arrest. Although they are non-proliferative, senescent cells secrete a complex mix of cytokines and small molecules, named the senescence associated secretory phenotype (SASP), that have been shown to have pro-tumorigenic effects. To investigate how the SASP contributes to HGSOC progression, we used conditioned media from cisplatin therapy-induced senescent cells to culture naïve HGSOC spheroids. We report that while the SASP does not affect spheroid formation, the adhesion of cells within spheroids is altered, leading to cell detachment from spheroids. Interestingly, our data indicate that this occurs in an MMP-independent manner. Analysis of RNA-Seq samples indicates many adhesion-related genes and adhesion factors are transcriptionally downregulated by the SASP, particularly fibronectin and integrins, which was validated by immunofluorescence in spheroids. These data reveal that senescent cells contribute to a transcriptional program in nearby cancer cells in a paracrine fashion that decreases their adhesion, which may contribute to tumor dissemination.