The senescence-associated secretory phenotype (SASP) from mesenchymal stromal cells impairs growth of immortalized prostate cells but has no effect on metastatic prostatic cancer cells

Senescent cells secrete inflammatory cytokines, proteases, and other factors, which are indicated as senescence-associated secretory phenotype (SASP). There are contrasting studies on the role of the SASP in cancer. Studies suggested that cancer cells may misuse the senescent secretome for their growth. Other investigations evidenced that the SASP may induce cancer growth arrest, senescence, or apoptosis. These conflicting data can be reconciled considering that cancer cells can coax senescent cells to secrete factors for their survival, thus abrogating the SASP's anti-cancer effect. Cancer stage may also have an impact on the capacity of the SASP to block tumor proliferation and promote senescence. Indeed, senescence is associated with a permanent cell cycle arrest, which needs functional cell cycle checkpoints. We evaluated the SASP effect on the in vitro biological properties of PNT2 and PC3 cells, which are immortalized prostate cells and metastatic prostatic cancer cells, respectively. We evidenced that SASPs, coming either from mesenchymal stromal cells treated with H202 or with low X-ray doses, induced senescence of immortalized cells but not of cancer cells. Hence, the SASP released by acute senescent cells should be considered as an effective weapon against pre-tumorigenesis events rather than an anti-cancer mechanism acting on malignant cells.