Cellular senescence is a state of irreversible cell proliferation arrest provoked by a persistent DNA damage induced by a variety of potentially oncogenic signals, and it functions as a primary tumor-suppression mechanism. Recent studies, however, revealed that senescent cells have the potential to secrete numerous inflammatory cytokines, chemokines, growth factors and matrix-remodeling factors, since unlike apoptotic cells, senescent cells are viable for a long period of time. This newly identified phenotype of cellular senescence, called senescence-associated secretory phenotype(SASP or senescence-associated secretome), could potentially provide beneficial effects, such as tissue repair, but sometimes could induce deleterious side effects, such as cancer progression, depending on the biological context.