Cellular senescence, an unpopular yet trustworthy tumor suppressor mechanism

The term "cellular senescence" refers to the state in which normal cells irreversibly stop dividing. Historically, this condition was first inferred from the finding that normal human fibroblasts cease dividing after a limited number of cell divisions. Since then, cellular senescence has been discussed as a potential cause of aging of organisms. However, recent studies have significantly expanded our view of cellular senescence in terms of both mechanistics and biological significance. Accordingly, cellular senescence is now considered to play an important adaptive role, namely, a tumor suppressor function. This review will focus on recent findings that have contributed to the elucidation of the adaptive role of cellular senescence.