Cellular senescence signaling in cancer: A novel therapeutic target to combat human malignancies.

Senescence is a special state of tumor suppression induced by cell cycle arrest. However, releasing senescence-associated secretory phenotypes by senescent cells could provide tumorigenic conditions and epigenetic changes in neighboring cells. The conventional anticancer drugs activate therapy-induced senescence by several mechanisms which include an increase in mitochondrial biogenesis and reactive oxygen species, up-regulation of tumor suppressor proteins (e.g., p53, p21, p38, and p16) and modulation of dysregulated signaling mediators, including senescence-associated β-galactosidase, ataxia-telangiectasia mutated/ATM and Rad3-related, checkpoint kinase1/2, phosphatidylinositol 3-kinases/Akt, Ras/Raf pathway, and extracellular signal-regulated kinase/mitogen-activated protein kinase. On the other hand, conventional anticancer agents induce the secretion of procarcinogenic molecules, including inflammatory mediators, such as nuclear factor-κB, tumor necrosis factor-α, and interleukins, and angiogenic mediators, namely vascular endothelial growth factor, in the tumor microenvironment. This condition urges the need for finding novel alternative therapies, novel senolytics, senescence inducers and combination therapies in the regulation of senescence towards the regulation of multiple tumorigenic conditions. This comprehensive review highlights the therapeutic targets and signaling pathways in the senescence of tumor cells. The critical roles of anticancer drug-induced senescence, senolytics, and associated combined administrations are evaluated in the attenuation of cellular senescence pathways to achieve cancer prevention and efficient treatment. Current challenges/pitfalls, limitations, and future research are also discussed.