Characterisation of Novel Markers and Effectors of Senescence and their Role in Cancer and Ageing

Cellular senescence is a reversible cell cycle arrest that has been shown to play a role in aging and cancer. Senescent cells accumulation can occur prematurely, as seen in response of stress and oncogenic insults, or normally, as observed in organismal aging. Thus, identification and studying senescent cells in vivo and in vitro have an important diagnostic and therapeutic potential. In addition, the molecular mechanisms involved in establishing and maintaining senescence are not fully understood. Consequently, the current approach that is used for senescent identification has limitations. For this reason, we characterized a list of potential markers of senescence from a proteomic screening of plasma membrane of senescent cells. From the list, we have validated 10 of them, namely, DEP1, NTAL, EBP50, STX4, VAMP3, ARMCX3, B2MG, LANCL1, VPS26A and PLD3 that are differently expressed in different model of cell senescence. These markers can be combined to detect senescent cells in vitro or in tissue sections. We also proposed a FACS based method using two markers (DEP1 and B2MG) with known extracellular epitopes. This could facilitate the senescence detection and studying. From the proteomic screening, we also found that BTK is elevated in senescent cells. BTK was induced in response of p53 activation due to different stimuli. Moreover, phosphorylation of ATM, p53 at ser15 and γH2AX was increased after BTK overexpression, which suggested the involvement of BTK in DNA damage pathways. BTK was able to phosphorylate p53 directly at N-terminus. BTK inhibition with chemicals or RNAi depletion was sufficient to bypass senescence. In addition, BTK inhibitors were also able to extend life span in flies. p53 KO flies did not show any difference in life span after using BTK inhibitors, which showed the importance of BTK in p53-mediated senescence. BTK inhibition also decreased the senescent cells accumulation in flies. All these data collectively suggest the possibility of using BTK inhibitors to ameliorate aging-associated disorders.