Proteomic Profiling Identifies Novel Biomarkers of Aging and Potential Senolytic Therapeutic Targets

Cellular senescence is an irreversible program of cell cycle arrest to restrict proliferation. The irreversible mechanism of senescence constitutes a barrier against cancer cell development. In addition, senescent cells interact with their microenvironment through secretion of numerous inflammatory signals which modulate immune response and wound healing. As senescent cells accumulate in the aging tissue, they contribute to chronic inflammation and age-related diseases. Because of the importance of senescent cells in determining fate of human tissues, organs and lifespan, it is crucial to effectively identify senescent cells with specific biomarkers in order to a) measure the degree of aging and damage in tissue and b) be able to therapeutically target senescent cells for removal (aka senolytic therapies). Here, we used mass spectrometry-based proteomics to identify biomarkers of aging in primary human mammary epithelial cells (HMECs) undergoing senescence. We performed untargeted proteomic profiling on three conditions: 1) primary HMECs undergoing their natural replicative senescence, 2) senescent luciferase-expressing HMECs vs. immortalized telomerase-expressing HMECs, and 3) HMECs induced to senescence by inhibition of nucleotide synthesis. Through statistical analysis, we have identified a group of 38 proteins that are consistently upregulated and downregulated in senescent HMECs. Importantly, we then use this “senescence signature” to predict novel senolytic drug targets through bioinformatic analysis of publicly available gene essentiality screening databases (e.g., the Cancer Dependency Map). In summary, we report a novel senescence signature derived from proteomic analysis that can serve as novel biomarkers of senescence and provide new targets for designing senolytic therapies.