Therapy Induced Senescence Promote Expression of Death Receptors in Breast Cancer Cells

Abstract

Chemotherapeutic agents that cause DNA damage also induce cellular senescence known as therapy-induced senescence (TIS).Cells undergoing senescence may exert detrimental effects by promoting tumor progression in healthy cells or supporting metastases in cancer cells due to "senesence-associated secretory phenotype" (SASP), involving secretion of chemokines, cytokines, metalloproteinases, and growth factors. Death receptors belong to the tumor necrosis factor receptor superfamily and implicated in induction of apoptosis via activation of extrinsic pathway. The most recognized death receptors are FAS (CD95), TNFR1 and TRAIL-R1 / 2 (DR4-DR5) etc. and capable of directly inducing apoptosis in the cell. In this study we aimed to investigate the expression of cell death receptors in response to TIS of breast cancer cells for their potential use in elimination of senescent cells.Doxorubicin and etoposide were used to induce senescence selectively in MCF7 breast cancer cell line. Senescence induction was confirmed by β-galactosidase staining and cell cycle analysis. Activations of p53, p21, and γ-H2AX and expression levels of cell death receptors (FAS (CD95), TNFR1-2 and DR5 were tested by western blot analysis. Apoptosis was measured by Annexin V/7AAD analysis.Here, we show that chemotherapy agents etoposide and doxorubicin induced senescence by arresting MCF-12A and MCF-7 cells in G1 and G2/M phases of cell cycle, respectively. Induction of senescence is confirmed by SA-β-gal staining and by activation of -H2AX, p53 and p21 proteins. Neither etoposide nor doxorubicin induced significant apoptosis in MCF12A or MCF-7 cells.Importantly, TIS increased the protein levels of TNFR1, TNFR2 and DR5 receptors selectively in MCF-7 cells but not in MCF-12A cells. These data suggest that chemotherapy agents induce senescence increased the expression of death receptors in breast cancer cell line MCF-7 thus provide a basis for further investigation of death receptor mediated targeting of senescent cells as potential therapeutic strategy.