Currently, the options available for the treatment of various cancers including breast cancer, are associated with several limitations such as severe toxicity, drug resistance, poor prognosis, and high risk of recurrence. Therefore, there appears to be an increasing interest and necessity in investigating various phytochemicals from natural sources for a superior and safer alternative treatment strategy. The bioactive phytochemical alpha (α) and beta (β)-asarone from Acorus calamus is a traditional medicine system that has been shown to have anti-tumor and chemo-inhibitory activities in numerous preclinical studies both in vitro and in vivo.Various experimental studies with human malignant cell lines and animal models have also confirmed the anti-tumor and anticancer activities of β-asarone. In this study, we aimed to investigate the anti-cancer effects of β-asarone alone or together with etoposide buy measuring cellular responses such as cell viablity, cell cycle arrest and apoptosis using breast cancer cell line MCF-7 cells. In order to get insight in to the mechanism, we also tested the expression of of NF-κB / p65 activity and the expression of Bcl-2 family member pro-apoptotic Bax protein together with p53 and p21 activities in response to β-asarone alone or together with etoposide treatment. As a result, it was concluded that the use of β-asarone alone in breast cancer cells is effective in reducing cell viability, but when used together with Etoposide, it does not cause a synergistic effect. Here we suggest that that in particular activation of NF-kB/p65 may be lead resistance to etoposide treatment.

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.

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