Abstract 899: Selective clearance of cells undergoing therapy-induced senescence in a model of triple negative breast cancer

Abstract

Despite the ability of chemotherapy (and/or radiation) to eliminate the majority of tumor cells, some residual surviving cells may be able to escape cell death by entering into a prolonged senescence-based growth arrest. In addition to apoptosis, the majority of anti-cancer therapies induce senescence that has long been considered to be a favorable outcome of treatment due to its perceived irreversibility. However, accumulating studies in the literature demonstrate that therapy induced senescence may reflect one form of tumor dormancy and disease recurrence, when senescent cells are able to regain proliferative capacity. Tumor cells that escape dormancy often demonstrate an aggressive phenotype and are refractory to further treatment. Senescent cells are characterized by a specific (though often heterogeneous) secretory profile (Senescence Associated Secretory Phenotype or SASP), some components of which have been shown to promote tumorigenesis and may assist in neoplastic escape after therapy. In the current work, we evaluated the capacity of the BCL protein family inhibitor, ABT 263, to selectively clear breast tumor cells induced into senescence by doxorubicin. MDA-MB231-231 human breast cancer cells (a model of triple negative breast cancer) were induced into senescence upon exposure to a clinical concentration of the chemotherapeutic agent, doxorubicin (Dox). While a fraction of the MDA-MB-231 cell population underwent cell death, a large subpopulation entered into a state of prolonged growth arrest that lasted for several days, after which time the cells recovered proliferative capacity and formed colonies. At the time points when cells were arrested, prominent Senescence Associated β-Galactosidase staining marker indicative of senescence. In addition, tumor tissue collected from mice that received injections of Dox also were positive for β-Galactosidase staining. Cells induced into senescence and treated with ABT263 for 18 hours showed a significant increase in apoptosis and did not regain colony forming capabilities. We therefore postulate that senescence and escape from senescence may represent a form of tumor dormancy and disease recurrence, respectively. Consequently, if Therapy Induced Senescence is a deleterious outcome of treatment, it is of importance to identify strategies that might prevent senescent cells from neoplastic escape and induce cell death in order to completely eliminate residual tumors and thereby interfere with disease recurrence. Citation Format: Liliya Tyutyunyk, Tareq Saleh, David A. Gewirtz. Selective clearance of cells undergoing therapy-induced senescence in a model of triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 899.