HSP27 AND BETA CATENIN ARE IMPORTANT KEY REGULATORS IN THE RESPONSE TO CHEMOTHERAPY

GISELA PENNACCHIO; MARIA EVELYN CÓRDOBA; NIUBYS CAYADO-GUTIÉRREZ; DARÍO CUELLO-CARRIÓN; SILVINA NADIN; LAURA M. VARGAS-ROIG; FANELLI MARIEL

Congreso; XXXVII Reunión Científica Anual Sociedad de Biología de Cuyo; 2019

Cellular senescence is a feature of cancer that can be induced by multiple mechanisms in tumors, and can exerts both beneficial anddetrimental effects on tumor initiation, growth, therapeutic efficacy, and tumor recurrence. The treatment of triple-negative breastcancers (TNBC) involves the administration of the conventional chemotherapeutic drug doxorubicin, given the lack of specific targetedagents. Furthermore, doxorubicin enhances cellular senescence in other tumor cell lines which is considered as a tumor suppressivemechanism. Recent evidence indicates however that senescent cells secrete various growth factors and cytokines, some of which mayparadoxically promote cancer progression such as TGFb, EGF, Wnt ligands, IL8, and IL6. They are known for their ability to promotetumor progression through the inhibition of apoptosis, induction of epithelial-mesenchymal transition (EMT) and/or resistance totherapy. The present study sought to examine the role of the Wnt/β-catenin and Hsp27 signaling pathway in response to cisplatin(CisPt)/doxorubicin (Doxo) treatment in human triple-negative (TN) breast cancer cell lines and their participation in chemoresistance.MDA MB231 (TN) and MCF10A cell lines were used. Cellular senescence was assayed by measuring SA-β-galactosidase (SA-β-Gal)activity. Apoptosis was evaluated by TUNEL assay and Annexin V-FITC Apoptosis Detection Kit. β-catenin and active β-catenin,Hsp27, phospho Hsp27, survivin, N-cadherin, vimentin, caspase 8 and cleaved PARP expressions were measured by westernblot.Results: Increased numbers of senescent cells (larger and flatter) were observed in both MDA-MB231 and MCF10A cells exposedto the IC50 dose of Doxo while CisPt treatment induced apoptosis in MDA-MB231 cells. After 48 h exposure to doxo and recoveryfor another 48 h, elicited high expressions levels of beta-catenin, Hsp27, N-cadherin, vimentin and survivin, with respect to control.With CisPt treatment an important decreased expression of these proteins were observed. On the other hand, HSP27 downregulationproduced significantly decreased expression of HSP27 and b-catenin. The simultaneous treatment with siRNA and doxorubicin for 48h kept low expression levels of both proteins. Under these conditions, we observed a decreased number of senescent cells and anincreased percentage in apoptosis, measured through the expression the cleaved PARP and caspase 8 by western blot. Conclusions:CisPt induced apoptosis and Doxo elicited senescence. Hsp27 and beta catenin may be involved in the cell decision(apoptosis/senescence) after chemotherapy. Doxo treatment promoted high expression levels of EMT related proteins. The downregulation of HSP27 and β-catenin sensitizes the cells to Doxo treatment by decreasing senescence and leading to apoptosis