Effects of cadmium on the expression of beta-catenin, caveolin-1 and HSPs in ERalpha-positive and ERalpha-negative cancer cell lines

SHORTREDE J.; ALVAREZ OLMEDO D.; CUELLO CARRION F. D.; CIOCCA D. R.; FANELLI M. A.

Porto Alegre

Workshop; IX Cell Stress Society International Workshop on the Molecular Biology of Stress Responses; 2012

Cell Stress Society International

Introduction: The metal Cd is an environmental pollutant that enters the body through diet and cigarette smoke. It is a class 1 carcinogen associated with different human cancer types. Cd works at all stages of the oncogenic process through multiple non-exclusive mechanisms that affect different intracellular pathways. As a metalloestrogen, Cd acts via estrogen receptor alpha (ERalpha). However, ER-independent pathways are also affected. At the level of distal tubule cells of the kidney, Cd induced disruption of adherents junctions mediated by E-cadherin and beta-catenin. In these cells, Cd induced beta-catenin translocation from the cytoplasm to the nucleus promoting cell proliferation and survival. Protein location is emerging as a key factor to understand tumor cell biology. In addition, there are interactions of beta-catenin with Hsp27 (HSPB1) and Caveolin-1 (Cav-1), proteins that are important in several regulatory pathways. Objetives: To evaluate the effects of Cd on the expression and localization of beta-catenin, Hsp27 and Cav-1 in ERalpha positive and negatives cancer cells lines, correlating with cytotoxicity as well as with cell survival and apoptosis. Methodology: HeLa, MDA-MB-231 and MCF-7 cells were exposed to different CdCl2 concentrations (0, 1, 5, 10, 25, 50, 100 uM), during 3 hours. Cytotoxicity was evaluated by MTT and clonogenic assay. The localization and expression of beta-catenin, Hsp27 and Cav-1 were evaluated by immunocytochemistry. Apoptosis was studied by the TUNEL and by the Bax/Bcl-2 ratio. Results: Cd treatment (100 uM) reduced the viability of HeLa cells to 26%, MDA-MB-231 to 84% and MCF-7 cells to 85%. Long term survival was inhibited in HeLa and MCF-7 at 10 and 50 uM CdCl2 respectively, while in MDA-MB-231 few colonies were detected at 100 ìM CdCl2. Apoptosis did not change significantly in HeLa cells but significant changes were observed in MCF-7 cells line. With increasing CdCl2 concentrations beta-catenin acquired, in MDA-MB-231 cells, para/peri nuclear location, while in HeLa cells this protein showed an intricate distribution pattern. In MCF-7 beta-catenin expression was modified passing from membrane to the cytoplasmic/peri-nuclear region. Cav-1 changed from a cytoplasmic distribution to a para-nuclear location in the three cell lines after Cd administration. In all cell lines Hsp27 expression was observed in the cytoplasm but Cd induced noticeable dots in the nuclei. Conclusions: Cd differentially modulated the distribution of beta-catenin, Cav-1 and Hsp27 in the ERalpha-positive and negative cancer cell lines. These changes might explain the differences in the viability and colony formation.