Modulation of beta-catenin, Hsp27 and caveolin-1 by cadmium in HeLa cells

ALVAREZ OLMEDO D.; CUELLO CARRIÓN F. D.; MARTINIS E.; WUILLUOD R.; GIBERT B.; ARRIGO A. P.; CIOCCA D. R.; FANELLI M. A.

Woods Hole, MA, USA.

Congreso; Heat Shock Proteins in Cancer and Immunology; 2010

Cell Stress Society International

The metal cadmium (Cd) is an environmental pollutant that enters the body through diet and/or through cigarette smoke. It has been classified as a class 1 carcinogen associated with different human cancer types. It works in all stages of the oncogenic process through multiple non-exclusive mechanisms that affect different intracellular pathways. Cd is the best characterized metalloestrogen, acting via estrogen receptor alfa (ERa). Also, ER-independent pathways are affected by Cd. At the level of distal proximal tubule cells, Cd induced disruption of adherens junctions mediated by E-cadherin, beta-catenin was translocated to the cytosol and nucleus promoting cell proliferation and impeding apoptosis. Previously, we have demonstrated that beta-catenin was associated with Hsp27 and caveolin-1 in human breast cancer biopsies, and that beta-catenin was related with the disease prognosis. The aim of this study was to evaluate the effects of Cd on survival and apoptosis by modulating the expression and localization of beta-catenin, Hsp27 and caveolin-1 in an ERa-negative cell line. We studied HeLa cells under different CdCI2 concentrations (0, 1, 5, 10, 25, 50, 100 uM), the cells were exposed during three hours. Cytotoxicity was evaluated by MTT and clonogenic assay. The localization and expression levels of beta-catenin, Hsp27 and caveolin-1 were evaluated by immunocytochemistry and Western blots (in total protein extracts, cytosolic and nuclear fractions). Apoptosis was assessed by the TUNEL and Bax/BcI-2 ratio. We found that Cd treatment reduced the cell viability to 26% and drastically reduced colony formation starting from 5 uM CdCI2 and induced significant changes in the levels of the proteins studied. The localization of beta-catenin was modified and its expression increased in the cytoplasm. The Bax/BcI-2 ratio significantly decreased (>1) with respect to control. HeLa cells transfected with HSh27-2.2 (highly Hsp27-depleted) showed nuclear beta-catenin localization at low Cd levels. Cadmium would be modulating the express ion and localization of beta-catenin, Hsp27 and caveolin-1 in ER-negative cells affecting innate abilities such as colony formation without inhibiting completely their viability. Hsp27 seems to interfere with nuclear beta-catenin translocation.