High Bcl2/Bax ratio in Walker tumor cells protect

Authors: Karina G Zecchin Ana Luiza O Seidinger Marcos R Chiaratti Giovanna R Degasperi Flávio V Meirelles Roger F Castilho Aníbal E Vercesi

Publish Date: 2007/04/12

Volume: 39, Issue: 2, Pages: 186-194

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Abstract

It has been previously shown that Walker 256 tumor cells express a high content of the antiapoptotic protein Bcl2 which protects mitochondria against the damaging effects of Ca2+ In the present study we analyze H2O2induced apoptotic death in two different types of tumor cells Walker 256 and SCC25 Treatment with H2O2 4mM increased reactive oxygen species generation and the concentration of cytosolic free Ca2+ These alterations preceded apoptosis in both cell lines In Walker cells which show a high Bcl2/Bax ratio apoptosis was dependent on calcineurin activation and independent of changes in mitochondrial membrane potential Δ eqid1 m as well as cytochrome c release In contrast in SCC25 cells which show a lower Bcl2/Bax ratio apoptosis was preceded by a decrease in Δ eqid2 m mitochondrial permeability transition and cytochrome c release Caspase3 activation occurred in both cell lines The data suggest that although the high Bcl2/Bax ratio protected the mitochondria of Walker cells from oxidative stress it was not sufficient to prevent apoptosis through calcineurin pathways

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