Molecular mechanisms of different sensitivity of tumor cells to dexamethasone.

The response of two cell lines, CSML-0 (does not express metastasin) and CSML-100 (high expression of metastasin) to cytolytic action of glucocorticoid was studied. Dexamethasone (1 microM) induced apoptosis of CSML-0 cells, while CSLM-100 cells were resistant to its cytolytic action. Apoptotic death of CSLM-100 cells was induced by incubation with dexamethasone in the presence of Ca-ATPase inhibitors, vanadate or thapsigargin. Metastasin, a proteins of the S-100 family, activated Ca-ATPase and ATP-dependent Ca2+ transport in plasmolemmal fraction of CSML-100 cells. Experiments showed that metastasin-induced activation of Ca-ATPase is a possible mechanisms of CSML-100 cell resistance to cytolytic dexamethasone action.