ER functions of oncogenes and tumor suppressors: Modulators of intracellular Ca2Â + signaling

Intracellular Ca2 + signals that arise from the endoplasmic reticulum (ER), the major intracellular Ca2 +-storage organelle, impact several mitochondrial functions and dictate cell survival and cell death processes. Furthermore, alterations in Ca2 + signaling in cancer cells promote survival and establish a high tolerance towards cell stress and damage, so that the on-going oncogenic stress does not result in the activation of cell death. Over the last years, the mechanisms underlying these oncogenic alterations in Ca2 + signaling have started to emerge. An important aspect of this is the identification of several major oncogenes, including Bcl-2, Bcl-XL, Mcl-1, PKB/Akt, and Ras, and tumor suppressors, such as p53, PTEN, PML, BRCA1, and Beclin 1, as direct and critical regulators of Ca2 +-transport systems located at the ER membranes, including IP3 receptors and SERCA Ca2 + pumps. In this way, these proteins execute part of their function by controlling the ER-mitochondrial Ca2 + fluxes, favoring either survival (oncogenes) or cell death (tumor suppressors). Oncogenic mutations, gene deletions or amplifications alter the expression and/or function of these proteins, thereby changing the delicate balance between oncogenes and tumor suppressors, impacting oncogenesis and favoring malignant cell function and behavior. In this review, we provided an integrated overview of the impact of the major oncogenes and tumor suppressors, often altered in cancer cells, on Ca2 + signaling from the ER Ca2 + stores. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen.