Store-operated Ca2+ entry is remodelled and controls in vitro angiogenesis in endothelial progenitor cells isolated from tumoral patients.

Background: Endothelial progenitor cells (EPCs) may be recruited from bone marrow to sustain tumor vascularisation and promote the metastatic switch. Understanding the molecular mechanisms driving EPC proliferation and tubulogenesis could outline novel targets for alternative anti-angiogenic treatments. Store-operated Ca 2+ entry (SOCE), which is activated by a depletion of the intracellular Ca 2+ pool, regulates the growth of human EPCs, where is mediated by the interaction between the endoplasmic reticulum Ca 2+ -sensor, Stim1, and the plasmalemmal Ca 2+ channel, Orai1. As oncogenesis may be associated to the capability of tumor cells to grow independently on Ca 2+ influx, it is important to assess whether SOCE regulates EPC-dependent angiogenesis also in tumor patients. Methodology/Principal Findings: The present study employed Ca 2+ imaging, recombinant sub-membranal and mitochondrial aequorin, real-time polymerase chain reaction, gene silencing techniques and western blot analysis to investigate the expression and the role of SOCE in EPCs isolated from peripheral blood of patients affected by renal cellular carcinoma (RCC; RCC-EPCs) as compared to control EPCs (N-EPCs). SOCE, activated by either pharmacological (i.e. cyclopiazonic acid) or physiological (i.e. ATP) stimulation, was significantly higher in RCC-EPCs and was selectively sensitive to BTP-2, and to the trivalent cations, La 3+ and Gd 3+ . Furthermore, 2-APB enhanced thapsigargin-evoked SOCE at low concentrations, whereas higher doses caused SOCE inhibition. Conversely, the anti-angiogenic drug, carboxyamidotriazole (CAI), blocked both SOCE and the intracellular Ca 2+ release. SOCE was associated to the over-expression of Orai1, Stim1, and transient receptor potential channel 1 (TRPC1) at both mRNA and protein level The intracellular Ca 2+ buffer, BAPTA, BTP-2,