Orai2 Modulates Store-Operated Ca Entry and Cell Cycle Progression in Breast Cancer Cells.

Breast cancer is a heterogeneous disease from the histological and molecular expression point of view, and this heterogeneity determines cancer aggressiveness. Store-operated Ca entry (SOCE), a major mechanism for Ca entry in non-excitable cells, is significantly remodeled in cancer cells and plays an important role in the development and support of different cancer hallmarks. The store-operated CRAC (Ca release-activated Ca) channels are predominantly comprised of Orai1 but the participation of Orai2 and Orai3 subunits has been reported to modulate the magnitude of Ca responses. Here we provide evidence for a heterogeneous expression of Orai2 among different breast cancer cell lines. In the HER2 and triple negative breast cancer cell lines SKBR3 and BT20, respectively, where the expression of Orai2 was greater, Orai2 modulates the magnitude of SOCE and sustain Ca oscillations in response to carbachol. Interestingly, in these cells Orai2 modulates the activation of NFAT1 and NFAT4 in response to high and low agonist concentrations. Finally, we have found that, in cells with high Orai2 expression, Orai2 knockdown leads to cell cycle arrest at the G0-G1 phase and decreases apoptosis resistance upon cisplatin treatment. Altogether, these findings indicate that, in breast cancer cells with a high Orai2 expression, Orai2 plays a relevant functional role in agonist-evoked Ca signals, cell proliferation and apoptosis resistance.