ORAI1 and cancer: Moreover, as both, the SK3-Orai1 and SPCA2-Orai1 co-regulation have been elucidated in breast cancer cells, it is of interest whether SPCA2 and SK3 synergistically contribute to a co-regulation with Orai1 in lipid rafts in cancer cells and supports the initiation of constitutive Ca2+ entry via Orai1.