Calcium Independent Effect of Orai1 and STIM1 in Non-Hodgkin B Cell Lymphoma Dissemination.

Ca2+ release-activated Ca2+ channels, composed of Orai1 and STIM1 (stromal interaction molecule 1) proteins, are the main Ca2+ entry mechanism in lymphocytes. Their role in cell migration and metastasis is demonstrated in solid cancers but it remains elusive in malignant hemopathies. Diffuse large B cell lymphoma (DLBCL) is characterized by the dissemination of neoplastic B cells throughout the organism which is under the control of chemokines such as Stromal Derived Factor 1 (SDF-1) and its receptor CXCR4. CXCR4 activation triggers a complex intracellular signaling including an increase in intracellular Ca2+ concentration whose role is still unclear. Using pharmacological and genetic approaches, we revealed that STIM1 and Orai1 were responsible for Ca2+ influx induced by SDF-1. Furthermore, we provide in vitro and in vivo evidence that they are necessary for basal or SDF-1-induced DLBCL cell migration which is independent of Ca2+ entry. We identify that they act as effectors coupling RhoA and ROCK dependent signaling pathway to MLC2 phosphorylation and actin polymerization. Finally, we revealed an alteration of Orai1 and STIM1 expression in extra-nodal DLBCL. Thus, we discovered a novel Ca2+-independent but Orai1 and STIM1-dependent signaling pathway involved in basal and CXCR4 dependent cell migration, which could be relevant for DLBCL physiopathology.