Human ORAI1 blocking peptide

Esophageal cancer (EC) is the 6th leading cause of cancer mortality worldwide with poor prognosis, hence more effective chemotherapeutic drugs for this deadly disease are urgently needed. We previously reported that high expression of Orai1, a store-operated Ca2+ entry (SOCE) channel, was associated with poor survival rate in EC patients and Orai1-mediated intracellular Ca2+ oscillations regulated cancer cell proliferation. Previous studies suggested that Orai1-mediated SOCE is a promising target for EC chemotherapy. Here, we evaluated the anticancer effect of a novel SOCE inhibitor, RP4010, in cultured EC cells and xenograft models. Compared to other previously reported SOCE channel inhibitors, RP4010 is more potent in blocking SOCE and inhibiting cell proliferation in EC and other cancer cells. Treatment with RP4010 resulted in reduction of intracellular Ca2+ oscillations, caused cell cycle arrest at G0/G1 phase in vitro, decreased nuclear translocation of nuclear factor kappa B (HP-kappa B) in vivo and in vitro, and inhibited tumor growth in vivo. Taken together, data demonstrated the therapeutic potential of RP4010 in EC patients via inhibition of SOCE-mediated intracellular Ca2+ signaling.

Ca2+ channels play an important role in the development of different types of cancer, and considerable progress has been made to understand the pathophysiological mechanisms underlying the role of Ca2+ influx in the development of different cancer hallmarks. Orai1 is among the most ubiquitous and multifunctional Ca2+ channels. Orai1 mediates the highly Ca2+ -selective Ca2+ release-activated current (I-SOC) and participates in the less Ca2+ -selective store-operated current (Isoc), along with STIM1 or STIM1 and TRPC1, respectively. Furthermore, Orai1 contributes to a variety of store-independent Ca2+ influx mechanisms, including the arachidonate-regulated Ca2+ current, together with Orai3 and the plasma membrane resident pool of STIM1, as well as the constitutive Ca2+ influx processes activated by the secretory pathway Ca2+-ATPase-2 (SPCA2) or supported by physical and functional interaction with the small conductance Ca2+-activated K+ channel 3 (SK3) or the voltage-dependent K(v)10.1 channel. This review summarizes the current knowledge concerning the store-independent mechanisms of Ca2+ influx activation through Orai1 channels and their role in the development of different cancer features.