Inhibition of stromal-interacting molecule 1-mediated store-operated Ca2+ entry as a novel strategy for the treatment of acquired imatinib-resistant gastrointestinal stromal tumors

: Imatinib has revolutionized the treatment of gastrointestinal stromal tumors (GIST); however, primary and secondary resistance to imatinib is still a major cause of treatment failure. Multiple mechanisms are involved in this progression. In the present study, we reported a novel mechanism for the acquired resistance to imatinib, which was induced by enhanced Ca2+ influx via stromal-interacting molecule 1 (STIM1)-mediated store-operated Ca2+ entry (SOCE). We found that the STIM1 expression level was related to the acquired resistance to imatinib in our studied cohort. The function of STIM1 in imatinib-resistant GIST cells was also confirmed both in vivo and in vitro. The results showed that STIM1 overexpression contributed to SOCE and drug response in imatinib-sensitive GIST cells. Blockage of SOCE by STIM1 knockdown suppressed the proliferation of imatinib-resistant GIST cell lines and xenografts. In addition, STIM1-mediated SOCE exerted an antiapoptotic effect via the MEK/ERK pathway. The results from this study provide a basis for further research into potential novel therapeutic strategies in acquired imatinib-resistant GIST.