Abstract
BACKGROUND: Store-operated Ca(2+) entry (SOCE) has been implicated in the migration of some cancer cell lines. The canonical SOCE is defined as the Ca(2+) entry that occurs in response to near-maximal depletion of Ca(2+) within the endoplasmic reticulum. Alternatively, arachidonic acid (AA) has been shown to induce Ca(2+) entry in a store-independent manner through Orai1/Orai3 hetero-multimeric channels. However, the role of this AA-induced Ca(2+) entry pathway in cancer cell migration has not been adequately assessed. METHODS: The present study investigated the involvement of AA-induced Ca(2+) entry in migration in BON cells, a model gastro-enteropancreatic neuroendocrine tumor (GEPNET) cell line using pharmacological and gene knockdown methods in combination with live cell fluorescence imaging and standard migration assays. RESULTS: We showed that both the store-dependent and AA-induced Ca(2+) entry modes could be selectively activated and that exogenous administration of AA resulted in Ca(2+) entry that was pharmacologically distinct from SOCE. Also, whereas homomeric Orai1-containing channels appeared to largely underlie SOCE, the AA-induced Ca(2+) entry channel required the expression of Orai3 as well as Orai1. Moreover, we showed that AA treatment enhanced the migration of BON cells and that this migration could be abrogated by selective inhibition of the AA-induced Ca(2+) entry. CONCLUSIONS: Taken together, these data revealed that an alternative Orai3-dependent Ca(2+) entry pathway is an important signal for GEPNET cell migration.