Additionally, the CD14+HLA‐DR−/low MDSCs cultured with the ascites from patients with ovarian cancer in vitro exhibited upregulated expression of ARG1 and iNOS.53 Treatment with inhibitors of IDO1, ARG1 or iNOS, or with L‐arginine abolished the suppressive effects of MDSCs derived from/induced by ascites on T‐cells.52, 53 Interestingly, the extracellular vesicles (EVs) in the ovarian cancer ascites also exhibit ARG1 expression.51In vitro studies have demonstrated that EVs containing ARG1 can inhibit T‐cell proliferation, which can be mitigated by ARG1 inhibitor or l‐arginine. This evidence concerns the gene IDO1 and ovarian cancer.