IDO1 and ovarian cancer: While Zhang et al. have observed that IL-27 expression by plasmid transfected SKOV3 cells leads to suppression of ovarian cancer cells' proliferation and enhanced cytotoxicity [15], other studies have shown that IL-27 helps ovarian tumors' progression by escalating production of IDO, PDL-1 [23], and CD39 [25] and thus induction of immunosuppressive environment in favor of ovarian cancer progression.