Indoleamine 2,3-dioxygenase (IDO) is a tryptophan-catabolizing enzyme that has immunoregulatory functions. Our prior study showed that tumoral IDO overexpression is involved in disease progression and impaired patient survival in human ovarian cancer, although its mechanism remains unclear. The purpose of the present study is to clarify the role of IDO during the process of peritoneal dissemination of ovarian cancer. Indoleamine 2,3-dioxygenase cDNA was transfected into the murine ovarian carcinoma cell line OV2944-HM-1, establishing stable clones of IDO-overexpressing cells (HM-1-IDO). Then HM-1-IDO or control vector-transfected cells (HM-1-mock) were i.p. transplanted into syngeneic immunocompetent mice. The HM-1-IDO-transplanted mice showed significantly shortened survival compared with HM-1-mock-transplanted (control) mice. On days 11 and 14 following transplantation, the tumor weight of peritoneal dissemination and ascites volume were significantly increased in HM-1-IDO-transplanted mice compared with those of control mice. This tumor-progressive effect was coincident with significantly reduced numbers of CD8+ T cells and natural killer cells within tumors as well as increased levels of transforming growth factor-β and interleukin-10 in ascites. Finally, treatment with the IDO inhibitor 1-methyl-tryptophan significantly suppressed tumor dissemination and ascites with reduced transforming growth factor-β secretion. These findings showed that tumor-derived IDO promotes the peritoneal dissemination of ovarian cancer through suppression of tumor-infiltrating effector T cell and natural killer cell recruitment and reciprocal enhancement of immunosuppressive cytokines in ascites, creating an immunotolerogenic environment within the peritoneal cavity. Therefore, IDO may be a promising molecular target for the therapeutic strategy of ovarian cancer.

Programmed cell death ligand 1 ( PD ‐L1) on tumor cells suppresses anti‐tumor immunity and has an unfavorable prognostic impact in ovarian cancer patients. We herein report the pathophysiological and therapeutic impacts of PD ‐L1 disruption in ovarian cancer. PD ‐L1 was genetically disrupted in the murine ovarian cancer cell line ID 8 using clustered regularly interspaced short palindromic repeats ( CRISPR )/Cas9‐mediated genome editing. PD ‐L1 knockout ( KO ) and control ovarian cancer cells were intraperitoneally inoculated into syngeneic mice, and survival and tumor dissemination were evaluated. Survival times were significantly longer in the PD ‐L1‐ KO ID 8‐inoculated groups than in their control groups, and its therapeutic benefit was enhanced in combination with the cisplatin treatment. Tumor weights and ascites volumes were significantly lower in the PD ‐L1‐ KO ID 8 groups than in their control groups. Immunohistochemical and immunofluorescence analyses showed that intratumoral CD 4 + T cells, CD 8 + T cells, NK cells and CD 11c + M1 macrophages were significantly increased, whereas regulatory T cells were significantly decreased in the PD ‐L1‐ KO ID 8 groups compared with those in their control groups. The intratumoral mRNA expression of interferon‐γ, tumor‐necrosis factor‐α, interleukin ( IL )‐2, IL ‐12a, CXCL 9 and CXCL 10 was significantly stronger, while that of IL ‐10, vascular endothelial growth factor, CXCL 1 and CXCL 2 was significantly weaker in the PD ‐L1‐ KO ID 8 groups. These results indicate that CRISPR /Cas9‐mediated PD ‐L1 disruption on tumor cells promotes anti‐tumor immunity by increasing tumor‐infiltrating lymphocytes and modulating cytokine/chemokine profiles within the tumor microenvironment, thereby suppressing ovarian cancer progression. These results suggest that PD ‐L1‐targeted therapy by genome editing may be a novel therapeutic strategy for ovarian cancer.

Liquid biopsies of circulating tumor DNA (ctDNA) have recently been used as a non-invasive diagnostic tool for detecting tumor-specific mutations. We present a study of ctDNA liquid biopsies in gynecological cancer using an ultrasensitive next-generation sequencing-based method for ctDNA detection named CAncer Personalized Profiling by deep Sequencing (CAPP-Seq). We performed CAPP-Seq with plasma-ctDNA obtained from 16 patients with gynecological cancer. In all cases, at least one non-synonymous somatic mutation was detected in the ctDNA. In the pre-treatment ctDNA, 4 of 16, 4/16, 5/16, 2/16, 2/16, and 2/16 patients had TP53 , KRAS , APC , PIK3CA , BRCA1 , and EGFR mutations, respectively. MET gene copy-number gains were detected in the ctDNA of 2 of 16 patients, and FISH analysis of the paired tumor samples confirmed these results. In 2 neoadjuvant chemotherapy-treated ovarian cancer patients, the changes in gene mutation patterns were associated with the treatment response. These findings suggest that CAPP-Seq-based liquid biopsies can be used for the genetic characterization of independent gynecological cancers with high frequency, and might be clinically useful for non-invasive tumor genotyping and therapeutic response monitoring.

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