The ligands for programmed cell death 1 (PD-1), an immunoinhibitory receptor belonging to CD28/cytotoxic T lymphocyte antigen 4 family, are PD-1 ligand 1 and 2 (PD-Ls). Recent reports suggest that the aberrant expression of PD-Ls on tumor cells impairs antitumor immunity, resulting in the immune evasion of the tumor cells. Although an inverse correlation between the expression level of PD-Ls and patients' prognosis has been reported for several malignant tumors, the follow-up period was limited because of the lack of the antibody (Ab) applicable to paraffin-embedded specimens. Here we generated a new Ab against PD-1 ligand 1 (PD-L1) and analyzed the expression level of PD-Ls in human ovarian cancer using paraffin-embedded specimens. Patients with higher expression of PD-L1 had a significantly poorer prognosis than patients with lower expression. Although patients with higher expression of PD-1 ligand 2 also had a poorer prognosis, the difference was not statistically significant. A significant inverse correlation was observed between PD-L1 expression and the intraepithelial CD8 ؉ T lymphocyte count, suggesting that PD-L1 on tumor cells directly suppresses antitumor CD8 ؉ T cells. Multivariate analysis showed the expression of PD-L1 on tumor cells and intraepithelial CD8 ؉ T lymphocyte count are independent prognostic factors. The PD-1/ PD-L pathway can be a good target for restoring antitumor immunity in ovarian cancer.costimulation ͉ tumor immunity ͉ immunohistochemistry

This study, to our knowledge, is the first to explore the effects of nivolumab against ovarian cancer. The encouraging safety and clinical efficacy of nivolumab in patients with platinum-resistant ovarian cancer indicate the merit of additional large-scale investigations (UMIN Clinical Trials Registry UMIN000005714).

Background:PD-L1 (programmed cell death 1 ligand 1) on tumour cells suppresses host immunity through binding to its receptor PD-1 on lymphocytes, and promotes peritoneal dissemination in mouse models of ovarian cancer. However, how PD-L1 expression is regulated in ovarian cancer microenvironment remains unclear.Methods:The number of CD8-positive lymphocytes and PD-L1 expression in tumour cells was assessed in ovarian cancer clinical samples. PD-L1 expression and tumour progression in mouse models under conditions of altering IFN-γ signals was assessed.Results:The number of CD8-positive cells in cancer stroma was very high in peritoneally disseminated tumours, and was strongly correlated to PD-L1 expression on the tumour cells (P<0.001). In mouse models, depleting IFNGR1 (interferon-γ receptor 1) resulted in lower level of PD-L1 expression in tumour cells, increased the number of tumour-infiltrating CD8-positive lymphocytes, inhibition of peritoneal disseminated tumour growth and longer survival (P=0.02). The injection of IFN-γ into subcutaneous tumours induced PD-L1 expression and promoted tumour growth, and PD-L1 depletion completely abrogated tumour growth caused by IFN-γ injection (P=0.01).Conclusions:Interferon-γ secreted by CD8-positive lymphocytes upregulates PD-L1 on ovarian cancer cells and promotes tumour growth. The lymphocyte infiltration and the IFN-γ status may be the key to effective anti-PD-1 or anti-PD-L1 therapy in ovarian cancer.

Emerging evidence has highlighted the host immune system in modulating the patient response to chemotherapy, but the mechanism of this modulation remains unclear. The aim of this study was to analyze the effect of chemotherapy on antitumor immunity in the tumor microenvironment of ovarian cancer. Treatment of ovarian cancer cell lines with various chemotherapeutic agents resulted in upregulated expression of MHC class I and programmed cell death 1 ligand 1 (PD-L1) in a NF-kB-dependent manner and suppression of antigen-specific T-cell function in vitro. In a mouse model of ovarian cancer, treatment with paclitaxel increased CD8 þ T-cell infiltration into the tumor site, upregulated PD-L1 expression, and activated NF-kB signaling. In particular, tumor-bearing mice treated with a combination of paclitaxel and a PD-L1/PD-1 signal blockade survived longer than mice treated with paclitaxel alone. In summary, we found that chemotherapy induces local immune suppression in ovarian cancer through NF-kB-mediated PD-L1 upregulation. Thus, a combination of chemotherapy and immunotherapy targeting the PD-L1/PD-1 signaling axis may improve the antitumor response and offers a promising new treatment modality against ovarian cancer. Cancer Res; 75(23);5034-45. Ó2015 AACR.

Purpose: Endometriotic cysts are known to transform into ovarian cancers, such as clear cell and endometrioid carcinomas. We hypothesized that an iron-rich environment produced by the repetition of hemorrhage in the endometriotic cysts during the reproductive period may play a crucial role in carcinogenesis in the cysts through the iron-induced persistent oxidative stress. Experimental Design: Contents of human ovarian cysts, including 21 endometriotic cysts, 4 clear cell carcinomas, and 11nonendometriotic cysts, were analyzed for the concentrations of free ''catalytic'' iron, lactose dehydrogenase, potential antioxidant, lipid peroxide, and 8-hydroxy-2 ¶-deoxyguanosine (8-OHdG). Iron deposition and 8-OHdG levels were also analyzed histologically. Reactive oxygen species and the mutagenicity of the contents in endometriotic cyst were determined in vitro. Results: The concentration of free iron in endometriotic cysts (100.9 mmol/L) was significantly higher than that in nonendometriotic cysts (0.075 mmol/L; P < 0.01). The average concentrations of lactose dehydrogenase, potentialantioxidant, lipidperoxide, and 8-OHdG were alsosignificantly higher in endometriotic cysts (P < 0.01).There was a correlation between the concentration of free iron and that of 8-OHdG (P <0.01). Histologically, we could observe iron deposits more abundantly in endometriotic cysts than in nonendometriotic cysts (P < 0.01).The level of 8-OHdG in carcinoma associated with endometriosis was higher than that of carcinoma without endometriosis (P <0.05).