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.

VEGF expression in ovarian cancer induced MDSCs, inhibited local immunity, and contributed to poor prognosis. Clin Cancer Res; 23(2); 587-99. ©2016 AACR.

Snail is a major transcriptional factor that induces epithelial-mesenchymal transition (EMT). In this study, we explore the effect of Snail on tumor immunity. Snail knockdown in mouse ovarian cancer cells suppresses tumor growth in immunocompetent mice, associated with an increase of CD8+ tumor-infiltrating lymphocytes and a decrease of myeloid-derived suppressor cells (MDSCs). Snail knockdown reduces the expression of CXCR2 ligands (CXCL1 and CXCL2), chemokines that attract MDSCs to the tumor via CXCR2. Snail upregulates CXCR ligands through NF-kB pathway, and most likely, through direct binding to the promoters. A CXCR2 antagonist suppresses MDSC infiltration and delays tumor growth in Snail-expressing mouse tumors. Ovarian cancer patients show elevated serum CXCL1/2, which correlates with Snail expression, MDSC infiltration, and short overall survival. Thus, Snail induces cancer progression via upregulation of CXCR2 ligands and recruitment of MDSCs. Blocking CXCR2 represents an immunological therapeutic approach to inhibit progression of Snail-high tumors undergoing EMT.

Background V-domain Ig suppressor of T cell activation (VISTA) is a novel inhibitory immune-checkpoint protein. VISTA expression on tumour cells and the associated regulatory mechanisms remain unclear. We investigated VISTA expression and function in tumour cells, and evaluated its mechanism and activity. Methods VISTA in tumour cells was assessed by tissue microarray analysis, immunohistochemical staining and western blot. A series of in vitro assays were used to determine the function of tumour-expressed VISTA. In vivo efficacy was evaluated in syngeneic models. Results VISTA was highly expressed in human ovarian and endometrial cancers. Upregulation of VISTA in endometrial cancer was related to the methylation status of the VISTA promoter. VISTA in tumour cells suppressed T cell proliferation and cytokine production in vitro, and decreased the tumour-infiltrating CD8+ T cells in vivo. Anti-VISTA antibody prolonged the survival of tumour-bearing mice. Conclusions This is the first demonstration that VISTA is highly expressed in human ovarian and endometrial cancer cells, and that anti-VISTA antibody treatment significantly prolongs the survival of mice bearing tumours expressing high levels of VISTA. The data suggest that VISTA is a novel immunosuppressive factor within the tumour microenvironment, as well as a new target for cancer immunotherapy.