The role of regulatory T cells in ovarian cancer

Long non-coding RNA HOTTIP enhances IL-6 expression to potentiate immune escape of ovarian cancer cells by upregulating the expression of PD-L1 in neutrophils

Background

Long non-coding RNA (lncRNA) HOXA transcript at the distal tip (HOTTIP), has been demonstrated to be a vital biomarker when evaluating the prognosis of multiple cancers. Nevertheless, the potential function of HOTTIP in ovarian cancer (OC), a prevalent cancer among women worldwide, remains elusive. Hence, the current study aimed to elucidate the functional relevance of HOTTIP in the development of OC.

Methods

Positive expression of PD-L1 and IL-6 was determined using immunohistochemical staining in the collected OC and normal tissues. The correlation of IL-6 and PD-L1 was analyzed using flow cytometry, Western blot analysis as well as Pearson’s correlation coefficient. The interaction among HOTTIP, c-jun and IL-6 was investigated with the use of RIP, ChIP and dual luciferase reporter gene assays. Finally, the effects of HOTTIP on T cell proliferation and infiltration were identified through gain- and loss-of-function studies in vitro and in vivo.

Results

HOTTIP, IL-6 and PD-L1 were all highly expressed in OC tissues. A positive correlation was observed between IL-6 and PD-L1 and that between HOTTIP and IL-6 in OC tissues. HOTTIP was noted to promote the expression of IL-6 by binding to c-jun, which resulted in a promoted PD-L1 expression in neutrophils and immune escape while inhibiting T cell proliferation as well as tumor immunotherapy.

Conclusion

Taken together, our study unveiled that HOTTIP could promote the secretion of IL-6, and consequently up-regulate the expression of PD-L1 in neutrophils, thus inhibiting the activity of T cells and ultimately accelerating immune escape of OC cells. Our study provides a potential therapeutic strategy by targeting HOTTIP in OC.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1394-6) contains supplementary material, which is available to authorized users.

Small extracellular vesicles containing arginase-1 suppress T-cell responses and promote tumor growth in ovarian carcinoma

Tumor-driven immune suppression is a major barrier to successful immunotherapy in ovarian carcinomas (OvCa). Among various mechanisms responsible for immune suppression, arginase-1 (ARG1)-carrying small extracellular vesicles (EVs) emerge as important contributors to tumor growth and tumor escape from the host immune system. Here, we report that small EVs found in the ascites and plasma of OvCa patients contain ARG1. EVs suppress proliferation of CD4⁺ and CD8⁺ T-cells in vitro and in vivo in OvCa mouse models. In mice, ARG1-containing EVs are transported to draining lymph nodes, taken up by dendritic cells and inhibit antigen-specific T-cell proliferation. Increased expression of ARG1 in mouse OvCa cells is associated with accelerated tumor progression that can be blocked by an arginase inhibitor. Altogether, our studies show that tumor cells use EVs as vehicles to carry over long distances and deliver to immune cells a metabolic checkpoint molecule – ARG1, mitigating anti-tumor immune responses.

Cancer cells employ a variety of ways to escape the immune system. Here, the authors show that ovarian cancer cells produce small extracellular vescicles containing arginase 1 that are taken up by dendritic cells in the draining lymph nodes, resulting in inhibition of antigen-specific T-cell proliferation.

Resistance to anticancer immunity in cancer patients: potential strategies to reverse resistance

In the 1990s, the application of immunotherapy approaches to target cancer cells resulted in significant clinical responses in patients with advanced malignancies who were refractory to conventional therapies. While early immunotherapeutics were focused on T cell-mediated cytotoxic activity, subsequent efforts were centered on targeted antibody-mediated anticancer therapy. The initial success with antibody therapy encouraged further studies and, consequently, there are now more than 25 FDA-approved antibodies directed against a range of targets. Although both T cell and antibody therapies continue to result in significant clinical responses with minimal toxicity, a significant subset of patients does not respond to immunotherapy and another subset develops resistance following an initial response. This review is focused on describing examples showing that cancer resistance to immunotherapies indeed occurs. In addition, it reviews the mechanisms being used to overcome the resistance to immunotherapies by targeting the tumor cell directly and/or the tumor microenvironment.

Differential distribution of tumor-associated macrophages and Treg/Th17 cells in the progression of malignant and benign epithelial ovarian tumors

Epithelial ovarian cancer (EOC) is one of the predominant causes of cancer-associated mortality in women with gynecological oncology. Tumor-associated macrophages (TAMs), regulatory T cells (Treg cells) and T helper cell 17 (Th17) cells have been hypothesized to be involved in the progression of EOC. However, the association between TAMs and T cells remains to be elucidated. The aim of the present study was to investigate the differential distribution of TAMs, Treg cells and Th17 cells in benign ovarian tumor tissues and in tissues from patients with EOC, and to examine their association with the clinical pathology of EOC. A total of 126 tissue samples from patients with EOC and 26 tissue samples from patients with benign ovarian tumors were analyzed, and it was identified that the distribution of TAMs, Treg cells, Th17 cells and the ratio of Treg/Th17 cells were higher in the patients with EOC using triple color immunofluorescence confocal microscopy. The high frequency of TAMs and ratio of Treg/Th17 cells in late tumor grades suggested that they may be significant in tumor progression. The frequency of TAMs was different between the histological types of EOC. Immunohistochemistry was used to investigate the microvessel density (MVD) in the EOC and benign ovarian tumor tissues. A higher MVD was observed in the EOC patient tissues, particularly, in the late tumor grade tissues. The present study provided clinical data demonstrating the high distribution of TAMs and T-cells in EOC, which may contribute to tumor progression through angiogenesis. The mechanisms by which TAMs are associated with Treg cells and Th17 cells requires further investigation as prognostic factors and therapeutic targets for EOC.

Immune suppressive effect of cinnamaldehyde due to inhibition of proliferation and induction of apoptosis in immune cells: implications in cancer

Background

Besides its anti-inflammatory effects, cinnamaldehyde has been reported to have anti-carcinogenic activity. Here, we investigated its impact on immune cells.

Methods

Activation of nuclear factor-κB by cinnamaldehyde (0–10 µg/ml) alone or in combination with lipopolysaccharide was assessed in THP1XBlue human monocytic cell line and in human peripheral blood mononuclear cells (PBMCs). Proliferation and secretion of cytokines (IL10 and TNFα) was determined in primary immune cells and the human cell lines (THP1, Jurkat E6-1 and Raji cell lines) stimulated with cinnamaldehyde alone or in conjunction with lipopolysaccharide. Nitric oxide was determined in mouse RAW264.7 cells. Moreover, different treated PBMCs were stained for CD3, CD20 and AnnexinV.

Results

Low concentrations (up to 1 µg/ml) of cinnamaldehyde resulted in a slight increase in nuclar factor-kB activation, whereas higher concentrations led to a dose-dependent decrease of nuclear factor-kB activation (up to 50%) in lipopolysachharide-stimulated THP1 cells and PBMCs. Accordingly, nitric oxide, interleukin 10 secretion as well as cell proliferation were reduced in lipopolysachharide-stimulated RAW264.7 cells, PBMCs and THP1, Raji and Jurkat-E6 immune cells in the presence of cinnamaldehyde in a concentration-dependent manner. Flow cytometric analysis of PBMCs revealed that CD3+ were more affected than CD20+ cells to apopotosis by cinnamaldehyde.

Conclusion

We attribute the anti-inflammatory properties of cinnamaldehyde to its ability to block nuclear factor-κB activation in immune cells. Treatment with cinnamaldehyde led to inhibition of cell viability, proliferation and induced apoptosis in a dose-dependent manner in primary and immortalized immune cells. Therefore, despite its described anti-carcinogenic property, treatment with cinnamaldehyde in cancer patients might be contraindicated due to its ability to inhibit immune cell activation.

Breaking immunotolerance of tumors: a new perspective for dendritic cell therapy

The use of dendritic cells (DC) in cancer immunotherapy is based on their potent abilities to present antigens, so they can act as 'natural adjuvants' to enhance immunogenicity of tumor antigens and stimulate specific cytotoxic T-cells. Large amounts of DC can be generated from bone marrow, neonatal cord blood, and peripheral blood CD34(+) hematopoietic stem cells, or from peripheral blood monocytes. The DC can then be pulsed with tumor antigens and re-infused. In vitro, antigen-pulsed DC can stimulate allogeneic T-cell proliferation and induction of autologous specific cytotoxic T-cells; in vivo, the cells inhibit the growth of tumors or protect hosts (i.e. mice) from development of inoculated tumors. The results of preliminary clinical trials have shown that DC vaccines are safe and elicit immune responses; however, the rates of clinical responses are low. It has become quite clear that one key reason for unsatisfactory clinical results is tumor-induced immunosuppression. Among the factors contributing to this type of immunosuppression are populations of regulatory cells including: T-regulatory (T(reg)) cells, myeloid-derived suppressor cells (MDSC), tumor-associated macrophages (TAM), and DC expressing 2,3-dioxygenase indoleamine (IDO-DC). This review presents an overview of the current understanding about populations of regulatory cells and the most current research efforts directed to overcome immunosuppressive activity due to the tumor microenvironment.

Variants in the Signaling Protein TSAd are Associated with Susceptibility to Ovarian Cancer in BRCA1/2 Negative High Risk Families

A substantial fraction of familial ovarian cancer cases cannot be attributed to specific genetic factors. The discovery of additional susceptibility genes will permit a more accurate assessment of hereditary cancer risk and allow for monitoring of predisposed women in order to intervene at the earliest possible stage. We focused on a population with elevated familial breast and ovarian cancer risk. In this study, we identified a SNP rs926103 whose minor allele is associated with predisposition to ovarian but not breast cancer in a Caucasian high-risk population without BRCA1/BRCA2 mutations. We have found that the allelic variation of rs926103, which alters amino acid 52 of the encoded protein SH2D2A/TSAd, results in differences in the activity of this protein involved in multiple signal transduction pathways, including regulation of immune response, tumor vascularization, cell growth, and differentiation. Our observation provides a novel candidate genetic biomarker of elevated ovarian cancer risk in members of high-risk families without BRCA1/2 mutations, as well as a potential therapeutic target, TSAd.

Spontaneous and bleomycin-induced chromosome damage in non cancer thyroid patients

BACKGROUND

Presence of chromosome damage in lymphocytes of patients affected by several diseases, including cancer, was detected by the micronucleus (MN) assay. Individual susceptibility to DNA damage, considered as a risk factor for cancer, can be also evaluated using the bleomycin (BLM) sensitivity test.

MATERIALS AND METHODS

We aimed to evaluate spontaneous or BLM-induced MN frequencies in autoimmune (AI, n = 19) and non autoimmune (NAI, n = 11) thyroid patients, not receiving (131)I radiometabolic therapy with respect to a control group of 18 healthy subjects. According to thyroid function, patients were also divided into hypothyroid (n = 10), euthyroid (n = 13) or hyperthyroid (n = 7) subjects.

RESULTS

Spontaneous MN frequencies of AI and NAI patients did not differ from those of controls. Hypothyroid patients had more elevated MN basal levels (9.00 + or - 1.71 per thousand) than hyperthyroid (3.75 + or - 1.17 per thousand, P < 0.05) and euthyroid (5.38 + or - 0.97 per thousand, P < 0.01) patients or healthy subjects (4.17 + or - 0.63 per thousand, P < 0.01). In particular, the hypothyroid AI group showed the highest value (9.79 + or - 2.26 per thousand, P < 0.01). All thyroid patients responded differently to BLM than controls (39.90 + or - 2.48 per thousand vs. 31.08 + or - 2.51 per thousand, P = 0.0377). The NAI group had BLM-induced MN levels (45.00 + or - 2.56 per thousand) significantly higher (P = 0.0215) than AI patients (36.95 + or - 3.49 per thousand) or healthy subjects (31.08 + or - 2.51 per thousand). No significant difference was seen when patients were stratified according to autoimmunity.

CONCLUSIONS

We report that hypothyroid patients exhibit a moderate increase in the level of spontaneous genome damage, and that AI thyroid patients resulted to be less sensitive than NAI patients to the mutagen sensitivity test. In prospective, it may be of interest to reinvestigate hypothyroid patients when correction of their dysfunction is achieved.