Abstract
PD1(programmed cell death protein 1), a molecule negatively regulated by immunity,is highly expressed in a wide variety of human malignancies making it an attractive immunotherapeutic target. PD-L1 is one of the ligands for PD-1 and expressed both on T cells and tumor cells. The purpose of this study was to investigate the expression levels of PD1, PD-L1, regulatory T cells (Tregs), identified as CD4+CD25+CD127-/low, and related cytokines during the development and progression of cervical cancer(CC). Through different groups to simulate the process of the occurrence and development of CC, peripheral blood of each group was collected, and different indicators were detected by ELISA and flow analysis. It was found that except for INF-γ, PD1, PD-L1, IL-2, IL6, IL-10, TGF-β expression increased gradually with the development of CC, and the differences between groups were statistically significant (P<0.05). This situation also appears on the tracking of preoperative CC patients and postoperative follow-up on test results. And Tregs in peripheral blood, compared with normal control(NC) group, the expression increased CC group, the PD1 expression in the Tregs membrane also increases at the same time. In CC tissues, we found an interesting phenomenon through multiplex immunohistochemical staining that CD8+ T cells mainly infiltrated in the tumor cell aggregation area, while CD4+ T cells mainly appeared around. Therefore, we speculated that CD8+ T cells mainly played an anti-tumor immune role in CC tumor tissues.
INTRODUCTION
Cervical cancer(CC) is the third most common cancer in women worldwide and the most frequent gynecological cancer in developing countries(1-3). The prime causal factor for this cancer is persistent infection with human papillomavirus(HPV). In most cases, the human immune system can be aware of HPV infection, and only a small number of women with persistent high-risk HPV, such as type 16 or 18, will lead to cervical precancerous lesions and develop into cervical cancer(2,4). CC, like all solid tumors, can be treated surgically in early or isolated recurrence. The vast majority of CC is squamous cell carcinoma, which is sensitive to radiation. Through in vitro and intracavitary radiotherapy, local cervical cancer reaches the maximum radiation dose of tumor death. And mid- and late-stage CC tumors are treated with chemoradiotherapy. Immunotargeted therapy is a new method to treat advanced recurrent or metastatic CC in recent years(5-8). According to the report, the prognosis of patients with metastatic CC is poor with a median survival of 8-13 months(9).
PD1/PD-L1, as a key molecule of immune checkpoint, is an important target of immunotherapy and has changed the pattern of tumor treatment(10-11). Especially for patients with terminal and critical cancer, such as melanoma(12), non-small-cell lung cancer(13), ovarian cancer(14), breast cancer(15), including CC(9,16). PD1, a member of the CD28 receptor family, is a co-inhibitory receptor expressed on the cell surface. PD1 and its ligand PD-L1 bind as an immunocheckpoint to play an immunosuppressive role(17-18). PD1 and PD-L1 signal pathway activation contributes to tumor immune escape and provides important negative signals to limit, terminate or impair T cell immune response, and blocking the pathway can reduce tumor inhibition of the anti-tumor immunity effect, to better improve the body’s own immune system to resist the ability of the tumor. Thereby the signal pathway as anti-tumor immune and autoimmune diseases such as novel targets for therapeutic intervention, theoretically PD1 and PD-L1 signal pathway with ability for the treatment of various types of tumors(19-21). Therefore, the application value of PD1 and PD-L1 in patients with cervical cancer is also worth expecting.
Regulatory T cells (Tregs) and PD-1/PD-L1 pathways are both key to terminate the immune response(22). It is report that targeting endoglin expressing Tregs in the tumor microenvironment enhances the effect of PD1 checkpoint inhibitor immunotherapy(23). Tregs are mainly divided into natural regulatory T cells(n-Tregs) and adaptive regulatory T cells(a-Tregs). N-Tregs are mainly CD4+CD25+CD127-/lowor Foxp3+ T cells. Foxp3 is not only a marker molecule for CD4+CD25+ Treg, but also a key gene that determines the function of CD4+CD25+ Treg. A-Tregs are developed from peripheral naive T cells induced by low doses of antigens or immunosuppressive cytokines, including Tr1(type 1 regulatory T cell) and Th3(T helper 3) cells, which mainly secrete IL-10 and TGF-β to play a negative role in immune regulation(24-29). In this paper, the expression of n-Tregs in cervical cancer and its correlation with the expression of PD1/PD-L1 were mainly discussed.
In this study, groups were set to simulate the occurrence and development of cervical cancer caused by long-term infection of high-risk HPV. In addition, during the development of cervical cancer, the expression levels of PD1, PD-L1, regulatory T cells and related cytokines in the peripheral blood of patients were investigated. At the same time, the changes of PD1, PD-L1 and related cytokines before and after operation in patients with cervical cancer treated by surgery were followed up. This study laid the foundation for further research on the immune regulation mechanism and immunotherapy of the immunoregulatory molecule PD1 and its ligand PD-L1 in cervical cancer.