Clinical Significance Of PD-L1 Expression In Human Non-small-cell Lung Cancer And The Study Of Its Biological Function

With the deterioration of the living environment of human beings, the malignant tumor has become one of the most deadly diseases in the world. Both the incidence and the mortality of lung cancer rank first among all malignant tumors. Lung cancer can be divided into small cell lung cancer(NSCLC) and cell lung cancer SCLC(small). NSCLC, 80%-85%, the ratio of NSCLC cases in the lung adenocarcinoma has been increasing year by year, and this cancer type is rapidly developing, the majority of patients with NSCLC are usually dignosed at advanced stage, with little chance for surgery, and high ratio of occurrence, and poor prognosis, and the 5 year survival rate of patients with lung cancer still remains poor. The therapy of NSCLC has become a big problem in clinical treatment, and the chemotherapy and targeted therapy come across the bottleneck to improve the therapeutic effect and postoperative rate. It is important to find novel and more useful methods for the treatment of lung cancer. It is of great possibility using checkpoint therapy to become an important part of routine therapy for lung cancer. Combined targeted therapy and immunotherapy will be a future treatment model. This study attempts to explore the relationship between these two therapeutic targets and their relevance.The checkpoints molecules, such as B7 family negative co-stimulatory members, PD-L1, B7-H3, B7-H4, could be abnormally expressed in many human cancer tissues as well immune cells, and involved in tumor immune escape, closely related to the clinical pathological parameters and prognosis. On the one hand, these checkpoint molecules can regulate the anti-tumor response mediated by T cells, and on the other hand, they are involved in the development of tumor by regulating the biological behavior of tumor cells themselves. As of now, the clinical significance, the biological function and the mechanism of PD-L1 expression in human lung cancer still remain elusive. In the present study, we used RNAi method, lentivirus transfection, flow sorting, cell proliferation, transwell method, cell cycle and apoptosis analysis, to investigate the function of abnormal expression of PD-L1 in human lung cancer cell lines. Then, in combination of the targeted therapy of lung cancer patients, we further retrospectively studied the PD-1/PD-L1 expression in human lung adenocarcinoma and its correlation with EGFR as well as KRAS mutation status, in order to illustrated the contribution of the combination of checkpoint therapy and targeted therapy in lung cancer patients, and finally pave the way for the comprehensive therapeutics against human lung cancer.Our present study showed that,(1). The PD-L1 is highly expressed in human lung cancer cell lines, and we constructed the knockdown model of PD-L1 expression in human lung cancer cell lines A549, SK-MES-1, by using RNAi, lentivirus and flow sorting methods.(2). The cell proliferation, scrape assay, transwell assay, cell cycle and apoptosis results showed that, the down expression of PD-L1 in A549 as well as SK-MES-1 could significantly inhibit the ability of cell proliferation, migration, invasion, and cell cycle in lung cancer cell lines.(3). Moreover, we also found that the down expression of PD-L1 in A549 as well as SK-MES-1 cell lines could inhibit the EGFR expression, which suggested the potential value of the combination of checkpoint therapy and targeted therapy in lung cancer patients.(4). We collected 100 cases of lung adenoma patients from our hospital, the PCR method was used to detect EGFR mutation and the immunochemical staining was used to detect PD-L1 expression. The correlation between PD-L1 expression and EGFR mutation was analyzed, and we found a negative correlation between PD-L1 expression and EGFR mutation.(5). Tumor tissues were obtained from 98 lung adenoma patients. PCR method was used to detect KRAS mutation. Immunochemical staining was used to detect PD-1 expression. The correlation between PD-1 expression and EGFR mutation was analyzed. And the PD-1 expression does not correlate with KRAS mutation status.(6). There was no statistical significance between PD-1/PD-L1 in tumor-infiltrating lymphocytes and EGFR/KRAS mutation status. PD-1/PD-L1 in tumor was significantly negatively correlated with EGFR mutation. Patients with mutated EGFR status, higher PD-L1 expression, larger tumor size, lymph node metastasis or later AJCC stages had a longer progression-free time.In summary, we report the biological role and clinical significance of PD-L1 expression in lung cancer. It is confirmed that PD-L1 can promote the development and progression of lung cancer by regulating cell proliferation, migration, invasion, metastasis and cell cycle regulation. The combination of PD-L1 intervention and targeted therapy is effective for the treatment of lung cancer.