High Expression Of Foxp3in Lung Cancer Cells Inhibits The Antitumor Effect Of T Lymphocytes

BackgroundIn recent years, the incidence of malignant tumors is getting higner and higner, and it is a seriousthreat to human health. The formation and metastasis of tumor is a complex and multi-stage continuousprocess, it is influenced by a variety of factors. Whether the tumor cells can escape the immune systemmonitoring is one of the main reason. The immune system can identifit、control and eventually eliminatetumor through immune surveillance, but the tumor cells can escape immune system monitoring and survivethrough unclear mechanism. Therefore, the mechanism of tumor immune escape has been an important partof tumor research, but there is still no significant progress so far.Regulatory T cells have immunosuppressive functions. The regulatory T cell-mediated immuneregulations is criticed to maintain the immune tolerance. Tregs can play its regulatory function through todirect contact between the cells, also through the secretion of immune inhibitory cytokines, such as IL-10and IL-35. IL-10can inhibit the activity of T cell, IL-35can inhibit the proliferation of T cell. But Foxp3regulate the expression of IL-10and IL-35. In recent years, researchers found that Foxp3is a surfacemarker of Treg. Foxp3is a transcriptioned inhibitor. Foxp3mainly plays a negative regulatory role to itstarget genes, and play a crucial role in the development and function maintenance of Treg.Treg play a critical role in the regulation of autoimmune, so people started to pay attention to whetherthe tumor cells evade immune surveillance initiativty through Treg cells. The research results show thatTreg cell is indeed closely related to tumor formation and metastasis. Researchers found a high percentageof Treg cells in human colon cancer, liver cancer, breast cancer, bladder cancer and other tumor tissue.They also found that the Treg cells was positively correlated with the invasion and metastasis of tumors in non-small cell lung cancer, pancreatic cancer and prostate cancer. These results suggest that it may be justthe existence and accamulation of Treg cells in the tumor tissue make the tumor cells evade immune systemsurveillance and eventually form tumors.Recent studies have found that some tumor cells with high expression of Foxp3in haveimmunosuppressive effects which are similar to Treg cells, such as human lymphoma cells and pancreaticcancer cells can inhibit T cell proliferation. Our preliminary study got similar results in some tumor cells,such as PC-3, MDA-MB-231, NCI-H157, NCI-H727and other tumor cell lines. They have differentdegrees of the expression of Foxp3. We also found that Foxp3have the highest expression levels inprostate cancer cell line (PC-3) and lung cancer cell lines (NCI-H727).These findings suggest that Foxp3may confer the ability of active defense to tumor cells, So thatFoxp3-positive tumor cells can actively influence the immune surveillance. Therefore, in this experiment,we want to further explore which specific capabilities and characteristics were given to the tumor cells byFoxp3. So that we can provide instructional strategies for cancer treatment and prevention, and also cancontribute to the research and development of anticancer drugs.AimsIn this experiment, we mainly study the immunosuppressive effects of lung cancer cells with highexpression of Foxp3to T lymphocytes. So we can provide a theoretical basis to cancer treatment and drugdevelopment.MethodsWe use Liposome-mediated transfection method to establish a NCIH-1299cell line with stable highexpression of Foxp3, as positive control. At the same time pcDNA-3vector was transfect to NCIH-1299cells, as a negative control. We use ELISA method to detect changes in the expression level of cytokines in transfected cells such as IL-8and IL-10, and to detect changes in the amount of expression of IL-2in Tlymphocyte when it co-culture with transfected cells. We use MTT method to observe the change of thecell proliferation ability in transfected cells, to observe the impact of T cell in the cell proliferation abilityof transfected cells when it co-culture with transfected cells, and to observe the cell killing effect of T cellsto transfected cells. We use immunocytochemical method to observe the interaction of the transfected cellsand T lymphocytes. We have established a tumor transplantation mouse model to observe the role of Foxp3in tumor formation in mice.ResultsNCIH-1299lung cancer cell lines with high expression of Foxp3were established. As compared to thenegative control, expression of IL-8was decreased in cells with high expression of Foxp3,while theexpression of IL-10was increased,and when they were co-cultured with T cells,the expression of IL-2inT cells would be inhibited. We detected that high expression of Foxp3inhibited proliferation and invasionof T cells by methods of MTT assay and immunocytochemistry. The fact that high expression of Foxp3promoted tumor formation and proliferation in xenograft mouse models was observed.Conclusions1. The high expression of Foxp3in lung cancer cells inhibited the activity of T lymphocytes and itseffect on tumor cells.2. The high expression of Foxp3promotes the formation and growth of the tumor.