Study On The Effects And Mechanisms Of Tetrabromobisphenol A On Lewis Lung Cancer Progression

Tetrabromobisphenol A(TBBPA)is presently one of the most widely produced and used of brominated flame retardants worldwide,which is widespread in environment with bioaccumulation.TBBPA has endocrine toxicity,neurotoxicity,immunotoxicity,reproductive toxicity and carcinogenicity,seriously threatening ecological environment and human health.Previous studies have found that exposure to TBBPA at environmental concentrations interfered with immune homeostasis and induce inflammatory responses in mice.Inflammation is closely related to the occurrence,development,invasion and metastasis of tumors.Tumor is the result of a combination of genetic alterations in tumor cells and tumor microenvironment.Therefore,we hypothesize that TBBPA could interfere with tumor progression by affecting both tumor cell proliferation and tumor microenvironment through in this study.To clarify the effects of TBBPA on tumor progression,a TBBPA-exposed mouse lung tumor model was constructed in this study.After 14 days of intragastric administration of TBBPA,C57BL/6J mice were subcutaneously inoculated with homologous mouse-derived Lewis lung cancer cells(LLC cells).The mouse body weight,food intake and tumor volume were recorded during the experiment.The results showed that TBBPA exposure had no significant impact on the body weight and daily food intake of mice.Compared with the control group,the tumors in the TBBPA-treated group appeared earlier(about 1-2 days),tumor development progressed faster,and the final tumor volume was larger(P<0.05).Then,TBBPA exposure promoted lung cancer progression.To clarify the effects of TBBPA on the proliferation and migration ability of lung cancer cells,LLC cells were treated with TBBPA at environmental concentrations,and the proliferation and migration ability of LLC cells were analyzed by MTT assay and Real Time Cellular Analysis,respectively.The results showed that TBBPA exposure at environmental concentrations had no significant effect on the proliferation and migration ability of LLC cells.Therefore,it was hypothesized that tumor microenvironment plays an important role in TBBPA-promoted lung cancer progression.In order to investigate the regulatory role of tumor microenvironment in TBBPA promoted tumor progression,the transcriptomic analysis of tumor tissue was performed.The results showed that TBBPA significantly interfered with immune homeostasis in lung tumor tissues,affecting T cell receptor signaling pathway,B cell receptor signaling pathway,nuclear factor-κB(NF-κB)signaling pathway,etc.In addition,TBBPA affected the expression of angiogenesis-related genes.Therefore,TBBPA might promote tumor progression by interfering with the tumor immune microenvironment and angiogenesis pathways.In order to clarify the role of immune cells in the tumor immune microenvironment in the promotion of tumor progression by TBBPA,the receptor expression,localization and proportion of immune cells in tumor tissues were analyzed by immunohistochemistry and flow cytometry,respectively.The immunohistochemical results showed that TBBPA inhibited the expression of CD3 and CD4,and promoted the expression of PD-1 and PD-L1 in tumor tissues.Flow cytometry showed that TBBPA exposure significantly reduced the proportion of CD4~+T cells in tumor tissues,but the proportion of CD8~+T cells had no significant change.The proportion of CD4~+T cells was slightly reduced and the proportion of CD8~+T cells was significantly increased in the spleen.Therefore,TBBPA exposure inhibited the proportion of CD4~+T cells in tumor tissues,restricted the recruitment of CD8~+T cells from the spleen tissue,and helped tumor cell immune escape via the PD-1/PD-L1 pathway,ultimately accelerated tumor progression.In conclusion,TBBPA promotes lung tumor progression by inhibiting CD4~+T cell infiltration and CD8~+T cell recruitment,facilitating tumor cell immune escape,and promoting angiogenesis in the tumor microenvironment,which provides a new research entry point for investigating the carcinogenicity of TBBPA,an environmental persistent organic pollutants.