Study On The Tumor-promoting Effect And Mechanism Of Cancer-associated Fibroblasts-derived IL-8 In Breast Cancer

Background:Breast cancer is the most common cancer in the world,seriously endangering women’s physical and mental health.As the most abundant stromal cells in the tumor microenvironment(TME),cancer-associated fibroblasts(CAFs)provide a suitable soil for tumor cell growth by secreting cytokines,exosomes,and extracellular matrix,driving cancer development and progression.Chemotherapy is an important treatment for breast cancer,but the relapse and metastasis caused by chemotherapy resistance are the main cause of death in breast cancer patients.It has been reported that endothelial cells and tumor-associated macrophages after chemotherapy can further promote tumor progression,but the role and molecular mechanism of CAFs in tumors after chemotherapy are currently unknown.Methods:1.We obtained primary fibroblasts through enzyme digestion and identified CAFs and normal fibroblasts(NFs)by molecular assays and compared the differences in terms of cell morphology and function.Furthermore,we explored the potential function of CAFs in breast cancer through bioinformatics.We explored the role of CAFs after chemotherapy in tumors and the potential mechanisms through in vitro and vivo experiments.2.Through bioinformatics,we explored the prognostic value,potential functions,and immune characteristics of IL-8 in breast cancer.The effect of IL-8 in epithelial-mesenchymal transition(EMT)was explored through cellular and animal models.Results:1.Through molecular detection,we confirmed the successful isolation and cultivation of primary CAFs and matched NFs from postoperative tissues of breast cancer patients.In terms of cell morphology,both CAFs and NFs were spindle-shaped,but CAFs were slightly larger than NFs,with different lengths and irregular arrangements of cells.Irregular protrusions could be seen on the cell surface,and there were indented nuclei and branched cytoplasm.Functionally,compared with NFs,CAFs endowed tumor cells with stronger chemoresistance,healing,and invasion abilities.In addition,the high infiltration score of CAFs indicated a poor prognosis.It was worth noting that compared to CAFs,CAFs after chemotherapy had a more tumor-promoting effect,which might be related to the promotion of IL-8 expression by chemotherapy.Through the GEO database and in vitro experiments,we confirmed that chemotherapy promoted the IL-8 expression in CAFs.CAFs derived-IL-8 significantly promoted tumor cell proliferation,wound healing,invasion,and colony formation.Moreover IL-8 inhibited tumor cell apoptosis by activated the NF-κB pathway and led to chemotherapy resistance.In addition,we found a significant correlation between high expression of IL-8 and chemotherapy resistance and poor prognosis.2.Through bioinformatics,we found that high IL-8 expression was associated with poor prognosis in breast cancer patients.Functional analysis revealed that IL-8 was enriched in multiple cancer-related signaling pathways and immune-related pathways.In addition,IL-8 was associated with most immune infiltration cells,immune checkpoint genes,and tumor mutational burden,and high IL-8 expression indicated poor immunotherapy response.Through cellular and animal models,we demonstrated that IL-8 contributes to breast cancer progression by promoting EMT.Conclusions:CAFs and NFs are distinguished mainly by cell morphology and function.Compared to CAFs,CAFs that after chemotherapy have a more tumor-promoting effect,which may be related to the promotion of IL-8 expression by chemotherapy.CAFs-derived IL-8 inhibits tumor cell apoptosis by activating the NF-κB pathway and led to chemoresistance.High IL-8 expression is associated with immunotherapy resistance and poor prognosis,which suggesting that IL-8 may be the potential prognostic marker in breast cancer.Furthermore,CAFs-derived IL-8 promotes EMT by activating the PI3K/AKT pathway leading to breast cancer progression.