Exosomes Derived From Tumor-adipocyte Microenvironment Recruit Macrophages To Accelerate Tumor Progression

Part 1 Alterations in immune-related genes as potential marker of prognosis in breast cancerThe tumor microenvironment(TME)is a heterogeneous system that contributes to breast cancer progression.The Cancer Genome Atlas(TCGA)database provides global gene expression profiling data for further analysis of various malignancies,including breast cancer.Based on the ESTIMATE algorithm,immune and stromal scores were calculated according to immune or stromal components in the TME.We divided breast cancer cases into high-and low-score groups and identified differentially expressed genes(DEGs)that were significantly associated with overall survival.We performed enrichment analysis and constructed a protein-protein interaction network and found that the DEGs were mainly involved in primary immunodeficiency,T cell receptor signaling pathway and cytokine-cytokine receptor reaction.Furthermore,we explored the effect of aging on immune and stromal scores,which was validated by lower immune/stromal scores,lower infiltration of T cells and lower expression of immune checkpoints in the elder group.In conclusion,certain differentially expressed immune-related genes contribute to longer overall survival,and aging influences the immune microenvironment and immunotherapy efficacy by changing the tumor-infiltrating lymphocyte(TIL)abundance and checkpoint expression in breast cancer.Part 2 Monocarboxylate transporter 1 triggers immunosuppressive macrophage infiltration to expedite breast cancer progressionMonocarboxylate transporter 1(MCT1)participates in the influx of lactate to facilitate metabolic reprogramming during tumor progression.Tumor-associated macrophages(TAMs)are also involved in the inflammatory adaptation of the tumor microenvironment(TME).This study aimed to determine the correlation between metabolite changes and the polarization of macrophages in the TME.We demonstrated that the expression of CD163 on macrophages was significantly higher in breast cancer tissues than in normal tissues,especially in the HER2 subtype,although it was not statistically associated with recurrence-free survival(RFS).The presence of MCT1~+and CD163~+macrophages in the invasive margin was significantly correlated with decreased RFS.A significant correlation existed between MCT1 and CD163 expression in the margin,and high infiltration of MCT1~+CD163~+macrophages into the margin predicted rapid progression and poor survival outcomes for breast cancer patients.These data suggested that MCT1 at least partially promoted the alternative polarization of macrophages to inhibit antitumor immunity,and blocking this interaction may be a promising method for breast cancer therapy.Part 3 Exosomes derived from tumor-adipocyte microenvironment recruit macrophages to accelerate tumor progressionAdipose tissue macrophages(ATMs)particularly contribute to the progression of obesity-related tumor.However,the mechanisms that the tumor-adipocyte crosstalk may enable the properties and plasticity of macrophages remain still unclear.Here we demonstrate that CD163-positive macrophages aggregated to surround adipocytes in breast cancer tissues,which was associated with tumor relapse.The expression of chemokines,CCL2 and CCL5,elevated in tumor-adipocyte microenvironment and contributed to macrophage recruit and M2-like polarization via phosphorylating STAT3.In coculture of tumor cells and adipocytes,the level of exosomal miRNA-155 was high,then it promoted the generation and release of CCL2 and CCL5 from adipocytes through targeting SOCS6/STAT3 pathway.Inhibition of exosomal miRNA-155 in tumor cells reduced the CCL2 and CCL5 levels in tumor-adipocytes coculture,and further retarded tumor growth.Consistently,the eliminated macrophages partially inhibited tumor proliferation.We propose that the exosomal miRNA-155 from tumor-adipocyte interaction increases the secretion of CCL2 and CCL5 in adipocytes via targeting SOCS6/STAT3 signaling,further recruits M2-like macrophages to promote progressive disease.