Poor Clinical Outcomes and Immunoevasive Contexture in Intratumoral IL-10-Producing Macrophages Enriched Gastric Cancer Patients.

OBJECTIVE: To investigate the clinical significance of IL-10+ tumor-associated macrophages (TAMs) in gastric cancer. BACKGROUND: Due to the plasticity and diversity of TAMs, it is necessary to phenotypically and functionally classify subsets of TAMs to better understand the critical role of TAMs in cancer progression. TAMs expressing interleukin-10 (IL-10) have been found to facilitate immune evasion in many malignancies, but the role of IL-10+ TAMs in gastric cancer remains obscure. METHODS: Four hundred and sixty-eight tumor tissue microarray specimens, 52 fresh tumor tissue samples of gastric cancer patients from Zhongshan Hospital, and data of 298 gastric cancer patients from the Cancer Genome Atlas (TCGA) were analyzed. IL-10+ TAM level and immune contexture were examined by CIBERSORT, immunohistochemistry, and flow cytometry. Clinical outcomes were analyzed by Kaplan-Meier curves and Cox model. RESULTS: Gastric cancer patients with high IL-10+ TAM infiltration exhibited poor prognosis and inferior therapeutic responsiveness to fluorouracil-based adjuvant chemotherapy. IL-10+ TAM infiltration yielded an immunoevasive tumor microenvironment featured by regulatory T cell infiltration and CD8+ T cell dysfunction. The combinational analysis of IL-10+ TAM and CD8+ T cell infiltration stratified patients into distinct risk groups with different clinical outcomes. Moreover, IL-10+ TAM infiltration was correlated with tumor-intrinsic characteristics including EBV status, PD-L1 expression, and genome stability in gastric cancer. CONCLUSIONS: This study revealed that IL-10+ TAMs might drive an immunoevasive microenvironment and determine poor prognosis and inferior therapeutic responsiveness to fluorouracil-based adjuvant chemotherapy, indicating IL-10+ TAMs could be applied as a potential target for immunotherapeutic approach in gastric cancer.