Tumor‐associated macrophages and risk of recurrence in stage III colorectal cancer

Abstract

Abstract Tumor‐associated macrophages (TAMs) have a unique favorable effect on the prognosis of colorectal cancer (CRC), although their association with stage‐specific outcomes remains unclear. We assessed the densities of CD68+ and CD163+ TAMs at the invasive front of resected CRC stage III CRC from 236 patients, 165 of whom received post‐surgical FOLFOX treatment, and their relationship with disease‐free survival (DFS). Associations between macrophage mRNAs and clinical outcome were investigated in silico in 59 stage III CRC and FOLFOX‐treated patients from The Cancer Genome Atlas (TCGA). Biological interactions of SW480 and HT29 cells and macrophages with FOLFOX were tested in co‐culture models. Low TAM densities were associated with shorter DFS among patients receiving FOLFOX (CD68+, p = 0.0001; CD163+, p = 0.0008) but not among those who were untreated. By multivariate Cox analysis, only low TAM (CD68+, p = 0.001; CD163+, p = 0.002) and nodal status (CD68+, p = 0.009; CD163+, p = 0.007) maintained an independent predictive value. In the TCGA cohort, high CD68 mRNA levels were associated with better outcome (p = 0.02). Macrophages enhanced FOLFOX cytotoxicity on CRC cells (p < 0.01), and drugs oriented macrophage polarization from M2‐ to M1‐phenotype. Low TAM densities identify stage III CRC patients at higher risk of recurrence after adjuvant therapy, and macrophages can augment the chemo‐sensitivity of micro‐metastases.

Keywords

• colorectal cancer
• tumor‐associated macrophages
• adjuvant therapy
• cancer immunology
• macrophage polarization