The prognostic value of cancer stem-like cell markers SOX2 and CD133 in stage III colon cancer is modified by expression of the immune-related markers FoxP3, PD-L1 and CD3

Cancer stem-like cells are highly tumourigenic cells that can repopulate entire tumours after apparent successful treatment. Recent evidence suggests they interact with other cells in the tumour microenvironment, including immune cell subsets, to enhance their survival. The aim of this study was to determine whether the expression of immune cell markers in primary colon cancer impacts the prognostic significance of cancer stem-like cell marker expression. Immunohistochemistry was used to assess the expression of putative stem cell markers (ALDH1, CD44v6, CD133, Lgr5, SOX2) and immune cell related markers (CD3, CD8, FoxP3, PD-L1) in 104 patients with stage III colon cancer. Associations of marker expression with overall and cancer-specific survival were determined using Kaplan-Meier analysis. High SOX2 expression in the central tumour area was found to be an independent factor for poor cancer-specific survival [hazard ratio (HR) 6.19; 95% confidence interval (CI) 2.24-17.14; p = 0.001]. When immune-related factors were taken into account, patients categorised as SOX2low/FoxP3high had good outcome (HR 0.164; 95%CI 0.066-0.406; p < 0.0001) whereas patients categorised as SOX2high/PD-L1low had poor outcome (HR 8.992; 95%CI 3.397-23.803; p < 0.0001). The prognostic value of the SOX2 cancer stem-like cell marker in colon cancer is modified by expression of immune-cell related factors FoxP3 and PD-L1.