Given the fact the SIGLEC9 antibody treatment blocked radiotherapy-induced M2 polarization of TAMs and growth of the co-cultured ESCC cells, we opine that low or high doses of radiotherapy upregulate SIGLEC9 to induce M2 polarization of macrophages, therefore promoting radioresistance in ESCC. Here, SIGLEC9 is linked to esophageal squamous cell carcinoma.