ICAM-1 deficiency impairs the systemic antitumor effect of RT. (A) Schedule of X-ray RT in the WT or ICAM-1 KO C57BL/6 mice bearing bilateral MC38 tumors. (B, C) Individual tumor growth curves of the primary tumors (B) and distant tumors (C) of MC38 tumor-bearing mice after RT as illustrated in (A) (n = 5-7 per group). (D) Schedule of RT in combination with ICAM-1 blocking with an anti-ICAM-1 antibody (αICAM-1) in the C57BL/6 WT mice bearing bilateral MC38 tumors. (E, F) Average tumor growth curves of primary tumors (E) and distant tumors (F) in the MC38 tumor-bearing mice after indicated treatments (n = 4-7 per group). (G-I) Frequencies of CD3+ T cells (G), CD4+ T cells (H), and CD8+ T cells (I) among CD45+ cells from distant tumors harvested from WT C57BL/6 mice after indicated treatments as described in (D) (n = 6-7 per group). (J-L) Frequencies of NK cells (J), DCs (K), and macrophages (L) among CD45+ cells from distant tumors harvested from WT C57BL/6 mice after indicated treatments as described in (D) (n = 6-7 per group). Data are represented as mean ± SD. P values were determined using unpaired Student's t-test (B, C, G-L), or two-way ANOVA with Tukey's multiple-comparisons test (E, F); NS, not significant (P > 0.05).