Figure 2.

Blocking T-cell migration to tumors with FTY720 eliminates ICAM-1 expression in tumors and abrogates the systemic antitumor effect of RT. (A) Schedule of the flow cytometric analysis of WT C57BL/6 mice bearing MC38 tumors. (B, C) Frequencies of ICAM-1⁺ cells among CD3⁺ T cells (B) and CD8⁺ T cells (C) in tumors and spleens (n = 7 per group). (D) Mean fluorescence intensity (MFI) of ICAM-1 expression levels in CD8⁺ T cells in the spleens and tumors (n = 7 per group). (E) Schedule of X-ray RT in combination with FTY720 treatment in WT C57BL/6 mice bearing bilateral MC38 tumors. (F, G) Frequencies of CD4⁺ and CD8⁺ T cells among CD45⁺ cells (F), and MFI of ICAM-1 in total cells (G) of distant tumors harvested from mice after the indicated treatments as described in (E) (n = 5 per group). (H) Representative images of immunofluorescence staining of ICAM-1 in distant tumor tissues harvested from mice treated with RT or RT plus FTY720. (I, J) Representative small-animal PET images (I) and quantified tumor (distant tumor) uptake (J) of ⁸⁹Zr-DFO-αICAM-1/Fab at 24 h postinjection in MC38 tumor-bearing mice (n = 5 per group). Distant tumors are indicated by red circles. (K, L) Individual tumor growth curves of primary tumors (K) and distant tumors (L) in WT C57BL/6 mice bearing bilateral MC38 tumors after indicated treatments as described in (E) (n = 8 per group). Data are represented as mean ± SD. P values were determined using unpaired Student's t-test (B-D, F, G, and J-L); NS, not significant (P > 0.05).