Figure 1. CD8⁺ T cells contribute to anti-tumor effects of imatinib.

GIST and WT mice were treated with vehicle or imatinib and analyzed on days 4 (a) or 8 (a–i) using flow cytometry, PET, and IHC. (a) Tumor weight. (b) Tumor uptake of ¹⁸FDG by PET. Heart (H), tumor (T), and bladder (B) are indicated. (c) Number of CD8⁺ T cells in the DLN and inguinal node (IN) of GIST mice and mesenteric node of WT mice. Mean fluorescence intensity (MFI), and frequency of CD8⁺CD69⁺ T cells in the DLN of GIST mice. (d) Purified DLN CD8⁺ T cells from treated GIST mice were cultured with T cell-depleted splenocytes (APC) and tumor cells (Tu). IFN-γ secretion was determined by ELISPOT. Average spots per well ± s.e.m. (n = 3 wells) are shown and represent two independent experiments. (e) Gating of CD8⁺ T cells as a frequency of CD45⁺ lymphocytes (left). Absolute number of intratumoral CD8⁺ T cells (right). (f) Gating and frequency of intratumoral CD8⁺Ki67⁺ T cells. (g) Histograms, MFI, and frequency of intratumoral CD8⁺CD69⁺ and CD8⁺granzyme B⁺ T cells. (h) Tumors were stained for CD8 (arrows). (i) GIST mice were depleted of CD8⁺ or CD4⁺ T cells or NK cells during 1 week of imatinib treatment and tumors were weighed (left panel) or during 2 weeks of treatment and measured with magnetic resonance imaging (right panel). Data in (a–g, and i) represent means ± s.e.m. with n ≥ 6 per group. *P < 0.05.