Figure 7.

Anti-tumor immune responses induced by LTX-315 are tumor-specific. (A) After the adoptive transfer of splenocytes from cured rats, surviving rats (n = 3) were s.c. rechallenged with 1·10⁵ rTMSCs in the right flank and subsequently s.c. inoculated with a different syngeneic tumor cell line, Roser's T-cell leukemia (RL, 1·10⁵ cells) in the contralateral flank. Tumor growth was monitored by measurements of tumor diameter using calipers. (B) A schematic presentation of growth curves (mean ± SD), demonstrating specificity and the inhibition of rTMSC growth. On day 30, when the left-flank RL tumors reached 100 mm² in size, the tumors were resected and processed for flow cytometric characterization. (C) Representative dot plot showing the morphological characteristics of single-cell suspensions from RL tumors. Gating on the lymphocyte population and staining with anti-CD3 and anti-NKR-P1A revealed the frequency of T (CD3⁺ NKR-P1A⁻) cells. Phenotypic analysis of the T cell fraction is shown in the histograms, indicating the percentage of CD4⁺ and CD8⁺ T cells. A standard 4-h ⁵¹ Cr release assay was performed to quantitatively measure the cytolytic effect of tumor-specific T cells. T cells were enriched from the spleens of long-term survivors (week 60) after the adaptive transfer of tumor-reactive splenocytes. One naïve rat was included as a control. Without in vitro activation, isolated T cells were tested in cytotoxicity assays at a varying effector: target (E: T) ratios against (D) rTMSCs and (E) RL target cells. The results are reported as a mean of cpm ± SD of technical triplicates. ****P < 0.0001, with Student's t test.