Expression of CD27-trunc on MC57 fibrosarcoma promotes tumor rejection. (A) The amino acid sequences corresponding to CD27 receptor (top) or CD27-trunc (bottom) are shown. (B) Expression of CD27 on MC57 and MC57-CD27-trunc cells, analyzed by flow cytometry (1 representative experiment out of 3 is shown). Red: isotype; blue: CD27. (C) Growth curves of MC57 and MC57-CD27-trunc cells in vitro. Cells (0.5 × 10⁶) were cultured in triplicate and counted on the days indicated. Total number of cells per well are shown. Results are representative of 3 independent experiments. (D-E) Tumor growth curves of MC57 and MC57-CD27-trunc tumors. MC57 and MC57-CD27-trunc tumor fragments were transplanted SC into the flanks of BL/6 (D) or CD27^−/− mice (E) and tumor growth was monitored at the time points indicated. Data are shown as mean ± SEM of 5 to 10 mice in each group. Pooled data from 3 independent experiments are shown. Statistics: 2-way ANOVA (C-E). aa, amino acid; max, maximum; n.s., not significant; Tx, transplantation.