In vitro antitumor effects by CD44v6-targeted T cells. T cells were activated with CD3/CD28 beads, transduced with an RV encoding for the CD44v6-specific CAR (CD44v6.CAR28z) or a control CAR (CTR.CAR28z), and cultured with IL-7/IL-15. (A) Percentages of CAR⁺ T cells by FACS in a representative donor at 14 days. (B) Expansion of CAR⁺ T cells measured as fold increase (see “Material and methods”) at different time points after bead activation (mean ± SD from n = 5 donors). (C) CD44v6 expression (RFI, see “Material and methods”) on T cells at the respective time points (mean ± SD from n = 3 donors). (D) CD44v6.CAR28z⁺ or CTR.CAR28z⁺ T cells from healthy donors (n = 2) were cultured with CD44v6⁺ or CD44v6⁻ leukemic blasts from AML patients (n = 7) in the presence (+) or absence (−) of MSCs (E:T ratio = 1:5/10). After 4 days, residual leukemic blasts (CD33⁺/CD3^–) and T lymphocytes (CD33^–/CD3⁺) were counted and analyzed by FACS. Left: results from a representative experiment. Right: antileukemia effects by CD44v6.CAR28z⁺ T cells measured as the elimination index (see “Material and methods”) for each combination. (E) Expansion of CD44v6.CAR28z⁺ or CTR.CAR28z⁺ T cells in response to CD44v6⁺ leukemic blasts measured as fold increase (see “Material and methods”) at the end of culturing. (F) The same experimental setting was used for CD44v6⁺ or CD44v6^– malignant plasma cells from MM patients (n = 6). Malignant plasma cells were identified as CD38⁺/CD45^–. Left: results from a representative experiment. Right: antimyeloma effects by CD44v6.CAR28z⁺ T cells measured as the elimination index for each combination. (G) Expansion of CD44v6.CAR28z⁺ or CTR.CAR28z⁺ T cells in response to CD44v6⁺ malignant plasma cells measured as fold increase at the end of the culture. Results from a paired Student t test or 1-way ANOVA are shown when statistically significant (*P < .05; **P < .01; ***P < .001).