Safety profile of CD44v6-targeted T cells toward nonhematopoietic cells. (A) CD44v6 expression in primary leukemic blasts, cultured primary keratinocytes, and a panel of normal tissues was analyzed by RT-qPCR. CD44v6 expression from a CD44v6⁺ AML sample was used as a reference (gray). (B) CD44v6.CAR28z⁺ or CTR.CAR28z⁺ T cells from healthy donors (n = 3) were cultured with primary keratinocytes (n = 6), primary leukemic blasts from AML#12, CD44v6⁺ MM1.S, or CD44v6^– U266 myeloma cells at different E:T ratios. After 4 days, residual cells were counted and analyzed by FACS. Left: results from a representative experiment. Right: elimination index by CD44v6.CAR28z⁺ T lymphocytes at each E:T ratio (see “Material and methods”). Results from a 1-way ANOVA test comparing the elimination of leukemic blasts and keratinocytes are shown (*P < .05; ***P < .001). (C) CAR⁺ T cells were analyzed for IL-2 and interferon-γ production upon coculture with MM1.S or keratinocytes (concentration, mean ± SD). Results from a Student t test are shown when statistically significant (***P < .001).