did not reach statistical significancep < 0.0001
In addition, in an in vivo experiment including the treatment of non-targeting PG CAR-IL15 T cells, no significant body weight loss was seen in the mice of this group, although we indeed observed a trend toward slower tumor growth in those treated mice from Day 18 after treatment, which did not reach statistical significance (mean tumor volume on Day 21: 39.5 vs 454.1 or 301.7 mm 3 for H9 CAR-IL15 vs UN-T or PG CAR-IL15, p < 0.0001; Figure S4F ); this observation is possibly explained by the fact that IL-15 itself produced from non-activated CAR-T cells may induce the antitumor activity when it accumulates to a certain level, which is consistent with previous studies showing that IL-15 has modest anticancer activity as a single agent ( 24 ).