CD4 and neoplasm: Potent in vivo anti-tumor efficacy of TCR gene-engineered CD4+ T cells was demonstrated using MHC class I-restricted tyrosinase-specific T cells in immunocompetent mice by Frankel et al. [7] In our human tumor xenograft models in immunodeficient NSG mice, there is no endogenous tumor-reactive CD8+ T cells that could be activated by CD4+ T cells and collaboratively suppress tumor growth, suggesting that 19305DP-TCR-transduced CD4+ T cells directly inhibited tumor growth.