In order to exclude the possibility that the enhanced antitumor activity of MC-CAR T cells is in part due to tumor cell recognition by the endogenous αβ TCR of MC-CAR T cells, we generated (a) MC-CAR T cells in which the TCR α constant (TRAC) region was knocked out by CRISPR/Cas9 gene editing (MC TRAC KO-CAR T cells) or (b) MC-CAR T cells that expressed an MC-CAR in which the 6 tyrosines in the immunoreceptor tyrosine-based activation motifs (ITAMs) of the ζ-signaling domain were replaced with phenylalanine (MC mutITAM-CAR). Here, TRAC is linked to neoplasm.