To understand how DT could induce tumor regression in mice lacking DTR alleles, we treated tumor-bearing FVB TetO-EGFRL858R; CCSP-rtTA mice with 0.5 μg DT or CRM197, a DT mutant harboring a single amino acid substitution (G52E) in the catalytic domain. This evidence concerns the gene SCGB1A1 and neoplasm.