HSF4 and neoplasm: We analyzed the properties of the shortest of these constructs (CTM + 12EC) in a xenograft in vivo model with critical results: T cells transduced with the CTM + 12EC IFP induced toxicities in all mice receiving this treatment (regardless of combination with an anti-CD19 CAR or not) and led to premature termination of the experiment within this treatment group, even before the development of a tumour signal.