Targeting of acute myeloid leukemia by five-gene engineered T cells expressing transgenic T-cell receptor specific to WT1, chimeric antigenic receptor specific to GM-CSF receptor, bispecific T-cell engager specific to CD33, and tEGFR suicide gene system.

Background: Cancer immunotherapy with transgenic T-cell receptor-engineered T cells (TCR-T) enables the targeting of intracellular tumor-specific antigens; in contrast, chimeric antigen receptor-modified T cells (CAR-T) mediate tumor cell killing via the recognition of surface antigens. In the case of acute myeloid leukemia, the lack of leukemia-specific surface antigens limits the efficacy of CAR-T cells; therefore, TCR-T cells may represent a more targeted immunotherapy approach. However, the tumor immunosuppressive environment eliminates the best-functioning, high-avidity TCR-T cells, thus creating a need for novel, enhanced TCR-T cells.

Methods: The piggyBac transposon vector used for gene modification of T cells expresses a T-cell receptor specific to the WT1 tumour antigen, an NFAT promoter-regulated CAR specific to GM-CSF receptor, a CD3xCD33 bispecific T-cell engager, and a truncated EGFR suicide gene system. The transgenic T cells were generated by electroporation using a single expression vector, and the efficiency of these engineered TCR-T cells was evaluated using models that utilized AML cell lines and primary AML cells.

Results: The NFAT-driven GM-CSF CAR significantly enhances the antileukemic activity of WT1-specific TCR-T cells, which importantly maintain specificity for their HLA/peptide antigenic complex. Next, by inserting the CD3xCD33 bispecific T-cell engager into the transposon vector, both TCR-T cells and recruited non-transfected bystander T cells can efficiently target the CD33 antigen, providing more robust antileukemic effects.

Conclusion: The presented strategy, utilizing a single piggyBac transposon vector, enables the complex redirection of T-cell specificity against acute myeloid leukemia by inserting TCR, CAR, BiTE constructs, along with a tEGFR gene suicide system.