Therapeutic potential of FLT4-targeting peptide in acute myeloid leukemia

Abstract

Abstract Fms-related tyrosine kinase-4 (FLT4) is involved in tumor progression. Previously, we found that dysfunctional natural killer (NK) cells with low interferon-gamma (IFN-γ) were restored in acute myeloid leukemia (AML) by the FLT4 antagonist MAZ51. In this work, we developed 12 peptides targeting FLT4 for clinical application and ultimately selected 4 of them to examine whether they restored the frequency of lymphocytes, especially T cells and NK cells, and high IFN-γ expression, as MAZ51 treatment did in our previous study. Although clinical data from using intracellular kinase domain–targeting peptides are currently available, peptides targeting FLT4 to modulate immune cells have not been fully elucidated. In this study, we focus on novel peptide 4 (P4) from the intracellular domain of FLT4 because it had dominant negative activity. Similar to MAZ51, high IFN-γ levels were expressed in AML-mononuclear cells (MNCs) exposed to P4. In addition, T and NK cell levels were restored, as were high IFN-γ levels, in a leukemic environment when P4 was co-cultured with cytosine β-D-arabinofuranoside. Interestingly, the frequency of regulatory T cells was significantly decreased by P4, implying that the peptide plays a role in modulating the tumor niche. Overall, we demonstrated the therapeutic value of functionally modulating lymphocytes using a peptide targeting FLT4 and propose the development of advanced therapeutic approaches against AML by using immune cells.