MYD88 Inhibitor ST2825 Suppresses the Growth of Lymphoma and Leukaemia Cells

Background/Aim: Myeloid differentiation primary response gene 88 (MYD88), which activates the nuclear factor kappa B (NF-kappa B) pathway, is important for the growth of lymphoma and leukaemia cells. In this study, we investigated the effects of ST2825, a synthetic peptidomimetic compound which inhibits MYD88 homodimerization, on their growth. Materials and Methods: Seven lymphoma and leukaemia cell lines including TMD8, a B-cell lymphoma line with MYD88-activating mutation, were treated with ST2825 and analysed for cell proliferation and expression of NF-kappa B signalling-related molecules. Results: ST2825 suppressed the growth of all cell lines by inducing apoptosis and down-regulating phosphorylation of NF-kappa B pathway components inhibitor of nuclear factor kappa B kinase (I kappa B) and reticuloendotheliosis oncogene A (RelA), as well as of MYD88 activator Bruton tyrosine kinase (BTK), suggesting that MYD88 may affect BTK activity. ST2825 effects were specific as MYD88-targeting siRNA also suppressed phosphorylation of NF-kappa B signalling proteins and BTK in TMD8 cells. Conclusion: ST2825 may be a novel drug targeting not only B-lymphoid malignancies with MYD88 mutations, but also lymphoma and leukaemia with wild-type MYD88.