MYD88 Inhibitor ST2825 Suppresses the Growth of Lymphoma and Leukaemia Cells

Myeloid differentiation primary response gene 88 (MYD88), which activates the nuclear factor kappa B (NF-κB) 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.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-κB signalling-related molecules.ST2825 suppressed the growth of all cell lines by inducing apoptosis and down-regulating phosphorylation of NF-κB pathway components inhibitor of nuclear factor kappa B kinase (IκB) 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-κB signalling proteins and BTK in TMD8 cells.ST2825 may be a novel drug targeting not only B-lymphoid malignancies with MYD88 mutations, but also lymphoma and leukaemia with wild-type MYD88.