To achieve a cure of multiple myeloma (MM), we have been developing novel therapies targeting epigenetic aberrations. EZH2 and its homolog EZH1 are the histone lysine methyltransferases inducing the repressive mark of H3K27me3. UNC1999 is a dual inhibitor of EZH2 and EZH1, showing significant anti-MM activities. It also synergizes with proteasome inhibitors, associated with derepression of NR4A1 and downregulation of MYC. Moreover, UNC1999 and a selective Akt inhibitor TAS-117 synergistically inhibit the growth of MM cells through epigenetic mechanisms. TAS-117 induces downregulation of EZH2 and compensatory upregulation of EZH1, which is inhibited by UNC1999. Interestingly, a microtubule polymerization inhibitor PTC596 cooperatively downregulates BMI1 protein with proteasome inhibitors, exhibiting in-vitro and in-vivo cytotoxicity in MM cells. Finally, our mouse model with concurrent loss of the histone demethylase Utx and the activating mutation of Braf V600E in post germinal center B cells demonstrates mature B-cell malignancies including plasma cell neoplasms. Our ongoing analyses will reveal the pathogenesis of MM induced by somatic mutations, and this model is a useful tool for the development of novel molecular-targeted therapies for MM patients.
Keywords: Epigenetic therapy; Histone modulation; Mouse model; Multiple myeloma.