Dual targeting of MYC and CYCLON by BET bromodomain inhibition optimizes Rituximab response in lymphoma.

Immuno-chemotherapy regimens elicit high response rates in B-cell non-Hodgkin lymphoma but heterogeneity in response duration is observed, with some patients achieving cure and others showing refractory disease or relapse. Using a transcriptome-powered targeted proteomics screen, we discovered a gene regulatory circuit involving the nuclear factor CYCLON which characterizes aggressive disease and resistance to the anti-CD20 monoclonal antibody, Rituximab, in high-risk B-cell lymphoma. CYCLON knockdown was found to inhibit the aggressivity of MYC-overexpressing tumors in mice and to modulate gene expression programs of biological relevance to lymphoma. Furthermore, CYCLON knockdown increased the sensitivity of human lymphoma B cells to Rituximab in vitro and in vivo. Strikingly, this effect could be mimicked by in vitro treatment of lymphoma B cells with a small molecule inhibitor for BET bromodomain proteins (JQ1). In summary, this work has identified CYCLON as a new MYC cooperating factor that drives aggressive tumor growth and Rituximab resistance in lymphoma. This resistance mechanism is amenable to next-generation epigenetic therapy by BET bromodomain inhibition, thereby providing a new combination therapy rationale for high-risk lymphoma.

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Emadali A, Rousseaux S, Bruder-Costa J, Rome C, Duley S, Hamaidia S, Betton P, Debernardi A, Leroux D, Bernay B, Kieffer-Jaquinod S, Combes F, Ferri E, McKenna CE, Petosa C, Bruley C, Garin J, Ferro M, Gressin R, Callanan MB, Khochbin S