MYD88 mutations are one of the most recurrent mutations in hematologic malignancies. However, recent mouse models suggest that MYD88 L265P alone may not be sufficient to induce tumor formation. Interplay between MYD88 L265P and other genetic events is further supported by the fact that TNFAIP3 (A20) inactivation often accompanies MYD88 L265P . However, we are still lacking information about the consequence of MYD88 L265P in combination with TNFAIP3 loss in human B cell lymphoma. Review of our genetic data on diffuse large B cell lymphoma (DLBCL) and Waldenstrom macroglobulinemia (WM), found that a large percentage of DLBCL and WM cases that have a MYD88 mutation also harbor a TNFAIP3 loss, 55% DLBCL and 28% of WM, respectively. To mimic this combination of genetic events, we used genomic editing technology to knock out TNFAIP3 in MYD88 L265P non-Hodgkin’s lymphoma (NHL) cell lines. Loss of A20 expression resulted in increased NF-κB and p38 activity leading to upregulation of the NF-κB target genes BCL2 and MYC. Furthermore, we detected the increased production of IL-6 and CXCL10 which led to an upregulation of the JAK/STAT pathway. Overall, these results suggest that MYD88 L265P signaling can be enhanced by a second genetic alteration in TNFAIP3 and highlights a potential opportunity for therapeutic targeting.
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