Loss of TNFAIP3 enhances MYD88 L265P -driven signaling in non-Hodgkin lymphoma.

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.