Amlexanox Downregulates S100A6 to Sensitize KMT2A/AFF1-Positive Acute Lymphoblastic Leukemia to TNFα Treatment

Acute lymphoblastic leukemias (ALL) positive for KMT2A/AFF1 (MLL/AF4) translocation, which constitute 60% of all infant ALL cases, have a poor prognosis even after allogeneic hematopoietic stem cell transplantation (allo-HSCT). This poor prognosis is due to one of two factors, either resistance to TNFα, which mediates a graft-versus-leukemia (GVL) response after allo-HSCT, or immune resistance due to upregulated expression of the immune escape factor S100A6. Here, we report an immune stimulatory effect against KMT2A/AFF1-positive ALL cells by treatment with the anti-allergy drug amlexanox, which we found to inhibit S100A6 expression in the presence of TNF-α. In KMT2A/AFF1-positive transgenic (Tg) mice, amlexanox enhanced tumor immunity and lowered the penetrance of leukemia development. Similarly, in a NOD/SCID mouse model of human KMT2A/AFF1-positive ALL, amlexanox broadened GVL responses and extended survival. Our findings show how amlexanox degrades the resistance of KMT2A/AFF1-positive ALL to TNFα by downregulating S100A6 expression, with immediate potential implications for improving clinical management of KMT2A/AFF1-positive ALL. Cancer Res; 77(16); 4426-33. ©2017 AACR.