MLL/AF4 Positive Acute Lymphoblastic Leukemia Has Resistance to Tumor Necrosis Factor-Alpha Caused by up-Regration of S100A6

Abstract 2477 Mixed-lineage leukemia (MLL)/AF4 positive acute lymphoblastic leukemia (ALL), which is common in infant leukemia, is associated with a poor prognosis even after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The resistance to graft versus leukemia (GVL) effect may be the possible reason of the poor effect of allo-HSCT on MLL/AF4 positive ALL. Cytotoxic effector mechanisms, which are mediated by tumor necrosis factor-alpha (TNF-alpha), Fas ligand (FasL), or perforin were reported to contribute to GVL effect. We analyzed the sensitivity to TNF-alpha of MLL/AF4 positive ALL cell lines (SEM and RS4;11) together with MLL/AF4 negative leukemia cell lines (MOLT4, Raji and K562) and found that the growth inhibition by TNF-alpha of MLL/AF4 positive ALL cell lines group was significantly lower than those of another MLL/AF4 negative leukemia cell lines group (P Disclosures: No relevant conflicts of interest to declare.