Oroxylin a Heightens Tumor Necrosis Factor a-Induced Differentiation Effects on Acute Myeloid Leukemia Cells Via Modulation on AKT and NF-Kb Pathways Involving RXRa

Tumor necrosis factor alpha (TNFα) is a complicated cytokine which could induce differentiation of acute myeloid leukemia (AML) cells. We have found that Oroxylin A, a natural compound isolated from Scutellariae radix, markedly enhanced TNFα-induced NBT reduction and CD11b/CD14 expression of AML cells. Besides, Giemsa staining also displayed that the combination group induced U937-MDR cells to differentiate into monocyte-like cells yet NB4 and HL-60-resistant cells to granulocytic-like cells. Further study showed that TNFα induced PI3K subunit p85α binding to N-terminal truncated nuclear receptor RXRα (tRXRα) proteins and activating AKT. On the contrary, these could be inhibited by Oroxylin A through inhibiting interaction between tRXRα and p85α in NB4 and HL-60-resistant cells. Moreover, Oroxylin A inhibited the activation of NF-κB signaling and the DNA binding activity by TNFα proved by EMSA in these two AML cells. All these suggested that Oroxylin A was able to inhibit NF-κB signaling and RXRα-dependent AKT signaling, the negative effects of TNFα for AML therapy, suggesting that combination of Oroxylin A and TNFα might be a novel candidate for differentiation therapy for AML cells and required further investigation.