Oroxylin A, a natural anticancer flavonoid compound, induces differentiation of t(8;21)-positive Kasumi-1 and primary acute myeloid leukemia cells

AML1/ETO fusion gene is one of disease-causing genes of t(8;21)-positive acute myeloid leukemia (AML). Oroxylin A (OA) has showed anticancer effects on other cancer cells. Here, studies were conducted to determine the antileukemia effect of OA on t(8;21)-positive AML cells in vitro and in vivo. The effects of OA on cell viability of t(8;21)-positive Kasumi-1 and primary AML cells were analyzed by MTT assay. Cell differentiation was examined by NBT reduction assay, flow cytometry analysis for CD11b/CD14, and Giemsa stain. Protein expressions were determined by Western blots. Immunofluorescence assay was used to verify the effect of OA on HDAC-1 expression in vivo. Immunohistochemical staining was applied to evaluate leukemic infiltration of AML-bearing NOD/SCID mice. OA enhanced NBT reduction activity and CD11b/CD14 expression of AML1/ETO-positive AML cells markedly. Results of Giemsa staining also demonstrated that OA could induce the morphologic changes with reduction of nuclear/cytoplasmic ratios, suggesting the cell differentiation induced by OA. Further study showed that OA decreased the expression of fusion protein AML1/ETO and down-regulated HDAC-1 protein levels in vitro and in vivo. Moreover, OA increased the expression of differentiation-related proteins C/EBP alpha and P21. Acetylation levels of histones were also advanced obviously after treatment of OA. In vivo study indicated that OA could prolong the survival of AML-bearing NOD/SCID mice and reduce leukocytic infiltration of the spleen. All these results suggested that OA might be a novel candidate agent for differentiation therapy for AML1/ETO-positive AML and the mechanism required further investigation.