Edited by Tamas DalmayKeywords: HOTAIR miR-193a c-KIT Acute myeloid leukemia a b s t r a c t HOTAIR is significantly overexpressed in various cancers and facilitates tumor invasion and metastasis. However, whether HOTAIR plays oncogenic roles in acute myeloid leukemia (AML) is still unknown. Here, we report that HOTAIR expression was obviously increased in leukemic cell lines and primary AML blasts. Clinically, AML patients with higher HOTAIR predicted worse clinical outcome compared with those with lower HOTAIR. Importantly, HOTAIR knockdown by small hairpin RNA inhibited cell growth, induced apoptosis, and decreased number of colony formation. Finally, HOTAIR modulated c-KIT expression by competitively binding miR-193a. Collectively, our data suggest that HOTAIR plays an important oncogenic role in AML and might serve as a marker for AML prognosis and a potential target for therapeutic intervention.

BackgroundmiR-15a and miR-16-1(miR-15a/16-1) have been implicated as tumor suppressors in chronic lymphocytic leukemia, multiple myeloma, and acute myeloid leukemic cells. However the mechanism of inhibiting the proliferation of leukemic cells is poorly understood.MethodsK562 and HL-60 cells were transfected with pRS-15/16 or pRS-E, cell growth were measured by CCK-8 assay and direct cell count. Meanwhile WT1 protein and mRNA level were measured by Western blotting and quantitative real-time PCR.ResultsIn this study we found that over-expression of miR-15a/16-1 significantly inhibited K562 and HL-60 cells proliferation. Enforced expression of miR-15a/16-1 in K562 and HL-60 cells significantly reduced the protein level of WT1 but not affected the mRNA level. However enforced expression of miR-15a/16-1 can not reduce the activity of a luciferase reporter carrying the 3'-untranslated region(3'UTR) of WT1. Silencing of WT1 by specific siRNA suppressed leukemic cells proliferation resembling that of miR-15a/16-1 over-expression. Anti-miR-15a/16-1 oligonucleotides (AMO) reversed the expression of WT1 in K562 and HL-60 cells. Finally, we found a significant inverse correlation between miR-15a or miR-16-1 expression and WT1 protein levels in primary acute myeloid leukemia (AML) blasts and normal controls.ConclusionsThese data suggest that miR-15a/16-1 may function as a tumor suppressor to regulate leukemic cell proliferation potentially by down-regulating the WT1 oncogene. However WT1 is not directly targeted by miR-15a/16-1 through miRNA-mRNA base pairing, therefore more study are required to understand the mechanism by which miR-15a/16-1 downregulate WT1.

Suppressors of cytokine signaling, SOCS1 and SOCS3, are important negative regulators of Janus kinase 2/signal transducers and activators of transcription signaling, which is constitutively activated in myeloproliferative neoplasms (MPNs) and leukemia. Curcumin has been shown to possess anticancer activity through different mechanisms. However, whether curcumin can regulate the expression of SOCS1 and SOCS3 is still unknown. Here, we found that curcumin elevated the expression of SOCS1 and SOCS3 via triggering acetylation of histone in the regions of SOCS1 and SOCS3 promoter in K562 and HEL cells. As a novel histone deacetylases (HDACs) inhibitor, curcumin inhibited HDAC enzyme activities and decreased the levels of HDAC1, 3 and 8 but not HDAC2. Knockdown of HDAC8 by small interfering RNA markedly elevated the expression of SOCS1 and SOCS3. Moreover, ectopic expression of HDAC8 decreased the levels of SOCS1 and SOCS3. Thus, HDAC8 plays an important role in the modulation of SOCS1 and SOCS3 by curcumin. Also, trichostatin A (TSA), an inhibitor of HDACs, increased the levels of SOCS1 and SOCS3. Furthermore, curcumin increased the transcript levels of SOCS1 and SOCS3 and significantly inhibited the clonogenic activity of hematopoietic progenitors from patients with MPNs. Finally, curcumin markedly inhibited HDAC activities and decreased HDAC8 levels in primary MPN cells. Taken together, our data uncover a regulatory mechanism of SOCS1 and SOCS3 through inhibition of HDAC activity (especially HDAC8) by curcumin. Thus, being a relative non-toxic agent, curcumin may offer a therapeutic advantage in the clinical treatment for MPNs.

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miR-15a and miR-16-1 (miR-15a/16-1) have been implicated in apoptosis, cell cycle regulation and chemosensitivity of tumor cells, but little is known about the role of miR-15a/16-1 in the differentiation of leukemic cells. In this study, we found that the expression level of miR-15a/16-1 was up-regulated by all-trans retinoic acid (ATRA) treatment in NB4, HL-60 and U937 cell lines and primary leukemic cells. Overexpression of miR-15a/16-1 could not directly drive cells to undergo differentiation but enhanced ATRA-induced differentiation in NB4 and U937 cells. Up-regulation of miR-15a/16-1 was also observed in 36 patients with acute myeloid leukemia (AML) who achieved a complete remission (CR), and two of them showed sharp down-regulation of miR-15a/16-1 when they had a molecular relapse. These data indicate that miR-15a/16-1 plays an important role in the ATRA-induced differentiation of leukemic and primary AML cells.