Epigenetic deregulated miR-375 contributes to the constitutive activation of JAK2/STAT signaling in myeloproliferative neoplasm.

Constitutive activation of Janus kinase 2/signal transducers and activators of transcription (JAK2/STAT) signaling caused by JAK2V617F and other mutations is central to the pathogenesis of myeloproliferative neoplasm (MPN). Negative regulators such as suppressors of cytokine signaling (SOCS) inhibit activated JAK2/STAT signaling. However, whether silencing of negative regulators facilitates JAK2/STAT signaling is unclear. Here, we report that loss of miR-375 expression contributes to the constitutive activation of JAK2/STAT signaling. MiR-375 reduced JAK2 protein level and repressed the activity of a luciferase reporter by binding 3'-untranslated regions, which was abolished by the mutation of the predicted miR-375-binding site. Meanwhile, a significant inverse correlation between the expressions of miR-375 and JAK2 was found in multiple types of leukemic cell lines and bone marrow mononuclear cells from MPN patients, suggesting that JAK2 may be a miR-375 target gene. Furthermore, forced expression of miR-375 inhibited constitutive and inducible JAK2/STAT signaling, suppressed cell proliferation, and decreased colony formation in hematopoietic progenitors from MPN patients. Finally, histone deacetylation (HDAC) inhibitors restored miR-375 expression, which was much lower in patients with MPN compared with healthy volunteers. Collectively, our data suggest that the loss of miR-375 expression enhances the constitutive and persistent activation of JAK2/STAT signaling. Restoration of miR-375 expression might contribute to the clinical treatment for MPN patients.

miR-29a and miR-142-3p downregulation and diagnostic implication in human acute myeloid leukemia.

Expression profiling of microRNAs (miRNAs) in most diseases might be popular and provide the possibility for diagnostic implication, but few studies have accurately quantified the expression level of dysregulated miRNAs in acute myeloid leukemia (AML). In this study, we analyzed the peripheral blood mononuclear cells (PBMCs) from 10 AML patients (subtypes M1 to M5) and six normal controls by miRNA microarray and identified several differentially expressed miRNAs. Among them miR-29a and miR-142-3p were selectively encountered in Northern blot analysis and their significantly decreased expression in AML was further confirmed. Quantitative real-time PCR in 52 primarily diagnosed AML patients and 100 normal controls not only verified the expression properties of these 2 miRNAs, but also established that the expression level of miR-142-3p and miR-29a in PBMCs could be used as novel diagnostic markers. A better diagnostic outcome was achieved by combining miR-29a and miR-142-3p with about 90% sensitivity, 100% specificity, and an area under the ROC curve (AUC) of 0.97. Our results provide insights into the involvement of miRNAs in leukemogenesis, and offer candidates for AML diagnosis and therapeutic strategy.

[Effect of hydroquinone on expression of topoisomerase enzyme IIα in human bone marrow mononuclear cells].

OBJECTIVE: To investigate the effects of hydroquinone (HQ) on expression of topoisomerase IIα (TOPOIIα) in human bone marrow mononuclear cells, and to explore the role and possible regulatory mechanism of TOPOIIα involved in toxicity of HQ to hematopoietic cells. METHODS: After human bone marrow mononuclear cells were exposed to 50 µmol/L HQ (used the cells which were exposed to sterile distilled water as control); the activity of TOPOII was measured by TOPOII assay kit; the expression levels of TOPOIIα mRNA and protein were detected by RT-PCR technique and Western blotting method respectively; the chromatin immunoprecipitation (ChIP) assay was carried out to study the possible mechanism of TOPOIIα expression changes. RESULTS: (1) The activity of TOPOII was inhibited obviously; the protein and mRNA expression of TOPOIIα were 0.017 ± 0.029 and 0.610 ± 0.128, significantly lower than that in the control with the significant difference (P < 0.01) after treated with HQ for 10 h; (2) The decreased content of TOPOIIα was associated with descended level of histone H4 acetylation than in the control, from 1.198 ± 0.056 to 0.324 ± 0.229, with the significant difference (P < 0.01), without accompanied descended level of histone H3 acetylation, from 1.253 ± 0.045 to 1.177 ± 0.025 (P > 0.05); (3) TOPOIIα mRNA expression decreased gradually after HQ processing, and the chemical modification (histone H4 acetylation) of TOPOIIα promoter happened prior to the mRNA expression. CONCLUSION: HQ could repress the expression of TOPOIIα in human bone marrow mononuclear cells; the change of histone chemical modification plays an important role in the benzene's hematopoietic toxicity.

[Apoptosis induced by hydroquinone in bone marrow mononuclear cells in vitro].

OBJECTIVE: To study the effect of hydroquinone on apoptosis of bone marrow mononuclear cells, and to evaluate the toxic effect of benzene on stem cells. METHODS: Cell morphology was observed by HT fluorescent stain method, and DNA fragments were analyzed by agarose gel electrophoresis. Anti-Annexin V FITC plus PI staining for apoptotic and necrotic rate was examined by flow cytometer. RESULTS: After adding different concentrations of hydroquinone to the cells for 6 h culture, the fluorescent intensity of nucleus increased, the color of nucleus became deep and inhomogeneous, and the chromatin was condensed and distributed around the neucleus. DNA ladder was detected in all samples. Cell apoptotic rate in different concentration of hydroquinone groups was significantly higher than that in blank control group (P < 0.05). With the increase of the concentration of hydroquinone, the apoptotic and necrotic rate also increased. The optimal concentration of hydroquinone was 50 micro mol/L. When it was >or= 75 micro mol/L, the necrotic rate increased significantly. Hydroquinone-induced apoptosis was associated with culture time at the concentration of 50 micro mol/L, and the peak apoptotic time was 10 h, then the apoptotic rate decreased and necrotic rate increased. CONCLUSION: Hydroquinone can induce apoptosis of bone marrow mononuclear cells in vitro with dose-effect and time-effect relationship.