MicroRNA-204 Potentiates the Sensitivity of Acute Myeloid Leukemia Cells to Arsenic Trioxide.

Although arsenic trioxide (ATO) is a well-known antileukemic drug used for acute promyelocytic leukemia treatment, the development of ATO resistance is still a big challenge. We previously reported that microRNA-204 (miR-204) was involved in the regulation of acute myeloid leukemia (AML) cell apoptosis, but its role in chemoresistance is poorly understood. In the present study, we showed that miR-204 was significantly increased in AML cells after ATO treatment. Interestingly, the increased miR-204 level that was negatively correlated with ATO induced the decrease in cell viability and baculoviral inhibition of apoptosis protein repeat-containing 6 (BIRC6) expression. Overexpression of miR-204 potentiated ATO-induced AML cell growth inhibition and apoptosis. Furthermore, miR-204 directly targets to the 3'-UTR of BIRC6. Upregulation of miR-204 decreased BIRC6 luciferase activity and expression, which subsequently enhanced the expression of p53. Restoration of BIRC6 markedly reversed the effect of miR-204 on the regulation of AML cell sensitivity to ATO. Taken together, our study demonstrates that miR-204 decreases ATO chemoresistance in AML cells at least partially via promoting BIRC6/p53-mediated apoptosis. miR-204 represents a novel target of ATO, and upregulation of miR-204 may be a useful strategy to improve the efficacy of ATO in AML treatment.

[Arsenic trioxide inhibits cell growth in imatinib-resistant bcr-abl mutant cell lines in vitro].

OBJECTIVE: To explore the effect of arsenic trioxide (As2O3) on the growth inhibition of imatinib (IM)-resistant bcr-abl mutant cell lines in vitro. METHODS: Cell growth of one IM-sensitive cell line, 32Dp210 and 15 IM-resistant cell lines including T315I and other 14 bcr-abl mutants were detected by MTT assay after treatment with IM and As2O3. The cell lines with 5 frequently observed mutants in CML patients were analyzed for apoptosis by flow cytometry with Annexin V and PI staining as well as the expression of bcr-abl fusion protein, phosphorylated CRKL protein and apoptosis-related proteins by Western blot. RESULTS: The fifty percent inhibition concentration (IC50) values of As2O3 for 15 IM-resistant cell lines were 2.6-5.3 fold lower than that for IM-sensitive cell line. For the 5 bcr-abl mutants frequently happened in CML patients, As2O3 significantly inhibited the expression of bcr-abl fusion protein and phosphorylated CRKL and induced apoptosis in a dose-dependent manner as compared with that for 32Dp210. Coincidently, the cell apoptosis was induced through caspase-3, 8 and 9 pathways. CONCLUSION: As2O3 remarkably inhibits cell growth and induces apoptosis of IM-resistant bcr-abl mutant cell lines in vitro, suggesting that it might be a potential therapeutic agent for IM-resistant CML patients.

[Growth inhibition and differentiation of imatinib-resistant chronic myeloid leukemia cell induced by cell differentiation agent in vitro].

OBJECTIVE: To investigate the effects of uroacitide (CDA-2), a cell differentiation agent, on the growth inhibition and differentiation of imatinib-(IM) resistant chronic myeloid leukemia (CML) cells. METHODS: IM resistant CML cell line K562R was established from the line K562. K562 and K562R CML cells were cultured with CDA-2 of different concentrations. MTI method was used to detect the survival rates. Bone marrow cells of IM-resistant and non-IM-resistant CML patients were collected and co-incubated with K562 and K562R cells. MTT and colony-forming assays were used to evaluate the efficacy of CDA-2 treatment for cell growth in K562 and K562R cell lines, and IM-resistant or non-IM-resistant bone marrow cells of the CML patients; Annexin-V staining was employed to detect the apoptosis. Cell differentiation was assessed by flow cytometry analysis with CD11b/CD14 markers, reverse transcriptase PCR (RT-PCR) for mRNA levels of NCF-1 and ORM-1 genes and Giemsa staining for the observation in morphology. Cell cycle distribution was detected by stained with propidium iodide and then analyzed by flow cytometer. RT-PCR also was employed for the expression of DNA methyltransferase. RESULTS: Significant cell growth inhibition was found at a dose-dependent manner in the IM-resistant K562R cell line and IM-resistant bone marrow cells of the CML patients compared with the non-resistant K562 cell line and bone marrow cells of the CML patients following 7 days exposure to CDA-2. Although CDA-2 could significantly induce the apoptosis of K562R (15.38%) compared with K562 (5.28%) (P < 0.05), the major reason for the cell growth inhibition of K562R is CDA-2-induced cell differentiation, including the increase of expression of differentiation-related antigens CD11b/CD14, mRNA expression of NCF-1 and ORM-1, and cell cycle arrest in G1-phase at a dose-dependent manner. Because CDA-2 could significantly activate the p21 and p27 gene expression, downregulate the expression of cyclin D1, and down-regulate the expressions of DNMT1 and DNMT(3B) at mRNA level, CDA-2 might be a DNMT inhibitor for restoring some gene function that involved in cell cycle control by demethylation. CONCLUSION: Inhibiting the growth and inducing the differentiation of K562R cells, CDA-2 is very likely to be a potential agent for the treatment of IM resistance CML patients.