[The Role and Mechanism of MiR-451 in Multidrug Resistance of Leukemia Cell Line K562/A02].

OBJECTIVE: To detect the differential expressions of miR-451, ABCB1 and ABCC2 in drug-sensitive leukemia cell line K562 and drug-resistant cell line K562/A02, and explore the regulatory relationship between miR-451 and the expressions of ABCB1 and ABCC2 , and the mechanism of miR-451 involved in drug resistance in leukemia. METHODS: CCK-8 assay was used to detect the drug resistance of K562/A02 and K562 cells. Quantitative Real-time PCR (qRT-PCR) was used to verify the differential expressions of miR-451 in K562 and K562/A02 cells. MiR-451 mimic and negative control (miR-NC), miR-451 inhibitor and negative control (miR-inNC) were transfected into K562 and K562/A02 cells respectively, then qRT-PCR and Western blot were used to detect the expression levels of mRNA and protein of ABCB1 and ABCC2 in K562 and K562/A02 cells and the transfected groups. RESULTS: The drug resistance of K562/A02 cells to adriamycin was 177 times higher than that of its parent cell line K562. Compared with K562 cells, the expression of miR-451 in K562/A02 cells was significantly higher (P <0.001), and the mRNA and protein expression levels of ABCB1 and ABCC2 in K562/A02 cells were significantly higher than those in K562 cells (P <0.001). After transfected with miR-451 inhibitor, the expression of miR-451 was significantly down-regulated in K562/A02 cells (P <0.001), the sensitivity to chemotherapy drugs was significantly enhanced (P <0.05), and the mRNA and protein expressions of ABCB1 and ABCC2 were significantly decreased (P <0.01). After transfected with miR-451 mimic, the expression of miR-451 was significantly upregulated in K562 cells (P <0.001), and the mRNA and protein expressions of ABCB1 and ABCC2 were significantly increased (P <0.01). CONCLUSION: There are significant differences in the expressions of miR-451, ABCB1 and ABCC2 between the drug-sensitive leukemia cell line K562 and drug-resistant cell line K562/A02, which suggests that miR-451 may affect the drug resistance of leukemia cells by regulating the expression of ABCB1 and ABCC2.

Multiple myeloma characterized by synovial fibrinoid necrosis: a case report.

A number of patients with multiple myeloma (MM) have joint lesions with the main feature of amyloidosis or tumor cell infiltration. We report a case of MM that presented as synovial fibrinoid necrosis. The rarity of this condition and the difficulty diagnosing the disease are discussed. In addition, we discussed the characteristics of amyloid arthropathy and the findings in this case.

[Effect of 5-aminoimidazole-4-formamide Ribonucleotide Combined with Interferon on Chronic Myeloid Leukemia K562 Cells].

OBJECTIVE: To study the effect of 5-aminoimidazole-4-formamide ribonucleotide (AICAR) combined with interferon (IFN-α-2b) on the proliferation and apoptosis of chronic myeloid leukemia K562 cells, and explore its possible mechanism. METHODS: CCK-8 method was used to detect the inhibition of cell proliferation. Wright Giemsa method was used to stain and cell morphology was observed by light microscopy. FITC Annexin V/PI double staining method was used to analyze the change of apoptosis rate. Immunocytochemistry method was used to detect the expression of wild-type P53 protein. RESULTS: Different concentration of AICAR was inhibitory effect on K562 cells at different time point of action for 24 h, 48 h, and 72 h, and the inhibition was time and dose-dependent (r=0.71, r=0.84). The combination of AICAR and IFN-α-2b could effectively inhibit the proliferation and promote apoptosis of K562 cells. The inhibition rate of K562 cells was (45.26±2.54)%, and the early apoptosis rate was (33.72±0.23)%, which was statistically significantly different from the control group, AICAR or IFN-ɑ-2b alone (P<0.05). The combination of two drugs promoted the expression of wild-type p53 protein. CONCLUSION: AICAR and/or IFN-ɑ-2b can inhibit the cell proliferation and promote the apoptosis of K562 cells. The combination of two drugs shows synergistic antitumor effect, and its mechanism may be related to the promotion of high expression of wild-type p53 protein.

PBK/TOPK expression during TPA-induced HL-60 leukemic cell differentiation.

OBJECTIVE: This study concerns expression of PBK/TOPK during differentiation of HL-60 leukemic cells induced by tetradecanoyl phorbol acetate (TPA). METHODS: Wright-Giemsa staining was performed to observe morphological changes in the HL-60 cells, and flow cytometry was used to assess the cell cycle and CD11b, CD14, CD13, and CD33 expression. PBK/TOPK levels were determined by Western blot analysis. RESULTS: After treating HL60 cells with 5.1×10⁻9 mmol/L of TPA for three days, the number of nitroblue-tetrazolium-positive cells and CD11b, CD13, and CD14 expression increased, whereas the PBK/TOPK levels decreased. CONCLUSIONS: TPA can inhibit proliferation and induce differentiation of HL60 cells of the granulocytic or monocytic lineage. PBK/TOPK expression was downregulated during this process, whereas the Pho-PBK/TOPK expression was increased.

[Rac1 expression and its effects on the cell cycle progression and apoptosis in human acute leukemic cell line HL-60].

The study was aimed to investigate the expression of Rac1 in human acute leukemic cell line HL-60 and effect of Rac1 on cell cycle progression and apoptosis. The mRNA expression of Rac1 in HL-60 cell line and normal human peripheral blood mononuclear cells (PBMNC) were examined by semi-quantitative RT-PCR. After transfection of HL-60 cells with different concentrations of Rac1 antisense oligodeoxynucleotide (ASODN) by means of FuGENE6, the survival, cell cycle, apoptosis of HL-60 cells were observed through MTT assay, FCM test, Wright-Giemsa, acridine orange/ethidium bromide (AO/EB) and Annexin V-FITC/PI staining test respectively. The results showed that Rac1 relative amount in HL-60 was 0.84 +/- 0.13, while it in the normal PBMNC was 0.26 +/- 0.1 (P < 0.01); the expression of Rac1 in HL-60 cells was significantly upregulated. Compared with sense oligodeoxynucleotide (SODN), HL-60 cell viability, after exposure to ASODN at a concentration of 2.0 g/L decreased, (73.7 +/- 5.0)% vs (93.2 +/- 3.0)% (P < 0.01), while the proportion of G(1) cells increased as (52.1 +/- 6.8)% vs (31.6 +/- 4.7)% (P < 0.05), the percentage of Annexin V positive cells increased, (19.2 +/- 2.1)% vs (4.1 +/- 1.7)% (P < 0.01), and HL-60 cells were observed to have formation of apoptotic bodies. The data presented indicate that Rac1 may be involved in regulation of HL-60 cell cycle and apoptosis, promote overproliferation of HL-60 cells and inhibit their apoptosis.