[Effect of ultraviolet irradiation on the proliferation of acute promyelocytic leukemia cells under hypoxic conditions and related mechanisms].

OBJECTIVE: To study the effect of 280 nm-LED ultraviolet irradiation on the proliferation of acute promyelocytic leukemia (APL) HL-60 cells under hypoxic conditions and related mechanism. METHODS: HL-60 cells in the logarithmic growth phase were selected and divided into control, hypoxia, ultraviolet and hypoxia+ultraviolet groups. The cells in the hypoxia group were treated with cobalt chloride (with a final concentration of 150 µmol/L), those in the ultraviolet group were irradiated by 280 nm-LED ultraviolet with an energy intensity of 30 J/m2, and those in the hypoxia+ultraviolet group were treated with cobalt chloride and then irradiated by 280 nm-LED ultraviolet. After 48 hours of treatment, the cells were placed under an invert microscope to observe cell morphology. CCK-8 assay was used to measure the inhibition rate of cell proliferation. Annexin V-FITC/PI double staining flow cytometry was used to evaluate cell apoptosis. Quantitative real-time PCR was used to measure the mRNA expression of Bcl-2. Each experiment above was repeated three times independently. RESULTS: Compared with the control group, the experimental groups showed shrinkage, decreased brightness, and disordered arrangement of cells, and the number of cells decreased over the time of culture. There were significant differences in the inhibition rate of cell proliferation and cell apoptosis rate among the groups (P<0.01), and the hypoxia+ultraviolet group showed the strongest inhibition of cell proliferation and induction of cell apoptosis, followed by the ultraviolet group and the hypoxia group. Compared with the control group, the other three groups had a gradual reduction in the mRNA expression of Bcl-2, and the hypoxia+ultraviolet group had a significantly greater reduction than the hypoxia and ultraviolet groups (P<0.01). CONCLUSIONS: Both hypoxia and ultraviolet irradiation can inhibit the proliferation of HL-60 cells and induce cell apoptosis, and ultraviolet irradiation has a better effect on proliferation inhibition and cell apoptosis under hypoxic conditions than under normoxic conditions, possibly by downregulating the mRNA expression of Bcl-2.