Effects Of Lovastatin On Proliferation And Apoptosis Of HL-60 Cells And Its Molecular Mechanisms

Lovastatin is an inhibitor of 3-hydroxy-3-methylglutaryl-coenzymeA- (HMG-CoA) reductase, the rate-limiting enzyme of endogenous cholesterol biosynthesis. It is commonly used for the clinical treatment of hyperchole- sterolaemia. Recently, numerous studies have suggested that lovastatin could suppress the proliferation and arrest cell cycle in G0/G1 phase, induce apoptosis in varieties of malignant cells in vitro. Moreover, it has little side effect on normal cells. However, the molecular mechanisms for its anticancer effect have not been completely elucidated. In this report, we investigated the effects of lovastatin at the dosages of 4~16μmol/L on proliferation and apoptosis of the human leukemia cell line HL-60 and its possible molecular mechanisms. First, MTT test and the observation of morphological characteristics were used to assay the proliferative capacity, and apoptotic cell death was evaluated by flow cytometry (FCM), DNA ladder, DNA fragmentation rate and ultrastructural analyses. Then, FCM was used to analyses the expression of Fas antigen, reverse transcription polymerase chain reaction (RT-PCR) was used to estimate the mRNA expression of Bcl-2, Caspase-3. Additionally, the protein expression of Bcl-2 and Caspase-3 was detected by Western blotting.The results showed that: (1) lovastatin at the dosages of 4~16 μmol/L significantly inhibited the proliferation of HL-60 cells via G0/G1 phases arrest of the cell cycle in a time and dose dependent manner. Meanwhile, the morphology of HL-60 cells were obviously changed under the optical microscope, There were some fragments of dead cells in the highest dosage group. (2) lovastatin induced HL-60 cells apoptosis effectively. " Apoptotic peaks " were observablein lovastatin-treated cells by FACS analysis, the apoptotic rate and the DNA fragmentation rate were increased in HL-60 cells treated with lovastatin, DNA ladder was observable by agarose gel electrophoresis of DNA, and apoptotic changes were detectable by the electron microscope in lovastatin-treated cells. (3) The expression of HMG-CoA reductase mRNA was increased in HL-60 cells treated with low dosage lovastatin (4μmol/L), whereas it was decreased by median (8μmol/L) and high dosages (16μmol/L) of lovastatin. (4) lovastatin increased the expression of Caspase-3 protein and Fas antigen, down-regulated the levels of Bcl-2, but the expression of Caspase-3 mRNA didn't change in HL-60 cells treated with lovastatin. These observations suggest that: lovastatin could inhibit the cellular proliferation and induce apoptosis significantly in HL-60 cells. The up-regulated expression of Caspase-3 protein and Fas antigen, down-regulated expression of Bcl-2 in HL-60 cells maybe play key role in lovastatin inhibiting proliferation and inducing apoptosis of HL-60 cells.