Leptin promotes proliferation and inhibits apoptosis of prostate cancer cells by regulating ERK1/2 signaling pathway

OBJECTIVE: The aim of this study was to investigate the effect of leptin (Lep) on the proliferation, invasion and apoptosis of prostate cancer cells through the extracellular regulated protein kinase 1/2 (ERK1/2) signaling pathway. MATERIALS AND METHODS: Prostate cancer DU145 cells in the logarithmic growth phase were randomly divided into Lep (10, 20, 40, 80, 160 and 320 ng/mL) groups and blank control (Con) group. After culture, the cells were treated for 6 h, 12 h and 24 h, respectively. The effects of Lep on the proliferation and invasion of DU145 cells were detected via methyl thiazolyl tetrazolium (MTT) assay and transwell chamber assay, respectively. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was carried out to examine the messenger ribonucleic acid (mRNA) expressions of ERK1/2, b-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax) in DU145 cells after Lep treatment for 24 h. Thereafter, immunofluorescence assay was performed to detect the localization of ERK1/2 protein in prostate cancer DU145 cells. In addition, the expressions of phosphorylated (p)-ERK, ERK1/2 and apoptosis-related proteins, Bcl-2, Bax and cleaved cysteinyl aspartate specific proteinase (c-Caspase 3) in prostate cancer DU145 cells after treatment with different concentrations of Lep for 24 h were examined by Western blotting. RESULTS: MTT assay results showed that the proliferation rate of DU145 cells increased significantly at 6 h, 12 h and 24 h after 5-320 ng/mL of Lep treatment (p<0.05). Transwell assay manifested that the number of invasive cells was significantly raised after Lep treatment for 24 h (p<0.05). Meanwhile, the invasion ability of cells increased gradually with the elevation of Lep concentration. Subsequent qRT-PCR results demonstrated that after treatment with different concentrations of Lep, the mRNA expressions of ERK1/2 and Bcl-2 rose markedly (p<0.05). However, the mRNA expression of Bax was remarkably down-regulated (p<0.05) with the increase of Lep concentration in a concentration-dependent manner. According to the detection using a laser scanning confocal microscope, ERK1/2 red fluorescence showed punctiform aggregation, which was gradually raised with the increase of Lep concentration for 24 h. Moreover, Western blotting results denoted that with the increase of Lep concentration, the protein expressions of p-ERK, ERK1/2 and Bcl-2 were notably elevated (p<0.05), while those of Bax and c-Caspase 3 were distinctly reduced (p<0.05). CONCLUSIONS: Lep activation induces the proliferation, promotes the invasion and inhibits the apoptosis of prostate cancer cells through the ERK1/2 signaling pathway.