Human chorionic gonadotropin promotes cell proliferation through the activation of c-Met in gastric cancer cells

Abstract

Hormones and their receptors affect the development process of gastric cancer. Previous studies have revealed that human chorionic gonadotropin (hCG) is expressed in gastric cancer tissue. However, the mechanism by which hCG exerts its effects on gastric cancer cells had not been reported. In the present study, the expression of hCG and its receptor was detected in gastric cancer tissues and para-carcinoma tissues of 62 patients with gastric carcinoma. Following the treatment of gastric cancer cells SGC-7901 with hCG, a cell counting kit-8 assay, flow cytometry, a colony formation assay and a xenograft tumor model in nude mice were used to detect the effect of hCG on cell proliferation; and the expression of c-Met was determined by western blot analysis. The expression of hCG and its receptor were significantly higher in gastric cancer tissues compared with that of the matched para-carcinoma tissue (P<0.01). Proliferation of SGC-7901 cells treated with hCG was significant higher and the number of cells at the G₂/M phase of the cell cycle increased compared with the control cells. Hepatocyte growth factor transmembrane protein receptor expression was increased in hCG-treated cells compared with the control cells, which relies on the protein kinase A signaling pathway. The present study revealed the potential function of hCG in the development of gastric cancer, suggesting that hCG may be a molecular marker and potential drug target in gastric cancer.

Keywords: gastric cancer; hepatocyte growth factor transmembrane protein receptor; human chorionic gonadotropin; proliferation.

Figure 1.

High expression of hCG and hCGR in gastric cancer tissue confirmed by immunohistochemistry. (A) hCG expression in para-carcinoma tissue. (B) hCG expression in gastric cancer tissue. (C) hCGR expression in para-carcinoma tissue. (D) hCGR expression in gastric cancer tissue. hCG, human chorionic gonadotropin; hCGR, human chorionic gonadotropin receptor.

Figure 2.

SGC-7901 cell proliferation increased by hCG. Cells at a density of 2×10³ cells per well in 96-well plates were cultured for 5 days with hCG at concentration of 0, 0.09 and 0.89 IU/ml. Cell proliferation was measured at 450 nm using a plate reader using following treatment with cell counting kit-8 dye. Data represent the mean ± SD of 3 experiments at each concentration. *P<0.01 and **P<0.001 with comparisons shown by lines. hCG, human chorionic gonadotropin; DMSO, dimethylsulfoxide.

Figure 3.

Increased cell number of SGC-7901 cells at the G₂/M stage as a result of treatment with hCG. Representative images of cell cycle assays using flow cytometry in SGC-7901 cells with hCG at concentrations of 0, 0.09 and 0.89 IU/ml. Data represent the mean ± SD of 3 experiments at each concentration. hCG, human chorionic gonadotropin; DMSO, dimethylsulfoxide.

Figure 4.

Promotion of SGC-7901 cell colony formation ability following hCG treatment. (A) Colony formation assay (Left, control group; middle, 0.09 IU/ml hCG treatment group; right, 0.89 IU/ml hCG treatment group). (B) Quantitative analysis of the colony formation assay. Data represent the mean ± SD of 3 experiments at each concentration. **P<0.01 with comparisons shown by lines. hCG, human chorionic gonadotropin; DMSO, dimethylsulfoxide.

Figure 5.

Increased expression of c-Met promoted by hCG relies on the protein kinase A signaling pathway. (A) Detection of the protein expression of c-Met following hCG exposure using western blot analysis. (B) Analysis of the protein expression of c-Met following PKAI treatment using western blot analysis. Data represent the mean ± SD of 3 experiments at each concentration. GAPDH was used as the reference gene. c-Met, hepatocyte growth factor transmembrane protein receptor; PKAI, protein kinase A inhibitor; hCG, human chorionic gonadotropin; DMSO, dimethylsulfoxide.

Figure 6.

Increased tumor growth in response to hCG treatment in vivo. Nude mice bearing SGC-7901 cancer cells were treated with or without hCG (890 IU/kg/day) via intraperitoneal injection for 20 consecutive days. (A) Images of nude mice and the tumors. (B) Relative transplantation tumor volume. (C) Relative transplantation tumor weight. Data represent the mean ± SD of 3 experiments at each concentration. **P<0.01 with comparisons shown by lines. hCG, human chorionic gonadotropin; DMSO, dimethylsulfoxide.