CD14 knockdown reduces lipopolysaccharide-induced cell viability and expression of inflammation-associated genes in gastric cancer cells in vitro and in nude mouse xenografts

Abstract

Abstract. The present study examined the role of CD14 in the regulation of lipopolysaccharide (LPS)-induced effects on gastric cancer cells. MGC-803 cells were stably transfected with CD14 short hairpin (sh)RNA and treated with LPS, followed by assessment of cell proliferation, apoptosis and gene expression using a cell counting kit-8 assay, flow cytometry, reverse transcription-polymerase chain reaction and western blot analysis, respectively. The cells subjected to CD14 knockdown were treated with 10 g/ml LPS and injected into nude mice to form tumor xenografts. CD14 shRNA-transfected MGC-803 cells did not exhibit any significant changes in cell viability compared with the control cells (P>0.05), but cell viability was markedly increased in the wild-type (WT) + LPS group (P<0.05). In contrast to the WT + LPS group, the cell viability of the sh-CD14 + LPS group was markedly decreased (P<0.05). In addition, compared with those in the controls, the level of sh-CD14 cell apoptosis did not change significantly; however, it was markedly reduced in the LPS group. Compared with that in the WT + LPS group, the rate of apoptosis in the sh-CD14 + LPS group increased to a certain extent, while it remained lower in the control group. In addition, compared with that in the control, the expression of tumor necrosis factor-α, interleukin (IL)-1, IL-6 and IL-12, and human β-defensin 2 was significantly increased in the WT + LPS group, while, compared with that in the WT + LPS group, the expression of these genes was markedly reduced in the sh-CD14 + LPS group (P<0.05). The nude mouse experiments further confirmed the in vitro data, including the finding that LPS promoted the growth of xenografts, but knockdown of CD14 expression reduced the response of tumor cells to LPS treatment. In conclusion, LPS induced cell viability and the release of inflammatory cytokines, but inhibited gastric cancer cell apoptosis. Knockdown of CD14 expression had no significant effect on gastric cancer malignancy, but mediated LPS signal transduction. IntroductionGastric cancer is one of the most common types of cancer globally and accounted for 989,600 ovel cases and 738,000 cancer-associated fatalities in 2008 (1). >70% of novel gastric cancer cases and fatalities occur in the developing countries, while they have declined in the majority of developed countries, including countries in North America and Europe in previous decades (1). The risk factors for gastric cancer include Helicobacter (H.) pylori infection, history of tobacco smoking, and consumption of smoked foods, salted meat or fish and pickled vegetables. However, intake of fresh fruits and vegetables appears to lower the risk of gastric cancer (1). Regional variations in gastric cancer prevalence reflect the differences in dietary patterns and the prevalence of H. pylori infection (2). H. pylori is an aerobic Gram-negative bacterium found in the stomach, which causes chronic gastritis, peptic ulcers and gastric cancer. Thus, H. pylori infection has been classified as a class I carcinog...

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