Gastric cancer is the second most common cause of cancer mortality worldwide. Most gastric cancer patients are asymptomatic until the advanced stages, for which current therapeutic treatments are suboptimal. 5-Fluorouracil (5-FU), an antimetabolite agent, is widely used in gastric cancer therapy. However, the presence of drug resistance in gastric cancer patients reduces the cytotoxic activity of 5-FU. In gastric cancer, no research has yet been conducted to analyze the effect of alpha 7-nicotinic acetylcholine receptor (A7-nAChR) on the therapeutic response to 5-FU. In this study, we generated A7-nAChR knockdown (A7-nAChR-KD) AGS cells by a small interfering RNA (siRNA) technique in gastric cancer cells. The anti-proliferative effects of 5-FU were determined by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, a terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) assay, and cell cycle determination. We found that A7-nAChR-KD cells were more resistant to 5-FU treatment compared with the scrambled control cells according to the MTT assay. The apoptotic cell population was increased more in scrambled control cells treated with 5-FU than A7-nAChR-KD cells according to the cell cycle distribution and TUNEL assays. We analyzed expression levels of survival and apoptosis-associated proteins (pAkt, Akt, Mcl-1, Bcl-2, Bad, and Bax) altered by 5-FU treatment. Survival and antiapoptosis signaling (pAkt, Akt, Mcl-1 and Bcl-2) was downregulated, and the proapoptotic proteins (Bad and Bax) were upregulated in 5-FU-treated control cells but expression levels of Bcl-2, Bad, and Bad were not altered in 5-FU-treated A7-nAChR-KD cells. This is consistent with A7-nAChR-KD cells exhibiting more resistance to 5-FU treatment. In our study, we carried out an in vitro study on AGS gastric cancer cell line to elucidate the anticancer efficacy and molecular mechanisms of A7-nAChR silencing on 5-FU-induced cell death. The results clearly showed that depletion of A7-nAChR suppressed the drug sensitivity of gastric cancer cells to 5-FU treatment.
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