The aim of the present study was to investigate the effect of downregulation of the c-Met gene on signal transduction and apoptosis in gastric cancer MKN-45 cells; furthermore, the study aimed to determine whether altered c-Met gene expression affected MKN-45 sensitivity to gefitinib. Three c-Met-specific small interfering RNAs (siRNAs) were synthesized and transfected into MKN-45 cells. Messenger RNA (mRNA) and protein levels of c-Met and its downstream signaling molecules [phosphoinositide

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... inase (PI3K) and AKT] were examined using reverse transcription polymerase chain reaction and western blot analysis 48 h following transfection. Cell apoptosis was evaluated using Annexin-V/propidium iodide double staining and fluorescence-activated cell sorting analysis. An MTT assay was performed in order to measure the 50% inhibitory concentration (IC 50 ) of gefitinib on MKN-45 cells. The results of the present study demonstrated that 48 h post-transfection with c-Met siRNA, MKN-45 cells showed significantly downregulated expression of c-Met mRNA and protein as well as an increased rate of apoptosis (P<0.05). In addition, following c-Met siRNA transfection mRNA and protein levels of PI3K and AKT were not significantly altered in MKN-45 cells (P>0.05); however, a marked decrease in the expression levels of phosphorylated (p)-PI3K and p-AKT was observed (P<0.05). Furthermore, the IC 50 of gefitinib in MKN-45 cells was not significantly decreased. In conclusion, knockdown of the c-Met gene promoted gastric cancer cell apoptosis and inhibited downstream p-PI3K and p-AKT; however, the sensitivity of MKN-45 cells to gefitinib was not increased.