OBJECTIVETo investigate the effects of overexpression of exogenous Notch1 in human tongue squamous cell carcinoma (TSCC) cells on cell growth and expression of epidermal growth factor receptor (EGFR) in vitro.

METHODSHuman TSCC cell line Tca8113 cells were transiently transfected with the eukaryotic expression plasmid pRAMIC-IRES2-EGFP encoding exogenous intracellular fragment of Notch1 and control plasmid pIRES2-EGFP by Lipofectamine 2000, respectively. Untransfected parental Tca8113 cells served as control. The cell proliferation was evaluated by methyl thiazolyl tetrazolium(MTT) assay. The apoptosis was assessed by flow cytometry. The mRNA and protein levels of Notch1 and EGFR in Tca8113 cells were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot. The expression of EGFR protein in Tca8113 cells was detected by immunocytochemistry.

RESULTSMTT assay showed that the cell proliferation of Tca8113 cells transfected with pRAMIC-IRES2-EGFP was significantly inhibited as compared with controls (P < 0.05). After transfected with pRAMIC-IRES2-EGFP for 48 h, the apoptosis rate of Tca8113 cells was significantly higher than those of Tca8113 cells transfected with pIRES2-EGFP and untransfected Tca8113 cells (P < 0.05), and Notch1 expression was significantly increased at mRNA (P < 0.05) and protein (P < 0.05) levels, while EGFR expression was significantly decreased at mRNA (P < 0.05) and protein (P < 0.05) levels.

CONCLUSIONOverexpression of exogenous Notch1 may inhibit cell growth and down-regulate EGFR expression in TSCC cells.