Notch2 regulates matrix metallopeptidase 9 via PI3K/AKT signaling in human gastric carcinoma cell MKN-45

AIM: To clarify the role of activated Notch2 in the invasiveness of gastric cancer. METHODS: To investigate the invasiveness of silencing Notch2 gene expression, we established a Notch2 small interfering RNA (siRNA) transfected cell line using the MKN-45 gastric cancer cell line. After the successful transfection confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting, migration and invasion assays were employed to evaluate the aggressiveness of the gastric cancer. RT-PCR and Western blottings were employed to confirm the down-regulation of Notch2 and to evaluate the expression of epithelial mesenchymal transition-related gene matrix metallopeptidase 9 (MMP9), Akt, p-Akt. To confirm the relationship between PI3K-Akt and MMP9, the PI3K inhibitor LY294002 was used to treat MKN-45 cells. RESULTS: Notch2 expression was dramatically decreased after Notch2 siRNA transfection (100.00% +/- 9.74% vs 11.61% +/- 3.85%, P < 0.01 by qRT-PCR). There was also a marked reduction of Notch target gene Hes1 (100.00% +/- 4.74% vs 61.61% +/- 3.58%, P < 0.05) at the mRNA, indicating an inhibition of Notch signaling. Inhibition of Notch signaling was also confirmed by the marked reduction of Notch2 intracellular domain at the protein levels (100.00% +/- 9.74% vs 65.61% +/- 7.58%, P < 0.05). Down-regulation of Notch2 by siRNA enhanced tumor cell invasion (100.00% +/- 21.64% vs 162.22% +/- 16.84%, P < 0.05) and expression of MMP9 (1.56 fold, P < 0.05), and activated the pro-MMP9 protein to its active form (1.48 fold, P < 0.05). There was no significant difference in the protein levels of Akt between the two groups (100.00% +/- 10.87% vs 96.61% +/- 7.33%, P > 0.05), while down-regulation of Notch2 elevated p-Akt expression (100.00% +/- 9.87% vs 154.61% +/- 13.10%, P < 0.05). Furthermore, p-Akt and MMP9 was down-regulated in response to the inhibitor LY294002 (p-Akt 100.00% +/- 8.87% vs 58.27% +/- 5.01%, P < 0.05; MMP9 100.00% +/- 9.17% vs 50.03% +/- 4.88%, P < 0.05). CONCLUSION: Notch2 may negatively regulate cell invasion by inhibiting the PI3K-Akt signaling pathway in gastric cancer. (C) 2012 Baishideng. All rights reserved.