Dual Target of EGFR and mTOR Suppresses Triple-Negative Breast Cancer Cell Growth by Regulating the Phosphorylation of mTOR Downstream Proteins.

Objective: To detect the activation of the EGFR and mTOR signaling pathways in the triple negative breast cancer cell line MDA-MB-468 and investigate the inhibitory effect of gefitinib, an epidermal growth factor receptor inhibitor, and everolimus, a target protein inhibitor of rapamycin, on triple negative breast cancer cells.

Methods: Triple negative human breast cancer MDA-MB-468 cells were cultured and blank control group, single EGFR inhibitor gefitinib group, single mTOR inhibitor everolimus group, and two drug combination group were set up respectively to detect the effects of single and combined drugs on cell proliferation activity, cell cycle and apoptosis, and the expression of EGFR and mTOR signal pathway proteins in cell lines after single and combined drug intervention was detected again by Western blot.

Results: The level of EGFR and p-mTOR protein in triple negative breast cancer was higher than in non triple negative breast cancer (P<0.05). The level of mTOR, S6K1, p-EGFR, p-S6K1 was significantly increased when treated with EGF (0ng/mL, 10ng/mL, 100ng/mL) for 1h, compared to without EGF stimulation (P<0.05). The level of p-EGFR, p-mTOR, p-S6K1 protein increased significantly when the cells were exposed to EGF for 2h, respectively (P<0.05). EGFR inhibitor gefitinib alone and the mTOR inhibitor everolimus alone could significantly inhibit the proliferation of human triple negative breast cancer MDA-MB-468 cells in a dose-dependent manner (P<0.05). The level of p-4EBP1 protein in EGFR and mTOR signal pathway was significantly increased after the intervention of gefitinib alone, everolimus alone, and the combination of two drugs (P<0.05).

Conclusion: EGFR and mTOR signaling pathways can be activated in triple negative breast cancer; Both the EGFR inhibitor gefitinib alone and the mTOR inhibitor everolimus alone can significantly inhibit the proliferation of human triple negative breast cancer MDA-MB-468 cells. The combination of the EGFR inhibitor gefitinib and the mTOR inhibitor everolimus may achieve anti-tumor effect similar to that of single drug by reducing the drug dose.