Metformin Reverses The Resistance Of Erlotinib-resistant Human Lung Adenocarcinoma Cell Line A549ER In Vitro

BackgroundThe global cancer statistics which published in the journal of <CA: A Cancer Journal for Clinicians> found that lung cancer is not only one of the most common malignant tumor, but also one of the major causes of cancer-related deaths [1]. Recently, the use of targeted therapies drug provides a new method for the treatment of lung cancer, and achieved good therapeutic effect. Erlotinib is one kind of epidermal growth factor receptor- tyrosine kinase inhibitors(EGFR-TKI). Erlotinib is widely used in the targeted therapies of lung cancer recently and achieved good therapeutic effect, even was suggest as first-line treatment [2-4]. However, gradually produce resistance during the treatment of some patient directly affect the late therapeutic effect [5].Metformin is one of biguanides, has been widely used as a oral hypoglycemic drug in the treatment of type 2 diabetes mellitus(T2DM). Metformin as an insulin sensitizer agent has a good safety. It is mainly by reducing insulin resistance and increase insulin sensitivity to lower blood glucose. Metformin has no significant hypoglycemic effect for normal people, and single-use metformin generally does not cause hypoglycemia [6]. Recent study suggested that metformin can inhibit the proliferation of tumor cells, increase the sensitivity of chemotherapy drugs [7]. Therefore, metformin as a drug already approved with good safety probably may play an important role in the treatment of malignant tumors. This study was to investigate whether the combined use of metformin can reverse the resistance of erlotinib-resistant human lung adenocarcinoma cell line.ObjectiveThe aim of this study was to investigate whether the combined use of metformin can reverse the resistance of erlotinib-resistant human lung adenocarcinoma cell line A549 ER.Methods1. The half maximal inhibitory concentrations(IC50) of erlotinib for A549 cell and A549 ER cell were detected with CCK-8 assay, respectively. And the resistance index of A549 ER cell were calculated.2. The cell growth inhibitions of metformin on human lung adenocarcinoma cell line A549 and erlotinib-resistant human lung adenocarcinoma cell line A549 ER were detected with cell counting kit-8(CCK-8) assay. The half maximal inhibitory concentrations(IC50) of erlotinib for the combination group A549 ER cell was detected with CCK-8 assay, respectively. And the reversal index of metformin for A549 ER cell were calculated.3. The cell apoptosis and cell cycles of the blank group, the erlotinib group, the metformin group and the combination group A549 ER cell were detected with flow cytometry. And the cell proliferation indexes of the four groups A549 ER cell were calculated.Results1. The IC50 of erlotinib of A549 cell and A549 ER cell were 15.15μmol/L and 118.8μmol/L. The resistance index for erlotinib of A549 ER cell was 7.84.2. Metformin inhibit growth of A549 cell and A549 ER cell, and the inhibitions increase with increasing concentration of metformin. There was no significant difference on the growth inhibition rates of metformin between A549 cell and A549 ER cell when the concentration within the scope of 0 to 5 mmol/L. And the growth inhibition rate of metformin was higher in A549 ER cell than in A549 cell when the concentration within the scope of 5 to 20 mmol/L(P<0.01). The IC50 for erlotinib of the combination group A549 ER cell was 73.55μmol/L. The resistance index for erlotinib of the combination group A549 ER cell was 4.85. The reversal index of metformin on the resistance of erlotinib was 1.62.3. The cell apoptosis rates of the blank group A549 ER cell was(5.53±3.00) %, the cell apoptosis rates of the erlotinib group A549 ER cell was(7.51±3.73) %, the cell apoptosis rates of the metformin group A549 ER cell was(10.25±4.23) %, and the cell apoptosis rates of the combination group A549 ER cell was(16.92±1.20) %. The cell apoptosis rate of the combination group A549 ER cell was significant higher compared with the other there groups(P<0.01、P<0.01、P<0.05). The proliferation index of the blank group A549 ER cell was 0.84±0.15, the proliferation index of the erlotinib group A549 ER cell was 0.78±0.10, the proliferation index of the metformin group A549 ER cell was 0.73±0.08, and the proliferation index of the combination group A549 ER cell was 0.60±0.09. The proliferation index of the combination group A549 ER cell was lower compared with the other three groups, but only the difference between the combination group A549 ER cell and the blank group A549 ER cell was significant(P<0.05).Conclusions1. A549 ER has significant resistance of erlotinib.2. Metformin inhibit growth of both A549 cell and A549 ER cell,and can reverse the resistance of erlotinib of A549 ER cell.3. Metformin can promote cell apoptosis, inhibit the cell proliferation and slow the cell cycle process of A549 ER cell.4. Metformin reverse the resistance of erlotinib of A549 ER cell maybe by inhibiting the cell growth, slowing the cell cycle process, inhibiting the cell proliferation and promoting the cell apoptosis.