Establishment of lapatinib-resistant breast cancer and preliminary study on the resistance-reversing function of metformin

Abstract:

Objective：To establish a model of lapatinib-resistance in breast cancer and explore the reversal effect of metformin on the resistance. Methods：The model of lapatinib-resistance in breast cancer was established in vitro. The experiment cells were divided into the parent group，blank resistance group，lapatinib group，metformin group and lapatinib-metformin group（n=3）. CCK-8 method was used to detect and calculate the resistance times of blank resistance group and the resistance-reversing times of metformin group. The apoptosis rate and cycle of each group were detected by FCM，and the expressions of proteins related to PI3K signaling pathway in each group by Western blot. Results：The sensitivity of cells to lapatinib in blank resistance group was lowered. IC50 values in the parent group，blank resistance group，and metformin group were （2.64±0.12），（11.21±0.03），and （5.62±0.13） μmol/L respectively. The drug resistance was about 4.25 and the reversal of drug resistance was approximately 2.0. Compared with the blank resistance group，the cell proliferation index significantly decreased in both metformin group（0.73±0.04 vs. 1.11±0.02）（P=0.004） and the lapatinib-metformin group（0.63±0.06 vs. 1.11±0.02）（P=0.031），while the cell apoptosis rate significantly increased in both metformin group（[（10.70±0.76）%] vs. [（5.05±0.59）%]）（P=0.007）and the lapatinib-metformin group（[（24.68±1.52）%] vs. [（5.05±0.59）%]）（P=0.006）. The expressions of PI3K signaling pathway-associated phosphorylated and non-phosphorylated proteins in lapatinib-metformin group were lower than those in the blank resistance group. Conclusion：The lapatinib-resistant model of breast cancer has been successfully established. Metformin can reverse the drug resistance of lapatinib in breast cancer cell by inhibiting the PI3K signaling pathway.