Metformin reverses the resistance mechanism of lung adenocarcinoma cells that knocks down the Nrf2 gene

Abstract

The nuclear factor, er ythroid 2 like 2 (Nrf2)/antioxidant response element (ARE) pathway has an important role in the drug resistance of adenocarcinoma, and may act via different mechanisms, including the mitogen-activated protein kinase (MAPK) pathway. However, it has remained elusive whether metformin affects Nrf2 and regulates Nrf2/ARE in adenocarcinoma. In the present study, reverse-transcription quantitative polymerase chain reaction, cell transfection, western blot analysis, a Cell Counting kit-8 assay and apoptosis detection were used to investigate the above in the A549 cell line and cisplatin-resistant A549 cells (A549/DDP). The results indicated that Nrf2, glutathione S-transferase α 1 (GSTA1) and ATP-binding cassette subfamily C member 1 (ABCC1) were dose-dependently reduced by metformin, and that the effect in A549 cells was greater than that in A549/DDP cells. Treatment with metformin decreased the proliferation and increased the apoptosis of A549 cells to a greater extent than that of A549/DDP cells, and the effect was dose-dependent. After transfection of A549/DDP cells with Nrf2 short hairpin RNA (shRNA), GSTA1 and ABCC1 were markedly decreased, compared with the shRNA-control group of A549/DDP, and low dose-metformin reduced the proliferation and increased apoptosis of A549/DDP cells. Metformin inhibited the Akt and extracellular signal-regulated kinase (ERK)1/2 pathways in A549 cells and activated the p38 MAPK and c-Jun N-terminal kinase (JNK) pathways. Furthermore, in the presence of metformin, inhibitors of the p38 MAPK and JNK signaling pathway at different concentrations did not affect the levels of Nrf2, but inhibitors of the Akt and ERK1/2 pathway at different doses reduced the expression of Nrf2. In addition, inhibitors of p38 MAPK and JNK did not affect the effect of metformin on Nrf2, while inhibitors of Akt and ERK1/2 dose-dependently enhanced the inhibitory effects of metformin in A549 cells. In conclusion, metformin inhibits the phosphoinositide-3 kinase/Akt and ERK1/2 signaling pathways in A549 cells to reduce the expression of Nrf2, GSTA1 and ABCC1. Metformin also reverses the resistance of A549/DDP cells to platinum drugs, inhibits the proliferation and promotes apoptosis of drug-resistant cells. These results may provide a theoretical basis and therapeutic targets for the clinical treatment of tumors.

Metformin reverses chemoresistance in non-small cell lung cancer via accelerating ubiquitination-mediated degradation of Nrf2

“…Raf-ERK signaling attenuation was shown to be involved in the regulation of Nrf2 by metformin in the treatment of lung cancer (25). However, the p38 MAPK and JNK signaling pathways were not found to affect Nrf2 protein expression (21). Our study produced similar results.…”

“…"Nrf2 addiction" refers to hyperactivation of the Nrf2 pathway in lung cancer cells, which promotes the development of NSCLC and can also enhance chemoresistance (19,20). Emerging evidence has shown that targeting Nrf2 is a potential therapeutic strategy for overcoming cisplatin resistance (21). Intriguingly, Truong Do M revealed that metformin suppresses the expression of Nrf2 at the transcriptional level by inhibiting Sirtuin 1 (Sirt1) (22), while another study reported the opposite result, with metformin also upregulating Sirt1 expression for decreasing the acetylation of Nrf2 and preventing its nuclear distribution (23).…”

Metformin Actions on the Liver: Protection Mechanisms Emerging in Hepatocytes and Immune Cells against NASH-Related HCC

“…It was recently found that metformin augmented the cytotoxic effect of cisplatin to NSCLC cells by promoting NRF2 degradation through a mechanism similar to that of HepG2 cells, which is done by inhibiting Raf-ERK [ 122 ]. When treating lung adenocarcinoma cells with metformin, Zhang et al found that NRF2 expression was also reduced through ERK1/2 and PI3K-AKT pathway inhibition by metformin [ 123 ]. Isocitrate dehydrogenase 1- (IDH1) mediated chemoresistance in endometrial cancer cells can be abated by metformin treatment, which inhibits the IDH1-induced NRF2 expression [ 124 ].…”

Nrf2 and the Nrf2-Interacting Network in Respiratory Inflammation and Diseases

“…Metformin reduces the risk of lung cancer during anti-diabetic treatment [166]. A recent study showed that metformin suppresses proliferation and induces apoptosis of the human lung carcinoma A549 cells through the inhibition of the Akt and ERK1/2 signaling pathways and activation of Nrf2 [167]. These studies indicate the potency of Nrf2 phosphorylation pathways as therapeutic targets for lung diseases.…”