Metformin inhibits growth of human non-small cell lung cancer cells via liver kinase B-1-independent activation of adenosine monophosphate-activated protein kinase

Abstract

Metformin, the most widely administered oral anti-diabetic therapeutic agent, exerts its glucose-lowering effect predominantly via liver kinase B1 (LKB1)-dependent activation of adenosine monophosphate-activated protein kinase (AMPK). Accumulating evidence has demonstrated that metformin possesses potential antitumor effects. However, whether the antitumor effect of metformin is via the LKB1/AMPK signaling pathway remains to be determined. In the current study, the effects of metformin on proliferation, cell cycle progression, and apoptosis of human non-small cell lung cancer (NSCLC) H460 (LKB1-null) and H1299 (LKB1-positive) cells were assessed, and the role of LKB1/AMPK signaling in the anti-growth effects of metformin were investigated. Cell viability was determined using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, cell cycle distribution and apoptosis were assessed by flow cytometry, and protein expression levels were measured by western blotting. Metformin inhibited proliferation, induced significant cell cycle arrest at the G0–G1 phase and increased apoptosis in NSCLC cells in a time- and concentration-dependent manner, regardless of the level of LKB1 protein expression. Furthermore, knockdown of LKB1 with short hairpin RNA (shRNA) did not affect the antiproliferative effect of metformin in the H1299 cells. Metformin stimulated AMPK phosphorylation and subsequently suppressed the phosphorylation of mammalian target of rapamycin and its downstream effector, 70-kDa ribosomal protein S6 kinase in the two cell lines. These effects were abrogated by silencing AMPK with small interfering RNA (siRNA). In addition, knockdown of AMPK with siRNA inhibited the effect of metformin on cell proliferation in the two cell lines. These results provide evidence that the growth inhibition of metformin in NSCLC cells is mediated by LKB1-independent activation of AMPK, indicating that metformin may be a potential therapeutic agent for the treatment of human NSCLC.

Casticin suppresses the carcinogenesis of small cell lung cancer H446 cells through activation of AMPK/FoxO3a signaling

“…It was reported that AMPK acts as an upstream regulator of Foxo3a (8-10, [14][15][16]24,25). This study provided several lines of evidence that casticin activates Foxo3a in an AMPK-dependent manner.…”

Antitumor effects of metformin are a result of inhibiting nuclear factor kappa B nuclear translocation in esophageal squamous cell carcinoma

“…Patients treated with metformin have shown a lower incidence of cancer than the other treatment groups . In addition, metformin reportedly affects various cancers, such as gastric cancer, non‐small cell lung cancer, and colorectal cancer . Metformin exerts its antitumor effects in various ways, including inducing cell cycle arrest, enhancing the immune system, inhibiting EMT, inducing hypersusceptibility for chemotherapy, and inhibiting inflammatory signals through NF‐κB/TGF‐β …”

Diabetes mellitus and survival of non‐small cell lung cancer patients after surgery: A comprehensive systematic review and meta‐analysis

“…12 Moreover, the impact of DM on the prognosis of patients with NSCLC could be complicated with the administration of an anti-diabetic therapeutic agent, such as metformin, which exerts its anti-diabetic effect predominantly via liver kinase B1 (LKB1)-dependent activation of adenosine monophosphate-activated protein kinase (AMPK). 38 Because it regulates the LKB-1/AMPK signal pathway, metformin has also been proven to significantly inhibit cell proliferation, induce apoptosis, and block cell cycle progression in NSCLC cells, 39 thus exerting an antitumor effect in NSCLC patients with DM. Therefore, further studies are needed to elucidate the actual interaction of DM with lung cancer.…”