Metformin triggers the intrinsic apoptotic response in human AGS gastric adenocarcinoma cells by activating AMPK and suppressing mTOR/AKT signaling

Abstract

Metformin is commonly used to treat patients with type 2 diabetes and is associated with a decreased risk of cancer. Previous studies have demonstrated that metformin can act alone or in synergy with certain anticancer agents to achieve anti-neoplastic effects on various types of tumors via adenosine monophosphate-activated protein kinase (AMPK) signaling. However, the role of metformin in AMPK-mediated apoptosis of human gastric cancer cells is poorly understood. In the current study, metformin exhibited a potent anti-proliferative effect and induced apoptotic characteristics in human AGS gastric adenocarcinoma cells, as demonstrated by MTT assay, morphological observation method, terminal deoxynucleotidyl transferase dUTP nick end labeling and caspase-3/7 assay kits. Western blot analysis demonstrated that treatment with metformin increased the phosphorylation of AMPK, and decreased the phosphorylation of AKT, mTOR and p70S6k. Compound C (an AMPK inhibitor) suppressed AMPK phosphorylation and significantly abrogated the effects of metformin on AGS cell viability. Metformin also reduced the phosphorylation of mitogen-activated protein kinases (ERK, JNK and p38). Additionally, metformin significantly increased the cellular ROS level and included loss of mitochondrial membrane potential (ΔΨm). Metformin altered apoptosis-associated signaling to downregulate the BAD phosphorylation and Bcl-2, pro-caspase-9, pro-caspase-3 and pro-caspase-7 expression, and to upregulate BAD, cytochrome c, and Apaf-1 proteins levels in AGS cells. Furthermore, z-VAD-fmk (a pan-caspase inhibitor) was used to assess mitochondria-mediated caspase-dependent apoptosis in metformin-treated AGS cells. The findings demonstrated that metformin induced AMPK-mediated apoptosis, making it appealing for development as a novel anticancer drug for the treating gastric cancer.

Anticancer Activity of Metformin: A Systematic Review of the Literature

“…The recently published study by Wang et al . investigated the possible antitumor mechanism of metformin on human esophageal cells [22]. The study aimed to decipher the role of PELP1 in the progression of esophageal squamous cell carcinoma (ESCC).…”

Metformin in Cervical Cancer: Metabolic Reprogramming

“…The imbalance of metabolic regulation and the resulting overproduction of ROS in mitochondrial ETC cause oxidative stress, which, at some point, becomes toxic to cancer cells, and that escalation of ROS elicits apoptosis-inducing factors and triggers death program through multiple mechanisms. In compliance, it has been newly reported that Met significantly increased ROS level, altered apoptosis-associated signaling, and induced cell death in human gastric adenocarcinoma cells [31] and human cervical cancer HeLa cells [32]. We found that in HTB-35 cervical cancer cells, Met caused excessive generation of mitochondrial ROS and elicited apoptosis [11,22].…”

<p>Novel mTOR Inhibitor Enhances the Sensitivity of Hepatocellular Carcinoma Cells to Molecular Targeting Agents</p>

“…Rabbit antibodies against human phospho-p70S6K (Thr389), p70S6K, phospho-AKT (Ser473), phospho-AKT (Thr308), AKT, phospho-ERK, ERK, phospho-rpS6 (Ser235/6), rpS6, β-actin and secondary antibodies were purchased from Cell Signaling Technology (Danvers, MA, USA). [53][54][55] In vivo Bioactivity Assessment of the Lead Compounds The nude mice model was used to test the bioactivity of candidate compounds in vivo. The animal experiments were approved by the Animal Ethics Committee of the Fifth Medical Center, Chinese PLA, and carried out in accordance with the UK Animals (Scientific Procedures) Act of 1986 and its associated guidelines.…”