AMPK/mTOR-mediated inhibition of survivin partly contributes to metformin-induced apoptosis in human gastric cancer cell

Abstract

Recent studies demonstrated that metformin exerts anti-neoplastic effect in a spectrum of malignancies. However, the mechanism whereby metformin affects various cancers, including gastric cancer, is poorly elucidated. Considering apoptosis plays critical role in tumorigenesis, we, in the present study, investigated the in vitro apoptotic effect of metformin on human gastric cancer cell and the underlying mechanism. Three differently-differentiated gastric cancer cell lines, MKN-28, SGC-7901 and BGC-823, along with one noncancerous gastric cell line GES-1 were used. We found that metformin treatment selectively induces apoptosis in the 3 cancer cell lines, but not the noncancerous one, as confirmed by flow cytometry, Caspase-Glo assay and western blotting against PARP and cleaved caspase 3. Moreover, the apoptotic effect of metformin seems to correlate negatively with the differentiation degree of gastric cancer. Metformin-induced apoptosis may be partially mediated through inhibition of anti-apoptotic survivin. Additionally, AMPK and mTOR, 2 important regulatory molecules responsible for metformin action, were investigated for their possible involvements in metformin-induced apoptosis of gastric cancer cell. AMPK knockdown by siRNA restores metformin-inhibited survivin expression and partially abolishes metformin-induced apoptosis. Similarly, forced overexpression of mTOR downstream effector p70S6K1 relieves metformin-induced inhibition of survivin and partly attenuates metformin-induced apoptosis. More importantly, survivin overexpression alleviates metformin-induced apoptosis. Xenograft nude mouse experiment also confirmed that AMPK/mTOR-mediated decrease of suvivin is in vivo implicated in metformin-induced apoptosis. Taken together, these evidences suggest that AMPK/mTOR-mediated inhibition of survivin may partly contribute to metformin-induced apoptosis of gastric cancer cell.

Enhanced anti-tumor activity and cytotoxic effect on cancer stem cell population of metformin-butyrate compared with metformin HCl in breast cancer

“…Since metformin is known to affect AMPK/mTOR signaling activity [32], we compared the effects of MFB and metformin in this regard. Various breast cancer cell lines (luminal type, MCF7 and BT474; TNBC type, BT20, MDA-MB-231, Hs578T and NDY-1) were treated with metformin or MFB (10 mM) for 12 h, and cell lysates were analyzed for their levels of p-AMPK (T172) and p-mTOR (S2448).…”

“…Metformin is known to inactivate mTOR via activation of AMPK, thereby directly inhibiting cell growth and tumorigenesis [9, 31]. Although the precise underlying mechanism(s) have not yet been fully elucidated, increasing evidence indicates that the P13K/Akt/mTOR pathway plays a crucial role in the survival and proliferation of cancer cells [9, 11, 15, 32, 35]. Therefore, it is clinically important that, compared to metformin, MFB markedly activated AMPK and inactivated mTOR with greater potency in all tested breast cancer cells in vitro and in vivo .…”

Metformin Inhibits TGF-β1-Induced Epithelial-to-Mesenchymal Transition via PKM2 Relative-mTOR/p70s6k Signaling Pathway in Cervical Carcinoma Cells

“…Silvestri et al [36] reported that metformin induced apoptosis and down-regulated PKM2 in breast cancer cells. These studies showed that the mechanism of metformin may be associated with the following observations: (1) metformin inhibits mTOR activation by AMPK-dependence in different cancers [37,38,39]; (2) mTOR signaling regulates P70S6K signaling in cervical carcinoma cells [40]; (3) metformin induce intrinsic apoptosis via the inhibition of the HIF1α/PKM2 signaling pathway [41]; and (4) metformin is also a poisoner of mitochondria by impairing the function of complex I [42], leading to the increased aerobic glycolysis as compensation.…”

Metformin inhibits the proliferation, metastasis, and cancer stem-like sphere formation in osteosarcoma MG63 cells in vitro

“…Previous studies reported that metformin downregulated mTOR signaling by activating AMPK in various tumors [31][32][33]. To examine whether this machinery worked in OS cells and CSCs, we carried out Western blotting.…”