Diabetes Metab J.  2015 Dec;39(6):518-527. 10.4093/dmj.2015.39.6.518.

Metformin Promotes Apoptosis but Suppresses Autophagy in Glucose-Deprived H4IIE Hepatocellular Carcinoma Cells

Affiliations
  • 1Department of Histology and Institute of Medical Science, Jeju National University School of Medicine, Jeju, Korea. parkdb@jejunu.ac.kr

Abstract

BACKGROUND
Metformin, a well-known anti-diabetic drug, has gained interest due to its association with the reduction of the prevalence of cancer in patients with type 2 diabetes and the anti-proliferative effect of metformin in several cancer cells. Here, we investigated the anti-proliferative effect of metformin with respect to apoptosis and autophagy in H4IIE hepatocellular carcinoma cells.
METHODS
H4IIE rat cells were treated with metformin in glucose-free medium for 24 hours and were then subjected to experiments examining the onset of apoptosis and/or autophagy as well as the related signaling pathways.
RESULTS
When H4IIE cells were incubated in glucose-free media for 24 hours, metformin and 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) reduced the viability of cells. Inhibition of AMP-activated protein kinase (AMPK) by compound C significantly blocked cell death induced by metformin or AICAR. Pro-apoptotic events (nuclear condensation, hydrolysis of intact poly ADP ribose polymerase and caspase-3) were stimulated by metformin and then suppressed by compound C. Interestingly, the formation of acidic intracellular vesicles, a marker of autophagy, was stimulated by compound C. Although the deprivation of amino acids in culture media also induced apoptosis, neither metformin nor compound C affected cell viability. The expression levels of all of the autophagy-related proteins examined decreased with metformin, and two proteins (light chain 3 and beclin-1) were sensitive to compound C. Among the tested inhibitors against MAP kinases and phosphatidylinositol-3-kinase/mammalian target of rapamycin, SB202190 (against p38MAP kinase) significantly interrupted the effects of metformin.
CONCLUSION
Our data suggest that metformin induces apoptosis, but suppresses autophagy, in hepatocellular carcinoma cells via signaling pathways, including AMPK and p38 mitogen-activated protein kinase.

Keyword

Apoptosis; Autophagy; H4IIE hepatocellular carcinoma cells; Metformin

MeSH Terms

Amino Acids
AMP-Activated Protein Kinases
Animals
Apoptosis*
Autophagy*
Carcinoma, Hepatocellular*
Cell Death
Cell Survival
Culture Media
Humans
Hydrolysis
Metformin*
Phosphotransferases
Poly(ADP-ribose) Polymerases
Prevalence
Protein Kinases
Rats
Sirolimus
AMP-Activated Protein Kinases
Amino Acids
Culture Media
Metformin
Phosphotransferases
Poly(ADP-ribose) Polymerases
Protein Kinases
Sirolimus
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