Evidence suggests that metformin, an antidiabetic drug, possesses antitumor effects in breast cancer. Although metformin is known to induce metabolic reprogramming, a detailed description of the metabolites altered by metformin in breast cancer cells is limited. In this study, we aimed to investigate metformin’s anti-tumor effect on breast cancer cell lines and to conduct an untargeted metabolic analysis in those cell lines post-metformin treatment. Metformin’s effect on cell viability of MCF-7 and MDA-MB-231 cell lines was done using a CCK-8 kit, and apoptosis assay was conducted using Annexin V staining. HPLC and LTQ XL Linear ion trap mass spectrometers were used for quantifying metabolites in both cell types post-metformin treatment. Metformin showed a reduction in cell viability in MCF-7 and MDA-MB-231, with IC50s of 14.21±1.33 mM and 12±5.8 mM respectively. It induced 2.1±0.5% and 22.1±2.8% apoptosis in MCF-7 and MDA-MB-231 cells respectively. Both cell lines showed different metabolites in response to treatment. Of 31 identified metabolites in MCF-7, 12 significantly differed with metformin, mostly up-regulated. Of 39 metabolites in MDA-MB-231, 30 significantly differed as compared to untreated cells. Enrichment pathway analysis showed metformin to alter major metabolic pathways. Of interest, was the upregulation of glutathione, sphingosine, and sphingosine-1-phosphate in MDA-MB-231, which could support investigating combining metformin treatment with drugs that can target these pathways. Metformin alters tumor metabolism in a cell-dependent manner in breast cancer cells which can open opportunities for new combination therapies, however, further studies are required to support and understand these findings in depth.
