Metformin Induces PRODH/POX-Dependent Apoptosis in Breast Cancer Cells

Thi Yen Ly Huynh; Ilona Oscilowska; Lukasz Szoka; Ewelina Piktel; Weronika Baszanowska; Katarzyna Bielawska; Robert Bucki; Wojciech Miltyk; Jerzy Palka

doi:10.3389/fmolb.2022.869413

Metformin Induces PRODH/POX-Dependent Apoptosis in Breast Cancer Cells

Front Mol Biosci. 2022 Jun 6:9:869413. doi: 10.3389/fmolb.2022.869413. eCollection 2022.

Authors

Thi Yen Ly Huynh¹, Ilona Oscilowska², Lukasz Szoka¹, Ewelina Piktel³, Weronika Baszanowska¹, Katarzyna Bielawska², Robert Bucki³, Wojciech Miltyk², Jerzy Palka¹

Affiliations

¹ Department of Medicinal Chemistry, Faculty of Pharmacy, Medical University of Bialystok, Bialystok, Poland.
² Department of Pharmaceutical and Biopharmaceutical Analysis, Faculty of Pharmacy, Medical University of Bialystok, Bialystok, Poland.
³ Department of Medical Microbiology and Nanobiomedical Engineering, Medical University of Bialystok, Bialystok, Poland.

Abstract

Although the antineoplastic activity of metformin (MET) is well established, the underlying mechanism of the activity is not understood. Since MET activates AMP kinase (AMPK) and proline dehydrogenase/proline oxidase (PRODH/POX) is stimulated by AMPK ligands (implicated in the regulation of cancer cell survival/apoptosis), the effect of MET on PRODH/POX-dependent apoptosis in wild-type MCF-7 cells (MCF-7^WT) and POX knockdown MCF-7 cells (MCF-7^crPOX cells) was studied. PRODH/POX catalyzes proline degradation generating ROS-induced apoptosis or autophagy. Availability of proline for PRODH/POX functions is regulated by the activity of prolidase (enzyme releasing proline from imidodipeptides), collagen biosynthesis (process consuming proline), and metabolism of proline, ornithine, and glutamic acid. We have found that MET is cytotoxic for MCF-7 cells (IC50∼17 mM), and to the lower extent for MCF-7^crPOX cells (IC50∼28 mM). In MCF-7^WT cells, the effect was accompanied by the inhibition of DNA biosynthesis, collagen biosynthesis, stimulation of ROS formation, AMPKα phosphorylation, and expression of prolidase, p53, caspase 8, caspase 9, and cleaved PARP. In MET-treated MCF-7^crPOX cells, the processes were less affected than in MCF-7^WT cells and the expression of caspase 9 was decreased, while cleaved caspase 8 and cleaved PARP were not detected. The effects were accompanied by an increase in the prolidase activity and proline concentration. The mechanism for MET-induced apoptosis involves the up-regulation of prolidase activity and a decrease in collagen biosynthesis contributing to an increase in the concentration of substrate (proline) for PRODH/POX-dependent ROS formation and activation of caspases -9 and -8. The data suggest that PRODH/POX participates in the MET-induced intrinsic and extrinsic apoptosis in MCF-7 cells.

Keywords: PRODH/POX; apoptosis; breast cancer cells; metformin; proline dehydrogenase; proline oxidase.