Anti-cancer Effects of 5-Aminoimidazole-4-Carboxamide-1-beta-D-Ribofuranoside (AICAR) on Triple-negative Breast Cancer (TNBC) Cells: Mitochondrial Modulation as an Underlying Mechanism

Background: Triple-negative breast cancer (TNBC) is known for Warburg effect and defects in the mitochondria. AMP-dependent kinase (AMPK) activates the downstream transcription factors PGC-1 alpha, PGC-1 beta, or FOXO1, which participate in mitochondrial biogenesis. 5-aminoimidazole-4-carboxamide riboside (AICAR) is an analog of adenosine monophosphate and is a direct activator of AMPK. Objectives: In the present study, we have made an attempt to understand the influence of AICAR on TNBC cells, MDA-MB-231, and the underlying changes in mitochondrial biogenesis, if any. Methods: We investigated AICAR induced changes in cell viability, apoptosis, migratory potential, and changes in the sensitivity of doxorubicin. Results: In response to the treatment of MDA-MB-231 breast cancer cells with 750 mu M of AICAR for 72 hours, followed by 48 hours in fresh media without AICAR, we observed a decrease in viability via MTT assay, reduction in cell numbers along with the apoptotic appearance, increased cell death by ELISA, decreased lactate in conditioned medium and decrease in migration by scratch and transwell migration assays. These changes in the cancer phenotype were accompanied by an increase in mitochondrial biogenesis, as observed by increased mitochondrial DNA to nuclear DNA ratio, a decrease in lactic acid concentration, an increase in MitoTracker green and red staining, and increased expression of transcription factors PGC-1 alpha, NRF-1, NRF-2, and TFAM, contributing to mitochondrial biogenesis. Pre-treatment of cells with AICAR for 72 hours followed by 48 hours treatment with 1 mu M doxorubicin showed an increased sensitivity to doxorubicin as assessed by the MTT assay. Conclusion: Our results show that AICAR exerts beneficial effects on TNBC cells, possibly via switching off the Warburg effect and switching on the anti-Warburg effect through mitochondrial modulation.