Metformin and oncogenic pathways: Crosstalk between energy sensing and tumor progression

Metformin, a widely prescribed oral biguanide for type 2 diabetes mellitus, has gained significant attention as a potential anti-cancer agent. Beyond its established role in improving insulin sensitivity and lowering blood glucose, preclinical and epidemiological studies suggest that metformin exerts anti-tumor effects through both insulin-dependent and insulin-independent mechanisms. Central to its activity is the activation of AMP-activated protein kinase (AMPK), which disrupts the mammalian target of rapamycin (mTOR) pathway, leading to cell cycle arrest, apoptosis, and reduced tumor growth. Additionally, metformin modulates oncogenic signaling networks such as PI3K/Akt, Erk, and receptor tyrosine kinases, while influencing tumor metabolism, angiogenesis, and immune responses. By inhibiting mitochondrial complex I, metformin interferes with cancer cell bioenergetics and the Warburg effect, further contributing to its anti-cancer potential. Clinical studies, however, have yielded mixed results, underscoring the complexity of metformin's effects and the need for rigorous investigation. This review highlights the multifaceted mechanisms by which metformin impacts tumor progression and discusses its promise and challenges as a therapeutic agent in cancer prevention and treatment.