Dual Metabolic Targeting of Cancer: Lessons from Metformin and 2-Deoxy-D-Glucose Combinations

Background: Metabolic reprogramming enables cancer cells to adapt to energetic stress and sustain proliferation. Simultaneous inhibition of glycolysis and mitochondrial respiration has emerged as a promising strategy to overcome metabolic plasticity. This study evaluated the antiproliferative effects of the glycolytic inhibitor 2-deoxy-D-glucose (2-DG) alone and in combination with metformin in human cancer cell lines. Methods: Human cervical carcinoma (HeLa), lung adenocarcinoma (A549), colorectal adenocarcinoma (HT-29), and normal lung fibroblasts (MRC-5) were treated with 2-DG or metformin individually, or with metformin in the presence of a fixed concentration of 2-DG (1 mM). Cell viability was assessed using the sulforhodamine B assay after 24 and 48 h. IC₅₀ values were calculated by nonlinear regression, Dose Reduction Index (DRI) analysis evaluated sensitization to metformin, and molecular docking was performed to investigate interactions with selected metabolic targets. Results: Both 2-DG and metformin inhibited cell proliferation in a concentration- and time-dependent manner. HeLa cells were the most sensitive to glycolytic inhibition, while A549 and HT-29 cells showed moderate susceptibility. Co-treatment with 2-DG significantly enhanced metformin activity, reducing its IC₅₀ in HeLa cells from 6.04 to 2.00 mM after 24 h and from 2.28 to 1.56 mM after 48 h. DRI analysis demonstrated increased sensitivity to metformin in all cancer cell lines, particularly HT-29 and A549, whereas normal MRC-5 fibroblasts remained comparatively less affected. Molecular docking revealed favorable binding of both 2-DG and metformin to proteins involved in cellular energy metabolism. Conclusions: Combined inhibition of glycolysis and mitochondrial respiration potentiates the antiproliferative effects of metformin, increases metabolic vulnerability in cancer cells, and is supported by molecular docking evidence of interactions with metabolic targets, while showing limited toxicity toward normal fibroblasts. These findings support dual metabolic targeting as a promising therapeutic strategy and warrant further mechanistic and in vivo studies.