Investigation of the relationship between autophagy and Warburg effect in osteosarcoma cells: An in vitro study

This study aims to investigate the interaction between autophagy and the Warburg effect in Saos-2 cells by assessing the effects of 2-deoxyglucose (2-DG) and chloroquine (CQ), alone and combined on cell survival, apoptosis, and metabolic/autophagic markers.

Saos-2 osteosarcoma cells were treated with 2-DG, CQ, or their combination for 24 h; cell viability (MTT), apoptosis (Cell Death ELISA), autophagy and glycolytic gene expression (qRT-PCR for Beclin-1, LC3, ATG3, HK2, PFKP; western blot for Beclin-1, LC3-II, ATG3), and extracellular lactate were evaluated.

Both CQ and 2-DG produced dose-dependent loss of Saos-2 viability (24-h IC₅₀ ≈45 µM for CQ and ≈389 µM for 2-DG) and their combination exerted greater cytotoxicity, increasing apoptosis from ∼6% (control) to ∼24% (CQ), ∼53% (2-DG) and ∼79% (CQ+2-DG) (p < 0.001). qRT-PCR revealed upregulation of autophagy transcripts: LC3 (CQ 1.8-fold, 2-DG 1.4-fold, combo 2.5-fold), Beclin-1 (CQ 1.1-fold, 2-DG 1.5-fold, combo 1.9-fold) and ATG3 (CQ ∼1.0-fold, 2-DG 1.7-fold, combo 2.25-fold) and Western blot analysis confirmed corresponding elevations (p < 0.05). Glycolytic genes were differentially regulated: HK2 (CQ 1.2-fold, 2-DG 1.8-fold, combo 2.5-fold) and PFKP (CQ 1.3-fold, 2-DG 0.8-fold, combo 1.1-fold) (p < 0.05). Extracellular lactate (normalized to protein) increased with CQ (∼2.7-fold), decreased with 2-DG (∼0.5-fold), and was intermediate with the combination (∼1.4-fold) (p < 0.05). Experiments were performed in triplicate.

This study reveals crosstalk between autophagy and the Warburg effect in Saos-2 cells, where glycolytic stress triggers protective autophagy and its inhibition alters metabolism, promoting apoptosis.