Anticancer Effects of Ascorbic Acid: Not All Sides Fit All

<b>Background/Objectives:</b> Ascorbic acid (AA)is a micronutrient with concentration-dependent anticancer properties, acting either as a reactive oxygen species (ROS) scavenger or inducer. <b>Methods</b>: Conventional redox-based assays such as MTS/MTT often overestimate cell proliferation due to AA's interaction with tetrazolium salts, leading to increased formazan production. To overcome this limitation, we employed the Propidium Iodide Triton X-100 (PI/TX-100) assay to evaluate AA's cytotoxic effects across a diverse panel of cancer and normal cell lines, including prostate (22Rv1, C4-2B, DU-145, LNCaP), breast (MCF-7, MDA-MB-231, MDA-MB-453), lung (A549), liver (HepG2, SK-HEP-1, Huh7), and kidney (Vero) cells. <b>Results</b>: AA significantly suppressed cancer cell viability compared to normal cells (RWPE1 and Vero), with the strongest effects observed in hormone receptor-positive lines. The relative sensitivity to AA followed distinct patterns within each cancer type. Mechanistically, AA-induced cell death involved ROS generation, lipid peroxidation, cell cycle arrest, ferroptosis, apoptosis, and downregulation of pyruvate dehydrogenase kinase 1 (PDHK1). <b>Conclusions:</b> These findings further support the potential of AA as a selective anticancer agent and highlight the importance of assay choice in evaluating its therapeutic efficacy.