Pharmacologic Vitamin C Triggers Mitochondrial Collapse via ROS-Iron-Calcium Crosstalk in Human Osteosarcoma

Osteosarcoma is a devastating disease, especially because it strikes early—most often during adolescence or young adulthood. It remains one of the most aggressive primary bone malignancies, and though treatment protocols have advanced over the past few decades, they haven’t done much to move the needle on long-term survival, particularly in cases that recur or metastasize. What’s more troubling is that the existing standard of care—typically a combination of chemotherapy, surgical resection, and sometimes radiotherapy—comes with a steep cost: not just the expected risks of treatment failure, but persistent toxicities that compromise heart function, kidney health, and future fertility. These are not minor trade-offs. They are life-altering. It’s within this landscape of unmet clinical need that unconventional approaches like high-dose vitamin C have started to resurface—not as fringe remedies, but as potentially serious therapeutic options. Pharmacologic ascorbate has long hovered at the periphery of oncology, championed by some, dismissed by others. Yet recent work has begun to lend it credibility, suggesting that, under the right conditions, vitamin C doesn’t act as a gentle antioxidant but rather as a pro-oxidant that can selectively dismantle cancer cells. The mechanism? That’s where things have remained unknown. Vitamin C exists in multiple redox states—ascorbic acid, dehydroascorbic acid, and various derivatives—and determining which of these is truly active in a therapeutic sense has proven difficult. Likewise, there’s been no consensus on how exactly the cell dies—through apoptosis, ferroptosis, or some alternative path.

Contributing to this evolving narrative, a new research paper published in Redox Biology ,  led by Assistant Professor Yool Lee and Prajakta Vaishampayan from the Elson S. Floyd College of Medicine at Washington State University, investigated the complex mechanisms of why vitamin C, under specific pharmacologic conditions, exerts such a profound and selective effect on osteosarcoma cells. The authors began with a fundamental question: which form of vitamin C exerts genuine cytotoxic effects in osteosarcoma? The researchers compared oxidizable ascorbic acid, its oxidized form (dehydroascorbic acid), and a non-oxidizable derivative across several human OS cell lines. Only the redox-active ascorbic acid triggered marked, dose-dependent cell death. This response was not limited to conventional monolayers; in 3D tumor spheroids—structures that better mimic in vivo tumors—ascorbic acid alone disrupted spheroid integrity and halted growth entirely. The other two forms, regardless of dose, produced minimal effects, reinforcing the idea that redox activity is central to therapeutic efficacy.

To understand the mechanism of action, Professor Yool Lee and Prajakta Vaishampayan used HyPer Red, a genetically encoded probe for hydrogen peroxide. Treatment with oxidizable ascorbic at at high dose caused a rapid surge in intracellular reactive oxygen species (ROS), metabolic saboteurs that disrupt cellular homeostasis. Notably, this oxidative burst was neutralized by catalase and iron chelators but unaffected by copper chelation. These findings positioned iron—not copper—as the key cofactor enabling ROS generation via Fenton chemistry, a reaction that produces highly reactive hydroxyl radicals from hydrogen peroxide and iron. However, classical ferroptosis inhibitors failed to prevent the cytotoxic effects which indicated that although iron was essential, the pathway diverged from canonical ferroptosis. Moreover, when the authors pretreated osteosarcoma cells with BAPTA-AM, a cell-permeable calcium chelator, they found that vitamin C-induced death was completely blocked. Additionally, fluorescence-based calcium imaging revealed a sharp increase in cytosolic calcium following treatment. This rise originated from the endoplasmic reticulum and was mediated by IP3 receptors. Knocking down IP3R isoforms, or the ER oxidase ERO1α, significantly attenuated both ROS accumulation and cell death, linking ER calcium release directly to mitochondrial stress. Subsequent mitochondrial assays completed the picture. High-dose ascorbic acid caused a collapse in mitochondrial membrane potential and sharply reduced ATP levels. Transcriptomic data showed suppression of genes encoding core components of the electron transport chain, particularly those of mitochondrial origin. Finally, in a mouse xenograft model, tumors exposed to high-dose vitamin C displayed slowed growth and diminished expression of mitochondrial ATP synthase, reinforcing the in vitro findings.

In conclusion, the research work of Professor Yool Lee and Prajakta Vaishampayan  reframes how high-dose vitamin C should be understood in the context of cancer therapy—not as a speculative antioxidant supplement, but as a mechanistically rigorous agent that selectively dismantles key metabolic dependencies in osteosarcoma cells. Indeed, it made a strong case for re-evaluating vitamin C as a focused metabolic disruptor with real clinical promise. What the authors have uncovered is not just another layer of redox biology, but a precise and coordinated collapse of intracellular systems. By tracing the path from vitamin C’s oxidation to ROS generation, iron mobilization, calcium dysregulation, and ultimately mitochondrial failure, the work highlights a vulnerability in osteosarcoma that is both specific and targetable. Rather than attributing cell death to general oxidative stress, the study identifies a tightly regulated, multistep process that converges on energy disruption and irreversible damage to tumor cell bioenergetics.

We believe one of the most compelling aspects of the new study is its ability to clarify longstanding confusion in the field. The distinction between vitamin C’s chemical forms has often been overlooked in clinical interpretations. Here, the data clearly show that only the redox-active form is capable of initiating this cascade and this has important implications in therapeutic design and formulation. The inability of both ferroptosis and apoptosis inhibitors to rescue the cells further pushes the narrative into new territory which suggest a hybrid or alternative death pathway that warrants deeper exploration. This could be especially meaningful in tumors that have developed resistance to canonical cell death signals. Moreover, the in vivo results provide an important translational bridge. Using orthotopic mouse model, the authors demonstrated that these mechanisms aren’t confined to cell culture artifacts—pharmacologic vitamin C led to measurable tumor regression, along with mitochondrial disruption mirroring the in vitro findings. This coherence across scales adds weight to the argument that the redox-calcium-mitochondria axis is a viable therapeutic target. More broadly, the implications of the findings of Vaishampayan and Lee may extend to other malignancies marked by high basal ROS and disrupted iron metabolism. There’s also potential relevance for targeting therapy-resistant cancer stem cell populations, which often switch to mitochondrial oxidative phosphorylation for survival, particularly when treated with anti-cancer drugs that target glycolysis, their preferred metabolic pathway.