Betel Nut Chemical Shields Oral Cancer Cells From Copper-Driven Cell Death

Betel nut chewing, practiced by hundreds of millions of people across South Asia, Southeast Asia and the Pacific, is one of the strongest known risk factors for oral squamous cell carcinoma, a malignancy that already accounts for the majority of oral cancers worldwide. The chief psychoactive and bioactive alkaloid in the areca nut, arecoline, has long been associated with malignant transformation of oral tissue, but the molecular machinery by which it actively drives cancer progression has remained only partially mapped. A new study published in Cell Death Discovery now reveals a surprising survival strategy that arecoline appears to hand to cancer cells: the ability to dodge a recently identified form of copper-dependent cell death known as cuproptosis.

Cuproptosis, first described as a distinct cell death modality in 2022, differs fundamentally from better-known death pathways such as apoptosis. Rather than dismantling the cell through caspase enzymes or membrane rupture, cuproptosis arises when copper ions bind directly to lipid-acylated components of the mitochondrial tricarboxylic acid cycle. This aberrant binding causes the affected proteins to aggregate, destabilizes iron-sulfur cluster proteins, and triggers a proteotoxic stress response that ultimately kills the cell. Because copper homeostasis is tightly regulated in healthy tissue, the discovery of cuproptosis opened an entirely new therapeutic frontier: if tumors can be pushed over the copper-death threshold, they might be eliminated by a mechanism they have never needed to resist during evolution.

The research team, led by Shuaiyuan Zhang, Xiaoyong Liu, Xu Jiang and corresponding author Zan Jiao, with affiliations spanning Sun Yat-Sen University, Shenzhen Longgang Otolaryngology Hospital and Southern Medical University, began by asking a simple question at the transcriptomic level. Do oral tumors from patients with a history of betel nut exposure look different, in terms of oxidative stress and copper-death biology, from oral tumors that arise without that exposure? The answer was emphatically yes. Betel nut-associated oral squamous cell carcinoma samples displayed enhanced oxidative stress signatures, reduced cuproptosis scores, and markedly elevated expression of a gene called MT2A, metallothionein 2A. Strikingly, high MT2A expression correlated with poorer overall survival and poorer progression-free survival, marking it as a potential prognostic indicator in its own right.

MT2A encodes a small, cysteine-rich metal-binding protein that can sequester heavy metal ions, including copper, and buffer them away from sensitive cellular targets. In the logic of cuproptosis, a protein that mops up free copper is exactly the kind of bodyguard a cancer cell would want. The researchers next turned to controlled laboratory experiments with oral cancer cell lines to test whether arecoline itself could induce this protective state. When cells were treated with arecoline, intracellular levels of reactive oxygen species, or ROS, rose. That surge in oxidative stress activated NRF2, nuclear factor erythroid 2-related factor 2, the master transcriptional regulator of the cellular antioxidant response. Once activated, NRF2 upregulated MT2A expression, and the cells became measurably more resistant to copper toxicity while their susceptibility to cuproptosis dropped.

This chain of events, from ROS to NRF2 to MT2A, constitutes what the authors define as a signaling axis, a causal pathway in which each link is necessary for the next. To prove causality rather than mere correlation, the team intervened at multiple points. When they scavenged ROS with pharmacological antioxidants, or when they genetically silenced NRF2 with interfering RNA, the arecoline-induced rise in MT2A was blunted. Crucially, blocking the axis restored the cells’ vulnerability to cuproptosis and weakened several hallmarks of malignancy: cell viability fell, colonies grew less efficiently in clonogenic assays, and the cells’ capacity to migrate and invade through surrounding matrix, the behaviors that make oral cancer so locally destructive, was attenuated in vitro.

To establish that NRF2 acts directly on the MT2A gene rather than through intermediaries, the researchers employed CUT&Tag profiling, a technique that maps where a transcription factor binds across the genome with base-level precision in living chromatin. The data showed direct occupancy of NRF2 on the MT2A promoter, the regulatory region that controls the gene’s transcription. This finding anchors the axis at the molecular level: arecoline-generated ROS liberate NRF2, NRF2 docks on the MT2A promoter, and MT2A protein accumulates to buffer copper. The team then performed the complementary rescue experiment. When NRF2 was knocked down, forcing MT2A back into the cells partially restored their pro-survival and anti-cuproptotic behavior, demonstrating that MT2A is a functional downstream effector, not merely a passive biomarker of NRF2 activity.

Cancer biology, however, is notoriously unforgiving of results that hold only in a culture dish. The team therefore extended their findings into xenograft models, in which human oral cancer cells are implanted into immunocompromised mice and allowed to form tumors. Knocking down either NRF2 or MT2A significantly inhibited tumor growth in these animals. Conversely, when the researchers enforced MT2A expression in tumors whose NRF2 had been depleted, the growth-suppressive effect was reversed, confirming the hierarchy of the axis in a living organism. In a final and particularly elegant test, the researchers used tetrathiomolybdate, or TTM, a clinical copper chelator originally developed for Wilson’s disease, to lower available copper in tumors lacking MT2A. Chelation rescued the tumor-suppressive effect of MT2A knockdown, meaning that removing the copper buffer mattered only when copper was present to be buffered, a result that further cements MT2A’s role in protecting oral cancer cells from cuproptosis in vivo.

Taken together, the study sketches a coherent and clinically provocative picture. Arecoline exposure floods oral epithelial cells with oxidative stress. The stress response, mediated by NRF2, inadvertently arms those cells with copper-binding metallothioneins. If and when malignant transformation occurs, the same machinery renders the resulting tumors resistant to copper-induced death and more aggressive in behavior. In this framing, the very alkaloid that helps initiate the cancer also appears to educate the tumor in how to survive one of the body’s most recently discovered lethal mechanisms. The paradox is that the ROS signal, usually cast as a tumor-promoting villain in cancer biology, here acts as the upstream trigger for a protective transcriptional program, illustrating how context determines whether oxidative stress harms or heals a cancer cell.

The therapeutic implications are twofold. First, the ROS-NRF2-MT2A axis offers a set of druggable nodes: disrupting NRF2 activation, silencing MT2A, or manipulating copper availability could each, in principle, resensitize arecoline-associated tumors to cuproptosis. Copper chelators and copper ionophores are already being explored in clinical trials for other malignancies, and the present findings suggest that betel nut-related oral cancers, which carry high MT2A expression and low cuproptosis scores, might represent a patient population particularly likely to benefit from copper-directed strategies. Second, MT2A expression could serve as a biomarker to stratify patients, identifying those whose tumors depend on this protective axis and who might therefore respond to combination approaches that pair conventional therapies with cuproptosis-inducing agents.

As with any preclinical study, important caveats remain. The work relies on cell lines, transcriptomic correlations and xenografts rather than human intervention trials, and the precise contribution of the axis relative to other arecoline-driven pathways, such as those involving epithelial-mesenchymal transition and inflammatory signaling, will require further dissection. Nevertheless, by connecting a specific environmental carcinogen to a specific cell death resistance mechanism, the study adds a compelling chapter to the fast-growing literature on copper and cancer. For the hundreds of millions of betel chewers worldwide, and for the clinicians treating the oral cancers that follow, the message is that the enemy’s chemistry may also reveal its weakness, and that the copper-handling machinery of the tumor cell is a vulnerability worth attacking.

Subject of Research: Arecoline-driven suppression of cuproptosis in oral squamous cell carcinoma via the ROS-NRF2-MT2A axis

Article Title: Arecoline suppresses cuproptosis and drives oral squamous cell carcinoma progression via a ROS-NRF2-MT2A axis

Article References: Zhang, S., Liu, X., Jiang, X., & Jiao, Z. (2026). Arecoline suppresses cuproptosis and drives oral squamous cell carcinoma progression via a ROS-NRF2-MT2A axis. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03387-2

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03387-2

Keywords: arecoline, betel nut, oral squamous cell carcinoma, cuproptosis, ROS, NRF2, MT2A, copper, cell death, oxidative stress, cancer progression, tetrathiomolybdate