Antibody-Drug Conjugate RC48 Ignites Ferroptosis to Rally Immune Cells Against HER2 Breast Cancer

An antibody-drug conjugate already showing promise against breast cancer may owe much of its power to a surprising mechanism: it forces tumor cells to die in a way that sounds the alarm for the immune system. A new study published in the Journal of Experimental & Clinical Cancer Research reports that disitamab vedotin, known as RC48, kills HER2-expressing breast cancer cells by triggering ferroptosis, an iron-dependent form of cell death driven by the runaway accumulation of lipid reactive oxygen species. Crucially, the researchers found that this death program does more than simply eliminate tumor cells. It converts the dying cells into beacons of immunological distress, releasing damage-associated molecular patterns that initiate immunogenic cell death and draw cytotoxic CD8-positive T cells into the tumor microenvironment. The work, led by Yingying Zhao and Chenwei Yuan of Renji Hospital, Shanghai Jiao Tong University School of Medicine, together with colleagues at Peking University Cancer Hospital, offers one of the clearest mechanistic accounts yet of how a modern anti-HER2 drug can do double duty as both a direct tumor killer and an immune activator.

HER2-positive breast cancer remains one of the most aggressive subtypes of the disease, and patients whose tumors metastasize or recur after standard treatment face a poor prognosis. The arrival of anti-HER2 antibody-drug conjugates has markedly improved outcomes in recent years. These engineered molecules pair an antibody that homes in on the HER2 protein with a potent cytotoxic payload, delivering chemotherapy directly to tumor cells while sparing healthy tissue. RC48 is a novel member of this class, and one of its most clinically intriguing features is that it exhibits antitumor activity not only against tumors with high HER2 expression but also against so-called HER2-low cancers, which were historically considered poor candidates for HER2-targeted therapy. Until now, however, the molecular details of how RC48 actually kills cancer cells, and what those deaths mean for the surrounding immune landscape, remained incompletely understood.

The research team set out to dissect that mechanism at the level of cell biology. Their experiments revealed that when RC48 engages HER2-expressing breast cancer cells, it sets off a cascade of oxidative damage: lipid reactive oxygen species accumulate in the cells’ membranes, pushing them toward ferroptosis. The team confirmed this using established experimental tools, including the C11-BODIPY fluorescence assay to measure lipid ROS, and showed that markers of the ferroptotic pathway, such as the proteins SLC7A11 and GPX4, changed in ways consistent with this form of cell death. Importantly, the ferroptotic and apoptotic programs ran in parallel rather than in sequence. When the researchers blocked ferroptosis with the inhibitor ferrostatin-1, or blocked apoptosis with QVD-O-Ph, they could dissect the relative contributions of each pathway to RC48’s killing effect, and necrostatin-1, an inhibitor of necroptosis, did not rescue cell viability, ruling out that alternative death route as a major player.

What elevates the finding beyond a simple cell-death study is the immunological consequence of that ferroptosis. As tumor cells succumb, they release a characteristic cocktail of damage-associated molecular patterns, including adenosine triphosphate, high-mobility group box 1 protein, and surface-exposed calreticulin. These three signals are the classic hallmarks of immunogenic cell death, a special category of cell demise that the immune system recognizes as dangerous rather than silent. In effect, the dying tumor cells hand the immune system a set of molecular breadcrumbs. The study showed that these emitted signals promote the maturation of dendritic cells, the sentinels that collect debris from dead cells and present fragments of it to T cells, thereby priming an adaptive immune response targeted at the tumor itself.

That priming translated into measurable changes inside the tumor microenvironment. The researchers documented increased infiltration of CD8-positive T cells into tumors following RC48 treatment, along with enhanced cytotoxic function of those cells. Flow cytometric analysis revealed higher levels of granzyme B, interferon gamma, and tumor necrosis factor alpha, the molecular weapons and signaling molecules that CD8-positive T cells deploy when they recognize and attack their targets. In co-culture experiments, CD8-positive T cells exposed to RC48-treated tumor cells showed markedly elevated granzyme B expression, and this effect was abolished when ferroptosis was blocked with ferrostatin-1, directly linking the cell-death program to the immune activation. The team also observed that RC48 treatment upregulated PD-L1 on the surface of surviving tumor cells, an adaptive escape response that tumors use to suppress attacking T cells.

That upregulation of PD-L1 pointed the investigators toward a rational combination strategy. If RC48 both kills tumor cells immunogenically and simultaneously induces the very checkpoint molecule that tumors use to evade immune attack, then pairing the drug with an antibody that blocks PD-L1 should unleash the full potential of the activated T cell response. In vivo mouse models bore this out. The researchers used engineered tumor models, including hHER2-4T1 mice bearing tumors that express human HER2, to evaluate RC48 both as a monotherapy and in combination with anti-PD-L1 therapy. The results confirmed the efficacy and safety of RC48 in both settings, with the combination offering a way to prevent the tumor from slamming the immune brakes just as the drug had floored the accelerator.

The specificity of the mechanism adds an important layer of clinical relevance. In HER2-negative cell lines, including E0771 and 4T1, RC48 did not induce ferroptosis, did not trigger the release of ATP or HMGB1, and did not produce the other signatures of immunogenic cell death. This dependence on HER2 expression means the immunostimulatory effects of the drug are concentrated where the drug is delivered, in tumors carrying the target antigen. The researchers also verified that HER2 expression itself was not significantly altered by RC48 treatment in the tumor tissues of the mouse models, suggesting the drug does not inadvertently select for antigen-loss variants during the treatment window examined. Supporting epidemiological analyses using the GEPIA2.0 and TIMER2.0 databases showed that ferroptosis-related gene signatures, including HMOX1 and ACSL4, correlate with the infiltration of effector T cells, Th1-like cells, and dendritic cells in breast cancer, lending population-level plausibility to the mechanistic story.

The study arrives at a moment when the field is actively rethinking what antibody-drug conjugates can do. These agents were originally conceived as targeted chemotherapy delivery vehicles, but accumulating evidence suggests that the way they kill cells matters as much as how many cells they kill. Immunogenic cell death, with its release of damage signals and recruitment of dendritic cells, can convert a tumor from an immunologically cold site into a hot one, primed for checkpoint blockade. By delineating a ferroptosis-to-immunogenic-cell-death-to-immunity axis for RC48, the Shanghai and Beijing team has provided a mechanistic rationale for combining this ADC with immune checkpoint inhibitors, a strategy their in vivo data already support. The findings also help explain why RC48 shows activity in HER2-low tumors, since the drug’s cytotoxic and immune-activating effects can operate wherever the conjugate can dock, even at lower antigen density.

Several caveats temper the immediate clinical implications. The mechanistic work rests heavily on cell lines and mouse models, including the hHER2-4T1 system, and the authors note that the article was shared early as a peer-reviewed, citable version of record that remains subject to further editorial processing. Translating the ferroptosis-ICD-immune axis into patient benefit will require clinical trials that test RC48 alone and in combination with PD-L1 blockade in patients with HER2-expressing breast cancer, with careful attention to the safety of combining a cytotoxic payload with immunotherapy. Nevertheless, the study was funded by the National Natural Science Foundation of China and Shanghai municipal research programs, and the corresponding authors, Chenwei Yuan, Jinsong Lu, and Wenjin Yin, argue that the data collectively support RC48’s continued clinical development both as a monotherapy and in combination regimens.

For patients and clinicians watching the antibody-drug conjugate field, the message is that RC48 may be more than a precision-guided toxin. By killing tumor cells through ferroptosis and thereby converting their deaths into an immune signal, the drug appears to engineer its own follow-up attack, mobilizing CD8-positive T cells that can hunt down surviving malignant cells. The demonstration that this process depends on HER2 expression, that it can be blocked by ferroptosis inhibitors, and that it pairs logically with checkpoint blockade gives researchers a coherent framework for designing the next generation of trials. If the ferroptosis-immunity axis holds up in human studies, RC48 and drugs like it could become foundational components of combination therapy for HER2-expressing breast cancer, turning a targeted chemotherapy agent into a personalized in situ cancer vaccine of sorts.

Subject of Research: Mechanism of the anti-HER2 antibody-drug conjugate disitamab vedotin in inducing ferroptosis and antitumor immunity in HER2-expressing breast cancer

Article Title: Disitamab vedotin triggers ferroptosis to activate CD8+ T-cell antitumor immunity in HER2-expressing breast cancer

Article References: Zhao, Y., Yuan, C., Wu, Q., Wu, Z., Peng, J., Lin, Y., Lu, J., & Yin, W. (2026). Disitamab vedotin triggers ferroptosis to activate CD8+ T-cell antitumor immunity in HER2-expressing breast cancer. Journal of Experimental & Clinical Cancer Research. https://doi.org/10.1186/s13046-026-03836-x

Image Credits: AI Generated

DOI: 10.1186/s13046-026-03836-x

Keywords: disitamab vedotin, RC48, HER2-positive breast cancer, antibody-drug conjugate, ferroptosis, immunogenic cell death, CD8-positive T cells, damage-associated molecular patterns, PD-L1, dendritic cells, lipid reactive oxygen species, tumor microenvironment