The first of the highlighted studies tackles a long-standing obstacle in cancer biology: the difficulty of studying tumors in their native spatial context. Goldschmidt and colleagues applied state-of-the-art spatial transcriptomics to formalin-fixed paraffin-embedded biopsy samples from nine dogs diagnosed with COSCC. Spatial transcriptomics is a technique that measures gene expression while preserving the physical location of each cell within the tissue, allowing researchers to see not just which genes are active but where that activity occurs. This matters because tumors are not uniform masses; they contain distinct compartments, including normal epithelium, pre-malignant dysplastic epithelium, the tumor microenvironment, and regions of surface and deep tumor, each of which may behave differently and respond differently to therapy.

The spatial analysis revealed striking molecular patterns. Gene signatures associated with EGFR, the epidermal growth factor receptor, a well-known driver of cell proliferation in many human cancers, and with epithelial-to-mesenchymal transition, a process by which cancer cells acquire invasive, migratory properties, were increased and shared between dysplastic epithelium and tumor samples. This suggests that the molecular changes driving malignancy begin early, before full transformation. Within the cancer samples themselves, the researchers found enrichment of KRAS gene sets, along with the transcripts KRT17 and SPP1, markers often associated with aggressive tumor behavior. Perhaps most intriguing were the findings in the tumor microenvironment, defined in the study as peritumoral mesenchymal stromal tissue infiltrated with leukocytes. There, the team detected signals associated with an increased presence of tumor-associated macrophages, immune cells that tumors frequently co-opt to suppress anti-cancer immunity, and induction of IL10, an immunosuppressive signaling molecule. Enrichment of ICOS and CTLA4 was also noted, and these signals correlated with CD4-positive T cell transcripts in the microenvironment, hinting at a complex immune landscape that could be exploited therapeutically.

The second and third studies demonstrate how such molecular insights can be translated directly into new treatments. Katt and co-workers established several new COSCC cell lines using a combination of patient-derived xenografts and tissue-cultured cell lines created directly from COSCC biopsies. Patient-derived models are prized in oncology research because they preserve more of the biology of the original tumor than long-established laboratory lines. When the team investigated these new models, they uncovered evidence of RAS activation in every one of them. RAS is a signaling protein that, when switched on, drives cells to proliferate uncontrollably, and it sits upstream of MEK1/2, a pair of serine/threonine kinases that relay the growth signal deeper into the cell.

That molecular logic pointed straight at a drug. Trametinib is a small-molecule inhibitor of MEK1/2, already used in human medicine for cancers with activated RAS pathway signaling. The researchers screened trametinib against other cytotoxic and targeted agents using their novel cell lines and found, as predicted, that it exerted anti-tumor activity both in vitro and in a canine xenograft model. These preclinical results were compelling enough to justify testing the drug in pet dogs with COSCC. In a preliminary study of four dogs, objective responses were documented in two of the treated patients. A subsequent dose-escalating study of twenty dogs with COSCC confirmed that trametinib was well tolerated and showed a thirty percent objective response rate, with a further twenty-five percent of dogs exhibiting stable disease, meaning their tumors neither grew nor shrank significantly.

Crucially, the correlative analyses in that trial revealed a biomarker that could transform how dogs are selected for treatment. Dogs whose tumors carried BRAF p.V595E mutations responded significantly better to trametinib than dogs with BRAF wild-type tumors. This alignment with trametinib’s known mechanism of action in activated RAS signaling illustrates the essence of precision oncology: rather than treating every patient identically, clinicians can profile a tumor’s mutations and predict which patients are most likely to benefit. Together, the cell line work and the clinical trials illustrate a rational pathway for introducing new targeted therapies in COSCC, moving systematically from bench to patient-side, a journey that in human oncology often takes many years but here was compressed into a remarkably short arc.

The fourth study extends the comparative approach to feline patients and to immunotherapy-adjacent territory. Signal transducer and activator of transcription 3, or STAT3, is a transcription factor that is hyperactivated in many cancers, including FOSCC, where it drives tumor cell proliferation, immunosuppression, and drug resistance. A prior phase 0 trial in humans with head and neck squamous cell carcinoma had shown that a STAT3 decoy, an engineered molecule that binds and sequesters the transcription factor’s activation machinery, could downregulate STAT3 target genes. Building on that human data, Grandis and colleagues evaluated a systemically administered linear STAT3 decoy in multiple preclinical murine models of head and neck squamous cell carcinoma and then undertook a phase 1 clinical trial of twenty cats diagnosed with FOSCC.

The feline trial produced results that are encouraging for one of the most aggressive malignancies in companion animal medicine. A thirty-five percent disease control rate was documented, comprising two partial responses and five cases of stable disease. Importantly, the favorable responses were accompanied by measurable biological changes: shifts in peripheral blood immune parameters and increased intratumoral expression of PDCD1, the gene encoding the PD-1 immune checkpoint protein. That last finding is particularly significant because PD-1 expression within tumors is a marker of T cell exhaustion, the state in which anti-tumor immune cells become dysfunctional. Its increase in responding patients suggests the STAT3 decoy may be relieving one layer of immunosuppression and potentially sensitizing tumors to checkpoint blockade, a class of drugs that releases the brakes on anti-tumor immunity. Beyond its clinical promise for cats, the study exemplifies the power of a comparative approach in cancer research, in which findings in one species inform and accelerate progress in others, with the aim of benefiting multiple species simultaneously.

Weaving these threads together, Atherton’s editorial argues that veterinary medicine is now entering the age of immune oncology, heralded in part by the roll-out of checkpoint blockade. The identification of CTLA4 upregulation within COSCC by the spatial transcriptomics study, alongside the prognostic implications of increased PDCD1 expression in FOSCC patients treated with the STAT3 decoy, provides impetus to investigate these molecules as mediators of T cell exhaustion. That, in turn, may set the scene for future trials of anti-CTLA-4 or anti-PD-1 therapy in oral squamous cell carcinoma patients of both species. Meanwhile, the early but encouraging clinical data from dogs treated with trametinib offers cautious optimism that this targeted therapy could be added to the currently limited arsenal of useful anti-cancer drugs for COSCC.

Ongoing studies are expected to determine the optimal way to incorporate trametinib into treatment regimens. The editorial notes several plausible roles: the drug could be applied in a neo-adjuvant setting, given before definitive surgery or radiation with the aim of improving the tolerability and outcomes of conventional treatment, or it could serve as an additional palliative option for more advanced COSCC cases where curative intent is no longer feasible. What makes this moment notable is not any single result but the demonstration that the full precision-oncology workflow, from spatially resolved molecular profiling through patient-derived models to biomarker-guided clinical trials, now functions in veterinary patients. For the dogs and cats facing these cancers, and for the humans whose head and neck cancers share many of the same molecular vulnerabilities, the comparative road ahead looks considerably brighter than it did only a few years ago.

Subject of Research: Recent advances in the diagnosis and targeted therapy of canine and feline oral squamous cell carcinoma

Article Title: An editorial spotlight on recent progress in veterinary oncology

Article References: Atherton, M. J. (2025). An editorial spotlight on recent progress in veterinary oncology. Veterinary Oncology, 2(1), Article 30. https://doi.org/10.1186/s44356-025-00047-y

Image Credits: AI Generated

DOI: 10.1186/s44356-025-00047-y

Keywords: veterinary oncology, oral squamous cell carcinoma, spatial transcriptomics, trametinib, MEK inhibitor, STAT3 decoy, tumor microenvironment, checkpoint blockade, BRAF mutation, comparative oncology, precision medicine, immunotherapy

Oral squamous cell carcinoma, or OSCC, is a formidable enemy in canine medicine. Oral tumors affect an estimated half a percent of dogs over their lifetimes and account for about six percent of the canine cancer burden, with OSCC making up roughly nineteen percent of all oral tumors. The disease is locally invasive, growing through multiple anatomical planes of the jaw and surrounding tissue, causing severe pain, difficulty eating, and in some cases pathological fractures of the bone. Up to twenty percent of affected dogs show signs of metastasis by the time they are diagnosed. Left untreated, it is deadly.

The current standard of care is blunt: wide-margin surgical excision. While surgery is highly effective when non-metastatic tumors are completely removed, with very low recurrence rates, it is also highly invasive and invariably disfiguring. Roughly thirty percent of dogs have difficulty eating after surgery, and larger operations bring longer healing times, greater postoperative pain, and higher risks of complications. Radiation is occasionally used for tumors that cannot be surgically removed or as an adjunct to surgery, but the fundamental treatment paradigm has not changed in decades, even as researchers have made major strides in understanding the molecular machinery driving the disease.

That machinery centers on the RAS signaling pathway. Recent studies have shown that canine OSCC displays highly activated RAS signaling compared with healthy gingival tissue, a finding confirmed by gene set enrichment analysis comparing tumor samples with normal tissue. RAS is a small GTPase that, when activated by extracellular signals binding to receptors on the cell surface, launches a cascade of molecular events that ultimately drive cell growth and survival. The most important arm of this cascade for tumor growth is the RAS-RAF-MEK-ERK pathway, which ends with ERK initiating the gene transcription programs that keep a tumor expanding. The question facing the Cornell team was whether this pathway could be pharmacologically attacked in a way that would benefit dogs whose tumors are driven by a variety of different upstream mutations.

The answer they settled on was trametinib, a small molecule that inhibits MEK1 and MEK2, the kinases sitting in the middle of the pathway. Trametinib binds to the non-phosphorylated form of MEK in an allosteric pocket near the ATP binding site, blocking its catalytic activity and its ability to activate ERK. Crystal structures show the drug does more than simply plug the pocket: it also prevents BRAF from binding to MEK and appears to stabilize MEK’s association with KSR, the kinase suppressor of RAS, further reducing MEK’s affinity for BRAF. Crucially, the team chose trametinib precisely because it works on wildtype, unmutated proteins. Since RAS itself is rarely mutated in canine OSCC and BRAF mutations appear in only about a third of tumors, drugs like sotorasib, which bind only mutant RAS, would have left most patients out in the cold. Trametinib, by contrast, targets the pathway regardless of what triggered its activation.

The drug also came with a reassuring safety pedigree. It is FDA-approved in humans for BRAF-mutant melanoma and non-small cell lung cancer, typically alongside the BRAF inhibitor dabrafenib. A phase I trial in eighteen dogs had already demonstrated an acceptable safety profile over nine weeks of treatment, and the European Medicines Agency reported the drug was well tolerated in beagles over thirteen weeks and fully eliminated within about seven days. Its high oral bioavailability in both species meant it could be given at home, avoiding the stress and expense of repeated hospital visits.

The trial itself was designed with a do-no-harm philosophy. Twenty dogs with histologically confirmed OSCC were enrolled between October 2023 and February 2025, after approval by Cornell’s Institutional Animal Care and Use Committee and with informed consent from owners. Dogs received daily oral trametinib at doses escalating from 0.015 to 0.035 milligrams per kilogram, with examinations every two weeks including caliper tumor measurements, complete blood counts, and serum chemistry panels. Full tumor staging with contrast-enhanced computed tomography was performed at the start, around day 28, and around day 56, and tumor volumes were measured from CT slices by a board-certified veterinary radiologist. Response was categorized using veterinary RECIST criteria, and any dog showing progressive disease was removed immediately and returned to standard care. Because the typical two-week wait before surgery would not be compromised, owners could try the drug without sacrificing the earliest opportunity for curative excision.

The results were remarkable in some patients. One dog achieved a complete response, with no tumor detectable by CT, and five achieved partial responses, giving an overall response rate of thirty percent. Five more dogs had stable disease, meaning fifty-five percent of the cohort derived clinical benefit. Some tumors responded with startling speed: two dogs’ tumors had shrunk to less than one cubic centimeter after just two weeks of treatment, and in five dogs the mean volume reduction at the first post-treatment evaluation was forty-five percent. In two responsive patients, bone window CT scans showed actual bone regrowth at the tumor site, visible at 28 and 56 days after treatment began, a sign of genuine tissue healing rather than mere tumor shrinkage. In some cases the visible portions of tumors became difficult or impossible to identify by external inspection.

Safety data were equally encouraging. No high-grade adverse events were detected in any dog, though about thirty percent of owners reported transient flatulence that resolved on its own. Bloodwork showed mostly grade 1 and grade 2 abnormalities that were typically no worse than pre-treatment values. The only two grade 3 events, elevated alkaline phosphatase in two dogs, were preceded by grade 2 liver enzyme elevations present before treatment began, suggesting preexisting liver pathology unrelated to the drug. No dog was removed from the study or had its dose modified because of side effects, and no neutropenia was observed. Notably, a prior phase I study had flagged hypertension and proteinuria in some dogs at similar doses, but the Cornell team did not observe owner-reported behaviors consistent with those conditions, though blood pressure and urinalysis were not directly monitored.

The most scientifically compelling finding emerged when tumors were stratified by BRAF mutational status. Seven dogs carried tumors harboring the BRAF p.V595E mutation, the canine equivalent of the human V600E mutation, and these responded dramatically better than BRAF wildtype tumors. Among BRAF-mutant cases, one dog had a complete response and four had partial responses, for a seventy-one percent objective response rate and a mean volume reduction of seventy-one percent in responding tumors. Wildtype tumors, by contrast, showed a mean reduction of only seven percent among responders, and total clinical benefit in that group was just eight percent. The difference was statistically significant at p equals 0.01. Because BRAF genotyping requires only simple PCR amplification and Sanger sequencing, the authors suggest it could readily be implemented by diagnostic laboratories to identify dogs most likely to benefit. The team recommends a starting dose of 0.030 milligrams per kilogram daily while cautioning that dose-response analyses were underpowered. Limitations remain, including the absence of an untreated control group, the lack of long-term recurrence and survival data, and the small cohort size, but the study establishes trametinib as a safe, orally available neoadjuvant option that can shrink tumors in about a third of dogs before surgery, and in the majority of those whose tumors are BRAF-mutant, with results visible in as little as two weeks.

Subject of Research: Clinical trial of the MEK inhibitor trametinib for treating oral squamous cell carcinoma in dogs

Article Title: Clinical application of the MEK inhibitor trametinib in dogs with oral squamous cell carcinoma

Article References: Katt, W. P., Balkman, C. E., Byron, M., Carney, P. C., Chrostek, E., Drozd, M. E., Duhamel, G. E., Fiani, N., Hume, K. R., King, A. L., Sylvester, S. R., Todd-Donato, A. B., Winokur, C. E., Wright, A. L., & Peralta, S. (2025). Clinical application of the MEK inhibitor trametinib in dogs with oral squamous cell carcinoma. Veterinary Oncology, 2(1), Article 31. https://doi.org/10.1186/s44356-025-00042-3

Image Credits: AI Generated

DOI: 10.1186/s44356-025-00042-3

Keywords: trametinib, MEK inhibitor, oral squamous cell carcinoma, canine cancer, BRAF mutation, RAS signaling, veterinary oncology, targeted therapy, clinical trial, neoadjuvant treatment, Cornell University, dog health