Matkowskyj, Kristina A.

SUMMARY Intraductal oncocytic papillary neoplasms (IOPNs) are rare tumors that develop from biliary and pancreatic ductal epithelium and progress to lethal cancers. Human IOPNs and IOPN-associated carcinomas are known to harbor the DNAJB1-PRKACA gene fusion, however the role of the oncogenic fusion in carcinogenesis is poorly understood. We developed a Cre-inducible mouse model of human DNAJB1-PRKACA expression and substantiated that the DNAJB1-PRKACA fusion gene is a bona fide driver of IOPN-associated biliary and pancreatic carcinoma. By analyzing the unique histopathologic and transcriptional changes that occur at each stage of tumor development, we found that these murine tumors closely mimic human DNAJB1-PRKACA driven tumors. Furthermore, we identified that many of the salient features of invasive carcinoma are established at the pre-invasive stage, including evidence of tumor cell metabolic dysregulation, immunosuppressive tumor stroma and expression of genes strongly associated with invasive DNAJB1-PRKACA driven cancer in humans. Finally, we found that Slc16a14 , a characteristic DNAJB1-PRKACA regulated super-enhancer associated gene, serves as a robust biomarker of malignant transformation from IOPN to invasive carcinoma.

Abstract Specialized immune niches located in the stroma-tumor junction promote interactions between tumor-resident antigen-presenting cells and effector lymphocytes that are required for immunotherapy efficacy. We have hypothesized that this stromal-based immune crosstalk may be regulated by provisional extracellular matrix signals, analogous to the early-stages of wound healing where provisional matrix hosts robust immune activity. A cardinal provisional matrix remodeling event, the regulated proteolysis of the large proteoglycan versican (VCAN) generates an immunomodulatory fragment (matrikine), versikine, that engages adaptive immunity. We have previously shown that VCAN proteolysis correlates with T-cell infiltration across multiple solid and liquid cancers with the most immune-evasive cancers showing low to negligible rates of VCAN proteolysis (e.g., 0% in pancreatic adenocarcinoma). A recent clinical trial generated informative prospective data linking VCAN proteolysis with immunotherapy outcomes: patients whose metastatic colorectal tumors categorized as VCAN proteolysis-weak (VPW, 60% of cases) demonstrated inferior responses to checkpoint inhibition (CPI, pembrolizumab) and worse outcomes compared to VCAN proteolysis-predominant (VPP, 40%) cases. Leveraging these prospective trial data, we hypothesized that versikine therapy may rationally reverse the immunosuppression associated with the prevalent VPW phenotype. To tailor versikine therapy to specific human biomarker-stratified tumor phenotypes, we studied experimental models replicating partially T-permissive VPW-VCANlo human cancers and poor-prognosis, immune-exclusionary VPW-VCANhi cancers. Across VPW-like tumors, versikine promoted the stromal accumulation of CD40lghiIcoshiFoxp3neg Tfh-like CD4+ T cells that engaged dendritic cells (DC) and CD8+ T cells in “immune triads” even at baseline (prior to CPI), concurrently with the intratumoral expansion of activated CD8+ T cells expressing cytolytic molecules (granzymes, perforin). In VPW-VCANlo tumors, versikine delivered as LNP-mRNA or recombinant protein demonstrated monotherapy activity, dependent on Batf3-lineage DC and CD8+ T cells. When combined with single-agent CPI, versikine cured most VPW-VCANlo tumors with memory to tumor re-challenge. In VPW-VCANhi tumors, versikine synergized with combination immunotherapy modulating “mature DCs enriched in immunoregulatory molecules” (mregDC). Our data provide mechanistic rationale for the biomarker-stratified, therapeutic restoration of a provisional matrix-regulated immune signaling network to reverse resistance to CPI. Moreover, the data highlight the need to reevaluate prior approaches to globally disrupt tumor stroma in favor of biomarker-driven, pathway-focused harnessing of stromal signals that modulate anti-tumor immunity. Citation Format: Daniel J. Lagal, Duncan Hong, Athanasios Papadas, Emma Geatches, George Yacu, Surabhi Naik, Alicia Gibbons, Alexander Cicala, Kersi Pestonjamasp, Peter Toth, Kristina Matkowskyj, Dustin A. Deming, Fotis Asimakopoulos. Biomarker-driven restoration of tumor provisional matrix signaling network reverses resistance to checkpoint inhibition immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 6746.

Abstract AI-powered pathology foundation models provide general-purpose representations of histopathological images by encoding image tiles into numerical embeddings. However, these embeddings are not directly interpretable in biological or clinical terms and must be translated into biologically meaningful features, such as cell-type composition or gene expression, to enable downstream clinical applications. To bridge this gap, we developed STpath, a framework that integrates histopathology image embeddings derived from existing pathology foundation models with matched, spatially resolved transcriptomics data. STpath consists of cancer-specific XGBoost models trained to infer cell-type compositions and gene expression from histopathology image tiles. We evaluated STpath in colorectal and breast cancer datasets and showed that it provides accurate estimates of the composition of major cell types and the expression of a subset of genes, with further performance gains achieved by combining embeddings from multiple foundation models. Finally, we demonstrated that STpath inferred features that can be used in downstream studies to evaluate their associations with clinical outcomes.

Background: Mastocytic enterocolitis has been proposed as a cause of chronic diarrhea and abdominal pain, characterized by increased mast cells in gastrointestinal mucosal biopsies. However, its clinical significance remains uncertain. Methods: We present a case report of a patient identified to have high levels of mast cells on gastrointestinal biopsies. We then reviewed cases at Mayo Clinic where patients had >20 mast cells per high-power field (HPF) on gastrointestinal biopsies. Patients with alternative explanations for mast cell elevation, including systemic mastocytosis were excluded. We analyzed demographics, clinical presentations, pathology reports, serum and urine mast cell mediators, inflammatory markers, bone marrow biopsies, motility testing, and treatment responses. Results: We identified 42 patients (30 female and 12 male) with elevated mast cells on biopsy (mean age: 41 y, range: 17 to 81). Mast cells were quantified using KIT (CD117) staining, with no abnormal clumping or morphology, and CD25 immunostaining was negative in all cases. Eosinophilic infiltration was absent in all but one case. Small intestinal bacterial overgrowth (SIBO) was found in 78% of patients tested. Treatments varied widely, with antihistamines and cromolyn being the most common. Among 21 patients with sufficient follow-up, only 5 (24%) reported partial or complete symptom improvement, while 76% experienced persistent symptoms. Conclusion: Routine assessment of mast cells on gastrointestinal biopsies is not supported by our findings. Elevated mucosal mast cells, in the absence of systemic mast cell disorders, may not indicate a distinct disease entity. Evaluation should focus on ruling out other inflammatory, allergic, infectious, and motility disorders, as well as SIBO. Further research is needed to determine the clinical significance of increased mucosal mast cells and their role in gastrointestinal symptomatology.

ABSTRACT Metastatic cancer to the pancreas is uncommon, accounting for only 2%–4% of pancreatic malignancies. Prostate cancer spreading to the pancreas is exceptionally rare. We present 2 cases of metastatic castration-resistant prostate cancer with histologic transformation from adenocarcinoma to neuroendocrine prostate cancer. Both patients developed new pancreatic lesions, in which endoscopic ultrasound-guided fine-needle biopsy confirmed the diagnosis. These cases highlight therapy-emergent neuroendocrine prostate cancer with loss of prostate lineage markers (prostate-specific antigen, NKX3.1), positive neuroendocrine markers (synaptophysin, INSM1, chromogranin), very high proliferative indices, and serum marker discordance that can mimic primary pancreatic cancer. These scenarios present a diagnostic challenge with an aggressive and complex nature, requiring multidisciplinary management. With newer therapies and prolonged survival of patients with prostate cancer, clinicians will likely encounter more cases in the future. Gastroenterologists can play a key role in diagnosis and palliative treatment.

A 32-year-old woman with Alport syndrome and prior history of diffuse leiomyomatosis of the oesophagus and bronchial tree presented with severe constipation. MRI revealed extensive leiomyomatosis of the anorectum with obstructed defecation. Colonic manometry showed megacolon, and the patient underwent total colectomy. Surgical pathology confirmed leiomyomatosis and neuronal loss in the anorectum and reduced enteric ganglion cells in the colon. Prior literature suggests obstruction-induced enteric neuropathy as a potential mechanism for megacolon. This report shows that Alport syndrome with diffuse leiomyomatosis may have other gastrointestinal involvement including megacolon in affected patients presenting with constipation.

ABSTRACT Background Several genetic syndromes that affect nerve development and functioning may involve the enteric nervous system and present clinically as dysmotility syndromes, typically in childhood. Aim To review the enteric neuromuscular manifestations, predominantly observed in adults, of neurofibromatosis type I at a tertiary referral center. Methods We conducted a medical records review at the Mayo Clinic and documented clinical manifestations and findings on radiology, pathology, and specialized motility tests of the esophagus, stomach, colon, and rectal evacuatory functions. The tests included scintigraphic gastrointestinal and colonic transit measurements, intraluminal esophageal, gastrointestinal, colonic, and anorectal manometry, and balloon expulsion test. Results Among 2406 with documented NF1, the gastrointestinal manifestations were obstruction or dysmotility, seen in 2% of the cohort. Thirteen patients had small bowel or colonic obstructions: 4 gastrointestinal stromal tumors, 3 malignant peripheral nerve sheath tumors, 3 neurofibromas, 1 diffuse ganglioneuromatosis, 1 schwannoma, and 1 inflammatory fibroid polyp. In addition, 38 patients had abnormal gut motility, including esophageal achalasia or spasm, delayed gastric emptying, slow colonic transit, and dyssynergic defecation. Gastric, small bowel, and colonic manometry were characterized by normal amplitude incoordinated contractions suggestive of neuropathy. In the few resected specimens, myenteric plexus proliferation or diffuse ganglioneuromatosis was identified histologically. Conclusions In addition to mechanical obstruction, typically due to benign tumors affecting smooth muscle or components of nerve (sheath or nerve fiber), patients with NF1 may present with dysmotility syndromes such as gastroparesis, slow colonic transit, or global dysmotility. Neuropathic dysmotility in NF1 can be identified by manometry and by histological evidence of myenteric plexus proliferation or diffuse ganglioneuromatosis.

Abstract Squamous cell carcinoma (SCC) development in mammals is thought to require months or years from the time that initial changes occur. We show that SCCs induced by the mouse papillomavirus MmuPV1, which are generally diagnosed 4-6 months post infection, can be found as soon as 2 weeks post infection. SCCs developed within 2 weeks in immune-competent, adult FVB (FVB/NTac) mice at sites prone to human papillomavirus (HPV)-induced tumors and cancers in human patients: the base of the tongue, the anus, and the skin. The anterior tongue, less susceptible than the base of the tongue to HPV-induced cancer in humans, was resistant to rapid-onset cancer. The presence of invasive cancer in histological tissue sections was verified by multiple pathologists. These diagnoses were corroborated by the results of a classic test of malignancy: skin tumors obtained two weeks post infection grew ectopically as subcutaneous grafts in immune-deficient hosts. Preventative treatment with a novel BRD4 inhibitor dramatically reduced the frequency of ear skin SCCs present 2 weeks post infection and significantly reduced overall disease severity. Like many human papillomaviruses, MmuPV1 lacks an E5 gene. Expression of HPV16 E5 driven by the Keratin 14 promoter in FVB mice (FVB/NTac-Tg(KRT14-HPV16E5*)33Plam/Plam) significantly increased the frequency of rapid-onset invasive cancers caused by MmuPV1 at the base of the tongue and in the anus. In an E5-transgenic mouse with a persistent MmuPV1-induced ear skin lesion, we detected a lymph node metastasis at 38 weeks - further demonstrating a cancer phenotype. Cancers and less severe dysplasia induced by infection at the base of the tongue or the anus spontaneously regressed within 4 to 8 weeks of infection; however, ear lesions persisted. When CD4+ and CD8+ T cells were depleted, lesions at the base of the tongue and anus also persisted, indicating that spontaneous regression involves a T cell-mediated immune response. These results indicate that papillomavirus infection alone is sufficient to induce rapid onset of invasive cancer, and that persistence of disease depends on the tissue-specific immune microenvironment. Citation Format: Andrea Bilger, Ella T. Ward-Shaw, Denis L. Lee, Renee E. King, Shwu-Yuan Wu, Michael A. Newton, Cheng-Ming Chiang, Darya Buehler, Kristina Matkowskyj, John P. Sundberg, Rong Hu, Paul F. Lambert. Rapid-onset squamous cell carcinoma and spontaneous regression following papillomavirus infection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 7237.

Abstract Recent evidence has highlighted the critical requirement for “immune triads” of CD8+ T cells, CD4+ T cells and dendritic cells (DC) for tumor elimination in response to checkpoint inhibition (CPI) immunotherapy. However, the mechanistic underpinnings of this cross-talk are poorly understood. Immune triads are often located in peripherally-distributed DC-rich niches within the tumor stroma. We have hypothesized that stromal remodeling in response to tumor expansion generates homeostatic signals that trigger an adaptive immune response that may ultimately fail through effector exhaustion or apoptosis. In particular, stromal proteolysis of the large matrix proteoglycan versican (VCAN) has been associated with T-cell infiltration across multiple tumor types. The objective of this study was to interrogate a mechanistic link between stromal remodeling, immune triad formation and response to CPI. We used HALO image analysis to determine the spatial relationship of CD4+ and CD8+ T cells in a panel of 95 human non-small cell lung cancers. Each tumor was VCAN proteolysis-scored based on a binning system measuring staining intensity for a neoepitope exposed through site-specific VCAN proteolysis. Tumors displaying VCAN proteolysis intensity of zero (0) had an average of 0.122 CD8+ T cells located with 10um of a CD4+ T cell vs. 0.216 in tumors with any VCAN proteolysis (intensity 1, 2, 3 combined); p=0.04. Similar results were obtained when measuring proximity of CD4+ to CD8+ T cells (0.124 vs 0.223, p=0.02). These data demonstrate that remodeling stroma promotes CD4+:CD8+ crosstalk. Site-specific VCAN proteolysis releases a 441 N-terminal bioactive fragment, versikine. Versikine constitutes a classical “matrikine”, i.e., a bioactive matrix fragment possessing novel functions compared to its parent macromolecule. To determine the mechanisms by which versikine may promote immune triad niches, we generated several transplantable syngeneic tumor cell lines engineered to stably secrete versikine into the TME. One CPI-refractory tumor cell line (Lewis Lung Carcinoma, LLC) and two partially CPI-responsive transplantable tumor lines (CT26 and MC38 colorectal carcinoma) were extensively characterized through flow cytometry, spatial immunofluorescence and scRNAseq. Our results demonstrate that in all contexts, versikine results in expansion of Tfh-like CD4+ T cells expressing Cd40lg and Icos. This expansion is associated with specific patterns of CD8+ T cell exhaustion that will be discussed. Therapeutically, versikine reversed anti-PD-1 pathway refractoriness in the poorly-immunogenic LLC model and demonstrated superior synergy with CPI in the more immunogenic CT26 and MC38 models, leading to tumor eradication with resistance to tumor rechallenge. Our data bolster the mechanistic rationale for exploitation of stromal remodeling signals to promote CD4+T:CD8+T:DC cross-talk for enhanced CPI efficacy. Citation Format: Daniel Lagal, Duncan Hong, Athanasios Papadas, Alicia Gibbons, Yun Huang, Yaling Dou, Alexander Cicala, Elsa Molina, Kristina Matkowskyj, Dustin Deming, Fotis Asimakopoulos. Stromal remodeling promotes immune triad formation in the tumor microenvironment (TME) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2588.

Cancers originating in the esophagus or esophagogastric junction constitute a major global health problem. Esophageal cancers are histologically classified as squamous cell carcinoma (SCC) or adenocarcinoma, which differ in their etiology, pathology, tumor location, therapeutics, and prognosis. In contrast to esophageal adenocarcinoma, which usually affects the lower esophagus, esophageal SCC is more likely to localize at or higher than the tracheal bifurcation. Systemic therapy can provide palliation, improved survival, and enhanced quality of life in patients with locally advanced or metastatic disease. The implementation of biomarker testing, especially analysis of HER2 status, microsatellite instability status, and the expression of programmed death-ligand 1, has had a significant impact on clinical practice and patient care. Targeted therapies including trastuzumab, nivolumab, ipilimumab, and pembrolizumab have produced encouraging results in clinical trials for the treatment of patients with locally advanced or metastatic disease. Palliative management, which may include systemic therapy, chemoradiation, and/or best supportive care, is recommended for all patients with unresectable or metastatic cancer. Multidisciplinary team management is essential for all patients with locally advanced esophageal or esophagogastric junction cancers. This selection from the NCCN Guidelines for Esophageal and Esophagogastric Junction Cancers focuses on the management of recurrent or metastatic disease.