Tolosa, Ezequiel J.

Abstract Background: Diffuse pleural mesothelioma (DPM) is a highly aggressive malignancy with limited treatment options and poor prognosis. Although immune checkpoint inhibitors have improved outcomes, particularly for non-epithelioid subtypes, there remains no approved targeted therapy for mesothelioma. EGFR and MET are receptor tyrosine kinases frequently overexpressed in DPM, suggesting susceptibility to targeted antibody therapy. Amivantamab is a bispecific EGFR/MET antibody, originally developed for EGFR-mutant lung cancer, that blocks growth signals and engaging immune mechanisms. Given the high levels of EGFR and MET expression in mesothelioma, we evaluated the therapeutic potential of amivantamab in preclinical models. Methods: EGFR and MET transcript levels in DPM were analyzed using TCGA. Eight human mesothelioma cell lines were assessed by Western blotting and flow cytometry. Amivantamab binding, internalization, and signaling inhibition were examined using flow cytometry, confocal microscopy, and ligand-stimulated phosphorylation assays. Cytotoxicity and immune-effector activity were quantified using PBMCs, NK cells, and monocytes from healthy donors, along with an ADCC reporter assay. In vivo efficacy was tested in a DPM patient-derived xenograft (PDX) model in NOD/SCID-γ (NSG) mice supplemented with human NK cells and treated with amivantamab or control IgG. Results: TCGA analysis showed frequent EGFR/MET co-expression in DPM. Mesothelioma cell lines expressed higher EGFR and MET levels compared with mesothelial cells. Amivantamab strongly bound both receptors, induced receptor internalization, and inhibited EGF- and HGF-stimulated phosphorylation of EGFR, MET, and downstream AKT/ERK signaling. Direct cytotoxicity was minimal; however, the addition of PBMCs or NK cells resulted in robust, dose-dependent tumor cell killing consistent with antibody-dependent cellular cytotoxicity (ADCC). Reporter assays demonstrated 7-11-fold Fcγ receptor activation in tumor cells compared with ∼2-fold activation in non-malignant mesothelial cells. Co-culture with monocytes revealed amivantamab-induced trogocytosis, evidenced by loss of EGFR and MET from tumor-cell membranes. In the DPM PDX model, amivantamab produced 89.1% tumor-growth inhibition (TGI) relative to controls (P < 0.0001), with no overt toxicity observed in treated mice. Conclusions: Dual EGFR/MET targeting with amivantamab produced potent antitumor effects in mesothelioma through coordinated receptor-signaling blockade, ADCC, and monocyte-mediated trogocytosis. These results support amivantamab as a promising targeted therapeutic strategy for EGFR/MET-positive DPM, particularly epithelioid subtypes that currently derive limited benefit from immunotherapy. Citation Format: Shinichiro Suzuki, Kaushal Parikh, Ezequiel Tolosa, Kuan-Li Wu, Jennifer Ayers-Ringler, Lin Yang, Katherine E. Smith, Farhad Kosari, Aaron S. Mansfield, . Enhancing antibody-dependent cellular cytotoxicityin mesothelioma through concurrent EGFR and MET targeting withamivantamab [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 5547.

For over a century, scientists reported the disruption of normal nuclear shape and size in cancer. These changes have long been used as tools for diagnosis and staging of malignancies. However, to date, the mechanisms underlying these aberrant nuclear phenotypes and their biological significance remain poorly understood. Using a model of pancreatic ductal adenocarcinoma (PDAC), the major histological subtypes of pancreatic cancer, we found that oncogenic mutant KRAS reduces nuclear size. Transcriptomic and protein expression analysis of mutant KRAS–expressing PDAC cells revealed differential levels of several nuclear envelope–associated genes. Further analysis demonstrated the nuclear lamina protein, Emerin (EMD), acted downstream of KRAS to mediate nuclear size reduction in PDAC. Analysis of human PDAC samples showed that increased EMD expression associates with reduced nuclear size. Finally, in vivo genetic depletion of EMD in a mutant KRAS–driven PDAC model resulted in increased nuclear size and a reduced incidence of poorly differentiated PDAC. Thus, our data provide evidence of a potentially novel mechanism underlying nuclear size regulation and its effect in PDAC carcinogenesis.

4155 Background: The tumor microenvironment (TME) that surrounds pancreatic ductal adenocarcinoma (PDAC) is a multi-faceted and dynamic ecosystem in which stromal fibroblasts communicate with cancer cells to mediate tumor growth, metastasis, and chemotherapy resistance. It is well recognized that both cancer-associated fibroblasts (CAFs) and its non-cellular, fibrotic components within the TME can foster a protumorigenic environment for PDAC. However, we still lack a comprehensive understanding of the precise mechanisms in which this dense, fibrotic matrix can help drive malignant behaviors. Here, we reveal a novel mechanism in which the zinc-finger transcription factor GLI2 regulates type 1 collagen expression within CAFs and how the soluble variant of this collagen promotes irinotecan chemoresistance. Methods: We leveraged transcriptomic data from The Cancer Genome Atlas, International Cancer Genome Consortium, and Clinical Proteomic Tumor Analysis Consortium to evaluate GLI2 expression and stromal content of human PDAC tumors through bulk RNA-sequencing deconvolution. Using single-nucleus RNA sequencing of human PDAC tumors, we validated the association of GLI2 expression and stromal matrix constituents in CAFs. Chromatin immunoprecipitation assays in human CAFs confirmed GLI2 binding at the COL1A1 promoter. Through RNAi-based inactivation of GLI2, we determined how loss of GLI2 impacts regulation of type 1 collagen. Additionally, we conducted MTT assays to assess tumor viability in response to irinotecan treatment. Results: Transcriptomic analysis revealed that GLI2 is highly enriched in CAFs and strongly correlated with stromal fibrosis compared to other non-tumor cell constituents within the TME. We have shown that GLI2 directly binds to the promoter of COL1A1, a key component of type 1 collagen, in CAFs and regulates its transcription in a manner dependent on TGFβ1 signaling. Interestingly, PDAC tumors exposed to type 1 collagen show increased expression of pro-tumorigenic pathways involved in inflammation, EGR signaling, cytokine-receptor interactions, and irinotecan resistance. We further validate that human PDAC cells pre-treated with collagen can confer chemoresistance to irinotecan with viability assays. Conclusions: Taken together, our study demonstrates a novel mechanism in which GLI2 regulates the secretion of collagen within CAFs, which in turn can enable PDAC to acquire resistance to standard-of-care treatments. These findings highlight not only the oncogenic functions for CAFs and their fibrotic secretome, but also open new avenues in which therapeutic targeting of the TME may provide clinical benefit for PDAC patients.

Abstract Background: Diffuse pleural mesothelioma (DPM) is a rare and aggressive cancer arising from mesothelial cells of the pleura. Over 2, 500 new cases are diagnosed annually in the United States, mainly attributable to asbestos exposure. The prognosis is poor, and while nivolumab (PD-1 inhibitor) and ipilimumab (CTLA-4 inhibitor) have been approved for first-line treatment of unresectable DPM, the three-year survival rate is only 23%. DPM tumors express high levels of epidermal growth factor receptor (EGFR) and mesenchymal-epithelial transition (MET), but targeted therapies like erlotinib (EGFR tyrosine kinase inhibitors) have shown no clinical benefit. We hypothesized that amivantamab, a bispecific antibody that targets both EGFR and MET, may have activity against DPM through antibody-dependent cellular cytotoxicity (ADCC). Objective: The purpose of this study was to assess the potential of amivantamab to mediate ADCC in tissue culture experiments with DPM cell lines. Methods: We assessed DPM for the expression of EGFR and MET using available data from bulk RNA sequencing. We also examined protein expressions of EGFR and MET by Western blot analysis in five epithelial (EM-Meso, H2452, H2461, Mero-41 and Mero-95), three sarcomatoid (H2373, H2596 and ONE58), and one normal mesothelial (MeT-5A) cell lines. Co-culture experiments were performed with the DPM and normal cell lines and NK cells in the presence of amivantamab to evaluate ADCC. Results: We identified high levels of EGFR and MET expression in both epithelial and sarcomatoid cases of DPM from 183 patients. This finding was corroborated by Western blot analysis of all eight DPM cell lines. In vitro experiments demonstrated that amivantamab induced dose-dependent ADCC in DPM cell lines, with robust NK cell-mediated ADCC observed across all tested DPM lines. Notably, sarcomatoid-type DPM cells were more sensitive to amivantamab-induced ADCC than epithelial-type cells. These findings suggest that amivantamab may offer therapeutic benefits for DPM tumors with high EGFR and MET expression. Conclusion: This study provides preclinical evidence supporting the potential of amivantamab as a novel therapeutic option for DPM, especially in sarcomatoid tumors. Ongoing in vivo studies including in patient-derived xenograft (PDX) models will further evaluate the efficacy of amivantamab in DPM. Citation Format: Shinichiro Suzuki, Lin Yang, Jennifer Ayers-Ringler, Ezequiel J. Tolosa, Kuan-Li Wu, Janet L. Schaefer-Klein, Farhad Kosari, Aaron S. Mansfield. Antitumor activity of amivantamab in diffuse pleural mesothelioma [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 7331.

Despite ongoing efforts to employ structure-based methods to discover targeted protein degraders (TPD), the prevailing strategy remains synthesizing a focused set of heterobifunctional compounds and screening them for target protein degradation.

Abstract Pancreatic cancer is a devastating malignancy in great need of new and more effective treatment approaches. In recent years, studies have indicated that nutritional interventions, particularly nutraceuticals, may provide novel avenues to modulate cancer progression. Here, our study characterizes the impact of ω-3 polyunsaturated fatty acids, eicosapentaenoic acid, and docosahexaenoic acid, as a nutraceutical intervention in pancreatic cancer using a genetically engineered mouse model driven by KrasG12D and Trp53R172H. This model closely resembles human pancreatic carcinogenesis, offering a disease relevant platform for translational research. Our findings showed that ω-3 polyunsaturated fatty acids intervention (using a diet supplemented with 6% cod liver oil) significantly reduced tumor volume as well as lung and liver metastasis and a trend toward improved survival rate compared with control treated mice. This antitumoral effect was accompanied by distinct changes in tumor membrane fatty acid profile and eicosanoids release. Furthermore, the eicosapentaenoic acid and docosahexaenoic acid intervention also reduced malignant histological parameters and induced apoptosis without affecting cell proliferation. Of note is the significant reduction in tumor fibrosis that was associated with decreased levels of Sonic Hedgehog, a major ligand controlling this cellular compartment in pancreatic cancer. All together our results demonstrate the impact of eicosapentaenoic acid and docosahexaenoic acid as antitumor regulators in pancreatic cancer, suggesting potential for ω-3 polyunsaturated fatty acids as a possible antitumoral dietary intervention. This research opens new avenues for integrating nutraceutical strategies in pancreatic cancer management.

Abstract Aberrant activation of GLI transcription factors has been implicated in the pathogenesis of different tumor types including pancreatic ductal adenocarcinoma. However, the mechanistic link with established drivers of this disease remains in part elusive. In this study, using a new genetically engineered mouse model overexpressing constitutively active mouse form of GLI2 and a combination of genome-wide assays, we provide evidence of a novel mechanism underlying the interplay between KRAS, a major driver of pancreatic ductal adenocarcinoma development, and GLI2 to control oncogenic gene expression. These mice, also expressing KrasG12D, show significantly reduced median survival rate and accelerated tumorigenesis compared with the KrasG12D only expressing mice. Analysis of the mechanism using RNA sequencing demonstrate higher levels of GLI2 targets, particularly tumor growth–promoting genes, including Ccnd1, N-Myc, and Bcl2, in KrasG12D mutant cells. Furthermore, chromatin immunoprecipitation sequencing studies showed that in these cells KrasG12D increases the levels of trimethylation of lysine 4 of the histone 3 (H3K4me3) at the promoter of GLI2 targets without affecting significantly the levels of other major active chromatin marks. Importantly, Gli2 knockdown reduces H3K4me3 enrichment and gene expression induced by mutant Kras. In summary, we demonstrate that Gli2 plays a significant role in pancreatic carcinogenesis by acting as a downstream effector of KrasG12D to control gene expression.

Acute pancreatitis (AP) is among the most common hospital gastrointestinal diagnoses; understanding the mechanisms underlying the severity of AP is critical for development of new treatment options for this disease. Here, we evaluate the biological function of phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) in AP pathogenesis in 2 independent genetically engineered mouse models of AP. PFKFB3 was elevated in AP and severe AP (SAP), and KO of Pfkfb3 abrogated the severity of alcoholic SAP (FAEE-SAP). Using a combination of genetic, pharmacological, and molecular studies, we defined the interaction of PFKFB3 with inositol 1,4,5-trisphosphate receptor (IP3R) as a key event mediating this phenomenon. Further analysis demonstrated that the interaction between PFKFB3 and IP3R promotes FAEE-SAP severity by altering intracellular calcium homeostasis in acinar cells. Together, our results support a PFKFB3-driven mechanism controlling AP pathobiology and define this enzyme as a therapeutic target to ameliorate the severity of this condition.

Abstract Antibody-drug conjugates (ADCs) are increasingly being used in clinic, and many novel ADCs are being tested in clinical trials. Most ADCs act by delivering cytotoxic payloads into target cells. The activity of most ADCs is predicated upon internalization to release the cytotoxic payloads intracellularly to act on the malignant cells. The degree of ADC internalization is incomplete or absent for many cell surface targets, limiting the activity of ADCs. PROTACs are heterobifunctional molecules that result in the polyubiquitylation of their targets by inducing proximity with E3 ligases. The proteasome then recognizes the poly-ubiquitin chains and degrades these targets. We hypothesized that PROTACs that act on the same targets as ADCs could improve the internalization and efficacy of these ADCs. Using multiple cell lines derived from breast, lung or pancreatic cancers that express the oncogenic cell surface proteins EGFR (ERBB1), HER2 (ERBB2) or MET (HGF), we measured antibody internalization with live cell imaging. Antibodies were labeled with a pH sensitive reagent that fluoresces red (640 nm) upon exposure to acidic environments. Fluorescence was measured over time to create an area under the curve which was compared between the cell lines that were treated with and without PROTACs. Antibody internalization was observed in all cell lines that expressed the targets recognized by the antibodies. The addition of PROTACs targeting the same oncogenic cell surface proteins as the antibodies significantly increased antibody internalization beyond that observed without PROTACs. Internalization of antibodies was confirmed by measuring intracellular immunoglobulins by Western blot. Antibody internalization with PROTACs was dose-dependent, increased over time and was blocked by either the clatharin inhibitor Dyngo4a or the proteasome inhibitor MG132. In the case of HER2 for which there are FDA-approved anti-HER2 ADCs, the cytotoxicity of trastuzumab emtansine (TDM1) significantly increased with the addition of a HER2-targeting PROTAC across a range of doses. PROTACs that target the same oncogenic cell surface proteins as antibodies improve antibody internalization and ADC cytotoxicity, in a process dependent upon clatharin and the proteasome. This novel application of PROTACs may impact the use of ADCs, and provides a rationale to combine these agents in clinical trials. Citation Format: Ezequiel J. Tolosa, Lin Yang, Jennifer Ayers-Ringler, Jayapal Mallareddy, Janet Schaefer-Klein, Farhad Kosari, Amar Natarajan, Aaron S. Mansfield. Proteolysis targeting chimera (PROTAC)-driven internalization of antibodies targeting oncogenic cell surface receptors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4518.

Abstract The sparse vascularity of pancreatic ductal adenocarcinoma (PDAC) presents a mystery: What prevents this aggressive malignancy from undergoing neoangiogenesis to counteract hypoxia and better support growth? An incidental finding from prior work on paracrine communication between malignant PDAC cells and fibroblasts revealed that inhibition of the Hedgehog (HH) pathway partially relieved angiosuppression, increasing tumor vascularity through unknown mechanisms. Initial efforts to study this phenotype were hindered by difficulties replicating the complex interactions of multiple cell types in vitro. Here we identify a cascade of paracrine signals between multiple cell types that act sequentially to suppress angiogenesis in PDAC. Malignant epithelial cells promote HH signaling in fibroblasts, leading to inhibition of noncanonical WNT signaling in fibroblasts and epithelial cells, thereby limiting VEGFR2-dependent activation of endothelial hypersprouting. This cascade was elucidated using human and murine PDAC explant models, which effectively retain the complex cellular interactions of native tumor tissues. Significance: We present a key mechanism of tumor angiosuppression, a process that sculpts the physiologic, cellular, and metabolic environment of PDAC. We further present a computational and experimental framework for the dissection of complex signaling cascades that propagate among multiple cell types in the tissue environment. This article is featured in Selected Articles from This Issue, p. 201