Intratumoral heterogeneity underlies therapeutic resistance in pancreatic ductal adenocarcinoma (PDAC). GATA6 plays pivotal role in regulating tumor cell plasticity in the classical subtype of PDAC. Here we investigated the immune features of GATA6+ tumor cells and exploited targeting strategies to enhance GATA6-dependent anti-tumor immune responses using preclinical PDAC models. Our findings revealed a positive correlation between GATA6 tumor expression and the presence of CD4+, FOXP3+, CD20+, and tumor-infiltrating CD8+ cells in human PDAC. Through cell-cell communication analysis and multiplex tissue imaging, we confirm strong spatial interactions between GATA6+ tumor cells and immune cells. Transcriptomic profiling of murine PDAC cell lines during pharmacological MAPK inhibition (MEKi) shows a specific enrichment of antigenicity-related gene sets in GATA6+ cancer cells. Targeted GATA6 degradation with an auxin-inducible degron knock-in in murine PDAC cells significantly diminished MEKi-induced MHCI and IFNγ expression. Functional effect of GATA6+ tumor cell-specific MHCI upregulation was confirmed by co-culturing murine PDAC carrying LCMV-gp33 as model antigen with cytotoxic gp33-TCR transgenic T cells in the presence of MEKi. In patient-derived xenografts and genetic mouse models of spontaneous PDAC, MEKi transiently boosted tumor MHCI expression in GATA6+ tumors, which was subsequently reduced upon a treatment-induced mesenchymal state switch. In vivo combined MAPH and HDAC inhibition with trametinib and domatinostat effectively restored GATA6+ tumor cell populations with increased MHCI, resulting in enhanced cytotoxic T cell infiltration, reduced tumor growth and improved survival. Multiplex spatial analysis confirmed higher MHCI expression in GATA6+ tumor cells sensitized to T cell cytotoxicity. We identified a GATA6-dependent MHCI upregulation in tumor cells upon MEKi, which is counterbalanced by a treatment-induced cell state switch. Combination MEKi with HDACi retained the responsive GATA6+ tumor population, proposing this combination therapy to potentiate immune-based anti-tumor responses.

Abstract Background & Aim: Progression and therapeutic resistance in pancreatic cancer depends on the ability of cancer cells to adopt specific cell states. These phenotypes largely depend on environmental tissue niches. Here, we investigated therapy-induced tumor dynamics in vivo at single-cell spatial and temporal resolution in different subtypes of PDAC using several genetically engineered mouse models, which reflect distinct human PDAC ecosystems. Methods & Results: We established orthotopic tumor models of pancreatic cancer with distinct tumor microenvironment (TME) formation (reactive vs deserted stroma), which were monitored for tumor growth to define tumor response patterns under MAPK inhibition. Serial ultrasound-guided biopsy sampling was performed to collect tissues from the same tumors at pre-treatment, responsive and recurrence periods.Transcriptomic analysis of biopsies using the Mfuzz algorithm delineated highly dynamic gene and pathway activities during treatment. Reactive, but not deserted, TME showed an upregulation of immune-related pathways (antigen presentation, T cell receptor, NK cytotoxicity) immediately after MAPK inhibition in regressed tumors that dropped dramatically during recurrence of tumors, in which upregulation of TGF-b signaling was observed. In the deserted stroma model, on the other hand, an enrichment in drug metabolic pathways during recurrence was observed.CAF cluster deconvolution analysis revealed an increase in a LRRC15+ CAF cluster, which was TGF-b-driven and immunosuppressive, during recurrence period only in the reactive model. The dynamic changes of immune cells and CAFs were validated at protein level by multiplex immunofluorescent imaging. Cmputational spatial analysis revealed a tumor-encapsulating and CD8+ cytotoxic T cell-repelling pattern exhibited by LRRC15+FAP+ CAFs, implying a potential role of this CAF subset in T cell suppression during recurrence in reactive subtype. Using spectral cell sorting with CellView image technology, specific CAF subsets, tumor cells as well as immune cell subsets based on 30+ markers and cell morphology were isolated, characterized and assessed by ex vivo functional assays to confirm the immunosuppressive and tumor protective mechanism mediated by CAFs. Conclusion: Longitudinal in vivo assessment of distinct PDAC subtypes provides deep mechanistic insights to accurately unlock specific response patterns of tumors with heterogeneous TME dynamics upon therapeutic perturbation, leveraging identification of key nodes for intervention. Citation Format: Jens T. Siveke, Rui Fang, Phyllis Fung-Yi Cheung, Jiajin Yang, Juanfei Peng, Kristina Althoff, Konstantinos Savvatakis. Individualized longitudinal assessment reveals therapy-induced tumor and microenvironment dynamics in preclinical pancreatic cancer models [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 1598.

Background Pancreatic ductal adenocarcinoma (PDAC) comprises two clinically relevant subtypes. Currently, determining the tumor subtype relies on tissue biopsies. Unfortunately, these biopsies are spatially biased, highly invasive, difficult to obtain, and unsuitable for monitoring tumor dynamics. Methods We employed whole transcriptome sequencing (WTS) on circulating cell-free (cf) RNA in plasma samples from patients with well-characterized tumor subtypes. Additionally, quantitative protein mass spectrometry was utilized to identify minimally invasive markers for tumor subtypes. We validated our findings using independent liquid and tissue samples from large clinical trials and investigated treatment-induced subtype dynamics and responses. Results An exploratory analysis of 10 patients (four basal-like and six classical) was conducted using whole transcriptome sequencing (WTS). Following differential transcript abundance analysis and integration with expression data from tumor and non-tumor samples (N > 200), we identified 32 protein-coding subtype-specific cfRNA-defined transcripts. The subtype specificity of these transcripts was validated in two independent tissue cohorts comprising 195 and 250 cases, respectively. Three disease-relevant cfRNA-defined subtype markers ( DEGS1, KDELC1 , and RPL23AP7 ) consistently associated with basal-like tumors across all cohorts and were validated using machine learning. Further analysis of these markers using RT-ddPCR in over 160 patient sera and 24 samples from healthy donors revealed their predictive and prognostic value, as well as subtype specificity and therapy-induced dynamics. In both tumor and liquid biopsies, the overexpression of these markers was associated with poor overall and progression-free survival. Moreover, elevated tissue/liquid levels of the identified markers were linked to a poor response to systemic therapy and rapid disease recurrence in resected patients. Conclusion Our data provide support for the clinical significance of cfRNA markers in determining tumor subtypes and monitoring disease recurrence and therapy-induced subtype switches in pancreatic ductal adenocarcinoma (PDAC). Consequently, further validation studies in larger independent cohorts are warranted to confirm the robustness and generalizability of these findings.

ABSTRACT Fibroblast heterogeneity is increasingly recognised across cancer conditions. Given their important contribution to disease progression, mapping out fibroblasts’ heterogeneity is critical to devise effective anti-cancer therapies. Cancer-associated fibroblasts (CAFs) represent the most abundant cell population in pancreatic ductal adenocarcinoma (PDAC). Whether CAF phenotypes are differently specified by PDAC cell lineages remains to be elucidated. Here, we reveal an important role for the MAPK signalling pathway in the definition of PDAC CAF phenotypes. We identify the myCAF transcriptional phenotype as uniquely dependent on proficient MAPK signalling. In addition, CAFs displaying elevated MAPK activity are specifically anchored to basal-like/squamous PDAC cells and define tumour subdomains with reduced frequency of CD8+ T cells. We characterize the single-cell transcriptome of mouse PDAC tumours in response to MAPK inhibition and identify gene expression signatures of MAPK high CAFs, which suggest immunoregulatory functions. Accordingly, a gene expression signature of MAPK high CAFs correlates with poor prognosis in several human cancer conditions, including PDAC, and with reduced response to immune checkpoint inhibition in immune-reactive solid tumours. Altogether, our data expand our knowledge on CAF phenotype heterogeneity and reveal a new strategy for targeting of myofibroblastic CAFs in vivo .

Fibroblast activation protein a (FAPa) is expressed at high levels in several types of tumors. Here, we report the expression pattern of FAPa in solitary fibrous tumor (SFT) and its potential use as a radiotheranostic target. Methods: We analyzed FAPa messenger RNA and protein expression in biopsy samples from SFT patients using immunohistochemistry and multiplexed immunofluorescence. Tracer uptake and detection efficacy were assessed in patients undergoing clinical 68Ga-FAPa inhibitor (FAPI)-46 PET,18F-FDG PET, and contrast -enhanced CT. 90Y-FAPI-46 radioligand therapy was offered to eligible patients with progressive SFT. Results: Among 813 patients and 126 tumor entities analyzed from the prospective observational MASTER program of the German Cancer Consortium, SFT (n 5 34) had the highest median FAPa messenger RNA expression. Protein expression was confirmed in tumor biopsies from 29 of 38 SFT patients (76%) in an independent cohort. Most cases showed intermediate to high FAPa expression by immunohistochemistry (24/ 38 samples, 63%), which was located primarily on the tumor cell surface. Nineteen patients who underwent 68Ga-FAPI-46 PET imaging demonstrated significantly increased tumor uptake, with an SUVmax of 13.2 (interquartile range [IQR], 10.2), and an improved mean detection efficacy of 94.5% (SEM, 4.2%), as compared with 18F-FDG PET (SUVmax, 3.2 [IQR, 3.1]; detection efficacy, 77.3% [SEM, 5.5%]). Eleven patients received a total of 34 cycles (median, 3 cycles [IQR, 2 cycles]) of 90Y-FAPI-46 radioligand therapy, which resulted in disease control in 9 patients (82%). Median progression -free survival was 227 d (IQR, 220 d). Conclusion: FAPa is highly expressed by SFT and may serve as a target for imaging and therapy. Further studies are warranted to define the role of FAPa-directed theranostics in the care of SFT patients.

BACKGROUND:Meteorin-like protein (METRNL)/Interleukin-41 (IL-41) is a novel immune-secreted cytokine/myokine involved in several inflammatory diseases. However, how METRNL exerts its regulatory properties on skin inflammation remains elusive. This study aims to elucidate the functionality and regulatory mechanism of METRNL in atopic dermatitis (AD). METHODS:METRNL levels were determined in skin and serum samples from patients with AD and subsequently verified in the vitamin D3 analogue MC903-induced AD-like mice model. The cellular target of METRNL activity was identified by multiplex immunostaining, single-cell RNA-seq and RNA-seq. RESULTS:METRNL was significantly upregulated in lesions and serum of patients with dermatitis compared to healthy controls (p <.05). Following repeated MC903 exposure, AD model mice displayed elevated levels of METRNL in both ears and serum. Administration of recombinant murine METRNL protein (rmMETRNL) ameliorated allergic skin inflammation and hallmarks of AD in mice, whereas blocking of METRNL signaling led to the opposite. METRNL enhanced β-Catenin activation, limited the expression of Th2-related molecules that attract the accumulation of Arginase-1 (Arg1)hi macrophages, dendritic cells, and activated mast cells. CONCLUSIONS:METRNL can bind to KIT receptor and subsequently alleviate the allergic inflammation of AD by inhibiting the expansion of immune cells, and downregulating inflammatory gene expression by regulating the level of active WNT pathway molecule β-Catenin.

5q-associated spinal muscular atrophy (SMA) is a motoneuron disease caused by mutations in the survival motor neuron 1 (SMN1) gene. Adaptive immunity may contribute to SMA as described in other motoneuron diseases, yet mechanisms remain elusive. Nusinersen, an antisense treatment, enhances SMN2 expression, benefiting SMA patients. Here we have longitudinally investigated SMA and nusinersen effects on local immune responses in the cerebrospinal fluid (CSF) - a surrogate of central nervous system parenchyma. Single-cell transcriptomics (SMA: N = 9 versus Control: N = 9) reveal NK cell and CD8+ T cell expansions in untreated SMA CSF, exhibiting activation and degranulation markers. Spatial transcriptomics coupled with multiplex immunohistochemistry elucidate cytotoxicity near chromatolytic motoneurons (N = 4). Post-nusinersen treatment, CSF shows unaltered protein/transcriptional profiles. These findings underscore cytotoxicity's role in SMA pathogenesis and propose it as a therapeutic target. Our study illuminates cell-mediated cytotoxicity as shared features across motoneuron diseases, suggesting broader implications. Cell-mediated cytotoxicity observed in untreated SMA patients' CSF and brain parenchyma. Spatial transcriptomic and multiplex immunohistochemistry linked cytotoxicity near affected motoneurons. Nusinersen treatment showed no impact on this profile.

Patients with pancreatic ductal adenocarcinoma (PDAC) have a dismal 5 year survival of 9%. One important limiting factor for treatment efficacy is the dense tumor-supporting stroma. The cancer-associated fibroblasts in this stroma deposit excessive amounts of extracellular matrix components and anti-inflammatory mediators, which hampers the efficacy of chemo- and immunotherapies. Systemic depletion of all activated fibroblasts is, however, not feasible nor desirable and therefore a local approach should be pursued. Here, we provide a proof-of-principle of using fibroblast activation protein (FAP)-targeted photodynamic therapy (tPDT) to treat PDAC. FAP-targeting antibody 28H1 and irrelevant control antibody DP47GS were conjugated to the photosensitizer IRDye700DX (700DX) and the chelator diethylenetriaminepentaacetic acid. In vitro binding and cytotoxicity were evaluated using the fibroblast cell-line NIH-3T3 stably transfected with FAP. Biodistribution of 111In-labeled antibody-700DX constructs was determined in mice carrying syngeneic tumors of the murine PDAC cell line PDAC299, and in a genetically engineered PDAC mouse model (CKP). Then, tPDT was performed by exposing the subcutaneous or the spontaneous PDAC tumors to 690 nm light. Induction of apoptosis after treatment was assessed using automated analyses of immunohistochemistry for cleaved caspase-3. 28H1-700DX effectively bound to 3T3-FAP cells and induced cytotoxicity upon exposure to 690 nm light, whereas no binding or cytotoxic effects were observed for DP47GS-700DX. Although both 28H1-700DX and DP47GS-700DX accumulated in subcutaneous PDAC299 tumors, autoradiography demonstrated that only 28H1-700DX reached the tumor core. On the contrary, control antibody DP47GS-700DX was only present at the tumor rim. In CKP mice, both antibodies accumulated in the tumor, but tumor-to-blood ratios of 28H1-700DX were higher than that of the control. Notably, in vivo FAP-tPDT caused upregulation of cleaved caspase-3 staining in both subcutaneous and in spontaneous tumors. In conclusion, we have shown that tPDT is a feasible approach for local depletion of FAP-expressing stromal cells in murine models for PDAC.

Characterization of stromal environment and Notch expression in FKP-based PDAC.

The goal of the PET Clinics is to keep practicing radiologists and radiology residents up to date with current clinical practice in positron emission tomography by providing timely articles reviewing the state of the art in patient care. TARGET AUDIENCEPracticing radiologists, radiology residents, and other health care professionals who provide patient care utilizing radiologic findings. LEARNING OBJECTIVESUpon completion of this activity, participants will be able to: 1. Review the benefits of fibroblast activation protein-a (FAP) as a universal target antigen.2. Discuss several promising and emerging applications FAP-imaging.3. Recognize fibroblast activation protein (FAP)-targeted and positron emission tomography (PET) imaging are emerging beyond tumor imaging and represent an excellent opportunity for assisting radiotherapy planning.

Pancreatic carcinoma lacks effective therapeutic strategies resulting in poor prognosis. Transcriptional dysregulation due to alterations in KRAS and MYC affects initiation, development, and survival of this tumor type. Using patient-derived xenografts of KRAS- and MYC-driven pancreatic carcinoma, we show that coinhibition of topoisomerase 1 (TOP1) and bromodomain-containing protein 4 (BRD4) synergistically induces tumor regression by targeting promoter pause release. Comparing the nascent transcriptome with the recruitment of elongation and termination factors, we found that coinhibition of TOP1 and BRD4 disrupts recruitment of transcription termination factors. Thus, RNA polymerases transcribe downstream of genes for hundreds of kilobases leading to readthrough transcription. This occurs during replication, perturbing replisome progression and inducing DNA damage. The synergistic effect of TOP1 + BRD4 inhibition is specific to cancer cells leaving normal cells unaffected, highlighting the tumor's vulnerability to transcriptional defects. This preclinical study provides a mechanistic understanding of the benefit of combining TOP1 and BRD4 inhibitors to treat pancreatic carcinomas addicted to oncogenic drivers of transcription and replication.

Stromal characterization of preneoplasia, early and late PDAC, and normal pancreas; and gating strategies in flow cytometry

Supplementary Table 1. Clinico-pathological features of HCC in relation to sGEP and sMICA levels. Supplementary Table 2. Cox regression analyses for recurrence-free survival on sGEP/sMICA levels and tumor stage. Supplementary Figure 1. Cytotoxicity of NK cells isolated by positive and negative selection. Supplementary Figure 2. Correlation between NKG2D expression on NK cells with (A) sGEP and (B) sMICA in sera of HCC patients. Supplementary Figure 3. Association of serum GEP or MICA levels with recurrence-free survival in HCC patients.

Nanostring PanCancer Immune profiling analysis and validation.

The cancer associated fibroblast (CAF) orchestrates an aberrant tumor microenvironment in pancreatic ductal adenocarcinoma (PDAC), contributing to poor patient survival. Fibroblast activation protein (FAP)-targeted depletion of the CAF in PDAC could modulate the tumor microenvironment and make it more susceptible to immune response or systemic therapies. Here, we developed a FAP-targeting minibody conjugated to the photosensitizer IRDye700DX for ablation of the CAF with photodynamic therapy. We characterized efficiency of the minibody-IRDye700X in vitro and in vivo in a murine subcutaneous PDAC model.

Fibroblast activation protein (FAP), expressed on cancer-associated fibroblasts, is a target for diagnosis and therapy in multiple tumour types. Strategies to systemically deplete FAP-expressing cells show efficacy; however, these induce toxicities, as FAP-expressing cells are found in normal tissues. FAP-targeted photodynamic therapy offers a solution, as it acts only locally and upon activation. Here, a FAP-binding minibody was conjugated to the chelator diethylenetriaminepentaacetic acid (DTPA) and the photosensitizer IRDye700DX (DTPA-700DX-MB). DTPA-700DX-MB showed efficient binding to FAP-overexpressing 3T3 murine fibroblasts (3T3-FAP) and induced the protein’s dose-dependent cytotoxicity upon light exposure. Biodistribution of DTPA-700DX-MB in mice carrying either subcutaneous or orthotopic tumours of murine pancreatic ductal adenocarcinoma cells (PDAC299) showed maximal tumour uptake of 111In-labelled DTPA-700DX-MB at 24 h post injection. Co-injection with an excess DTPA-700DX-MB reduced uptake, and autoradiography correlated with FAP expression in the stromal tumour region. Finally, in vivo therapeutic efficacy was determined in two simultaneous subcutaneous PDAC299 tumours; only one was treated with 690 nm light. Upregulation of an apoptosis marker was only observed in the treated tumours. In conclusion, DTPA-700DX-MB binds to FAP-expressing cells and targets PDAC299 tumours in mice with good signal-to-background ratios. Furthermore, the induced apoptosis indicates the feasibility of targeted depletion of FAP-expressing cells with photodynamic therapy.

Neither myeloid-specific Notch activation nor Rbpj knock out exerts systemic effect on immune system; and Stromal characterization of FKP tumors upon Notch modulation.

Supplementary Figure S1: IgG negative control demonstrated no added effect on the chemotherapy induced apoptosis; Supplementary Figure S2: Secretory GEP levels in Hep3B and Huh7 culture supernatants; Supplementary Figure S3: Combined GEP antibody and high dose cisplatin eradicated the established intrahepatic xenografts.