Precision-cut tumor slices (PCTS) maintain tissue heterogeneity concerning different cell types and preserve the tumor microenvironment (TME). Typically, PCTS are cultured statically on a filter support at an air–liquid interface, which gives rise to intra-slice gradients during culture. To overcome this problem, we developed a perfusion air culture (PAC) system that can provide a continuous and controlled oxygen medium, and drug supply. This makes it an adaptable ex vivo system for evaluating drug responses in a tissue-specific microenvironment. PCTS from mouse xenografts (MCF-7, H1437) and primary human ovarian tumors (primary OV) cultured in the PAC system maintained the morphology, proliferation, and TME for more than 7 days, and no intra-slice gradients were observed. Cultured PCTS were analyzed for DNA damage, apoptosis, and transcriptional biomarkers for the cellular stress response. For the primary OV slices, cisplatin treatment induced a diverse increase in the cleavage of caspase-3 and PD-L1 expression, indicating a heterogeneous response to drug treatment between patients. Immune cells were preserved throughout the culturing period, indicating that immune therapy can be analyzed. The novel PAC system is suitable for assessing individual drug responses and can thus be used as a preclinical model to predict in vivo therapy responses.

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive cancer often diagnosed at an advanced stage, leading to a poor prognosis. The tumor microenvironment (TME) plays a crucial role in driving metastasis, with inflammatory signaling pathways contributing to tumor progression and therapy resistance. However, the combined effects of inflammatory and oncogenic signaling on the epigenetic regulation of PDAC metastasis are poorly understood. Here, we demonstrate that tumor necrosis factor-alpha (TNFα) and epidermal growth factor (EGF) signaling converge to regulate PDAC cell migration through the activation of NF-κB and AP-1 transcription factors. Using single-cell RNA sequencing, in vitro and in vivo models, we show that the simultaneous activation of these pathways with TNFα and EGF cooperatively induces the expression of genes associated with cell motility and migration. Consistently, combinatorial induced genes are co-regulated by the transcription factors FOSL1 and RELA. Remarkably, inhibition of NF-κB transcriptional activity with a glucocorticoid receptor (GR) mixed agonist significantly reduced PDAC cell migration by decreasing RNA polymerase II recruitment to target genes. These findings reveal a novel mechanism by which inflammatory and oncogenic pathways cooperate to drive PDAC metastasis and highlight the therapeutic potential of GR agonists in mitigating tumor cell migration. Our study offers promising avenues for developing mechanism-based therapeutic strategies in PDAC management.

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours of the gastrointestinal tract and a key example for targeted therapy with tyrosine kinase inhibitors (TKIs), which have significantly improved survival rates. However, no effective treatments exist for TKI-resistant or mutation-negative tumours. Until now, research on the effects of TKIs has mainly used 2D cultures or mouse models, lacking patient-specific 3D GIST models. We investigated various 3D GIST models, including spheroids, organoids, patient-derived microtumours (PDMs), and precision-cut tumour slices (PCTSs), to assess their feasibility as alternatives for 2D cell culture or in vivo mouse models. Moreover, 2D monolayer and 3D spheroid GIST cell lines showed mutation-dependent responses to TKI treatment, but differences between 2D and 3D cultures were minimal. Thus, patient-derived 3D models, incorporating tumour microenvironment cells, were developed for more accurate in vivo representation. PDMs and PCTSs were successfully isolated from primary tumours and cultivated for up to two weeks. Three-dimensional models were immunohistochemically characterised, and the response to TKI therapies was tested and compared with expected clinical outcomes. In addition to already established 2D cell cultures and mouse models, PDMs and PCTSs are novel patient-derived 3D models that can be used to study tumour cell interactions within the microenvironment. Moreover, they could be used to investigate TKI resistance, and novel treatment options such as immunotherapies and combination therapies.

Pancreatic ductal adenocarcinoma (PDAC) remains a highly lethal cancer with a 5-year survival rate of 13%. Despite recent molecular stratification of tumors into distinct classical and basal-like cell states, most tumors are heterogeneous and contain both subtypes. Therefore, therapeutic approaches targeting only one subtype are unlikely to be effective as standalone PDAC treatments. Here, we integrated chromatin accessibility [assay for transposase-accessible chromatin with sequencing (ATAC-seq)], genome-wide occupancy [chromatin immunoprecipitation sequencing (ChIP-seq)] for epigenetic status (H3K27ac), and H3K4me3-anchored chromatin topology (HiChIP) to uncover subtype-independent highly interactive enhancers that interact with essential genes in PDAC. Motif analysis revealed that these common enhancers were bound by KLF5 with subsequent depletion leading to decreased cell viability via induction of apoptosis. To elucidate the transcriptional and epigenetic mechanisms by which KLF5 functions in PDAC, we used rapid depletion of KLF5 with dTAG technology and profiled the effects on the open and active chromatin landscape and transcription with nascent RNA and messenger RNA sequencing over time. Enhancer inactivation via KRAB domain Zim3-dCas9 fusion protein confirmed KLF5-bound enhancers regulate target genes, including the anti-apoptotic gene BCL2L1 . Multiplex immunofluorescence confirmed costaining of KLF5 and Bcl-xL in patient samples and overexpression of Bcl-xL rescued the induction of apoptosis after KLF5 depletion. Together, this study provides insights into common mechanisms to target highly heterogeneous PDAC tumors.

Pancreatic ductal adenocarcinoma (PDAC) remains a highly lethal cancer with a 5-year survival rate of 13%. Despite recent molecular stratification of tumors into distinct classical and basal-like cell states, most tumors are heterogeneous contain of both subtypes. Therefore, therapeutic approaches targeting one subtype may not be suitable for PDAC therapy. Here, we integrated chromatin accessibility (ATAC-seq), genome-wide occupancy (ChIP-seq) for epigenetic status (H3K27ac) and H3K4me3-anchored chromatin topology (HiChIP) to uncover subtype-independent highly interactive enhancers that interact with essential genes in PDAC. Motif analysis revealed these common enhancers were bound by KLF5 with subsequent depletion leading to decreased cell viability via induction of apoptosis. To elucidate the transcriptional and epigenetic mechanisms by which KLF5 functions in PDAC, we employed rapid depletion of KLF5 with dTAG technology and profiled the effects on the open and active chromatin landscape and transcription with nascent RNA and mRNA-seq over time. Enhancer inactivation via KRAB domain Zim3-dCas9 fusion protein confirmed KLF5-bound enhancers regulate target genes, including the anti-apoptotic gene BCL2L1. Multiplex immunofluorescence confirmed co-staining of KLF5 and Bcl-xL in patient samples and overexpression of Bcl-xL rescued the induction of apoptosis after KLF5 depletion. Taken together, this study provides new insights into common mechanisms to target highly heterogeneous PDAC tumors. Teaser: KLF5 controls subtype-independent highly interactive enhancers to regulate cell viability in pancreatic cancer.

Despite recent medical advances, colorectal cancer (CRC) remains the second-leading cause of cancer-related death worldwide. For patients with KRAS wild-type metastatic CRC, the monoclonal antibody cetuximab, which targets the epidermal growth factor receptor (EGFR), is an approved treatment option. However, therapeutic success is often limited by the emergence of drug-resistant cancer cell populations within a few months. Therefore, alternative strategies to effectively target cetuximab-refractory CRC are urgently needed. Here, we sought to identify second-line therapeutic strategies using a CRC cell line with acquired cetuximab resistance as a model. Transcriptomic profiling of the resistant cells identified the apoptosis pathway as a potential therapeutic target, which was supported by their increased susceptibility to BH3-mimetics targeting the anti-apoptotic proteins MCL-1 and BCL-xL under both 2D and 3D culture conditions. These findings were validated in organotypic CRC slice cultures generated from cetuximab-resistant patient-derived xenografts (PDXs). Multiplex immunofluorescence staining demonstrated that BCL-xL inhibition effectively triggered apoptosis in heterogeneous PDX tumor slice models, including models harboring oncogenic BRAF mutations. Our findings suggest that cetuximab-resistant CRC retains apoptotic competence, and that BCL-xL inhibition serves as a robust alternative therapeutic strategy that is largely independent of the tumor mutational profile.