Recent studies have thoroughly described genome-wide expression patterns defining molecular subtypes of pancreatic ductal adenocarcinoma (PDAC), with different prognostic and predictive implications. Although the reversible nature of key regulatory transcription circuits defining the two extreme PDAC subtype lineages “classical” and “basal-like” suggests that subtype states are not permanently encoded but underlie a certain degree of plasticity, pharmacologically actionable drivers of PDAC subtype identity remain elusive. Here, we characterized the mechanistic and functional implications of the histone methyltransferase enhancer of zeste homolog 2 (EZH2) in controlling PDAC plasticity, dedifferentiation, and molecular subtype identity. Utilization of transgenic PDAC models and human PDAC samples linked EZH2 activity to PDAC dedifferentiation and tumor progression. Combined RNA- and chromatin immunoprecipitation sequencing studies identified EZH2 as a pivotal suppressor of differentiation programs in PDAC and revealed EZH2-dependent transcriptional repression of the classical subtype defining transcription factor Gata6 as a mechanistic basis for EZH2-dependent PDAC progression. Importantly, genetic or pharmacologic depletion of EZH2 sufficiently increased GATA6 expression, thus inducing a gene signature shift in favor of a less aggressive and more therapy-susceptible, classical PDAC subtype state. Consistently, abrogation of GATA6 expression in EZH2-deficient PDAC cells counteracted the acquisition of classical gene signatures and rescued their invasive capacities, suggesting that GATA6 derepression is critical to overcome PDAC progression in the context of EZH2 inhibition. Together, our findings link the EZH2-GATA6 axis to PDAC subtype identity and uncover EZH2 inhibition as an appealing strategy to induce subtype-switching in favor of a less aggressive PDAC phenotype. Significance: This study highlights the role of EZH2 in PDAC progression and molecular subtype identity and suggests EZH2 inhibition as a strategy to recalibrate GATA6 expression in favor of a less aggressive disease.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with a dismal prognosis that is frequently diagnosed at an advanced stage. Although less common than other malignant diseases, it currently ranks as the fourth most common cause of cancer-related death in the European Union with a five-year survival rate of below 9%. Surgical resection, followed by adjuvant chemotherapy, remains the only potentially curative treatment but only a minority of patients is diagnosed with locally resectable, non-metastatic disease. Patients with advanced disease are treated with chemotherapy but high rates of treatment resistance and unfavorable side-effect profiles of some of the used regimens remain major challenges. Biomarkers reflect pathophysiological or physiological processes linked to a disease and can be used as diagnostic, prognostic and predictive tools. Thus, accurate biomarkers can allow for better patient stratification and guide therapy choices. Currently, the only broadly used biomarker for PDAC, CA 19-9, has multiple limitations and the need for novel biomarkers is urgent. In this review, we highlight the current situation, recent discoveries and developments in the field of biomarkers of PDAC and their potential clinical applications.

Metastatic pancreatic cancer (PDAC) has a poor clinical outcome with a 5-year survival rate below 3%. Recent transcriptome profiling of PDAC biopsies has identified 2 clinically distinct subtypes — the “basal-like” (BL) subtype with poor prognosis and therapy resistance compared with the less aggressive and drug-susceptible “classical” (CLA) subtype. However, the mechanistic events and environmental factors that promote the BL subtype identity are not very clear. Using preclinical models, patient-derived xenografts, and FACS-sorted PDAC patient biopsies, we report here that the axon guidance receptor, roundabout guidance receptor 3 (ROBO3), promotes the BL metastatic program via a potentially unique AXL/IL-6/phosphorylated STAT3 (p-STAT3) regulatory axis. RNA-Seq identified a ROBO3-mediated BL-specific gene program, while tyrosine kinase profiling revealed AXL as the key mediator of the p-STAT3 activation. CRISPR/dCas9-based ROBO3 silencing disrupted the AXL/p-STAT3 signaling axis, thereby halting metastasis and enhancing therapy sensitivity. Transcriptome analysis of resected patient tumors revealed that AXL ^hi neoplastic cells associated with the inflammatory stromal program. Combining AXL inhibitor and chemotherapy substantially restored a CLA phenotypic state and reduced disease aggressiveness. Thus, we conclude that a ROBO3-driven hierarchical network determines the inflammatory and prometastatic programs in a specific PDAC subtype.

Background: Brain metastases represent a severe complication in many gastrointestinal malignancies especially those arising from the upper gastrointestinal tract, including cancer of the esophagus, gastroesophageal junction, and stomach (GEC). However, there is little knowledge about the onset or potential risk factors for brain metastases (BRMs) in upper gastrointestinal cancers resulting in a lack of screening guidelines for BRMs. Methods: We analyzed 827 patients from our cancer registry suffering from gastroesophageal cancer (GEC) and treated at the University Medical Center Göttingen between January 2013 and December 2019 for the presence of BRMs. Results: From 827 patients with GEC we found 54 patients with BRMs, resulting in an incidence of 6.5%. BRMs are more frequent in male patients (90.74% vs 9.26%, p = 0.0051) and in adenocarcinomas (90.74% vs 9.26%, p = 0.0117). Mean duration for the onset of BRMs from initial cancer diagnoses was 20.9 months in limited disease (curative approach) and 9.3 months in advanced disease (palliative approach) (p = 0.0026). However, early detection of BRMs is a prognostic factor since patients with successful resection of BRMs have a better prognosis compared to those with unresectable BRMs (5.93 vs 2.07 months, p = 0.0091). Conclusion: In this single-center retrospective study, brain metastases (BRMs) occur with a high frequency (6.5%) in gastroesophageal cancer (GEC), significantly more often in male patients and adenocarcinomas. Since survival of these patients considerably correlates with successful BRMs resection, our observations propose further prospective trails to validate our hypothesis and ultimately the implementation of routine screening procedures to detect asymptomatic brain metastases.

Zusammenfassung: Hintergrund Granulomatöse Erkrankungen wie Sarkoidose können die Diagnostik bei onkologischen Erkrankungen erschweren, da Metastasen bildmorphologisch häufig nicht von Granulomen zu unterscheiden sind. Die vorliegende Kasuistik beschreibt Diagnostik und Therapie eines Patienten mit fortgeschrittener Sarkoidose und einem hepatisch metastasierten Rektumkarzinom mit schlussendlichem Erreichen eines kurativen Stadiums. Fallbeschreibung Bei einem 71-jährigen Patienten wurde im Rahmen der Abklärung ungewollten Gewichtsverlustes sowie einer Anämie ein Adenokarzinom des Rektums diagnostiziert. Die weitere Umfelddiagnostik ergab bildmorphologisch den hochgradigen Verdacht auf multiple rechtshepatische, pulmonale und splenische Metastasen. Histologisch zeigten sich nach bronchoskopischer Biopsie der mediastinalen Lymphknoten jedoch nichtverkäsende Epitheloidzellgranulome als Manifestation einer bis dato nicht bekannten Sarkoidose. Aufgrund des stenosierenden Tumors erfolgte eine Rektumresektion mit Milzextirpation bei intraoperativ hochgradigem Verdacht auf Milzmetastasen. Histologisch zeigten sich in der Milz eine Beteiligung im Rahmen der Sarkoidose. Bei bildmorphologisch weiterhin suspekten rechtshepatischen Leberläsionen erfolgte postoperativ eine Stanzbiopsie einer Läsion, die histologisch sowohl eine Metastase des bekannten Rektumkarzinoms als auch eine Sarkoidose ergab. Es erfolgte eine pseudo(neo)adjuvante Therapie mit 5-Fluorouracil, Leukovorin und Oxaliplatin (FOLFOX) und Panitumumab (Anti-EGF-Antikörper). Bildmorphologisch zeigten sich posttherapeutisch 2 Leberläsionen regredient, mehrere weitere größenstabil. Es erfolgte eine erweiterte Hemihepatektomie rechts mit histologischem Nachweis von sowohl Metastasen als auch Sarkoidose-Herden. Der zu diesem Zeitpunkt tumorfreie Patient wurde in die engmaschige Nachsorge entlassen, die sich im weiteren Verlauf (13 Monate) bildmorphologisch ohne Rezidivhinweis zeigte. Diskussion Das gleichzeitige Auftreten von metastasierten Tumorerkrankungen und Sarkoidoseherden führt zu einem diagnostischen Dilemma, da die Manifestationen bildmorphologisch kaum unterschieden werden können. Dieser Fallbereich zeigt, dass eine umfassende histologische Aufarbeitung der unterschiedlichen betroffenen Organe mit konsekutiven Resektionen schlussendlich zu einer Tumorfreiheit des Patienten führen kann.