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ObjectiveDesmoplasia and hypovascularity are thought to impede drug delivery in pancreatic ductal adenocarcinoma (PDAC). However, stromal depletion approaches have failed to show clinical responses in patients. Here, we aimed to revisit the role of the tumour microenvironment as a physical barrier for gemcitabine delivery.DesignGemcitabine metabolites were analysed in LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx-1-Cre(KPC) murine tumours and matched liver metastases, primary tumour cell lines, cancer-associated fibroblasts (CAFs) and pancreatic stellate cells (PSCs) by liquid chromatography-mass spectrometry/mass spectrometry. Functional and preclinical experiments, as well as expression analysis of stromal markers and gemcitabine metabolism pathways were performed in murine and human specimen to investigate the preclinical implications and the mechanism of gemcitabine accumulation.ResultsGemcitabine accumulation was significantly enhanced in fibroblast-rich tumours compared with liver metastases and normal liver. In vitro, significantly increased concentrations of activated 2′,2′-difluorodeoxycytidine-5′-triphosphate (dFdCTP) and greatly reduced amounts of the inactive gemcitabine metabolite 2′,2′-difluorodeoxyuridine were detected in PSCs and CAFs. Mechanistically, key metabolic enzymes involved in gemcitabine inactivation such as hydrolytic cytosolic 5′-nucleotidases (Nt5c1A, Nt5c3) were expressed at low levels in CAFs in vitro and in vivo, and recombinant expression of Nt5c1A resulted in decreased intracellular dFdCTP concentrations in vitro. Moreover, gemcitabine treatment in KPC mice reduced the number of liver metastases by >50%.ConclusionsOur findings suggest that fibroblast drug scavenging may contribute to the clinical failure of gemcitabine in desmoplastic PDAC. Metabolic targeting of CAFs may thus be a promising strategy to enhance the antiproliferative effects of gemcitabine.

Collagenous colitis is a rare cause of chronic watery diarrhea. In this condition, endoscopic findings are usually normal. Currently, the diagnosis relies on the histological presence of thick subepithelial bands of collagen deposits and an inflammatory infiltrate within the mucosa. However, these subepithelial bands may be developed only focally and may be too subtle to allow a definitive diagnosis upon routine hematoxylin and eosin (HE) and van Gieson's stainings. Recently, we and others were able to show a prominent staining of tenascin and type-VI collagen in the subepithelial band-like structures. In this study, we tested the diagnostic value of tenascin staining and type-VI collagen immunolocalization for the identification of collagenous colitis and compared it with conventional histology and histochemical detection of collagens. The analysis was based on 434 biopsy specimens of collagenous colitis, other forms of colitis, and normal mucosa. We were able to show that the immunohistochemical detection of increased amounts of tenascin, selectively in the subepithelial zone, is a specific test for collagenous colitis, with a sensitivity superior to conventional histological and histochemical detection, especially in minimal collagenous colitis (P<0.001). Of note, tenascin staining also allows the diagnosis of collagenous colitis in biopsies obtained only from the rectum and sigmoid colon, thus avoiding the need for colonoscopic investigations. Tenascin immunostaining is a simple and safe tool to complement conventional histological diagnostics in clinically and histopathologically unclear cases of diarrhea.

A 34-year-old woman with signs and symptoms of an acute abdomen was found to have a hepatic cyst on NMR- and CT-scan. With the tentative diagnosis of a liver hematoma, a rtght hemihepatectomy was performed. Histologically, an endometrial cyst of the liver was found.