Clinical outcomes and mechanisms of mesenteric fibrosis in small bowel neuroendocrine tumours

Small intestinal neuroendocrine tumours (SI NETs) are relatively rare, indolent tumours arising from the enterochromaffin cells of the small bowel. They can be associated with the development of fibrosis, most commonly in the heart (termed ‘carcinoid heart disease’) or the mesentery around a metastatic deposit (also known as mesenteric desmoplasia). A concise summary of our current understanding of the pathophysiology of neuroendocrine fibrogenesis is provided in Chapter 1. The development of mesenteric fibrosis can be asymptomatic, but in some patients, it can lead to significant complications, such as bowel obstruction or mesenteric ischaemia. However, the epidemiology and pathophysiology of mesenteric fibrosis have not been sufficiently explored. In addition, there is a lack of clinically useful biomarkers for the detection of image-negative mesenteric desmoplasia. The first aim of our study was to explore different clinical aspects of mesenteric desmoplasia and more specifically the epidemiological characteristics and clinical assessment of mesenteric fibrosis. An additional aim was to delineate further the pathogenesis of this process and evaluate a non-invasive, blood-based biomarker for the early detection of fibrosis. To investigate the clinical and epidemiological aspects of mesenteric desmoplasia, two large-scale retrospective studies were performed which are described in Chapter 2. The first study was a survival analysis of approximately 150 fibrotic SI NETs and the second was a survival analysis of almost 400 metastatic SI NETs investigating the effect of mesenteric fibrosis on prognosis in addition to other epidemiological data. We demonstrated that in a large cohort of almost 400 patients with metastatic small bowel neuroendocrine tumours the prevalence of mesenteric fibrosis was about 35% and that 50% of patients with mesenteric metastases had radiological evidence of desmoplasia. The presence of mesenteric fibrosis was associated with a worse overall survival compared to patients without mesenteric lymphadenopathy by both univariate and multivariate analysis. However, in a retrospective analysis of almost 150 patients with fibrotic small bowel neuroendocrine tumours we did not find a significant difference in overall survival or complications (bowel obstruction, mesenteric ischaemia) among patients with mild, moderate and severe mesenteric desmoplasia (patients were grouped using a radiological scoring system to grade the severity of desmoplasia). We determined that in midgut neuroendocrine tumours with radiological evidence of mesenteric fibrosis advanced age (>65) and elevated urinary 5-hydroxyindoleacetic acid (a product of serotonin metabolism measured in the urine) were independent predictors of survival. In addition, to explore the pathophysiology of mesenteric fibrogenesis, we performed a set of co-culture experiments using the small intestinal NET cell lines KRJ-I and P-STS and the stromal cell line HEK293 and these experiments are described in Chapter 3. This study evaluated the crosstalk between cancer and stromal cells in terms of effects on cell proliferation, metabolism, gene expression (RT2 PCR Profilers and RNA sequencing) and protein/cytokine secretion. A reduction in cell metabolic activity was observed in both KRJ-I and P-STS cells treated with HEK293 conditioned media, with no significant changes in cell proliferation. Furthermore, no significant changes were observed in HEK293 cell proliferation or metabolic activity upon culturing with conditioned media of cancer cells. The RT2 PCR arrays revealed that several genes with key regulatory functions in cancer biology and fibrogenesis were significantly up- or down-regulated in KRJ-I, P-STS and HEK293 cells (fold-change≥2, p<0.05). In addition, RNA sequencing and Ingenuity Pathway Analysis identified multiple pathways that were significantly activated or inhibited (p<0.05, z score ≥ |2|). These signalling pathways have a wide range of biological functions, such as involvement in protein synthesis (e.g. EIF2 pathway) or regulation of cell metabolism and energy production. Several changes in chemokine and growth factor secretion were also observed. A specific pathway that was activated in KRJ-I cells as a result of the paracrine effect - the integrin pathway - was further investigated in human tissue using qPCR, immunohistochemistry and Western blotting. This set of experiments is described in Chapter 4. A total of 34 patients were recruited into this prospective study and the gene/protein expression was evaluated in patients with graded severity of mesenteric fibrosis. The fibrosis grading was established using a complex and thorough assessment of the mesenteric desmoplasia which included a triangulation of different methodologies incorporating surgical, radiological and histological criteria. Using a variety of techniques, we provided evidence that the integrin pathway is activated in the fibrotic mesenteric mass of SI NETs. The detailed analysis of mesenteric desmoplasia (incorporating surgical, radiological and histological parameters), that was used to provide the grading of fibrosis severity, also revealed several cases of image-negative mesenteric fibrosis. This is a new concept, as traditionally the diagnosis of mesenteric fibrosis has been based on imaging studies. Finally, in Chapter 5, we evaluated a novel biomarker – the Fibrosome - that included 5 circulating transcripts from the NETest, which collectively exhibited high performance metrics for the detection of mesenteric fibrosis, even in the case of image-negative mesenteric desmoplasia. In conclusion, this study has provided useful epidemiological data about mesenteric fibrosis and more specifically regarding its prevalence, effect on overall survival and clinical outcomes, and has also provided insight into the assessment of the presence and severity of mesenteric fibrosis, demonstrating for the first time that a radiological evaluation alone is not sufficient. In addition, this is the first study to provide a comprehensive understanding of the bidirectional communication of cancer and stromal cells and we have validated the activation of the integrin pathway in the fibrotic microenvironment of SI NETs (human tissue). Finally, a novel circulating biomarker was developed with promising preliminary results, that warrant further validation in additional independent patient cohorts

What Causes Desmoplastic Reaction in Small Intestinal Neuroendocrine Neoplasms?

PURPOSE OF REVIEW: Mesenteric desmoplasia in small intestinal neuroendocrine neoplasms (SINENs) is associated with increased morbidity and mortality. In this paper, we discuss the development of desmoplasia in SINENs. RECENT FINDINGS: The fibrotic reactions associated with these tumours could be limited to the loco-regional environment of the tumour and/or at distant sites. Mesenteric fibrotic mass forms around a local lymph node. Formation of desmoplasia is mediated by interactions between the neoplastic cells and its microenvironment via number of profibrotic mediators and signalling pathways. Profibrotic molecules that are mainly involved in the desmoplastic reaction include serotonin, TGFβ (transforming growth factor β) and CTGF (connective tissue growth factor), although there is some evidence to suggest that there are a number of other molecules involved in this process. Desmoplasia is a result of autocrine and paracrine effects of multiple molecules and signalling pathways. However, more research is needed to understand these mechanisms and to develop targeted therapy to minimise desmoplasia

Predictive factors of antiproliferative activity of octreotide LAR as first-line therapy for advanced neuroendocrine tumours

background: The antiproliferative activity of octreotide LAR in neuroendocrine tumours (NETs) has been demonstrated by small retrospective studies and confirmed by a prospective phase III trial (PROMID). However, there are limited data about the duration and predictors of response. The aim of our retrospective study was to determine the time to radiological progression (TTRP) of disease and the factors that were associated with better response. methods: A total of 254 treatment naïve patients with advanced NETs and positive somatostatin receptor scintigraphy were included. Mean follow-up period was 42 months. results: The location of primary was in the small bowel in 204, pancreas in 22, lungs in 14, rectum in 7 and unknown in 7 patients. Most tumours were well-differentiated, G1 (58%) and G2 (23%). The majority of patients commenced octreotide LAR due to functional symptoms (57%), radiological progression (10%) or in the presence of asymptomatic and stable disease on the basis of data from the PROMID trial (18.5%). Partial response occurred in 5%. For all patients, the median TTRP was 37 months (95% confidence interval, CI: 32–52 months). There was a statistically significant shorter TTRP in patients with pancreatic tumours, liver metastases and intermediate grade tumours. Extremely raised (>10 times the upper limit of normal) baseline chromogranin A levels were associated with an unfavourable outcome. In contrast, male sex, carcinoid heart disease and initiation of treatment in the presence of stable disease were predictive of a better response. Age, extra-hepatic metastases, presence of mesenteric desmoplasia, previous resection and functional status of the primary tumour did not affect response. conclusions: The duration of the antiproliferative effect of octreotide LAR seems to be longer than previously reported. This study has identified several predictors of response in a large cohort of patients with NETs on somatostatin analogue therapy

Virtual Chromoendoscopy in Capsule Endoscopy: A Narrative Review

The usefulness of virtual chromoendoscopy (VC) in capsule endoscopy (CE) isa controversial issue, with conflicting studies regarding its efficacy. FICE and a blue filter were embedded in the PillCamTM software, with the aim to assist readers in identifying the source of obscure gastrointestinal (GI) bleeding (OGIB), coeliac disease mucosal changes and other small and large bowel lesions, including polyps and tumors. This review aims to summarize the existing evidence on the value of VC in the visualization and identification of different types of pathology. Overall, VC in CE with FICE 1 and 2 can be a useful adjunctive tool and may increase the visibility of pigmented lesions, such as angiectasias and ulcers. However, it does not appear to improve the detection of polyps or tumors. On the other hand, the role of FICE 3 and the blue filter appears to be limited. FICE may also be helpful in differentiating hyperplastic and adenomatous colonic polyps during colon capsule endoscopy, although more evidence is needed

Is Panenteric Pillcam^TM Crohn’s Capsule Endoscopy Ready for Widespread Use? A Narrative Review

Patients diagnosed with Crohn’s disease are increasingly subjected to repeat colonoscopic and radiological examinations to assess the extent of the disease severity and the effects of treatment. PillcamTM Crohn’s video capsule, a modified colon capsule, was developed to generate a minimally invasive mouth to rectum video of the gastrointestinal tract. The capsule provides a wide-angle panoramic mucosal view to assess inflammation, ulceration, stenosis, disease extent, and effect of treatment. This review summarizes the evidence of its utility in both adult and paediatric Crohn’s disease and reviews the scoring systems used to quantify findings. The literature survey indicates that the PillcamTM Crohn’s capsule offers high sensitivity and specificity for the detection of inflammatory lesions and the extent and distribution of disease, and it could be considered a reliable imaging modality in both adults and childhood with Crohn’s disease

Review: Colon Capsule Endoscopy in Inflammatory Bowel Disease

The COVID-19 pandemic has caused considerable disruption in healthcare services and has had a substantial impact on the care of patients with chronic diseases, such as inflammatory bowel disease. Endoscopy services were significantly restricted, resulting in long waiting lists. There has been a growing interest in the use of capsule endoscopy in the diagnostic pathway and management of these patients. This review explores the published literature on the role of colon capsule endoscopy in ulcerative colitis and Crohn&rsquo;s disease as a method for mucosal assessment of extent, severity, and response to treatment. Colon capsule preparation regimens and scoring systems are reported. The studies indicate that, despite inherent limitations of minimally invasive capsule endoscopy, there is increasing evidence to support the use of the second-generation colon capsule in inflammatory bowel disease evaluation, providing an additional pathway to expedite investigation of appropriate patients especially during and after the pandemic