Germline variant testing in serrated polyposis syndrome.

BACKGROUND AND AIM: Serrated polyposis syndrome (SPS) is now known to be the commonest polyposis syndrome. Previous analyses for germline variants have shown no consistent positive findings. To exclude other polyposis syndromes, 2019 British Society of Gastroenterology (BSG) guidelines advise gene panel testing if the patient is under 50 years, there are multiple affected individuals within a family, or there is dysplasia within any of the polyps. METHODS: A database of SPS patients was established at the Oxford University Hospitals NHS Foundation Trust. Patients were referred for genetic assessment based on personal and family history and patient preference. The majority were tested for a hereditary colorectal cancer panel including MUTYH, APC, PTEN, SMAD4, BMPR1A, STK11, NTLH1, POLD1, POLE, GREM1 (40-kb duplication), PMS2, and Lynch syndrome mismatch repair genes. RESULTS: One hundred and seventy-three patients were diagnosed with SPS based on World Health Organization 2019 criteria between February 2010 and December 2020. The mean age of diagnosis was 54.2 ± 16.8 years. Seventy-three patients underwent genetic testing and 15/73 (20.5%) were found to have germline variants, of which 7/73 (9.6%) had a pathogenic variant (MUTYH n = 2, SMAD4 n = 1, CHEK2 n = 2, POLD1 n = 1, and RNF43 n = 1). Only 60% (9/15) of these patients would have been recommended for gene panel testing according to current BSG guidelines. CONCLUSIONS: A total of 20.5% of SPS patients tested were affected by heterozygous germline variants, including previously unreported associations with CHEK2 and POLD1. This led to a change in management in seven patients (9.6%). Current recommendations may miss SPS associated with germline variants, which is more common than previously anticipated.

Bone Morphogenetic Protein Pathway Antagonism by Grem1 Regulates Epithelial Cell Fate in Intestinal Regeneration.

BACKGROUND & AIMS: In homeostasis, intestinal cell fate is controlled by balanced gradients of morphogen signaling. The bone morphogenetic protein (BMP) pathway has a physiological, prodifferentiation role, predominantly inferred through previous experimental pathway inactivation. Intestinal regeneration is underpinned by dedifferentiation and cell plasticity, but the signaling pathways that regulate this adaptive reprogramming are not well understood. We assessed the BMP signaling landscape and investigated the impact and therapeutic potential of pathway manipulation in homeostasis and regeneration. METHODS: A novel mouse model was generated to assess the effect of the autocrine Bmp4 ligand on individual secretory cell fate. We spatiotemporally mapped BMP signaling in mouse and human regenerating intestine. Transgenic models were used to explore the functional impact of pathway manipulation on stem cell fate and intestinal regeneration. RESULTS: In homeostasis, ligand exposure reduced proliferation, expedited terminal differentiation, abrogated secretory cell survival, and prevented dedifferentiation. After ulceration, physiological attenuation of BMP signaling arose through upregulation of the secreted antagonist Grem1 from topographically distinct populations of fibroblasts. Concomitant expression supported functional compensation after Grem1 deletion from tissue-resident cells. BMP pathway manipulation showed that antagonist-mediated BMP attenuation was obligatory but functionally submaximal, because regeneration was impaired or enhanced by epithelial overexpression of Bmp4 or Grem1, respectively. Mechanistically, Bmp4 abrogated regenerative stem cell reprogramming despite a convergent impact of YAP/TAZ on cell fate in remodeled wounds. CONCLUSIONS: BMP signaling prevents epithelial dedifferentiation, and pathway attenuation through stromal Grem1 upregulation was required for adaptive reprogramming in intestinal regeneration. This intercompartmental antagonism was functionally submaximal, raising the possibility of therapeutic pathway manipulation in inflammatory bowel disease.

Interfering with leukocyte trafficking in Crohn's disease.

The discovery of gut-specific leukocytes and the ability to modulate their function has been a groundbreaking development in the treatment of inflammatory bowel disease. Drugs target the interaction between lymphocytes and endothelial cells via integrins and their ligand cellular adhesion molecules. Safety, efficacy and sustainability of effect are key to this drug class, notwithstanding the association of natalizumab with fatal polyoma virus infection. Vedolizumab (2014) now licensed for the treatment of Crohn's disease around the world provides gut-specific immunosuppression. Targets for modulators of leukocyte trafficking include (examples in brackets) ICAM-1 (alicaforsen, efalizumab); MAdCAM-1 (PF-00547 659); α4 and related receptors (abrilumab, etrolizumab, natalizumab, vedolizumab); chemokine receptor CCR9 (vercirnon); and sphingosine 1-phosphate receptors (etrasimod, fingolimod, ozanimod). Oral and subcutaneous therapies are in development. The safety, efficacy and practice points of licensed drugs are discussed, in addition to initial results from therapeutic trials.

Evolutionary history of human colitis-associated colorectal cancer.

OBJECTIVE: IBD confers an increased lifetime risk of developing colorectal cancer (CRC), and colitis-associated CRC (CA-CRC) is molecularly distinct from sporadic CRC (S-CRC). Here we have dissected the evolutionary history of CA-CRC using multiregion sequencing. DESIGN: Exome sequencing was performed on fresh-frozen multiple regions of carcinoma, adjacent non-cancerous mucosa and blood from 12 patients with CA-CRC (n=55 exomes), and key variants were validated with orthogonal methods. Genome-wide copy number profiling was performed using single nucleotide polymorphism arrays and low-pass whole genome sequencing on archival non-dysplastic mucosa (n=9), low-grade dysplasia (LGD; n=30), high-grade dysplasia (HGD; n=13), mixed LGD/HGD (n=7) and CA-CRC (n=19). Phylogenetic trees were reconstructed, and evolutionary analysis used to reveal the temporal sequence of events leading to CA-CRC. RESULTS: 10/12 tumours were microsatellite stable with a median mutation burden of 3.0 single nucleotide alterations (SNA) per Mb, ~20% higher than S-CRC (2.5 SNAs/Mb), and consistent with elevated ageing-associated mutational processes. Non-dysplastic mucosa had considerable mutation burden (median 47 SNAs), including mutations shared with the neighbouring CA-CRC, indicating a precancer mutational field. CA-CRCs were often near triploid (40%) or near tetraploid (20%) and phylogenetic analysis revealed that copy number alterations (CNAs) began to accrue in non-dysplastic bowel, but the LGD/HGD transition often involved a punctuated 'catastrophic' CNA increase. CONCLUSIONS: Evolutionary genomic analysis revealed precancer clones bearing extensive SNAs and CNAs, with progression to cancer involving a dramatic accrual of CNAs at HGD. Detection of the cancerised field is an encouraging prospect for surveillance, but punctuated evolution may limit the window for early detection.

Serum- and Glucocorticoid-induced Kinase Sgk1 Directly Promotes the Differentiation of Colorectal Cancer Cells and Restrains Metastasis.

PURPOSE: The molecular events that determine intestinal cell differentiation are poorly understood and it is unclear whether it is primarily a passive event or an active process. It is clinically important to gain a greater understanding of the process, because in colorectal cancer, the degree of differentiation of a tumor is associated with patient survival. SGK1 has previously been identified as a gene that is principally expressed in differentiated intestinal cells. In colorectal cancer, there is marked downregulation of SGK1 compared with normal tissue.Experimental Design: An inducible SGK1 viral overexpression system was utilized to induce reexpression of SGK1 in colorectal cancer cell lines. Transcriptomic and phenotypic analyses of these colorectal cancer lines was performed and validation in mouse and human cohorts was performed. RESULTS: We demonstrate that SGK1 is upregulated in response to, and an important controller of, intestinal cell differentiation. Reexpression of SGK1 in colorectal cancer cell lines results in features of differentiation, decreased migration rates, and inhibition of metastasis in an orthotopic xenograft model. These effects may be mediated, in part, by SGK1-induced PKP3 expression and increased degradation of MYC. CONCLUSIONS: Our results suggest that SGK1 is an important mediator of differentiation of colorectal cells and may inhibit colorectal cancer metastasis.

The evolutionary landscape of colorectal tumorigenesis.

The evolutionary events that cause colorectal adenomas (benign) to progress to carcinomas (malignant) remain largely undetermined. Using multi-region genome and exome sequencing of 24 benign and malignant colorectal tumours, we investigate the evolutionary fitness landscape occupied by these neoplasms. Unlike carcinomas, advanced adenomas frequently harbour sub-clonal driver mutations-considered to be functionally important in the carcinogenic process-that have not swept to fixation, and have relatively high genetic heterogeneity. Carcinomas are distinguished from adenomas by widespread aneusomies that are usually clonal and often accrue in a 'punctuated' fashion. We conclude that adenomas evolve across an undulating fitness landscape, whereas carcinomas occupy a sharper fitness peak, probably owing to stabilizing selection.

Trends in UK endoscopy training in the BSG trainees' national survey and strategic planning for the future.

BACKGROUND: Improvements in the structure of endoscopy training programmes resulting in certification from the Joint Advisory Group in Gastrointestinal Endoscopy have been acknowledged to improve training experience and contribute to enhanced colonoscopy performance. OBJECTIVES: The 2016 British Society of Gastroenterology trainees' survey of endoscopy training explored the delivery of endoscopy training - access to lists; level of supervision and trainee's progression through diagnostic, core therapy and subspecialty training. In addition, the barriers to endoscopy training progress and utility of training tools were examined. METHODS: A web-based survey (Survey Monkey) was sent to all higher specialty gastroenterology trainees. RESULTS: There were some improvements in relation to earlier surveys; 85% of trainees were satisfied with the level of supervision of their training. But there were ongoing problems; 12.5% of trainees had no access to a regular training list, and 53% of final year trainees had yet to achieve full certification in colonoscopy. 9% of final year trainees did not feel confident in endoscopic management of upper GI bleeds. CONCLUSIONS: The survey findings provide a challenge to those agencies tasked with supporting endoscopy training in the UK. Acknowledging the findings of the survey, the paper provides a strategic response with reference to increased service pressures, reduced overall training time in specialty training programmes and the requirement to support general medical and surgical on-call commitments. It describes the steps required to improve training on the ground: delivering additional training tools and learning resources, and introducing certification standards for therapeutic modalities in parallel with goals for improving the quality of endoscopy in the UK.

The metaplastic mosaic of Barrett's oesophagus.

Barrett's oesophagus surveillance biopsies represent a significant share of the daily workload for a busy histopathology department. Given the emphasis on endoscopic detection and dysplasia grading, it is easy to forget that the benefits of these screening programs remain unproven. The majority of patients are at low risk of progression to oesophageal adenocarcinoma, and periodic surveillance of these patients is burdensome and costly. Here, we investigate the parallels in the development of Barrett's oesophagus and other scenarios of wound healing in the intestine. There is now increased recognition of the full range of glandular phenotypes that can be found in patients' surveillance biopsies, and emerging evidence suggests parallel pathways to oesophageal adenocarcinoma. Greater understanding of the conditions that favour progression to cancer in the distal oesophagus will allow us to focus resources on patients at increased risk.

Bone morphogenetic protein and Notch signalling crosstalk in poor-prognosis, mesenchymal-subtype colorectal cancer.

The functional role of bone morphogenetic protein (BMP) signalling in colorectal cancer (CRC) is poorly defined, with contradictory results in cancer cell line models reflecting the inherent difficulties of assessing a signalling pathway that is context-dependent and subject to genetic constraints. By assessing the transcriptional response of a diploid human colonic epithelial cell line to BMP ligand stimulation, we generated a prognostic BMP signalling signature, which was applied to multiple CRC datasets to investigate BMP heterogeneity across CRC molecular subtypes. We linked BMP and Notch signalling pathway activity and function in human colonic epithelial cells, and normal and neoplastic tissue. BMP induced Notch through a γ-secretase-independent interaction, regulated by the SMAD proteins. In homeostasis, BMP/Notch co-localization was restricted to cells at the top of the intestinal crypt, with more widespread interaction in some human CRC samples. BMP signalling was downregulated in the majority of CRCs, but was conserved specifically in mesenchymal-subtype tumours, where it interacts with Notch to induce an epithelial-mesenchymal transition (EMT) phenotype. In intestinal homeostasis, BMP-Notch pathway crosstalk is restricted to differentiating cells through stringent pathway segregation. Conserved BMP activity and loss of signalling stringency in mesenchymal-subtype tumours promotes a synergistic BMP-Notch interaction, and this correlates with poor patient prognosis. BMP signalling heterogeneity across CRC subtypes and cell lines can account for previous experimental contradictions. Crosstalk between the BMP and Notch pathways will render mesenchymal-subtype CRC insensitive to γ-secretase inhibition unless BMP activation is concomitantly addressed. © 2017 The Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

E-cadherin can limit the transforming properties of activating ß-catenin mutations.

Wnt pathway deregulation is a common characteristic of many cancers. Only colorectal cancer predominantly harbours mutations in APC, whereas other cancer types (hepatocellular carcinoma, solid pseudopapillary tumours of the pancreas) have activating mutations in ß-catenin (CTNNB1). We have compared the dynamics and the potency of ß-catenin mutations in vivo. Within the murine small intestine (SI), an activating mutation of ß-catenin took much longer to achieve Wnt deregulation and acquire a crypt-progenitor cell (CPC) phenotype than Apc or Gsk3 loss. Within the colon, a single activating mutation of ß-catenin was unable to drive Wnt deregulation or induce the CPC phenotype. This ability of ß-catenin mutation to differentially transform the SI versus the colon correlated with higher expression of E-cadherin and a higher number of E-cadherin:ß-catenin complexes at the membrane. Reduction in E-cadherin synergised with an activating mutation of ß-catenin resulting in a rapid CPC phenotype within the SI and colon. Thus, there is a threshold of ß-catenin that is required to drive transformation, and E-cadherin can act as a buffer to sequester mutated ß-catenin.

Microenvironmental control of stem cell fate in intestinal homeostasis and disease.

The conventional model of intestinal epithelial architecture describes a unidirectional tissue organizational hierarchy with stem cells situated at the crypt base and daughter cells proliferating and terminally differentiating as they progress along the vertical (crypt-luminal) axis. In this model, the fate of a cell that has left the niche is determined and its lifespan limited. Evidence is accumulating to suggest that stem cell control and daughter cell fate determination is not solely an intrinsic, cell autonomous property but is heavily influenced by the microenvironment including paracrine, mesenchymal, and endogenous epithelial morphogen gradients. Recent research suggests that in intestinal homeostasis, stem cells transit reversibly between states of variable competence in the niche. Furthermore, selective pressures that disrupt the homeostatic balance, such as intestinal inflammation or morphogen dysregulation, can cause committed progenitor cells and even some differentiated cells to regain stem cell properties. Importantly, it has been recently shown that this disruption of cell fate determination can lead to somatic mutation and neoplastic transformation of cells situated outside the crypt base stem cell niche. This paper reviews the exciting developments in the study of stem cell dynamics in homeostasis, intestinal regeneration, and carcinogenesis, and explores the implications for human disease and cancer therapies.

A liver lesion in primary sclerosing cholangitis.

Primary sclerosing cholangitis is associated with an increased risk of cholangiocarcinoma; appropriate surveillance should be undertaken for this. Our case illustrates an unexpected liver lesion in such a patient, which would not have been detected with imaging alone. In suspected cancer, if a patient is not a candidate for liver resection, liver biopsy should be considered in case there is a treatment option for an alternative cause of the liver lesion. This is a careful decision to be made due to the risk of tumour seeding compromising cure and needs to be discussed via the hepatobiliary multidisciplinary team.

Gastric amyloidosis presenting with severe weight loss.

A previously well 59-year-old lady with 70 kg weight loss and chronic diarrhoea over a 28-month period presented following collapse and subsequent diagnosis of pulmonary embolism. Previous investigations for this weight loss included normal gastroscopy and colonoscopy, CT and MRI abdomen, barium follow through and octreotide scan. She underwent echocardiogram which revealed myocardial speckling and asymmetrical left ventricular hypertrophy. Repeat oesophago-gastro-duodenoscopy and colonoscopy for rectal bleeding was performed. Colonoscopy revealed intramucosal haematomas and electron microscopy (EM) of the gastric biopsies confirmed amyloid deposition. Amyloidosis of the gastrointestinal (GI) tract and heart were confirmed on serum amyloid protein scan. GI amyloid is rare and symptoms include weight loss, diarrhoea, GI bleeding and gut dysmotility.1 GI amyloidosis should be considered as a diagnosis and sought when other common causes have been excluded. The greatest yield is by Congo red staining or EM of rectal specimens.