Long-term outcomes of pouch surveillance and risk of neoplasia in familial adenomatous polyposis.

BACKGROUND: Long-term pouch surveillance outcomes for familial adenomatous polyposis (FAP) are unknown. We aimed to quantify surveillance outcomes and to determine which of selected possible predictive factors are associated with pouch dysplasia. METHODS: Retrospective analysis of collected data on 249 patients was performed, analyzing potential risk factors for the development of adenomas or advanced lesions ( ≥ 10 mm/high grade dysplasia (HGD)/cancer) in the pouch body and cuff using Cox proportional hazards models. Kaplan-Meier analyses included landmark time-point analyses at 10 years after surgery to predict the future risk of advanced lesions. RESULTS: Of 249 patients, 76 % developed at least one pouch body adenoma, with 16 % developing an advanced pouch body lesion; 18 % developed an advanced cuff lesion. Kaplan-Meier analysis showed a 10-year lag before most advanced lesions developed; cumulative incidence of 2.8 % and 6.4 % at 10 years in the pouch body and cuff, respectively. Landmark analysis suggested the presence of adenomas prior to the 10-year point was associated with subsequent development of advanced lesions in the pouch body (hazard ratio [HR] 4.8, 95 %CI 1.6-14.1; P = 0.004) and cuff (HR 6.8, 95 %CI 2.5-18.3; P < 0.001). There were two HGD and four cancer cases in the cuff and one pouch body cancer; all cases of cancer/HGD that had prior surveillance were preceded by ≥ 10-mm adenomas. CONCLUSIONS: Pouch adenoma progression is slow and most advanced lesions occur after 10 years. HGD and cancer were rare events. Pouch phenotype in the first decade is associated with the future risk of developing advanced lesions and may guide personalized surveillance beyond 10 years.

Altered immunity to microbiota, B cell activation and depleted γδ/resident memory T cells in colorectal cancer.

The role of microbiota:immune system dysregulation in the etiology of colorectal cancer (CRC) is poorly understood. CRC develops in gut epithelium, accompanied by low level inflammatory signaling, intestinal microbial dysbiosis and immune dysfunction. We examined populations of intraepithelial lymphocytes in non-affected colonic mucosa of CRC and healthy donors and circulating immune memory to commensal bacterial species and yeasts. γδ T cells and resident memory T cells, populations with a regulatory CD39-expressing phenotype, were found at lower frequencies in the colonic tissue of CRC donors compared to healthy controls. Patterns of T cell proliferative responses to a panel of commensal bacteria were distinct in CRC, while B cell memory responses to several bacteria/yeast were significantly increased, accompanied by increased proportions of effector memory B cells, transitional B cells and plasmablasts in blood. IgA responses to mucosal microbes were unchanged. Our data describe a novel immune signature with similarities to and differences from that of inflammatory bowel disease. They implicate B cell dysregulation as a potential contributor to parainflammation and identify pathways of weakened barrier function and tumor surveillance in CRC-susceptible individuals.

Altered Mucosal Immune-Microbiota Interactions in Familial Adenomatous Polyposis.

INTRODUCTION: Familial adenomatous polyposis (FAP) is a condition caused by a constitutional pathogenic variant of the adenomatous polyposis coli gene that results in intestinal adenoma formation and colorectal cancer, necessitating pre-emptive colectomy. We sought to examine interaction between the mucosal immune system and commensal bacteria in FAP to test for immune dysfunction that might accelerate tumorigenesis. METHODS: Colonic biopsies were obtained from macroscopically normal mucosal tissue from 14 healthy donors and 13 patients with FAP during endoscopy or from surgical specimens. Intraepithelial and lamina propria lymphocytes were phenotyped. Intraepithelial microbes were labeled with anti-IgA/IgG and analyzed by flow cytometry. RESULTS: Proportions of resident memory CD103-expressing CD8 + and γδ T-cell receptor + intraepithelial lymphocytes were dramatically reduced in both the left and right colon of patients with FAP compared with healthy controls. In lamina propria, T cells expressed less CD103, and CD4 + CD103 + cells expressed less CD73 ectonucleotidase. IgA coating of epithelia-associated bacteria, IgA + peripheral B cells, and CD4 T-cell memory responses to commensal bacteria were increased in FAP. DISCUSSION: Loss of resident memory T cells and γδ T cells in mucosal tissue of patients with FAP accompanies intestinal microbial dysbiosis previously reported in this precancerous state and suggests impaired cellular immunity and tumor surveillance. This may lead to barrier dysfunction, possible loss of regulatory T-cell function, and excess IgA antibody secretion. Our data are the first to implicate mucosal immune dysfunction as a contributing factor in this genetically driven disease and identify potentially critical pathways in the etiology of CRC.

Regular endoscopic surveillance and polypectomy is effective in managing rectal adenoma progression following colectomy and ileorectal anastomosis in patients with familial adenomatous polyposis.

AIM: Total colectomy with ileorectal anastomosis (TC-IRA) is a surgical option for patients with familial adenomatous polyposis (FAP). Regular endoscopic surveillance of the rectum is recommended to prevent rectal cancer. We aimed to document polyp progression in the rectum following TC-IRA and evaluate the role of polypectomy during surveillance. METHOD: Patients with FAP who underwent TC-IRA between 1990 and 2017 were identified. Demographic, endoscopic and genetic data were retrieved. Cumulative rectal adenoma (polyp) counts were obtained, whilst accounting for any polypectomies during the study period. The rate of polyp progression and factors influencing secondary proctectomy were evaluated. RESULTS: One hundred and ninety-nine patients fulfilled our inclusion criteria, of which 44% were male. The median age at colectomy was 19 (range 11-70) years and median preoperative rectal polyp count was 7 (range 0-50). All patients had an APC pathogenic variant, of which 151 (79%) were 5' of the mutation cluster region (MCR), 19 (10%) in the MCR, six (3%) were 3' of the MCR and 15 (8%) had a gross deletion. After a median follow-up of 8.6 (range1-27) years and a median of 11 (range 2-37) flexible sigmoidoscopies per patient, the median rate of polyp progression was 5.5 polyps/year (range 0-70.2). There was no evidence of polyp regression. Eight (4%) patients underwent secondary proctectomy for neoplasia, of which one (0.5%) had rectal adenocarcinoma. A total of 13,527 polyps were removed, a median of 35 polyps/patient (range 0-829). The rate of polyp progression was not significantly associated with genotypic or phenotypic factors. CONCLUSION: Progression of rectal adenoma burden following TC-IRA appears to be slow and dependent on the length of follow-up. In the modern era of stringent endoscopic surveillance and therapeutic procedures such as cold snare polypectomy, the rate of secondary proctectomy and the risk of rectal cancer after TC-IRA are very low. These findings are important when counselling patients with regard to the choice of surgery for FAP and implementing endoscopic surveillance.

Bacteroides thetaiotaomicron-derived outer membrane vesicles promote regulatory dendritic cell responses in health but not in inflammatory bowel disease.

BACKGROUND: Bacteroides thetaiotaomicron (Bt) is a prominent member of the human intestinal microbiota that, like all gram-negative bacteria, naturally generates nanosized outer membrane vesicles (OMVs) which bud off from the cell surface. Importantly, OMVs can cross the intestinal epithelial barrier to mediate microbe-host cell crosstalk involving both epithelial and immune cells to help maintain intestinal homeostasis. Here, we have examined the interaction between Bt OMVs and blood or colonic mucosa-derived dendritic cells (DC) from healthy individuals and patients with Crohn's disease (CD) or ulcerative colitis (UC). RESULTS: In healthy individuals, Bt OMVs stimulated significant (p < 0.05) IL-10 expression by colonic DC, whereas in peripheral blood-derived DC they also stimulated significant (p < 0.001 and p < 0.01, respectively) expression of IL-6 and the activation marker CD80. Conversely, in UC Bt OMVs were unable to elicit IL-10 expression by colonic DC. There were also reduced numbers of CD103+ DC in the colon of both UC and CD patients compared to controls, supporting a loss of regulatory DC in both diseases. Furthermore, in CD and UC, Bt OMVs elicited a significantly lower proportion of DC which expressed IL-10 (p < 0.01 and p < 0.001, respectively) in blood compared to controls. These alterations in DC responses to Bt OMVs were seen in patients with inactive disease, and thus are indicative of intrinsic defects in immune responses to this commensal in inflammatory bowel disease (IBD). CONCLUSIONS: Overall, our findings suggest a key role for OMVs generated by the commensal gut bacterium Bt in directing a balanced immune response to constituents of the microbiota locally and systemically during health which is altered in IBD patients. Video Abstract.

Deficient Resident Memory T Cell and CD8 T Cell Response to Commensals in Inflammatory Bowel Disease.

BACKGROUND AND AIMS: The intestinal microbiota is closely associated with resident memory lymphocytes in mucosal tissue. We sought to understand how acquired cellular and humoral immunity to the microbiota differ in health versus inflammatory bowel disease [IBD]. METHODS: Resident memory T cells [Trm] in colonic biopsies and local antibody responses to intraepithelial microbes were analysed. Systemic antigen-specific immune T and B cell memory to a panel of commensal microbes was assessed. RESULTS: Systemically, healthy blood showed CD4 and occasional CD8 memory T cell responses to selected intestinal bacteria, but few memory B cell responses. In IBD, CD8 memory T cell responses decreased although B cell responses and circulating plasmablasts increased. Possibly secondary to loss of systemic CD8 T cell responses in IBD, dramatically reduced numbers of mucosal CD8+ Trm and γδ T cells were observed. IgA responses to intraepithelial bacteria were increased. Colonic Trm expressed CD39 and CD73 ectonucleotidases, characteristic of regulatory T cells. Cytokines/factors required for Trm differentiation were identified, and in vitro-generated Trm expressed regulatory T cell function via CD39. Cognate interaction between T cells and dendritic cells induced T-bet expression in dendritic cells, a key mechanism in regulating cell-mediated mucosal responses. CONCLUSIONS: A previously unrecognised imbalance exists between cellular and humoral immunity to the microbiota in IBD, with loss of mucosal T cell-mediated barrier immunity and uncontrolled antibody responses. Regulatory function of Trm may explain their association with intestinal health. Promoting Trm and their interaction with dendritic cells, rather than immunosuppression, may reinforce tissue immunity, improve barrier function, and prevent B cell dysfunction in microbiota-associated disease and IBD aetiology.

Chemokine (C-C Motif) Receptor 2 Mediates Dendritic Cell Recruitment to the Human Colon but Is Not Responsible for Differences Observed in Dendritic Cell Subsets, Phenotype, and Function Between the Proximal and Distal Colon.

BACKGROUND & AIMS: Most knowledge about gastrointestinal (GI)-tract dendritic cells (DC) relies on murine studies where CD103+ DC specialize in generating immune tolerance with the functionality of CD11b+/- subsets being unclear. Information about human GI-DC is scarce, especially regarding regional specifications. Here, we characterized human DC properties throughout the human colon. METHODS: Paired proximal (right/ascending) and distal (left/descending) human colonic biopsies from 95 healthy subjects were taken; DC were assessed by flow cytometry and microbiota composition assessed by 16S rRNA gene sequencing. RESULTS: Colonic DC identified were myeloid (mDC, CD11c+CD123-) and further divided based on CD103 and SIRPα (human analog of murine CD11b) expression. CD103-SIRPα+ DC were the major population and with CD103+SIRPα+ DC were CD1c+ILT3+CCR2+ (although CCR2 was not expressed on all CD103+SIRPα+ DC). CD103+SIRPα- DC constituted a minor subset that were CD141+ILT3-CCR2-. Proximal colon samples had higher total DC counts and fewer CD103+SIRPα+ cells. Proximal colon DC were more mature than distal DC with higher stimulatory capacity for CD4+CD45RA+ T-cells. However, DC and DC-invoked T-cell expression of mucosal homing markers (ß7, CCR9) was lower for proximal DC. CCR2 was expressed on circulating CD1c+, but not CD141+ mDC, and mediated DC recruitment by colonic culture supernatants in transwell assays. Proximal colon DC produced higher levels of cytokines. Mucosal microbiota profiling showed a lower microbiota load in the proximal colon, but with no differences in microbiota composition between compartments. CONCLUSIONS: Proximal colonic DC subsets differ from those in distal colon and are more mature. Targeted immunotherapy using DC in T-cell mediated GI tract inflammation may therefore need to reflect this immune compartmentalization.

Compartment-specific immunity in the human gut: properties and functions of dendritic cells in the colon versus the ileum.

OBJECTIVE: Dendritic cells (DC) mediate intestinal immune tolerance. Despite striking differences between the colon and the ileum both in function and bacterial load, few studies distinguish between properties of immune cells in these compartments. Furthermore, information of gut DC in humans is scarce. We aimed to characterise human colonic versus ileal DC. DESIGN: Human DC from paired colonic and ileal samples were characterised by flow cytometry, electron microscopy or used to stimulate T cell responses in a mixed leucocyte reaction. RESULTS: A lower proportion of colonic DC produced pro-inflammatory cytokines (tumour necrosis factor-α and interleukin (IL)-1ß) compared with their ileal counterparts and exhibited an enhanced ability to generate CD4(+)FoxP3(+)IL-10(+) (regulatory) T cells. There were enhanced proportions of CD103(+)Sirpα(-) DC in the colon, with increased proportions of CD103(+)Sirpα(+) DC in the ileum. A greater proportion of colonic DC subsets analysed expressed the lymph-node-homing marker CCR7, alongside enhanced endocytic capacity, which was most striking in CD103(+)Sirpα(+) DC. Expression of the inhibitory receptor ILT3 was enhanced on colonic DC. Interestingly, endocytic capacity was associated with CD103(+) DC, in particular CD103(+)Sirpα(+) DC. However, expression of ILT3 was associated with CD103(-) DC. Colonic and ileal DC differentially expressed skin-homing marker CCR4 and small-bowel-homing marker CCR9, respectively, and this corresponded to their ability to imprint these homing markers on T cells. CONCLUSIONS: The regulatory properties of colonic DC may represent an evolutionary adaptation to the greater bacterial load in the colon. The colon and the ileum should be regarded as separate entities, each comprising DC with distinct roles in mucosal immunity and imprinting.

Altered human gut dendritic cell properties in ulcerative colitis are reversed by Lactobacillus plantarum extracellular encrypted peptide STp.

SCOPE: The human/microbiota cross-talk is partially mediated by bacteria-derived peptides like Serine-Threonine peptide (STp), which is resistant to gut proteolysis, is found in the human healthy colon and induces regulatory properties on gut dendritic cells (DCs); here we characterized human gut DC in ulcerative colitis (UC) patients and studied the effect of STp on their properties. METHODS AND RESULTS: Human colonic DC from healthy controls and UC patients were isolated, conditioned for 24 h +/- STp and characterized by flow cytometry, immunohistochemistry, and electron microscopy. Expression of immature DC markers DC-SIGN and ILT3, and Toll-like receptors were increased on gut UC-DC. Langerin (involved in phagocytosis), lymph node homing marker CCR7, and activation markers CD40/CD80/CD86 were decreased in UC. Gut DC had restricted stimulatory capacity for T-cells in UC. Conditioning of DC with STp in vitro reduced Toll-like receptor expression, increased CD40 and CD80 expression, and restored their stimulatory capacity. CONCLUSION: Colonic DCs display an abnormal immature phenotype in UC, which was partially restored following STp treatment. Bacteria-derived metabolites, like STp, seem to have a role in gut homeostasis that is missing in UC so they might lead a new era of probiotic products setting the basis for nondrug dietary therapy in inflammatory bowel disease.

Validation of a novel method for assessing competency in polypectomy.

BACKGROUND: There is a gap in the formal assessment of technical skills in polypectomy that is now considered an integral part of colonoscopy. Polypectomy has been shown to reduce the incidence of colorectal cancer but does have associated complications. Polypectomy competency assessment should arguably be a part of the certification process for all endoscopists. A polypectomy competency assessment tool (Direct Observation of Polypectomy Skills [DOPyS]) has been developed and its reliability examined. This study examined the ability of the DOPyS to reliably distinguish between endoscopists with different levels of experience, ie, its construct validity. OBJECTIVE: To determine the construct validity of the DOPyS. DESIGN: Videos of 32 polypectomies (endoscopic view only) were collected from 2 expert (> 1000 colonoscopies) endoscopists (17 polyps) and 6 intermediate-level (100-500 colonoscopies) endoscopists (15 polyps). The videos were edited to include only the entire polypectomy procedure, arranged in random order, and assessed blindly by 4 experienced endoscopists, only 2 of whom were familiar with polypectomy assessment by using the DOPyS before scoring. The differences in overall competency scores (range 1-4; competency, scores ≥ 3) for the expert and intermediate groups were compared by using the Fisher exact test. SETTING: Single center. RESULTS: The analysis suggested that both trained assessors familiar with the DOPyS could reliably distinguish between the expert and intermediate endoscopists (P = .049 and P < .001), with the expert group scoring higher than the intermediate one. For the assessors with no previous experience of the DOPyS, no such difference could be seen (P = .71 and P = .15). LIMITATIONS: Small sample and polyp size. CONCLUSIONS: The results of the analysis suggested that the DOPyS could reliably differentiate between polypectomies performed by endoscopists of different levels of experience, but only if the assessors were trained in the use of the assessment tool. Training is therefore required to use this tool reliably.

Mucosectomy with handsewn anastomosis reduces the risk of adenoma formation in the anorectal segment after restorative proctocolectomy for familial adenomatous polyposis.

OBJECTIVE: The study compared the risk of adenoma or carcinoma formation in the anorectal segment after either mucosectomy with manual anastomosis or stapled ileoanal anastomosis (IAA) following restorative proctocolectomy (RPC) for familial adenomatous polyposis (FAP). BACKGROUND: Few data exist on the risk of adenoma formation after either technique in FAP. METHODS: All endoscopy and histology reports for patients having RPC for FAP attending for annual pouchoscopy from 1978 to 2007 were reviewed. The incidence, timing, and histological characteristics of adenoma or carcinoma formation were recorded. RESULTS: Of the 206 patients, 140 attended for endoscopic follow-up for a median of 10.3 years after RPC. Fifty-two patients developed neoplastic transformation in the anorectal segment, with a cumulative risk at 10 years of 22.6% after mucosectomy with manual anastomosis and 51.1% after stapled IAA (P < 0.001). The median time to first adenoma was longer after mucosectomy with handsewn anastomosis than after stapled IAA (10.1 vs 6.5 years, P < 0.001). On multivariate analysis, stapled IAA (hazard ratio= 3.45, 95% confidence interval = 1.01­4.98) and age at RPC older than 40 years (hazard ratio = 2.20, 95% confidence interval = 1.01­4.89) were significantly associated with increased risk of adenoma formation. Nine patients developed a large (>10 mm) adenoma. One patient (handsewn ileoanal anastomosis) developed adenocarcinoma in the anorectal mucosa at 13 years and required pouch excision. CONCLUSIONS: Adenoma formation in the anorectal mucosa after RPC for FAP is common but carcinoma is rare. The risk is lower after mucosectomy with handsewn anastomosis than after stapled IAA. Regular endoscopic surveillance after either technique is mandatory.

Development and validation of a training module on the use of narrow-band imaging in differentiation of small adenomas from hyperplastic colorectal polyps.

BACKGROUND: Experts are accurate in differentiating small adenomas from hyperplastic polyps at colonoscopy by using narrow-band imaging (NBI). OBJECTIVE: To prospectively evaluate the effectiveness of an NBI training module on individuals with varying colonoscopy experience. DESIGN: Prospective educational evaluation study. SETTING: Academic endoscopy unit. PARTICIPANTS: Twenty-one participants of varying colonoscopy experience (novices, trainees, and experienced gastroenterologists) and 5 experts in NBI. INTERVENTION: Participants completed a computer-based test module consisting of 30 NBI polyp images. No feedback was given. They then completed a computer-based training module on the use of NBI in the differentiation of adenomas and hyperplastic polyps. The test module was then completed a second time. MAIN OUTCOME MEASUREMENTS: Construct validity (the difference in baseline accuracy on the test module between different groups of participants) and content validity (difference in accuracy achieved on the test module before and after training) of the training module. RESULTS: There was a significant difference in the baseline accuracy (P < .001) between experts (0.95; 95% confidence interval [CI], 0.92-0.97), experienced colonoscopists (0.68; 95% CI, 0.68-0.74), trainees (0.75; 95% CI, 0.67-0.82), and novices (0.62; 95% CI, 0.46-0.77). Accuracy increased significantly (P < .001) for all 3 groups after training (novices 0.84; 95% CI, 0.78-0.88, trainees 0.90; 95% CI, 0.84-0.93, and experienced colonoscopists 0.84; 95% CI, 0.76-0.89). After training, the agreement was moderate at least (κ = 0.56 for novices, κ = 0.70 for trainees, and κ = 0.54 for experienced colonoscopists). LIMITATIONS: This study did not assess the accuracy of optical diagnosis in routine clinical practice. CONCLUSION: A short, computer-based training module can improve the diagnostic accuracy and interobserver agreement for the use of NBI to differentiate adenomas from hyperplastic polyps and could be used for the initial training in optical diagnosis.