Colorectal goblet cell sialomucin heterogeneity: its relation to malignant disease

Human Intestinal Defensin 5 Ameliorates the Sensitization of Colonic Cancer Cells to 5-Fluorouracil

BACKGROUND AND AIM

The increasing dilemma of multidrug-resistant cancer cells in response to currently available chemotherapeutic drugs and their associated side effect(s), calls for the investigation of alternative anticancer advances and molecules. Therefore, the present study aimed to elucidate the combinatorial potential against colon cancer of human defensin 5 in combination with 5-fluorouracil (5-FU), and against 5-FU resistant colon tumor cells.

METHODS

The in vivo combinatorial potential of HD-5 with 5-FU was elucidated in terms of tumor morphometrics, apoptosis assay, surface morphology histology of the colon(s), and transcriptional alterations. Changes in membrane dynamics with mucin expression were evaluated by fluorescence microscopy and histochemistry. The in vitro activity of the peptide/drug conjunction was explored by phase contrast microscopy, MTT, LDH assay, and AO/EtBr staining. Chemoresistance to 5-FU was determined by phase contrast microscopy, MTT assay, annexin V-FITC/PI flow cytometry, and MDR-1, Bak, and Bax expression.

RESULTS

In vivo decreases in tumor parameters, with a marked increase in apoptosis and neutrophil infiltrations indicated restoration of normal architecture with improved mucin content in the treated colons. This happened with substantial changes in key molecular markers of the intrinsic apoptotic cascade. Membrane dynamics revealed that peptides and chemotherapeutic drugs could bind to cancerous cells by taking advantage of altered levels of membrane fluidity.

CONCLUSION

Peptide treatment of drug-resistant Caco-2 cells promotes enhanced 5-FU uptake, in contrast to when cells were treated with 5-FU alone. Hence, HD-5 as an adjunct to 5-FU, exhibited strong cancer cell killing even against 5-FU-resistant tumorigenic cells.

Lineage tracing in human tissues

The dynamical process of cell division that underpins homeostasis in the human body cannot be directly observed in vivo, but instead is measurable from the pattern of somatic genetic or epigenetic mutations that accrue in tissues over an individual's lifetime. Because somatic mutations are heritable, they serve as natural lineage tracing markers that delineate clonal expansions. Mathematical analysis of the distribution of somatic clone sizes gives a quantitative readout of the rates of cell birth, death, and replacement. In this review we explore the broad range of somatic mutation types that have been used for lineage tracing in human tissues, introduce the mathematical concepts used to infer dynamical information from these clone size data, and discuss the insights of this lineage tracing approach for our understanding of homeostasis and cancer development. We use the human colon as a particularly instructive exemplar tissue. There is a rich history of human somatic cell dynamics surreptitiously written into the cell genomes that is being uncovered by advances in sequencing and careful mathematical analysis lineage of tracing data. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Colorectal Cancer Progression Is Potently Reduced by a Glucose-Free, High-Protein Diet: Comparison to Anti-EGFR Therapy

Simple Summary

To study the interplay between nutrition and intestinal metabolism in the context of colitis-driven colorectal carcinoma (CRC), we here investigated a nutritional therapy strategy in the presence or absence of EGFR-directed antibody therapy in mice to treat established colitis-driven CRCs in vivo. After CRC development, mice were fed a control diet or an isoenergetic glucose-free high-protein (GFHP) diet in the presence or absence of EGFR-directed antibody therapy. The GFHP diet was accompanied by a metabolic shift of the mice towards lower glycolysis activity. Both, GFHP diet or anti-EGFR antibody treatment, improved tumor differentiation and anti-tumor immune response, resulting in an efficient reduction of colonic tumor burden.

Abstract

To enable rapid proliferation, colorectal tumor cells up-regulate epidermal growth factor receptor (EGFR) signaling and aerobic glycolysis, resulting in substantial lactate release into the tumor microenvironment and impaired anti-tumor immune responses. We hypothesized that a nutritional intervention designed to reduce aerobic glycolysis may boost the EGFR-directed antibody (Ab)-based therapy of pre-existing colitis-driven colorectal carcinoma (CRC). CRC development was induced by azoxymethane (AOM) and dextran sodium sulfate (DSS) administration to C57BL/6 mice. AOM/DSS-treated mice were fed a glucose-free, high-protein diet (GFHPD) or an isoenergetic control diet (CD) in the presence or absence of an i.p. injection of an anti-EGFR mIgG2a or respective controls. AOM/DSS-treated mice on a GFHPD displayed a reduced systemic glucose metabolism associated with reduced oxidative phosphorylation (OXPHOS) complex IV expression and diminished tumor loads. Comparable but not additive to an anti-EGFR-Ab therapy, the GFHPD was accompanied by enhanced tumoral goblet cell differentiation and decreased colonic PD-L1 and splenic CD3ε, as well as PD-1 immune checkpoint expression. In vitro, glucose-free, high-amino acid culture conditions reduced proliferation but improved goblet cell differentiation of murine and human CRC cell lines MC-38 and HT29-MTX in combination with down-regulation of PD-L1 expression. We here found GFHPD to systemically dampen glycolysis activity, thereby reducing CRC progression with a similar efficacy to EGFR-directed antibody therapy.

The Histochemical Alterations of Mucin in Colorectal Carcinoma Quantified by Two Efficient Algorithms of Digital Image Analysis

The practical use of knowledge on the diagnostic-prognostic role of polysaccharide components of mucins in colorectal cancer (CRC) has been difficult, due to the number of histochemical (HC) reaction types, as well as lack of standard methods of computer-assisted analysis of tissue expression of these molecules. Using two algorithms of digital image analysis (by application of Image-Pro Premier and our originally designed program Filter HSV), we evaluated the expression of polysaccharides in tissue samples of CRC patients (n = 33), and fragments of normal colorectal tissue from the same patients (control) using periodic acid Schiff reaction (PAS) (neutral mucins) and alcian blue staining (AB) (acidic mucins). Our results indicate lower expression of the PAS+ and AB+ mucins in CRC, as compared to the control samples. The higher expression of PAS+ polysaccharides was detected in flat tumors than in protruded CRC, while higher AB+ mucins expression was a feature of mucinous CRC subtypes. Positive correlation between mutual PAS+ and AB+ expression, as well as correlations with glucose concentration (PAS+ mucins), and hemoglobin level (AB+ mucins) were observed exclusively in unchanged colorectal samples (control). Both algorithms of digital image analysis (smart segmentation and Filter HSV) work properly and can be used interchangeably in daily practice of pathologists, as useful tools of quantitative evaluation of HC reaction in both normal and cancerous tissues.

Fixation and Spread of Somatic Mutations in Adult Human Colonic Epithelium

We investigated the means and timing by which mutations become fixed in the human colonic epithelium by visualizing somatic clones and mathematical inference. Fixation requires two sequential steps. First, one of approximately seven active stem cells residing within each colonic crypt has to be mutated. Second, the mutated stem cell has to replace neighbors to populate the entire crypt in a process that takes several years. Subsequent clonal expansion due to crypt fission is infrequent for neutral mutations (around 0.7% of all crypts undergo fission in a single year). Pro-oncogenic mutations subvert both stem cell replacement to accelerate fixation and clonal expansion by crypt fission to achieve high mutant allele frequencies with age. The benchmarking of these behaviors allows the advantage associated with different gene-specific mutations to be compared irrespective of the cellular mechanisms by which they are conferred.

Mucin expression patterns in histological grades of colonic cancers in Ghanaian population

Introduction

Myriad roles of mucins in normal tissues have been well documented, including lubrication of the epithelial surfaces; protection from physical damage; facilitation in cell-cell signaling and suppression of inflammatory activity. Pathological expression of mucins has been noted in cancer development and progression. This study sought to identify and quantify the types of mucins produced during various histological grades of colon cancer and to assess the diagnostic significance.

Methods

Formalin fixed, paraffin-embedded tissue blocks, comprising three (3) normal colon and twenty-two (22) colon cancer tissues, were retrieved from the archives of the histopathology department of the Komfo Anokye Teaching Hospital. They were stained with Haematoxylin and eosin (H&E) for diagnosis and grading of tumours. Tissues were pre-digested with diastase and stained with Alcian blue (pH 2.5)/Periodic Acid Schiff to characterize the mucin variants present.

Results

Our findings indicated that normal colonic tissues expressed exceptionally high amount of acid mucin and low amount of neutral mucin. However, there was a general decrease in mucin expression in colon cancers compared to normal colon tissues. Additional findings suggested that as cancer progresses from low grade to high grade of adenocarcinoma of the colon, there was generally a considerable decrease in the acid mucin production and an increase in the neutral mucin expression. In contrast, a sizeable subpopulation of high-grade adenocarcinomas of colon showed a rather opposite mucin expression pattern- increase in acid mucin and a decrease in neutral mucin.

Conclusion

As colonic cancer progresses, there are corresponding changes in the mucin types and content such that there are decrease in acid mucin and increase in neutral mucin expressions.

High-fat diet alters the oligosaccharide chains of colon mucins in mice

Mucins are high molecular weight epithelial proteins, strongly glycosylated, and are the main component of the mucus. Since mucus secretion can be altered in diseases, colon mucins can be regarded as a biomarker of chronic inflammatory bowel diseases or preneoplastic changes. Conventional histochemistry and lectin histochemistry combined with chemical treatment and enzymatic digestion were carried out to analyze the colon mucins in mice fed a high-fat diet for 25 weeks, a period sufficient to induce simple liver steatosis, to check whether the carbohydrate features of mucus can be altered by an inadequate diet. An increase in the sialo/sulfomucins ratio with respect to control mice, assessed by computerized image analysis, was observed in the colon, although differences in sialic acid acetylation between control and mice fed a high-fat diet were not found. High-fat diet was also associated with altered lectin-binding pattern of the mucus, with a probable shortening of oligosaccharide chains of glycoproteins. This pattern was leading to over-expression of Galβ1,3GalNAc terminal dimers (TF antigen) and GalNAc terminal residues (Tn antigen). This altered composition of mucins can be related to a defect in the process of glycosylation, or to incomplete maturation of goblet cells, and may be an early indication of preneoplastic and neoplastic changes. In conclusion, our findings confirm that a fatty-rich diet (Western-style diet) induces alteration of mucins and may be associated with colon diseases. Our investigation corroborates the usefulness of lectins histochemistry in the early diagnosis of prepathological states of the colon.

Histochemical characterization of the sialic acid residues in mouse colon mucins

The mucins of colonic murine mucus are highly O-glycosilated sulfosialoglycoproteins. We have characterized the sialylation pattern of oligosaccharide chains of colonic murine mucins by conventional histochemical methods and by lectin histochemistry combined with chemical pretreatments and sialidase digestion. Oligosaccharide chains are strongly sulphated, with an increase of sulfation from the proximal toward the distal colon and a decrease of sialic acid expression and acetylation toward the distal colon. In the goblet cells of proximal colon, sialic acid bound α2,3 to Galβ1,3GalNAc subterminal dimers is diacetylated at C7,C8;C7,C9;C8,C9 or triacetylated at C7,8,9. In the distal colon, sialic acid-linked α2,3 to Galβ1,3GalNAc subterminal dimers shows reduced O-acetylation at C7 and/or C8, while acetyl substituents at C9 and at C4 are almost absent. Sialic acid is involved in different essential physiological functions; thus, alterations of its expression and acetylation in oligosaccharide chains of intestinal mucins are generally associated with diseases, such as ulcerative colitis and cancer. Mice may represent a suitable animal model to study alterations of oligosaccharidic chains in colonic mucins and lectin histochemistry combined with chemical pretreatments, and enzyme digestion may be a valuable tool for this study. Our present work may represent a landmark for further lectin histochemical studies to evaluate alterations of mouse colon mucins under different physiological, pathological, or experimental conditions, with possible translational value in humans.

[Role of mucinohistochemical analysis in verification of malignant potential of colorectal adenoma]

BACKGROUND/AIM

It is a general opinion that the biggest number of colorectal carcinoma (CRC) develops with the malignant alteration of colorectal adenomas (adenoma carcinoma sequence). Malignant potential of adenoma is in the function of its size, histological structure and the grade of dysplasia. An adequate analysis of colorectal adenomas helps their definition and timely removal, which significantly decreases carcinoma incidence. Mucin analysis can provide results which support the adenoma carcinoma sequence theory. The aim of the study was to present histochemical characteristics of adenomas and emphasize the significance of these analyses for the precise adenoma definition.

METHODS

This prospective study included analysis of 117 colorectal adenomas obtained by transcolonoscopic biopsy or polipectomy in 82 patients. The biopsy samples and the removed polyps were coloured by hematoxilin-eozin (HE) staining and histochemical stainings by Periodic Acid Schiff (AB-PAS) and High Iron Diamine/Alcian blue (HID-AB; pH = 2.5) to prove mucins.

RESULTS

Sulphomucins are more often found in adenomas of the left colon than of the right one (p < 0.001). Sialomucins are more reactive in adenomas of the right colon (p < 0.001). Sulphomucins are more reactive in adenomas of < 10 mm diameter (p < 0.05). The reactivity of all mucins is in negative correlation with the degree of dysplasia (p < 0.001). There is a significant difference in the reactivity of sialomucins in adenomas of the same histological type but different degree of dysplasia (chi2 = 25,743, df = 6, p < 0.001).

CONCLUSION

The difference in the presence of mucins between adenomas of the left and right colons supports the theory of adenoma carcinoma sequence, since adenomas of the right colon are more protected by sialomucins and therefore less malignantly altered, which is consistent with CRC topography. Histochemical analysis of colorectum is significant for more accurate gradation of dysplasia and confirmation of malignant alteration. The negative correlation between the degree of dysplasia and the production of mucin indicates the significance of the degree of dysplasia in malignant potential of colorectal adenomas.

Intestinal epithelial stem cells and progenitors

The adult intestinal epithelium contains a relatively simple, highly organized, and readily accessible stem cell system. Excellent methods exist for the isolation of intestinal epithelium from adults, and as a result collecting large quantities of intestinal stem and progenitor cells for study or culture and subsequent clinical applications should be routine. It is not, however, for two reasons: (1) adult intestinal epithelial cells rapidly initiate apoptosis on detachment from the basement membrane, and (2) in vitro conditions necessary for survival, proliferation, and differentiation are poorly understood. Thus to date the study of intestinal stem and progenitor cells has been largely dependent on in vivo approaches. We discuss existing in vivo assays for stem and progenitor cell behavior as well as current methods for isolating and culturing the intestinal epithelium.

Proximal versus distal hyperplastic polyps of the colorectum: different lesions or a biological spectrum?

BACKGROUND

Because of their suggested link with microsatellite instability high colorectal cancers, right sided hyperplastic polyps (HPs) may differ from their distally located counterparts. This is highlighted by the recognition of a variant HP, termed sessile serrated adenoma (SSA), which predominates in the proximal colon. HPs displaying the morphological features now associated with SSAs have been shown to have altered expression of "cancer associated" markers, but no studies have investigated whether this is dependent on anatomical location of the polyps.

AIMS

To evaluate morphological and functional features in right versus left sided HPs from patients without colorectal cancer with the aim of identifying distinguishing characteristics.

METHODS

HPs originating in the proximal and distal colorectum were histochemically and immunohistochemically stained to evaluate a panel of markers related to proliferation and differentiation. In addition, a series of morphological features was evaluated for each polyp.

RESULTS

Crypt serration, crypt dilatation, and horizontal crypt growth were more common among HPs from the right side, whereas histochemical factors including mucin changes, global methylation status, and expression of carcinoembryonic antigen were not significantly different. An age disparity was also seen between patients with right versus left sided lesions, with patients with right sided lesions being an average of more than 10 years younger than those with left sided lesions.

CONCLUSIONS

These findings suggest that right and left sided HPs differ mainly in terms of growth regulation rather than cellular differentiation, implying that these lesions belong to a continuous spectrum of serrated polyps that differ quantitatively rather than qualitatively.

Genetic and epigenetic mosaicism in cancer precursor tissues

The concept of field effects in cancer is old, but recent molecular data have substantiated it. Clones of cells that carry well-defined genetic or epigenetic aberrations, but which have not yet acquired the morphological hallmarks of neoplasia, have been documented in the precursor tissues of some of the most common pediatric and adult malignancies. Here I review this evidence, focusing on loss of heterozygosity (LOH) and gain of DNA methylation.

Gastrointestinal stem cells

Turnover of the epithelial cell lineages within the gastrointestinal tract is a constant process, occurring every 2-7 days under normal homeostasis and increasing after damage. This process is regulated by multipotent stem cells, which give rise to all gastrointestinal epithelial cell lineages and can regenerate whole intestinal crypts and gastric glands. The stem cells of the gastrointestinal tract are as yet undefined, although it is generally agreed that they are located within a 'niche' in the intestinal crypts and gastric glands. Studies of allophenic tetraparental chimeric mice and targeted stem cell mutations suggest that a single stem cell undergoes asymmetrical division to produce an identical daughter cell, and thus replicate itself, and a committed progenitor cell which further differentiates into an adult epithelial cell type. The discovery of stem cell plasticity in many tissues, including the ability of transplanted bone marrow to transdifferentiate into intestinal subepithelial myofibroblasts, provides a potential use of bone marrow cells to deliver therapeutic genes to damaged tissues, for example, in treatment of mesenchymal diseases in the gastrointestinal tract, such as fibrosis and Crohn's disease. Studies are beginning to identify the molecular pathways that regulate stem cell proliferation and differentiation into adult gastrointestinal cell lineages, such as the Wnt and Notch/Delta signalling pathways, and the importance of mesenchymal-epithelial interactions in normal gastrointestinal epithelium and in development and disease.

Altered mucin expression in the gastrointestinal tract: a review

Early studies of changes in mucin expression in disorders of the gastrointestinal tract focused on alterations in the carbohydrate chain. This review briefly considers the various mechanisms by which such alterations may come about: (a) normal variation, (b) sialic acid alterations, (c) defective assembly of carbohydrate side-chains, (d) changed expression of core proteins and (e) epithelial metaplasia. The availability of monoclonal antibodies to mucin core proteins adds a new dimension to mucin histochemistry. It is now possible to offer explanations for traditional mucin histochemical findings on the basis of lineage-specific patterns of mucin core protein expression. Changes in core protein expression are described in inflammatory, metaplastic and neoplastic disorders of the gastrointestinal tract. The possibility that mucin change could be important in the aetiology of some diseases such as ulcerative colitis and H. pylori gastritis is considered. It is more probable, however, that changes in mucin expression are secondary to reprogramming of cellular differentiation and altered cell turnover. As such they may serve as markers to explain pathogenesis and provide novel diagnostic and prognostic information.

Reduction of sialic acid O-acetylation in human colonic mucins in the adenoma-carcinoma sequence

The oligo-O-acetylation of sialic acids found in normal colonic mucins is greatly reduced in colorectal cancer. Mucins prepared from cancer tissue in adenocarcinoma showed this reduction, while normal O-acetylation was detected in resection margin and control cases and total mucin sialic acid content was significantly decreased in cancer vs. control samples. A reduction of the O-acetyl transferase activity catalysing the O-acetylation reaction was also found. A series of cultured human colorectal cell lines derived from the same premalignant adenomatous line, and representative of the adenoma-carcinoma sequence were examined and revealed a depletion of oligo-O-acetylation in the original diploid premalignant line, re-expression in a further premalignant line and reduction in malignant mucinous and adenocarcinoma cell lines. Reduction of sialic acid O-acetylation appears as an early event in the process of malignant transformation in human colorectal cancer.

Histochemistry of the surface mucous gel layer of the human colon

BACKGROUND AND AIMS

Histochemical analysis of the surface mucous gel layer of the human colon is difficult, as it dissolves in fixatives. This study was undertaken to explore the surface mucous gel layer on the normal mucosa and neoplastic tissues of the large intestine. In addition, the distribution of different mucins secreted from goblet cells was studied with a series of histochemical stains for mucins.

METHODS

Twenty four surgically resected specimens were fixed in Carnoy's solution and embedded in paraffin. In four cases, the surface mucous gel layer was also studied in frozen sections. Serial sections were stained by a battery of histochemical techniques characterising mucins.

RESULTS AND CONCLUSION

The surface mucous gel layer consisted of the inner and outer layers. The first covered the luminal surface of the mucosa, consisted of mucins, and showed a vertical striped pattern. The second overlaid the first, showed a lateral striped pattern, and was contaminated with bacteria and other substances. Their thickness in paraffin sections varied considerably among the sites in the large intestine, but was the thickest in the rectum and measured 12.7 (SEM 6.0) microns and 88.8 (SEM 80.1) microns respectively. Mucins forming the inner layer were obviously derived from goblet cells underlying it.

Correlative histochemical study providing evidence for the dual nature of human colorectal cancer mucin

Luminal secretions within colorectal cancers have been assumed to be the counterpart of normal goblet cell mucin. The aim of this study was to establish whether secretory material within colorectal cancers may in fact be traced to different lineages: goblet cells and columnar cells. The distribution of the apomucins MUC1 and MUC2, non-O-acetylated sialic acid and the carbohydrate structures sialosyl Tn, Tn, Lewis(x), sialosyl Lewis(x) and Lewis(y) was studied in normal colorectal mucosa and colorectal cancer specimens using standard histochemical techniques. Unmasking of MUC1 and MUC2 was achieved using periodic acid and saponification-neuraminidase-periodic acid pretreatment respectively. Within normal and malignant epithelium, correlations and/or co-localization could be demonstrated for goblet cells with MUC2, non-O-acetylated sialic acid, sialosyl Tn, Tn (Golgi region) and sialosyl Lewis(x), and for columnar cells with MUC1, Lewis(x), sialosyl Le(x), Tn (cytoplasm) and Lewis(y) (UEA-1). The goblet cell spectrum was associated with mucin-like (type I) luminal secretions within cancers, whereas the columnar cell spectrum characterized non-mucin-like (type II) secretions and intracytoplasmic lumina. These data indicate that colorectal cancer mucin can be broadly separated into two types: secretory mucin linked to cells of goblet lineage and up-regulated membrane-associated mucin of presumed columnar cell origin.

Mucin staining

Images

Mucin glycoproteins in neoplasia

Mucins are high molecular weight glycoproteins that are heavily glycosylated with many oligosaccharide side chains linked O-glycosidically to the protein backbone. With the recent application of molecular biological methods, the structures of apomucins and regulation of mucin genes are beginning to be understood. At least nine human mucin genes have been identified to date. Although a complete protein sequence is known for only three human mucins (MUC1, MUC2, and MUC7), common motifs have been identified in many mucins. The pattern of tissue and cell-specific expression of these mucin genes are emerging, suggesting a distinct role for each member of this diverse mucin gene family. In epithelial cancers, many of the phenotypic markers for pre-malignant and malignant cells have been found on the carbohydrate and peptide moieties of mucin glycoproteins. The expression of carbohydrate antigens appears to be due to modification of peripheral carbohydrate structures and the exposure of inner core region carbohydrates. The expression of some of the sialylated carbohydrate antigens appears to correlate with poor prognosis and increased metastatic potential in some cancers. The exposure of peptide backbone structures of mucin glycoproteins in malignancies appears to be due to abnormal glycosylation during biosynthesis. Dysregulation of tissue and cell-specific expression of mucin genes also occurs in epithelial cancers. At present, the role of mucin glycoproteins in various stages of epithelial cell carcinogenesis (including the preneoplastic state and metastasis), in cancer diagnosis and immunotherapy is under investigation.

Histochemical alterations of mucin in normal colon, inflammatory bowel disease and colonic adenocarcinoma

Loss of sialic acid o-acyl substitutions in colonic mucus was studied using specific histochemical techniques in individuals with a variety of large-bowel diseases and in a control population. Changes found included a focal or field (diffuse) loss of side-chain substitutions which were qualitatively similar in all groups studied. The results were tested statistically using a variety of assumptions that field and/or focal loss of o-acyl substitution may be either abnormal or a normal variant. No statistically significant differences in the prevalence of substitutions were detected between normal males and females or between normal individuals aged 0-29 years and 30-80 years. Significant differences were found between ascending and descending colon in both normal individuals and in the non-neoplastic mucosa of patients with cancer. There were also significant differences between the normal descending colon and cases with cancer of the descending colon. These differences seem unlikely to be due to non-specific factors, since for most assumptions there were also differences between colons containing cancer and those from patients with inflammatory bowel disease. In agreement with the work of other investigators, it seems likely that focal loss of o-acetylation results from an acquired gene mutation. It is not clear whether or not this plays a role in carcinogenesis.

Sialosyl-Tn antigen: initial report of a new marker of malignant progression in long-standing ulcerative colitis

BACKGROUND & AIMS

Expression of the mucin-associated carbohydrate antigen sialosyl-Tn (STn) correlates with malignant transformation in sporadic colonic neoplasms. The aim of this study was to analyze STn antigen expression in patients with long-standing ulcerative colitis (UC).

METHODS

STn antigen was assessed by immunohistochemistry in archival tissues. Study A was a retrospective chronological case-control study. Serial surveillance colonoscopic biopsy specimens without inflammation or dysplasia were analyzed in 7 patients who developed colon cancer and in 8 controls who did not develop colon cancer. Study B analyzed the anatomic distribution of STn expression in 17 cancer-bearing (case) and 6 cancer-free (control) colectomy specimens from patients with UC. In some colectomy specimens, STn was compared with aneuploidy, which was determined by flow cytometry.

RESULTS

In study A, among the 7 patients with UC who developed cancer, 6 patients (86%) expressed STn in at least one prior nondysplastic surveillance biopsy specimen from the same site. Only 3 of 8 control patients (38%) expressed STn. In study B, STn was expressed in 40 of 82 specimens (49%) from cancer-bearing colons but only 8 of 62 specimens (13%) from cancer-free colons. STn was expressed in most aneuploid areas but was also found in diploid, nondysplastic mucosa.

CONCLUSIONS

STn antigen seems to be a promising marker of cancer risk in patients with UC.

Monoclonal antibody TKH2 to the cancer-associated epitope sialosyl Tn shows cross-reactivity with variants of normal colorectal goblet cell mucin

It has been suggested that synthesis of mucin-type carbohydrate chains may be arrested at the core structure Tn. This may occur following premature sialylation of Tn giving the structure STn. TKH2, a monoclonal antibody to STn, is regarded as showing highly specific reactivity with colorectal and other epithelial neoplasms. In this study we have shown that TKH2 cross-reacts with normal colorectal goblet cells that are mild PAS positive (specific for non-O-acetylated sialic acid). Approximately 9% of caucasians secrete colorectal mucin in which sialic acid is non-O-acetylated. TKH2 also cross-reacts with mild PAS negative colorectal goblet cells when sections have been pre-treated with potassium hydroxide (to remove O-acetyl groups from sialic acid). These findings make it likely that the usual non-reactivity evidenced by TKH2 for normal colorectal goblet cells is due to the presence of sialic acid that is heavily O-acetylated. The reactivity of TKH2 for colorectal cancer mucin can be readily explained by the loss of sialic acid O-acetyl substituents and not necessarily by incomplete synthesis of mucin-type carbohydrate chains.

Unicryptal loss of heterozygosity in hereditary non-polyposis colorectal cancer

DNA mismatch repair genes are responsible for the condition hereditary non-polyposis colorectal cancer (HNPCC). Genomic destabilization caused by failure of DNA mismatch repair leads to the progressive accumulation of somatic mutations and so to accelerated oncogenesis. The aim of this study was to document the rate of background mutational activity in the normal colorectal mucosa of subjects with HNPCC. A naturally occurring model utilizing a genetic polymorphism (O-acetyltransferase) allows the development of unicryptal loss of heterozygosity (LOH) to be detected by means of mild PAS histochemistry and quantified. The rate of unicryptal LOH was measured in informative and affected members of 3 HNPCC families and found to be within the expected range. This result is consistent with the finding that normal cells in HNPCC subjects are DNA repair proficient and supports the view that the mutational effects of the HNPCC gene occur selectively within adenomatous epithelium and serve to accelerate the adenoma-carcinoma sequence.

Colorectal mucin histochemistry in health and disease: a critical review

Neoplastic, inflammatory and regenerative processes affecting colorectal mucosa are associated with alterations in structure of epithelial mucin. This review collates mucin-, lectin-, and immuno-histochemical observations on colorectal mucins and introduces recent molecular genetic insights into the structure of the protein backbone of mucins. The numerous structural modifications uncovered by the various technical approaches have been reduced to a few manageable principles that are of relevance to both researcher and diagnostic pathologist. Particular attention is drawn to the need to appreciate the limited specificities of probes, the confounding influences of anatomical site and genetic factors (necessitating the use of appropriate positive and negative control tissues) and the precise location of secretory material. In the past, insufficient attention has been given to the effects of altered differentiation including metaplasia and differing lineage expression in epithelial disorders of growth. It is likely that certain changes loosely ascribed to goblet cell mucin, such as neo-expression of blood group antigens and anomalous expression of core carbohydrate structures, do not occur at all. Critical examination of available data point to only two consistent and unequivocal changes affecting goblet cell mucin in pathological processes: loss of O-acetyl substituents at sialic acid C4 and C7,8,9 and increased sialylation. Furthermore, there are no neoplasia-specific alterations in mucins documented to date. All neoplasia-associated changes have been described in non-neoplastic lesions also.

Sialic acid and epithelial differentiation in colorectal polyps and cancer--a morphological, mucin and lectin histochemical study

Loss of O-acetyl substituents from sialic acid expressed in mucin secreted by hyperplastic polyps (21), adenomas (9), a mixed polyp (1) and adenocarcinomas (41) of the colorectum was investigated by mucin histochemistry (diastase PAS and mild PAS) and by lectin histochemistry (Arachis hypogaea or peanut agglutinin) with (nPNA) and without (PNA) prior neuraminidase digestion. Mild PAS and nPNA reactivity were closely correlated, indicating that loss of O-acetyl substituents at C7, C8 and C9 (hence mild PAS positive) and at C4 (hence neuraminidase labile) occur pari passu. These sialic acid alterations were characteristic of mucin secreted by both adenocarcinoma and hyperplastic polyp. The same changes occurred patchily or focally in adenoma. Five "serrated" adenocarcinomas resembled the hyperplastic polyp both morphologically and histochemically. Luminal secretions within cancers were classified as mucin-like (type I) and non-mucin-like (type II). Mild PAS was the most specific technique for mucin-like intraluminal material. However, accumulated luminal secretions (type I or II) and intracytoplasmic lumina were quite specific features of colorectal cancer and could be effectively highlighted by means of dPAS. PNA reactivity without prior neuraminidase digestion showed a distribution unlike nPNA. Whilst PNA expression was more cancer specific than either mPAS or nPNA, it was observed mainly in cancers secreting little or no mucus, thus limiting its value as a tumor marker.

Precursors of colorectal carcinoma. Biopsy and biologic markers

The term biologic marker (biomarker) of colorectal cancer refers in this article to an early preclinical phenotypic characteristic that relates to the risk for developing this cancer. Putative biologic markers in the normal colorectal mucosa of patients at risk include abnormal cell proliferation as determined by kinetic studies, ornithine decarboxylase activity, and polyamine synthesis. Alterations of mucin synthesis have been studied using both histochemical stains and lectin-binding techniques. Blood group and related carbohydrate antigens also have been evaluated as potential biomarkers in the normal mucosa. Biopsy small (less than 5 mm) polyps encountered at endoscopy has become a standard practice. Although a small polyp found to be an adenoma has a low likelihood of harboring high-grade dysplasia or invasive carcinoma, it represents an indicator of risk for colorectal neoplasia. Hyperplastic polyps, however, even though they have certain epidemiologic associations with colorectal neoplasia, are controversial as putative biomarkers of clinical relevance. Current research supports a concept of a field defect of the colorectal mucosa at risk for neoplasia, which may be identified by phenotypic abnormalities of the normal mucosa and the development of small adenomas.

Histochemical identification of 9-O-acyl sialic acids: studies of bovine submandibular and rat sublingual gland and human colon

Formalin-fixed tissue specimens containing glycoproteins with side chain O-acylated sialic acids were used to re-examine, compare and evaluate the usefulness of three methods based on the periodic acid-borohydride reduction-saponification-periodic acid-Schiff sequence (PA-Bh-KOH-PAS) for the histochemical identification of 9-O-acyl sialic acids (9-O-AcSA). Method I, modified from Veh et al. (1979), involved a comparison of the staining intensely obtained when both oxidation steps of the PA-Bh-KOH-PAS sequence were carried out with the selective oxidation technique of Volz et al. (1987) with that obtained when the initial oxidation step was carried out with 0.5 M periodic acid for 4 h at room temperature. Methods II and III, modified from Reid et al. (1978), involved an initial PA-Bh step under oxidation conditions that cleaved all the vicinal diols associated with neutral sugars and side chain unsubstituted and 7-O-acyl sialic acids. The Schiff staining obtained following subsequent re-oxidation with either 0.5M (method II) or 1% periodic acid (method III) for 4 h at room temperature (PA-Bh-PAS procedure) identifies 9-O-AcSa.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities of lectin histochemistry in familial polyposis coli and hereditary nonpolyposis colorectal cancer

A transformation in the composition of colonic glycoconjugates has been described in adenomas, carcinomas, and certain premalignant conditions. These changes have been detected histochemically by the labeling patterns of fluorescein-conjugated lectins, which bind specific carbohydrate structures on fixed tissue sections. This study was performed to determine whether abnormal lectin binding patterns are present in tissues from patients genetically predisposed to colonic neoplasms and whether these patterns could be used as phenotypic markers for inheritance of the genotype. Lectin staining patterns of 22 colectomy specimens from patients with familial polyposis coli (FPC) and rectal biopsy specimens from 47 patients at risk for hereditary nonpolyposis colorectal cancer (HNPCC) (also known as Lynch syndromes I and II) were compared with rectal biopsy specimens from 27 sex-matched controls. The fluorescein-conjugated lectins included the agglutinins derived from peanut, Dolichos biflorus, Ulex europeus, and wheat germ (including the succinylated derivative). Using a technique for quantitating lectin binding on the tissue sections that provided a score from 0 to 400, labeling with certain lectins was found to vary slightly as a function of age and sex. Histologically normal mucosa from patients with FPC bound significantly less wheat germ agglutinin but significantly more U. europeus and succinylated wheat germ agglutinins than controls. Adenomas and dysplastic flat mucosa from the colectomy specimens of patients with FPC showed significantly less binding with D. biflorus, succinylated wheat germ, and wheat germ agglutinins than controls. Rectal tissues from patients at risk for HNPCC were found to bind significantly less peanut agglutinin and D. biflorus agglutinin than controls. Of interest, staining of the tissues by peanut and wheat germ lectins increased as a function of patient age; the control subjects were older than the patients with familial colon cancer, which could possibly account for the observations made with these two lectins. These results provide evidence that the premalignant colonic epithelium in familial polyposis and the hereditary nonpolyposis colon cancer syndromes may be biologically different and indicate that glycoconjugate modifications are early events in the evolution of the neoplastic phenotype.

Sialic acid histochemistry and the adenoma-carcinoma sequence in colorectum

A change in sialic acid, notably loss of O acetyl substitution, was studied histochemically in a series of 93 colorectal adenomas that included 14 malignant polyps. Changes in sialic acid were uncommon in adenomas showing mild dysplasia but became increasingly common in moderately and severely dysplastic adenomas and were always present in carcinomatous areas. There was no correlation between a change in sialic acid and either size or villous architecture of benign adenomas. As mucin change often preceded the development of invasive cancer, it could not be used on its own to distinguish between epithelial displacement (pseudoinvasion) and malignant invasion. An abundant luminal accumulation of altered sialic acid in association with an epithelial lining that was non-mucin secreting, however, was specific for cancer. Conversely, the presence of unchanged intracellular or intraluminal O-acetyl sialic acid may help to exclude a diagnosis of malignancy in equivocal cases. The change is not specific for colorectal neoplasms and probably represents a metaplasia to a small intestinal phenotype.

Crypt restricted heterogeneity of goblet cell mucus glycoprotein in histologically normal human colonic mucosa: a potential marker of somatic mutation

Images

Histochemical studies of intestinal epithelial goblet cell glycoproteins during the development of the human foetus

Histochemical studies performed on specimens of intestine from 12 to 37-week human foetuses showed that the epithelial glycoproteins of the goblet cells of the small intestine are non-sulphated sialoglycoproteins containing neutral sugar (hexose, 6-deoxy hexose or N-acetyl hexosamine residues with Periodic acid-Schiff (PAS) reactive vicinal diols), sialic acids without O-acyl substituents, smaller and variable quantities of sialic acids with O-acyl substituents at positions C8 or C9 (or with two or three side chain substituents) and O-acyl sugars (neutral sugars with an ester substituent blocking PAS reactivity). In the lower small intestine glycoproteins containing 8 (or 9)-O-acyl sialic acids are first observed in goblet cells at the tips of the villi. As the foetus matures their quantity increases and they are found in goblet cells located along the length of the villi. Smaller quantities of O-acyl sialic acids and traces of O-acyl sugars occur in the goblet cells of the upper small intestine. The colonic goblet cells contain sulphosialoglycoproteins of two types. The first type, found in the majority of specimens, contains O-sulphate ester, neutral sugar, O-acyl sugars and 8 (or 9)-O-acyl sialic acids. The second type contains O-sulphate ester, neutral sugars, and sialic acids which are either without side chain O-acyl substituents or are a mixture of such acids and 8 (or 9)-O-acyl sialic acids; O-acyl sugars are reduced or absent.(ABSTRACT TRUNCATED AT 250 WORDS)

Epithelial-mesenchymal interactions can influence the phenotype of carcinoma metastases in the mucosa of the intestine

In this paper we report two cases in which morphological differentiation of gastric adenocarcinoma has occurred when metastatic tumour was present within the lamina propria of the intestinal mucosa. In one case, there were metastases in the small intestinal mucosa and in the second case, in the mucosa of the appendix. The morphology of the intramucosal tumour simulated that of an adenomatous neoplasm. The recognition of this occurrence may be important in the differential diagnosis of primary and secondary adenocarcinomas of the gastrointestinal tract. The phenomenon is not only of diagnostic interest: the data presented here provide in vivo evidence that gastrointestinal carcinomas may differentiate in response to epithelial-mesenchymal interactions in a similar way to that seen in experimental models.

Mucin histochemistry of virus-induced duodenal adenomas in guinea fowl

The type of mucoproteins in virus-induced duodenal adenomas in guinea fowl were compared with those in the normal duodenal mucosa. The mucin-producing cells in the latter contained a mixture of acid and neutral mucins. Neutral and sulphomucins prevailed in the crypts and in the lower part of the villi, while the amount of the sialomucins increased progressively toward the tip of the villi. In the adenomas, goblet cells were more numerous and were unevenly distributed. In their mucin profile the deeply located tumor glandular structures resembled normal crypts and lower parts of the villi and superficial portions of the adenomas were similar to the upper part of the villi. Qualitative changes in the mucin secretion with deviation from the normal vertical distribution of mucin types were rarely observed. The histochemical study carried out supplemented the histological characterization of the virus-induced duodenal adenomas and contributed to the elucidation of some aspects of their histogenesis.

Colorectal polyps in an Australian population. A histological and immunohistochemical study

The histology and immunohistochemistry of 896 polyps and other focal epithelial abnormalities detected macroscopically in 86 surgical resections from patients with colorectal adenocarcinoma and benign bowel disorders were studied. The lesions identified included 177 adenomas, 387 hyperplastic (metaplastic) polyps, and 202 non-neoplastic polyps designated 'focal cryptal hyperplasia'. Numbers of both neoplastic and non-neoplastic polyps were significantly increased in resections for carcinoma, with 72 per cent of all polyps in right and 10 per cent in left hemicolectomy specimens being neoplastic. Thirty per cent of adenomas were less than 2 mm in diameter and 6 per cent larger than 10 mm. Observations on polyp size, number, distribution, histological appearance, and antigenic composition suggested that focal cryptal hyperplasia evolves into the hyperplastic polyp. In doing so, there is loss of expression of a tissue specific antigen. Hyperplastic polyps were significantly larger in colons with adenoma than in those without.

Colorectal carcinogenesis

It is generally accepted that genetic and environmental factors combine in the aetiology of bowel cancer. Epidemiological studies have shown that the environmental factors effects are shown more clearly in the left colon, and that they are related to living in western societies whose diets contain high levels of protein, fat and energy. There has been recent awareness that consumption of alcoholic beverages, particularly beer, may be causally related to cancers of the left colon and rectum. This review attempts to relate the general epidemiological data to more specific mechanisms of colorectal carcinogenesis. Dimethylhydrazine (DMH) and N-nitroso chemicals are potent colorectal carcinogens in animals. They have not been thought very relevant to humans because their existence in appropriate forms in the environment has been debatable and analytical methods for the specific detection of non-volatile nitrosamines and nitrosamides have not been available. Recently, however, relevant alkylating activity has been detected in foods incubated in quasi-gastric conditions, and several epidemiological studies have shown a protective effect for Vitamin C, which may inhibit the development of rectal cancer through beer consumption. As Vitamin C prevents nitrosation and as precursors of nitrosamides are present in prepared foods, further dietary studies with hypotheses based on N-nitroso carcinogenesis are required. Unfortunately, these studies will probably not show clear dose-response relationships. Many of the complex reasons for this are discussed; however, one of the most important could be related to an interplay between inherited and environmental factors. The inherited factors demonstrated by chromosomal analysis in cancer and polyposis syndromes are a reminder that other genetic (oncogenetic) changes may occur in sporadic colorectal cancer.(ABSTRACT TRUNCATED AT 250 WORDS)

The histochemical specificity of high iron diamine-alcian blue

The specificity of the High Iron Diamine-Alcian Blue pH 2.5 (HID-AB 2.5) procedure was examined in tissue sites containing sialogycoproteins alone or differing proportions of sialo- and sulphosialoglycoproteins. Studies with HID in differing final concentrations of hydrochloric acid or sodium chloride confirmed that staining is dependent upon both the pH and the ionic strength of the dye bath and demonstrated a marked heterogeneity in the pKa of the anionic groups of sialosulphoglycoproteins. Use of the sequence High Iron Diamine-Alcian Blue pH 1.0 demonstrated that complete or almost complete staining of O-sulphate esters occurred when HID was prepared in water (final pH 1.3). However, under these conditions HID-AB 2.5 was shown to be non-specific because only black HID staining was observed in sites containing large quantities of sialic acids. This non-specificity was due either to the masking of Alcian Blue staining by HID and/or the black HID staining of anionic groups other than sulphate. These results may account for some of the conflicting data obtained by different groups of investigators who have studied 'transitional mucosa' in human colonic diseases. Caution should be used in drawing conclusions from the use of HID-AB 2.5 without confirmatory evidence from other more specific procedures.

Sialic acid in colonic mucin: an evaluation of modified PAS reactions in single and combination histochemical procedures

Two new histochemical procedures for detecting sulphated and non-sulphated sialomucin in colonic mucosa were assessed: the saponification-Alcian Blue pH 1-periodic acid-phenylhydrazine-Schiff method (KOH-AB pH 1-PAPS) and the mild periodic acid modification of this (KOH-AB pH 1-mPAS). Using normal colonic mucosa obtained from 11 non-cancer patients, the mPAS and PAPS techniques were tested for specificity and reproducibility for staining sialic acid, either alone or in combination with Alcian Blue. A spectrophotometric method was devised to quantify the uptake of both Schiff and Alcian Blue stain by sections. At low temperature and pH 5.5, the mPAS procedure had improved specificity over the PAPS procedure, and after saponification it could be used to stain O-acetyl-substituted sialic acid. When used in combination with Alcian Blue at pH 1, however, underestimation of the sialic acid content occurred owing to interference between Alcian Blue and Schiff dyes. Interference was even greater with KOH-AB pH 1-PAPS procedure for both sialic acid and sulphate components. We conclude that caution must be exercised in interpretation of the staining results obtained with these new combination methods and that more accurate information on the sialic acid and sulphate content of colonic mucin is obtained by staining serial sections with the mPAS technique and Alcian Blue pH 1 alone.

Mucin profiles in ulcerative colitis with dysplasia and carcinoma

Mucin secretion was assessed in Crohn's colitis, in ulcerative colitis with regeneration, dysplasia and carcinoma and in non-colitic adenocarcinoma. The high iron diamine-alcian blue (HID-AB) and periodate borohydride-saponification periodic acid Schiff (PB-KOH-PAS) techniques were used to demonstrate sulphomucins and sialomucins, and O-acylated sialomucins respectively. There was mucosal hyperplasia and increased sialomucin secretion in Crohn's disease, quiescent and active ulcerative colitis. In colitis with carcinoma inflamed mucosa away from the tumour had increased sialomucins as had colitis with dysplasia. They did not differ statistically from each other or from colitic controls without cancer. Dysplastic crypts frequently secreted sulphomucins and the increased sialomucins were in transitional-like glands in the surface fronds or adjacent to the dysplasia. A comparative study of the HID-AB technique gave total correct qualitative allocation of individual quantitatively assessed crypts. Routine HID-AB staining did not aid the recognition of dysplasia in ulcerative colitis. With the PB-KOH-PAS technique colorectal adenocarcinoma showed a significant diminution in O-acylated sialomucins compared with its adjacent mucosa. Mucosal dysplasia in ulcerative colitis displayed a similar trend in O-acylated sialic acid variants, differing with respect to age-and sex-matched colitic controls. The PB-KOH-PAS technique may be of help in assessing mucin secretion in ulcerative colitis as a guide to the evolution of malignancy.

Basis of sialic acid heterogeneity in ulcerative colitis

To test the suggestion that an inherited defect in colonic mucus rendering it susceptible to degradation by bacterial enzymes may be an important factor in the aetiology of ulcerative colitis, 650 colonoscopic and rectal biopsy specimens from 166 patients with colitis were stained by mild periodic acid Schiff (mPAS), which shows sialic acid that is deficient in O-acetyl substituents. There was an excess of mPAS positive sialic acid in patients with chronic ulcerative colitis, but the increased expression was patchy and coincided with a morphological change in the form of epithelial hyperplasia (metaplasia). Hyperplasia was more common in the rectum and in women and was associated with, and presumably secondary to, active inflammation. It is concluded that variation in the structure of sialic acid is acquired and is therefore unlikely to be implicated in the aetiology of ulcerative colitis.

The value of tissue mucin changes and CEA content in evaluation of benign colonic adenomas

A combined histopathologic, histochemical, and immunohistochemical study of benign colorectal adenomas is presented. Specimens of 39 adenomas were studied by hematoxylin and eosin (HE) stain, alcian blue-periodic acid Schiff (AB-PAS), and high-iron-diamine-alcian blue (HID-AB). Carcinoembryonic antigen (CEA) was demonstrated by peroxidase-antiperoxidase (PAP) technique. Variable amounts of neutral mucin and decreased sulfated acid mucin content, as well as increased CEA content, were found in the dysplastic epithelium of benign colonic adenomas. These changes were not seen in normal colonic mucosa. It is suggested that the above-mentioned methods may represent an aid in the evaluation of malignant potential of benign polyps.

Colorectal goblet cell mucins in familial adenomatous polyposis

Ninety two tissue blocks from the left colon and 52 from the right colon were obtained from 112 patients with familial adenomatous polyposis (FAP). Tissues from 137 patients with other conditions served as controls. Within the main study a smaller investigation was performed to compare sections from the left and right colon in the same subject. Several well known histochemical techniques were used to investigate possible changes in sulphation, sialic acid structure (loss of O-acetyl substituents), and changes in the ratio of sialic acid to neutral sugars. In patients with FAP, as in controls, there was increased expression of periodic acid Schiff positive mucin and fucose in the right colon. The only difference between patients with FAP and controls was the indirect demonstration of less neutral mucin in the right colon in FAP, but this did not seem to affect neutral sugars binding to UEA-1, PNL, or HPA. As in the general population, a small proportion of patients with FAP showed a lack of O-acetyl substituted sialic acid. Sialic acid heterogeneity probably has a genetic basis, but this is not associated with the genetic defect underlying FAP.