Oncofetal expression of the human intestinal mucin glycoprotein antigens in gastrointestinal epithelium defined by monoclonal antibodies

Relationship between biological behavior and phenotypic expression in undifferentiated-type gastric carcinomas

BACKGROUND

It has been proved that some differentiated-type gastric carcinomas have a gastric phenotype. Similarly, it can be conjectured that some undifferentiated-type gastric carcinomas have an intestinal phenotype and that there are biological differences between undifferentiated-type gastric carcinomas with a gastric phenotype and those with an intestinal phenotype. We classified the phenotypes of early undifferentiated-type gastric carcinomas and investigated the relationship between their biological behavior and the phenotypes.

METHODS

Sixty lesions of intramucosal undifferentiated-type gastric carcinoma were classified into four phenotypes; gastric type, incomplete-intestinal type, complete-intestinal type, and unclassified type, according to the expression of CD10, MUC2, small-intestinal mucinous antigen (SIMA), human gastric mucin (HGM), or concanavalin A (ConA).

RESULTS

The incidence of gastric-type carcinoma, incomplete-intestinal-type carcinoma, and complete-intestinal-type carcinoma was 33% (20 cases), 65% (39 cases), and 2% (1 case), respectively. There was no significant difference in any of the clinicopathological factors examined between the 20 gastric-type carcinomas and the 40 intestinal-type carcinomas, but there were significant differences in the morphological findings. Intestinal-type carcinomas had a glandular structure more frequently than the gastric-type carcinomas. The spreading pattern of gastric-type carcinomas showed a middle-layer type more frequently than the intestinal-type carcinomas.

CONCLUSION

Undifferentiated-type gastric carcinomas frequently expressed an intestinal phenotype. There were differences in the growth patterns between undifferentiated-type gastric carcinomas with a gastric phenotype and those with the intestinal phenotype.

Expression of MUC2 gene in gastric regenerative, metaplastic, and neoplastic epithelia

It has been reported that MUC2 mucin is expressed in goblet cells of gastric intestinal metaplasia, but not in its normal epithelium. To confirm this finding, we have examined the expression of the MUC2 gene by reverse transcriptase-polymerase chain reaction and immunohistochemical methods in gastric tissues obtained by routine upper gastrointestinal tract endoscopy and compared the results with pathological findings based on hematoxylin and eosin (H&E) staining. In 16.7% of the tissue specimens tested, MUC2 mRNA was detected in spite of the absence of intestinal metaplasia in HE specimens. A possible explanation for this was the identification by immunohistochemistry of MUC2 protein in regenerative gastric mucosal cells in biopsies that did not contain intestinal metaplasia. Sialyl-Le(x) epitope, which is suggested to be located on MUC2 mucin core protein (MUC2 protein), was also immunohistochemically detected in both goblet cells of intestinal metaplasia and regenerative epithelium. With regard to carcinoma, MUC2 protein was predominantly expressed in intestinal-type adenocarcinoma. These data indicate that MUC2 mucin is expressed in gastric regenerative epithelium in addition to intestinal metaplasia and intestinal type adenocarcinoma.

Expression of MUC2 gene in gastric regenerative, metaplastic, and neoplastic epithelia

It has been reported that MUC2 mucin is expressed in goblet cells of gastric intestinal metaplasia, but not in its normal epithelium. To confirm this finding, we have examined the expression of the MUC2 gene by reverse transcriptase-polymerase chain reaction and immunohistochemical methods in gastric tissues obtained by routine upper gastrointestinal tract endoscopy and compared the results with pathological findings based on hematoxylin and eosin (H&E) staining. In 16.7% of the tissue specimens tested, MUC2 mRNA was detected in spite of the absence of intestinal metaplasia in HE specimens. A possible explanation for this was the identification by immunohistochemistry of MUC2 protein in regenerative gastric mucosal cells in biopsies that did not contain intestinal metaplasia. Sialyl-Le(x) epitope, which is suggested to be located on MUC2 mucin core protein (MUC2 protein), was also immunohistochemically detected in both goblet cells of intestinal metaplasia and regenerative epithelium. With regard to carcinoma, MUC2 protein was predominantly expressed in intestinal-type adenocarcinoma. These data indicate that MUC2 mucin is expressed in gastric regenerative epithelium in addition to intestinal metaplasia and intestinal type adenocarcinoma.

Decreased expression of the metastasis suppressor gene KAI1 in gastric cancer

KAI1 was immunohistochemically detected in the lower part of fundic glands and intestinal metaplasia in non-cancerous gastric tissues, while only 11.0% (8/73) of cancerous tissues were shown to be positive. The relationship between various clinicopathological characteristics of patients with gastric cancer and KAI1 expression in their tumors was then analyzed to reveal that the incidence of positivity was 16.6% (8/48) of patients with stage Ia-IIIa and 0% (0/25) of patients with stage IIIb-IVb (P < 0.05) and that the incidence of peritoneal or hepatic metastasis tended to be lower in KAI1-positive tumors than in negative ones. These results suggest that decreased KAI1 expression may be related to the progression of gastric cancer.

Colonic chicken skin mucosa: an endoscopic and histological abnormality adjacent to colonic neoplasms

OBJECTIVES

We recently described an endoscopic finding of pale yellow-speckled mucosa adjacent to colonic neoplasms. This resembled the appearance of chicken skin and was named chicken skin mucosa (CSM). CSM differs from previously reported gastrointestinal xanthelasmas in that this entity always occurs in association with colonic neoplasms. The prevalence, endoscopic characteristics, clinical significance, and possible etiology were investigated.

METHODS

Eight hundred fifty-two consecutive colonoscopies were prospectively evaluated for the presence of CSM associated with either cancer or adenomas > or = 1 cm. Electron microscopy and histopathology using hemotoxylin and eosin, mucicarmine, and oil red O stains were performed. Twelve consecutive colon cancer resection specimens were prospectively examined to determine the presence of histologic CSM.

RESULTS

CSM was adjacent to eight of 10 distal colorectal cancers, one of four proximal colon cancers, 16 of 42 distal adenomas, and three of 44 proximal adenomas. Four of seven resected distal cancers demonstrated histological evidence of CSM. Biopsies of the CSM revealed that lipid-filled macrophages in the lamina propria were responsible for this endoscopic appearance. Electron microscopy showed that the surface epithelial cells had small intestine-like microvilli. CSM was not seen with other colonic conditions and was not associated with the laxative preparation. In four instances, identification of the CSM alerted the endoscopist to the presence of polyps in locations difficult to visualize.

CONCLUSIONS

CSM is an endoscopic entity that occurs as a result of fat accumulation in macrophages in the lamina propria of the mucosa adjacent to colonic neoplasms. Small intestine-like microvilli were present in CSM and the pathophysiological implications remain to be elucidated.

A novel gastric-cancer-associated mucin antigen defined by a monoclonal antibody A3D4

De-glycosylation of mucins may expose new tumor-associated core protein epitopes. In this study, to attempt to develop useful markers for gastric cancers, we have purified and de-glycosylated gastric mucin and tried to establish monoclonal antibodies (MAbs). A MAb designated A3D4 among established MAbs was shown to react with gastric cancer with high frequency, but not with normal gastric epithelium. Among normal digestive organs, only the colon and gall bladder were positive for MAb A3D4. The incidence of positivity in gastric cancer was 75% for intestinal-type adenocarcinoma (n = 28), 40% for solid-type adenocarcinoma (n = 5) and 33% for signet/scirrhous-type adenocarcinoma (n = 15). Interestingly, adenoma and intestinal metaplasia (IM) with chronic gastritis or peptic ulcer were negative for MAb A3D4, whereas 8 out of 13 cases (62%) of IM with gastric cancer was positive. Western-blot analysis using the lysate from normal colon tissues revealed a high-molecular-weight (> 300-kDa) smear-like band. Immunohistochemical analysis indicated that the reactivity of MAb A3D4 was clearly increased when tissue sections were pre-treated with periodic acid or O-glycanase, while it was decreased by pre-treatment with trypsin or protease V8. There was no reactivity with the synthetic peptide encompassing the tandem-repeat sequence of MUC2 or MUC3. These data suggest that MAb A3D4 detects a novel gastric-cancer-associated mucin antigen whose epitope may be peptide in nature.

Characterisation of the tumour-associated carbohydrate epitope recognised by monoclonal antibody 4D3

The tumour-associated epitope recognised by monoclonal antibody (MAb) 4D3 is expressed on a high m.w. mucin glycoprotein preparation known as small intestinal mucin antigen (SIMA). This epitope is detected in tissue from a high proportion of patients with colorectal cancer, and elevated levels occur in serum from a significant number of such patients, highlighting the potential clinical utility of MAb 4D3. In the present study, insight into the composition and structure of the carbohydrate epitope recognised by MAb 4D3 was gained following characterisation of 2 glycopeptides that co-purified with SIMA. Sequence analysis of 1 of these glycopeptides revealed that it was identical to the glycoprotein alpha-1-anti-chymotrypsin. This glycoprotein was subsequently deglycosylated to yield 5 forms corresponding to alpha-1-anti-chymotrypsin substituted with 4, 3, 2, 1 or no branched glycans. MAb 4D3 was reactive with each of the glycosylated forms, including the form carrying only 1 branched glycan, but did not react with fully deglycosylated alpha-1-anti-chymotrypsin. MAb 4D3 also reacted to different extents with ovine, bovine or porcine submaxillary mucins, each of which has a different amount of the O-linked sialylated disaccharide known as sialosyl Tn. Of these mucins, MAb 4D3 was most reactive with ovine submaxillary mucin, in which almost all of the carbohydrate chains are sialosyl Tn. Reactivity of MAb 4D3 towards isolated glycans, sialosyl Tn and related structures led to the conclusion that the preferred MAb 4D3 epitope involves the sialylated N-acetyl galactosamine disaccharide as well as an additional monosaccharide present on a neighbouring carbohydrate chain. Although the preferred epitope recognised by MAb 4D3 involves this sialylated disaccharide, the specificity of MAb 4D3 was different from that of other MAbs with a reported specificity for sialosyl Tn.

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.

Effect of TGF-beta on differentiated organoids of the colon carcinoma cell line LIM 1863

The LIM 1863 colon carcinoma cell line grows in suspension as morphologically and functionally organized organoids in serum-containing medium. Addition of TGF-beta caused the organoids to adhere and inhibited DNA synthesis. A 20 min incubation with TGF-beta was sufficient to induce adherence and this could be inhibited by cycloheximide. The adhesion and DNA synthesis inhibition were demonstrated to be separate events. We were not able to detect any changes in matrix or cell membrane antigens. Similarly there were no changes in synthesized proteins (by two-dimensional gel electrophoresis), and no upregulation of proteoglycan. When adhered organoids were lysed from the tissue culture plastic surface, untreated organoids adhered to this surface. This 'conditioned' surface was destroyed by trypsin but not collagenase or medium from normal LIM 1863 cultures. However, the adherent phenotype was prevented when organoids were treated with transforming growth factor-beta (TGF-beta) in the presence of medium conditioned by normal LIM 1863 cultures rather than in fresh medium. The adhesion process was inhibited by an antibody (QE2E5) against beta 1 integrin although no quantitative changes in integrins were observed (by immunoprecipitation or RNA analysis). A second anti-beta 1 integrin antibody (61.2C4) inhibited LIM 1863 adhesion to collagen but not TGF-beta induced adhesion, implying that TGF-beta induced a specific conformational change or interaction of a beta 1 integrin. In this morphologically structured system TGF-beta induced a number of subtle effects including formation of new extracellular matrix and conformational change of a beta 1 integrin, rather than the major quantitative changes in cell/matrix molecules reported previously.

Monoclonal antibody 4D3 detects small intestinal mucin antigen (SIMA)--glycoprotein in the serum of patients with colorectal cancer

We have developed a sensitive ELISA using MAb 4D3 for the detection of a novel epitope on Small Intestinal Mucin Antigen (SIMA) and report here that SIMA is present in the serum of patients with colorectal cancer. SIMA has been shown to occur in tissue from a high proportion of patients with colorectal cancer. SIMA derived from serum was similar to tissue-derived SIMA: both eluted in the void volume of a Superose 6 column indicating a molecular weight above 5,000 kDa and they exhibited similar buoyant densities on CsCl gradients. The ELISA was most reliable after pre-treatment of serum with 0.4 M perchloric acid to remove interfering substances. The upper limit for SIMA in normal serum was set as the mean plus 2 standard deviations determined from a group of 97 healthy control subjects. In a sample of 113 patients with colorectal cancer, SIMA serum levels were elevated in 15% of patients with Dukes' Stage A, 38% with Stage B, 32% with Stage C and 75% with Stage D colorectal cancer. SIMA serum levels were compared with those of the widely used tumor marker, carcinoembryonic antigen (CEA). The SIMA assay detected a significant number of sera that were not detected by the test for CEA. We propose that SIMA will prove to be a valuable serological tumor marker, in combination with CEA and other tumor markers, for the detection of colorectal cancer.

Expression of large intestinal mucin antigen (LIMA) epitopes in the normal and neoplastic gastrointestinal tract

This study has identified the expression in normal and neoplastic gastrointestinal (GI) tract of epitopes on the colonic mucin LIMA (large intestinal mucin antigen), which are unique markers of normal colonic differentiation. Six anti-LIMA monoclonal antibodies (MAbs) (22D4, 9B5, 2C3, 23B2, 46A2, and 10B3) were studied immunohistochemically in normal GI tract, colorectal adenomas, and colorectal and gastric cancers. All MAbs showed specificities consistent with distinct epitopes, five of which were neuraminidase-resistant and four periodate-sensitive. Each reacted with mucin in 60-100 per cent normal colons--MAbs 10B3 and 23B2 also with small intestinal mucin--but none with gastric mucin. Five MAbs showed crypt and regional gradients in normal colon, MAbs, 22D4, 9B5, and 2C3 showing a hierarchy of reactivities in the crypt. Individual adenomas showed decreasing goblet cell (GC) LIMA expression with increasing size. However, 30 per cent of familial adenomatous polyposis (FAP) patients had generalized background losses of 9B5 and 2C3 GC reactivity, retaining 22D4, whilst 44 per cent of non-FAP patients lost 22D4 GC reactivity, regaining 9B5 and 2C3--evidence for polymorphism of mucin expression. All colorectal cancers expressed LIMA epitopes (frequently weaker than normal), and three MAbs (22D4, 9B5, and 2C3) showed deeper than normal staining in adjacent crypts. Eighty-five per cent of gastric cancers also expressed LIMA epitopes.

Differentiation-associated changes in mucin glycoprotein antigenicity in mucosa adjacent to rare gastrointestinal tract tumours of non-mucosal origin

We have investigated changes in mucin antigenicity and morphology in the perineoplastic mucosa adjacent to rare, predominantly non-mucosal gastrointestinal (GI) tumours. Twenty-nine tumours of small and large intestine, including primary mesenchymal and ectodermal tumours, were examined immunohistochemically using 11 monoclonal antibodies (MAbs) raised against SIMA and LIMA (small and large intestinal mucin antigens). Non-epithelial GI tumours were essentially non-reactive, while adjacent mucosa showed altered mucin expression and morphology, in particular, features of transitional mucosa (TM). Combinations of different SIMA epitopes were detected adjacent to all colorectal tumours, and, similarly, LIMA epitopes adjacent to small intestinal tumours. Specific patterns adjacent to certain tumours may reflect influences of factors produced by individual tumours on mucin composition. Altered antigenicity and morphology in TM thus appear to be reactive changes in response to a wide range of GI tumours, presumably as a consequence of factors secreted by the tumour and/or a host response to the tumour.

Establishment of conditionally immortalized epithelial cell lines from both colon and small intestine of adult H-2Kb-tsA58 transgenic mice

Intestinal mucosal cells have proved difficult to culture in vitro. Many attempts have been made to develop long-term cultures of these cells either by direct culturing or by attempting to immortalize these cells by using a range of transforming viral genes, but with little success. The recent development of a transgenic mouse bearing a temperature-sensitive mutation of the simian virus 40 large tumor antigen gene (tsA58) has enabled us to initiate conditionally immortalized cultures of epithelial cells from both small intestinal and colonic mucosa of adult mice. Crypts were isolated from either the small intestines or colons of young adult mice and cultured at the permissive temperature (33 degrees C) in medium containing conditioned medium from a human colon carcinoma cell line, LIM1863. Crypts from both tissues yielded cultures of epithelial cells that have now been in culture for more than 12 months with regular passaging. The epithelial nature of the cells has been confirmed by staining with anti-keratin antibodies. The intestinal origin of the cells was demonstrated by the ability of the cells to synthesize low levels of both brush border peptidases and a disaccharidase. The levels of expression of these enzymes were modulated by the addition of sodium butyrate or phorbol myristate acetate to the medium, which resulted in an increase in the synthesis of the peptidases and a decrease in the synthesis of the disaccharidase. The cells proliferate continuously at the permissive temperature (33 degrees C), but proliferation ceases at the nonpermissive temperature (39.5 degrees C). To our knowledge, this is the first description of the establishment of epithelial cell lines from both small intestine and colon of the same mouse strain. The success reported here indicates that this transgenic mouse will be a useful source of tissue for the study of the mechanisms that control the proliferation and eventual differentiation and senescence of the cells of the intestinal mucosa. These mice will also be a useful source of cells for attempts to culture cells from other tissues that have proved difficult to culture in vitro.

Expression of epithelial antigens EPM-1 and EXO-1 in normal, transitional, inflammatory and neoplastic colorectal mucosa

EPM-1 (a high molecular weight glycoprotein) and EXO-1 (a carbohydrate epitope expressed on polar neutral glycolipids and mucins) are two developmental antigens of normal and neoplastic human epithelia and were characterised by monoclonal antibodies. Their distribution was investigated in normal and pathological human colorectal mucosa. In normal mucosa, EPM-1 and EXO-1 showed characteristic expression patterns. EPM-1 was differentially expressed along the crypt villus axis with maximum at the crypt basis. EXO-1 was present throughout the whole mucosa. The characteristic gradient of EPM-1 expression along the crypt axis in normal mucosa was no longer detectable in benign polyps. Intact gradient of EPM-1 staining discriminated between neoplastic changes of the benign adenomatous polyp and mucosal inflammation. Neoplastic mucosa in benign polyps and especially atypical glands in highly differentiated tumours showed essentially identical expression patterns. In colorectal carcinomas the overall reactivities for EPM-1 and EXO-1 were independently associated with the histopathological grade of tumour differentiation.

The adenoma-carcinoma sequence in the colorectum--early appearance of a hierarchy of small intestinal mucin antigen (SIMA) epitopes and correlation with malignant potential

The colorectal adenoma-carcinoma sequence was examined in relation to the ectopic expression of the oncofoetal Small Intestinal Mucin Antigen (SIMA), to the development of morphologic changes in the adenoma and perineoplastic mucosa and to indices of malignant potential. Four anti-SIMA MAbs, which define a novel hierarchy of SIMA epitopes in the normal small intestine and adjacent to colorectal cancers, were used in a retrospective immunohistochemical study of Familial Adenomatous Polyposis (FAP, n = 183) and non-familial (n = 44) adenomas. Inappropriate expression of SIMA epitopes was first detected in mucosa adjacent to minute microadenomas larger than three glands, and with increase in size, in increasing amounts within adenomas themselves, but not with microadenomas smaller than three glands or regions of flat mucosa free of adenomas. SIMA epitope expressed in mucosa adjacent to adenomas preceded changes in perineoplastic morphology, which progressed with adenoma growth to resemble transitional mucosa (TM) adjacent to cancers. Thus, the onset of both SIMA expression and morphological changes in TM were consistent with reactive rather than pre-existing field change phenomena. The previously reported hierarchy of four SIMA epitopes (5C5, 3D4, 4D3, 6C5) was also consistently observed in the adenoma-carcinoma sequence, and applied to (i) the order of epitope detection, (ii) the number of positive adenomas and (iii) extent of staining; (iv) the height in the crypt and (v) distance from the adenoma to which epitopes were expressed in perineoplastic mucosa. These observations are consistent with a progression of changes in mucin composition with adenoma development. The percentage of positive adenomas and reactivity scores for each anti-SIMA MAb correlated with increasing adenoma size, degree of dysplasia and growth pattern. SIMA expression appears to predate the earliest reported oncogene and tumour suppressor gene changes, was persistent and increased throughout adenoma development. SIMA epitopes are thus markers of very early neoplastic change, whose expression correlates with malignant potential and may contribute to the accumulation of changes necessary for tumourigenesis.

Different interactions of interferon-alpha subtypes at the surface of epithelial and lymphoid cells

The interaction of different interferon (IFN)-alpha subtypes with different cell types was investigated using a unique monoclonal antibody (MAb), I-4-A. This MAb reacts in immunoassays equally with IFN-alpha 2b and IFN-alpha 4a, but does not inhibit the binding of IFN to cell receptors. 125I-labeled I-4-A reacted with IFN-alpha 4a and IFN-alpha 2b bound to receptors on Daudi cells. However, in a "double assay" developed using Daudi cells to measure antiviral and antiproliferative activity, I-4-A neutralized both activities of IFN-alpha 4a, but neither of IFN-alpha 2b. Similarly, in studies on the activation of natural killer (NK) cells, I-4-A neutralized the effect of IFN-alpha 4a but not that of IFN-alpha 2b. In contrast, when cell lines other than lymphoid were studied, e.g., HEp 2 and WISH cells, I-4-A neutralized the antiviral activity of both IFN-alpha subtypes. The neutralization of one IFN-alpha subtype but not another on lymphoid cells suggests a difference either in the receptor-bound form of the subtypes, or in subsequent interactions prerequisite for activation of these cells. Furthermore, the neutralization of a particular IFN subtype, alpha 2b, on epithelial-derived but not lymphoid cells suggests differences in the IFN-receptor complex or the mechanisms of cell activation between these cell types. An implication from these studies is that some IFN-alpha subtypes can exert different functions on lymphoid and epithelial cells.

Retention of tissue-specific phenotype in a panel of colon carcinoma cell lines: relationship to clinical correlates

A panel of eight cell lines has been derived from colon carcinomas. These cell lines have both been characterized according to standard criteria of growth rate, response to mitogens (epidermal growth factor and basic fibroblast growth factor), xenograft growth and growth in soft agar, and according to the ability of the cells to express epitopes known to be expressed by cells in the normal intestinal mucosa. The expression of epitopes present in columnar (absorptive) cells has been assessed using a panel of monoclonal antibodies to brush border peptidases and disaccharidases, villin and brush border-specific peptides. Goblet cell epitopes have been determined by monoclonal antibodies to mucin and carcinoembryonic antigen. An antibody to chromogranin was used to identify endocrine cells. Using these antibodies we found that all the cell lines reacted with at least one of the antibodies to columnar cells. Similarly, varying proportions of cells in six of the eight cell lines stained with antibodies to mucin. None of the cells expressed chromogranin. Expression of a differentiated colonic phenotype, as measured from antibody staining, did not correlate with measurements of malignancy, such as the ability of the cells to grow in soft agar or as xenografts. Similarly, there was no correlation between retention of a colonic phenotype and the initial pathological stage of the tumour from which the cell lines were derived.

Patterns of growth and differentiation in the colon carcinoma cell line LIM 1863

The LIM 1863 colon carcinoma cell line grows in the form of morphologically and functionally organized organoids. Cells are arranged around a central lumen with a brush border and nuclei are polarized to the periphery. The organoids contain 3 morphological cell types (columnar, goblet and caveolated cells). By agar cloning it has been possible to isolate 29 subclones of the cell line, all of which display the same phenotype and percentage of morphological cell types as the parent line. Cell-sorting experiments showed that precursor cells of LIM 1863 cultures could express either mucin (large-intestinal-mucus antigen) or a brush-border enzyme (sucrase-isomaltase). Proliferating cells were predominantly found near the outer periphery of organoids with cell maturation towards the internal lumen. Dead cells were continuously shed from the organoids but terminal non-cycling cells were not observed within the organoids. The organoid structure was calcium-dependent and promoted cell survival. Suspension cultures of disaggregated cells could be grown in medium containing less than 100 microM calcium. No decrease in differentiation antigens was observed in the low-calcium cultures, although polarization of the cells was lost. The organoid cultures formed by this cell line represent a unique in vitro model for colonic crypt growth and organization.

Aberrant expression of intestinal mucin antigens associated with colorectal carcinoma defined by a panel of monoclonal antibodies

Small intestine mucin antigen (SIMA) is an oncofoetal antigen for the colon and is distinct from the normal large intestinal mucin antigen (LIMA). In the present study, a panel of anti-SIMA and anti-LIMA monoclonal antibodies (MAb) was used to charaterise altered mucin expression in colorectal adenocarcinomas, by immunohistochemistry and quantitative immunoassays of tissue extracts. These results are compared with CEA expression and correlated with various clinicopathological indices. All mucin MAb reacted with a high proportion of the 100 colon cancers of every stage, histological type (including non-mucinous cancers), differentiation, site, or size. Inappropriate SIMA production was detected by either anti-SIMA MAb 4D3 or 4A1, even in 85% of early stage cancers. MAb 4D3 reacted with a higher proportion of cancers of smaller size and better differentiation. At the subcellular level, both anti-SIMA MAb showed reactivity typical of normal mucin, i.e., goblet cell and extracellular mucin. The normal colonic antigen, LIMA, was also detectable in the majority of cases, but quantitatively overproduced in some cases and reduced in others. However, in contrast to SIMA, LIMA was detected in predominantly undifferentiated cancer cells but not in goblet cells. Heterogeneity of MAb reactivity between cases and complementarity within each cancer was frequently observed. Mucin reactive with at least one of the MAb was detected in all of the CEA-negative cancers. A high rate of inappropriate SIMA expression was also detected in the perineoplastic transitional mucosa (88%, c.f. CEA, 35%) and adjacent, morphologically normal mucosa (80% c.f. CEA, 24%), indicating biochemical changes similar to the cancer. This panel of anti-mucin MAb demonstrated altered mucin glycoprotein metabolism associated with the development and progression of most colorectal cancers, which emphasises their utility as indicators of neoplastic change in the colon, and their superiority to CEA.