Oncofetal mucin Ml epitope family: Characterization and expression during colonic carcinogenesis

Abstract

The gastric mucin M1 antigens, markers associated with colonic carcinogenesis, have been characterized by new antimucin monoclonal antibodies (MAbs). These MAbs, obtained against mucins isolated from a human ovarian mucinous cyst (MAbs 19M1, 21M1 and 45M1) and from a pancreatic adenocarcinoma (MAb 96RA), were compared with 5 other anti-M1 mucin MAbs described previously, which characterized the a, b, c, d and e mucin M1 epitopes. Using immunoperoxidase, these new MAbs exclusively stained the surface gastric epithelium of normal human gastro-intestinal tract and reacted with fetal, precancerous and cancerous colonic mucosa, but not with normal colon. Immunoradiofixation studies showed that these new MAbs are directed against 3 epitopes (f, g and h) which are different from the a, b, c, d and e mucin M1 epitopes, though present on the same a immunoreactive high-molecular-weight components (greater than 1,000 kDa) with a density of 1.4 by CsCl-density-gradient ultracentrifugation. M1 antigenicity is characterized by a family of 8 different M1 epitopes which were destroyed with beta-mercaptoethanol (except for the f epitope), sensitive to a 5 hr trypsin treatment and resistant to 5 mM periodate (except for the h epitope). Some epitopes (b, c and d) showed increasing immunoreactivity after 20 mM periodate treatment, suggesting cryptic location. In rat-colon adenocarcinomas, M1 mucin epitopes were masked but could be decrypted using high periodate treatment, similar to normal rat gastric mucosa, thus suggesting the absence of drastic changes in the saccharide coat of the peptide mucin portion bearing M1 epitopes. Cryptic location, periodate resistance, sensitivity to protease and conformational behavior strongly suggest that the peptidic core of gastric (or fetal colonic) mucin plays a role in M1 immunoreactivity. Indeed, the resurgence of M1 antigens during colonic carcinogenesis is due to re-expression of the peptide core of gastric (or fetal colonic) mucins.

Phenotypic Expression of Colorectal Adenocarcinomas with Reference to Tumor Development and Biological Behavior

“…[15][16][17][18] HGM is a specific marker for core protein of gastric foveolar cells. 19,20) The correlations between positivity to these antibodies and clinicopathologic features suggested that cell differentiation is inversely associated with tumor growth and aggressiveness.…”

“…We selected three immunohistochemical markers for cell differentiation: MUC2 for intestinal goblet cells, [12][13][14] CD10 for small intestinal brush border [15][16][17][18] and human gastric mucin (HGM) for gastric differentiation. 19,20) A representative section from each tumor was processed for immunohistochemical staining with monoclonal antibodies against MUC2 (Novocastra, Newcastle-upon-Tyne, UK, diluted 1:200), CD10 (Novocastra, diluted 1:200) and HGM (45M1, Novocastra, diluted 1:50). Four-micron-thick sections were cut, deparaffinized in xylene and dehydrated in an ethanol series.…”

pH-dependent Intraluminal Organization of Mucin Granules in Live Human Mucous/Goblet Cells

“…Differences in SHGFP-MUC5AC/CK mobility between the granule and endoplasmic reticulum were assessed by determining the apparent or effective diffusion coefficients (D eff ) (40), defined as the mean squared displacement of SHGFP-MUC5AC/CK over time. D eff integrates the absolute diffusion coefficient, which is largely due to the viscosity of the compartment, and effects caused by interactions and collisions with other proteins components.…”

Requirement of both mucins and proteoglycans in cell‐cell dissociation and invasiveness of colon carcinoma HT‐29 cells

“…18 -20 On the other hand, de novo appearance of a secreted mucin normally found in the stomach, MUC5AC, has been described in colon carcinomas. [21][22][23] Thus, mucinous differentiated cells are present in colorectal carcinomas and more particularly in mucinous carcinomas and in signet ring cell carcinomas. Until now, the significance of a differentiation characteristic into a mucin-secreting phenotype with regard to the tumor development is still unknown.…”