Characterization of monoclonal antibody 436 recognizing the Arg-Pro-Ala-Pro sequence of the polymorphic epithelial mucin (PEM) protein core in breast carcinoma cells.

Epithelial mucins have obtained increasing clinical relevance since they were found in the serum of cancer patients and were shown to be elevated in metastatic disease. We report here the characterization of the monoclonal antibody (MAb) 436 which recognises the protein core of the polymorphic epithelial mucin (PEM) of the human breast. MAb 436 was generated by immunizing Balb/c mice with membrane-enriched fractions prepared from metastatic lesions in the axillary lymph nodes. The antigenic determinant recognized by the MAb 436 is expressed on the surface of breast cancer cells and was measured by ELISA on all of 50 cytosol preparations of primary breast tumors. Immunohistochemistry showed 98% of primary and 100% of metastatic breast cancer lesions to be positive with the 436 antigenic determinant expressed both in the cytoplasm and at the plasma membrane level of the tumor cells. Moreover, the antigen was expressed in a homogeneous fashion (80-100% of the total number of tumor cells) in more than 60% of the tumors. Reactivity with normal tissues was rare and scattered and restricted to glandular structures particularly at the luminal border level except for the distal and collecting tubules of adult and fetal kidney, where a cytoplasmic 436 antigen distribution was observed. Other cancers proved positive but the reactivity was always variable and heterogeneous. The antigen recognized by MAb 436 appears in Western Blotting as a M(r) of more than 200,000 daltons protein resolved in two bands. Epitope mapping experiments using overlapping octapeptides in the repeat unit of the PEM identified in the RPAP (Arg-Pro-Ala-Pro) sequence the binding site of the 436 antigen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hydrolysis of a chitosan-induced milk aggregate by pepsin, trypsin and pancreatic lipase.

The addition of chitosan to whole milk results in dose dependent destabilization and coagulation of the casein micelles and milk fat. The present study evaluates how the presence of chitosan could affect the hydrolysis of this chitosan-induced aggregate by different gastrointestinal proteases (pepsin and trypsin) and by pancreatic lipase. The chitosan-milk aggregate was hydrolyzed by pepsin and trypsin, as evaluated by the UV absorbance of TCA-soluble peptides and by urea-PAGE. The kinetics and extent of hydrolysis were independent of the casein being soluble or aggregated. The release of soluble peptides from the aggregate was independent of the presence of chitosan. A progressive inhibition of pancreatic lipase was observed in proportion to the increase in molecular weight of the chitosan employed to induce the formation of the aggregate. Interestingly, the presence of chitosan not only affected the initial velocity of the reaction, but also reduced its extent. The results indicate that a milk aggregate induced by chitosan was very well digested by gastric and intestinal proteases independently of the molecular weight of the chitosan used, and that the aggregate could retain the lipid-lowering effect of chitosan.