Biochemical and immunohistochemical characterisation of mucins in 8 cases of colonic disease - a pilot study

Abstract

Objectives. To characterise mucins in cancer of the colon and compare these with controls using stringent biochemical measures to avoid endogenous proteolysis.
Design. Crude mucus scrapings were collected from 12 specimens obtained by colectomy. Specimens from 3 traumatic colectomies and 1 sigmoid volvulus were used as controls,
and compared with 6 specimens from colons resected for adenocarcinoma and 2 irradiated colons. Subjects. The median age of the 4 female patients was 76 years (range 49 - 82 years), and of the 8 male patients 46.5 years (range 16 - 74 years). Results and conclusions. The crude mucus scrapings in the 9 specimens ranged in weight from 353 mg to 7 697 mg (median 4 928 mg). The median of purified mucin in the 9 specimens was 0.72 μg/mg wet weight of scraped material. Eight samples gave non-extractable pellet material, and were treated with DTT to reduce disulphide bonds for further analysis. One of these 8 pellets was resistant to reduction and had to be digested with papain before analysis. Only 5 of these pellets had mucin. Gel filtration and SDS-PAGE (sodium dodecyl sulphate polyacrylamide gel electrophoresis) analysis revealed different populations of mucin based on size and extent of degradation. Western blotting and immunohistochemical analysis confirmed the presence of MUC2 in all samples, MUC5AC in 2 and MUC5B in 5 diseased specimens. Immunohistochemical analysis showed that there was no MUC1 in the normal specimens, MUC1 apoprotein (MUC1 core) in 2 cancer specimens and MUC1 in 1 cancer specimen. Histochemical analysis showed that normal tissue expressed neutral and acidic mucins and diseased specimens predominantly expressed acidic mucins. The electrophoretic behaviour of MUC2 in sigmoid volvulus was different from that in cancer of the colon.

South African Journal of Surgery Vol. 45 (1) 2007: pp. 18-23