Malignant Human Colon Research Articles

Quantitation of lectin binding sites in human colon mucins by use of peanut and wheat germ agglutinins.

We have developed a novel method for quantitation of lectin binding sites in mucins derived from colon tissues. Binding of peanut agglutinin and wheat germ agglutinin was measured in extracts from normal and malignant human colon epithelium. Binding of wheat germ agglutinin was used as an estimate of the total mucin present in the tissue extract. Peanut agglutinin was found to bind to mucin from normal colon, but at levels that may be difficult to appreciate by fluorescence microscopy. The yield of mucin extracted from colon cancer was more variable than that from normal colon, and the binding ratio of peanut agglutinin to wheat germ agglutinin was greater in extracts from tumors than in normal tissues. Our findings confirm the histological observation that peanut agglutinin binds more avidly to mucins from colon cancer than to those from normal colon. The finding of peanut agglutinin binding sites in mucins front normal colon was not expected. The quantitative technique may have detected small numbers of binding sites not readily appreciable by fluorescence microscopy. Alternatively, the chromatographic method for measuring lectin binding may be sufficiently sensitive to detect nonspecific binding of the lectin to terminal galactose residues other than the Thomsen-Friedenreich antigen.

Hypomethylation of DNA from benign and malignant human colon neoplasms.

The methylation state of DNA from human colon tissue displaying neoplastic growth was determined by means of restriction endonuclease analysis. When compared to DNA from adjacent normal tissue, DNA from both benign colon polyps and malignant carcinomas was substantially hypomethylated. With the use of probes for growth hormone, gamma-globin, alpha-chorionic gonadotropin, and gamma-crystallin, methylation changes were detected in all 23 neoplastic growths examined. Benign polyps were hypomethylated to a degree similar to that in malignant tissue. These results indicate that hypomethylation is a consistent biochemical characteristic of human colonic tumors and is an alteration in the DNA that precedes malignancy.

Pentagastrin stimulates in vitro growth of normal and malignant human colon epithelial cells

Five normal and four malignant human colon epithelial cultures initiated and maintained in our laboratories as well as the standardized in vitro human adenocarcinoma cell line HT-29 were plated in multiwell plates and incubated at 37 degrees C for 72 hours with either phosphate-buffered saline solution or pentagastrin (5 micrograms/ml). Pentagastrin stimulated normal cells to increase (p less than 0.05) in number by an average of 65 percent compared with saline control cells, whereas malignant cells increased an average of 59 percent compared with control cells. There was no difference in the magnitude of trophic effect between the normal and malignant cells. Further studies are indicated to elucidate the role of gastrin in either initiating, promoting, or both, the growth of carcinoma of the colon.

Inhibition of 6-phosphogluconate dehydrogenase by glucose 1,6-diphosphate in human normal and malignant colon extracts

Increased activity of 6-phosphogluconate dehydrogenase was found in human colon tumors as compared to the adjacent unaffected mucosa. Glucose 1,6-diphosphate (Glc-1,6-P 2), an endogenous potent regulator of glucose metabolism, markedly inhibited the activity of 6-phosphogluconate dehydrogenase (6-PGD) in extracts of the normal and malignant human colon. Glc-1,6-P 2 also inhibited the activity of hexokinase in these extracts. The endogenous levels of Glc-1,6-P 2 in the colon and tumors were measured. Since the pentose cycle can be inhibited by Glc-1,6-P 2, means to increase endogenous levels of Glc-1,6-P 2 or to introduce it into cells, might result in antitumor effects.

Cells from normal and malignant human colon mucosa differentially inhibit embryonic cell aggregation.

A model system for studying some aspects of the interaction of cancer cells in tumors and their surrounding nonmalignant tissue is the co-culture of cancer cells and embryonic chick neural retinal cells in gyratory shakers. Neural retina cell aggregation, under these conditions, has been shown to be differentially inhibited by small numbers of cultured mouse and human cancer cells. We extend here these observations to co-cultures of retinal cells with small numbers (60:1 ratio) of human cells isolated from normal colon mucosa or colonic adenocarcinoma tissue. The cells from the malignant tissue samples inhibited aggregation to a significantly greater extent than the cells from normal mucosa, even when both were from the same individual. Cells derived from nonmalignant tumors were more inhibitory than those from normal individuals, which is consistent with described differences in this 'transitional' region. Thus, the aggregation inhibition assay appears applicable to freshly isolated human tissues.

Concurrent measurements of carcinoembryonic antigen, glucosephosphate isomerase, gamma-glutamyltransferase, and lactate dehydrogenase in malignant, normal adult, and fetal colon tissues.

Carcinoembryonic antigen and activities of glucosephosphate isomerase (EC 5.3.1.9), gamma-glutamyltransferase (EC 2.3.2.2), and lactate dehydrogenase (EC 1.1.1.27) were measured in aqueous extracts of fetal, normal adult, and malignant human colon tissues. Fetal colon, as well as primary and metastatic colon tumor tissue, showed higher activities of these analytes than did normal adult human colon. Liver metastases of colon cancer gave the highest values, normal adult human colon the lowest. Statistically, these differences were more striking in the case of carcinoembryonic antigen and glucosephosphate isomerase than for gamma-glutamyltransferase or lactate dehydrogenase. In contrast to the other markers, gamma-glutamyltransferase activity was lower in fetal organs than in normal adult colon and colon tumors. These results are consistent with earlier observations that activities of these markers are significantly increased in the blood of patients with metastatic colon cancer.

Identification of [formula omitted] glycoprotein, [formula omitted] and antithrombin III as components of normal and malignant human tissues

α 1- Acid glycoprotein, α 2- macroglobulin , and antithrombin III have been identified, by immunological means, as components of the 90 000 × g supernatant fraction of malignant and adjacent normal human breast, colon, and anal tissues, as well as malignant stomach and ileum. Malignant lung tissue only contained α 1- acid glycoprotein. These protease inhibitors are immunologically equivalent to those present in human plasma.

Isolation and identification of alpha1-antitrypsin as a component of normal and malignant human breast and other tissues.

Alpha1-Antitrypsin has been detected using radial immunodiffusion in the 90,000g supernatant fraction of malignant and adjacent normal human breast, colon, and anal tissue, as well as malignant lung, stomach, and ileum. Immobilized chymotrypsin, bound to Sepharose or Affi-Gel 10 has been utilized to separate 11 peaks of antiproteolytic activity by affinity chromatography of normal and malignant human breast tissue extracts. Glycoproteins are associated with eight of the peaks. Peak 1 contains predominantly alpha1-antitrypsin in addition to a minor component. The purification of the inhibitors, as judged by disc gel electrophoresis, is extensive. In some peaks, only one or two protein bands are observed, suggesting that affinity chromatography on Sepharose- or Affi-Gel 10-chymotrypsin might be used for the isolation of alpha1-antitrypsin and other inhibitors in preparative amounts.

RNA and DNA of gastric and duodenal mucosa in antrectomized and gastrin-treated rats.

RNA and DNA of gastric and duodenal mucosa in antrectomized and gastrin-treated rats.