Martin Lipkin

Phase 1 and phase 2 proliferative lesions of colonic epithelial cells in diseases leading to colonic cancer.

Colonic epithelial cells in man begin to develop some of the characteristics of malignant cells while they still appear normal on conventional morphological examination. The cells pass through specific phases during which they express increasingly abnormal proliferative characteristics. As a Phase 1 proliferative lesion develops, colonic epithelial cells do not repress DNA synthesis during their maturation, and begin to develop an enhanced ability to proliferate. The over‐all kinetics of cell proliferation remain normal, without a net retention or accumulation of cells in the mucosa. As a Phase 2 proliferative lesion forms, the cells begin to develop properties that enable them to be retained in the mucosa in increasing numbers. The over‐all kinetics of cell proliferation become abnormal, and net retention and accumulation of cells begin to be observed. These changes are accompanied by differentiation‐specific molecular errors, resulting in the abnormal persistence of metabolic pathways leading to enhanced DNA synthesis. These proliferative cellular lesions arise in hereditary familial polyposis in man, in individuals in the general population who develop isolated colonic neoplasms, and in rodents after a chemical carcinogen is given, suggesting that they are major steps on a final common molecular pathway leading to malignant transformation. Their expression is accelerated in familial polyposis. The proliferative lesions and increasingly severe degrees of cellular atypia can be screened in familial polyposis, the utility of the screening procedure is being studied. The molecular lesions leading to persistent DNA synthesis, the interaction of suspected carcinogens leading to the appearance of the above changes in model systems, and the development of more effective chemotherapy and immunotherapy against the reactions leading to enhanced DNA synthesis are topics of importance at the present time.

CELL PROLIFERATION KINETICS IN THE GASTROINTESTINAL TRACT OF MAN. I. CELL RENEWAL IN COLON AND RECTUM

In studies of cell proliferation in the intestine of animals during the past few years, observations have been made that suggest points of interest concerning cell renewal in humans. In rodents, proliferating jejunal and colonic epithelial cells have mean generation times of about 12 to 18 hours, DNA synthesis (S phase) times of 5 to 8 hours, and premitosis (G2) and mitosis (M) times of 1 to 2 hours (1-3). Also, although many epithelial cells undergo a second generation cycle soon after mitosis, some cells appear to remain longer in interphase before dividing again (3). The rate of disappearance of labeled cells from the mucosa has also been shown to vary in different portions of the gastrointestinal tract in a number of species; e.g., more labeled cells are present in the colon and stomach 1 week after injection of H3-thymidine than in the duodenum or jejunum (4). In man, studies of mitotic indexes and radioautographic studies with H3-thymidine have suggested turnover times of intestinal epithelial cells in the order of several days (5-7). In the present study, we have measured the mean generation time and the phases of the proliferative cycle of human colonic and rectal epithelial cells after the administration of H3-thymidine. The results describe cell renewal and give data on the rate of disappearance of labeled cells from the mucosa of the human colon and rectum.

Gastrointestinal tract cancer

Section I Biological Organization of Gastrointestinal Mucosa.- 1 Proliferation and Differentiation of Gastrointestinal Cells in Health and Disease.- 2 T- and B-Cell Populations in Gut and Gut-Associated Lymphoid Organs: Arrangement, Migration, and Function.- Section IIA Individual and Familial Susceptibility to Gastrointestinal Malignancy: Immune Mechanisms.- 3 Immunodeficiency Diseases and Malignancy.- 4 Recognitive Immunity in Colon Cancer.- 5 Immunological Dysfunction with Atrophic Gastritis and Gastric Malignancy.- 6 The Digestive Form of a-Chain Disease.- Section IIB Individual and Familial Susceptibility to Gastrointestinal Malignancy: Environmental and Hereditary Factors.- 7 Epidemiology of Esophageal Cancer.- 8 Epidemiology of Gastric Cancer.- 9 Epidemiology of Colorectal Cancer.- 10 Heredity and Gastrointestinal Tract Cancer.- 11 Familial Polyposis Coli.- 12 Defining the Precursor Tissue of Ordinary Large Bowel Carcinoma: Implications for Cancer Prevention.- Section III Use of Experimental Models.- 13 Experimental Stomach Carcinogenesis.- 14 Experimental Colon Carcinogenesis.- 15 Mathematical Models of Carcinogenesis and Tumor Growth in an Experimental Rat Colon Adenocarcinoma.- 16 Development of Model Colorectal Cancer Systems for Pharmacological Research.- 17 Use of Experimental Models in the Study of Approaches to Treatment of Colorectal Cancer.- Section IV Future Directions in Early Detection and Diagnosis.- 18 Early Diagnosis and Detection of Colorectal Cancer in High-Risk Population Groups.- 19 Logic and Logistics of Monitoring Large Bowel Cancer.- 20 Enzymes of Normal and Malignant Intestine.- 21 Cancer in Inflammatory Bowel Disease: Risk Factors and Prospects for Early Detection.- 22 Cytopathology of Human Gastrointestinal Cancers.- 23 The Skin and Gastrointestinal Malignancy.- Section V Future Directions in Therapy.- 24 Early and Definitive Surgical Therapy for Colonic and Rectal Cancer.- 25 Chemotherapy of Colorectal Cancer: A Critical Analysis of Response Criteria and Therapeutic Efficacy.- 26 Adjuvant Chemotherapy and Immunotherapy in Colorectal Cancer.

Seventh-day Adventist vegetarians have a quiescent proliferative activity in colonic mucosa

The proliferation of epithelial cells in colonic mucosa was studied in humans at varying degrees of risk for colon cancer. Seventh-Day Adventist vegetarians, known to have significantly lower mortality from colon cancer than the general U.S. population, had the most quiescent proliferative activity of mucosal epithelial cells. Increased replication and expansion of the proliferative compartment accompanied increased colon cancer risk. The analytical methods of this study may be useful in assessing the influence of dietary components involved in the initiation, promotion or inhibition of colon cancer, and in developing strategies for nutritional intervention.

Cell Replication in the Gastrointestinal Tract of Man

Awareness of a rapid renewal of the epithelium of the gastrointestinal tract extends as far back as the latter part of the last century.2 Prior to the advent of radioactive isotopes and the technique of microautoradiography, the study of cell renewal was based on mitotic counting. Earlier studies of Leblond and his associates utilized mitotic indices and microautoradiography for the estimation of turnover times in the intestinal epithelium of animals.3, 4 Rapid renewal of cells based on mitotic counts in the human intestine has been observed by Bertalanffy and Nagy,5 by Padykula et al.,6 and Yardley et aJ.7 Experiments by Cole and McKalen,8 MacDonald and his associates,9 Shorter et aJ.45 and Lipkin et aJ.1°-12 with tritiated thymidine (H3TdR) and microautoradiography, have confirmed the finding of rapid renewal of cells in the human intestine. The development of microautoradiography has provided an approach that has allowed extension and amplification of the dynamics of cell renewal. The incorporation into DNA of precursors such as H 3TdR makes possible the labeling of cells at a precise time in their life cycle. The low fj-energy of the tritium permits precise localization of newly formed DNA on mi-

Colonic hyperproliferation induced in rats and mice by nutritional-stress diets containing four components of a human Western-style diet (series 2)

In a previous study colonic hyperplasia and hyperproliferation were induced in mice and rats by a nutritional-stress diet, based on the AIN-76A semisynthetic diet modified to contain four suggested high-risk components of the human Western-style diet: increased fat and phosphate and decreased calcium and vitamin D contents. In this study the effect of raising calcium alone to near the median level (0.22 mg/kcal) and to a high level (1.3 mg/kcal), comparable to adult human dietary intake, was tested in mice and rats while retaining the three other high-risk components. With median calcium intake the nutritional-stress diet induced hyperproliferation of epithelial cells in colonic crypts, with increased numbers of proliferating cells in crypt columns in sigmoid colon of mice (P less than 0.001) and rats (P = 0.02) and in the ascending colon of mice (P = 0.01). With high calcium intake, hyperproliferation was reduced almost to control amounts in the presence of unchanged fat, phosphate, and vitamin D.

Tissue culture of human epithelial cells from benign colonic tumors

SummaryHuman colonic epithelial cells from three classes of benign tumors have been reproducibly cultured free of fibroblasts for 8 wk using a supplemented Medium 199 (M 199S). The cultured colonic cells were identified as epithelial by the presence of junctional complexes (tight junctions, gap junctions, and desmosomes), a brush border on the apical surface, keratin fibrils, and by both a close-packed columnar or cuboidal morphology and the capability to transport water and ions to form hemicysts. Colony formation was initiated by groups of epithelial cells, not by single cells, and was inhibited by cocultivation with either lethally irradiated 3T3 cells or human diploid fibroblasts. Enhancement of epithelial colony formation was observed following culture on nonadherent, “floating” substrates compared with substrates attached directly to the bottom of the culture dish.Replication of epithelial cells in M 199S from the class of benign colonic tumors least prone to malignancy, the tubular, was significantly enhanced by epidermal growth factor (EGF). In contrast, EGF did not stimulate the growth of cells in M 199S from the other classes of benign tumors, the villotubular and the villous, which exhibit more malignant potential. These data imply that premalignant colonic epithelial cells lose responsiveness to growth modulation by EGF as they progress toward frank carcinoma.

Nondegradation of fecal cholesterol in subjects at high risk for cancer of the large intestine.

In previous studies subjects with familial polyposis, the autosomal dominant disease leading to colon cancer, excreted higher levels of fecal cholesterol than normal subjects, with decreased conversion to degradation products. Findings suggested fecal cholesterol degradation as a marker of hereditary predisposition to colon cancer. Current measurements now have shown that affected individuals and asymptomatic progeny in a second population group with inherited predisposition to colon cancer are low converters of fecal cholesterol. The latter group consisted of highly colon cancer prone families without polyposis, in which patterns of inheritance similar to the autosomal dominant pattern of familial polyposis were observed. 24-h stool collections were obtained from 72 subjects who consumed mixed western diets. Mean percent degradation of fecal cholesterol to coprostanol, coprostanone, cholestanol, and cholestanone revealed significant decreases in fecal cholesterol conversion in affected and asymptomatic subjects in colon cancer prone families without polyposis (P < 0.001) compared to controls. This is in addition to those with familial polyposis (P < 0.001), and extends this marker of colon cancer susceptibility to a second population group with hereditary predisposition to colonic neoplasia.

Defective recognitive immunity in family aggregates of colon carcinoma.

Cancer-free individuals from family agregates of seemingly hereditary colon carcinoma were studied to determine the nature of their cell-mediated immune capacities in miexed leukocyte culture. Members of families who demonstrated no evidence of a precancerous condition such as polyposis coli did demonstrate substantial cellular immunopathology. Of these, 44% showed a decreased responsiveness of their peripheral mononuclear cells to allogeneic stimuli, and in a number of these individuals this deficiency clearly manifested itself as an inappropriate suppression of potentially normal lymphocyte blastogenic capacities by an adherent population of mononuclear leukocytes. This in vitro defect of recognitive immunity appears to be the same type of defect that has already been described for individuals with established maligancies. The pattern of phenotypic expression of this immunopathology within these families is not inconsistent with an hereditary disorder. Individuals from families with a known hereditary somatic precancerous condition usually did not demonstrate this immunopathology. It is appropriate to speculate that the defect of recognitive immunity in the former families could be contributory to the genesis of the colon carcinoma.

Calcium plus vitamin D alters preneoplastic features of colorectal adenomas and rectal mucosa

Calcium and vitamin D are chemopreventive agents for colorectal neoplasia. Studies of the effects of calcium and vitamin D on early surrogate markers of reduced risk, such as proliferation, have been limited to evaluation of the flat colorectal mucosa. Biologic changes that may occur in colorectal adenomas after chemopreventive regimens have not been reported.