Expansion of the Epithelial Cell Proliferative Compartment and Frequency of Adenomatous Polyps in the Colon Correlate with the Strength of Family History of Colorectal Cancer

Expansion of the proliferative compartment of epithelial cells in colonic crypts and colonic adenomas have been described as phenotypic precursors to colon cancer in individuals affected with hereditary or sporadic colon cancer. This study measured the size of the proliferative compartment in colonic crypts and the frequency of adenomas in asymptomatic members of families having sporadic colorectai cancer. The subjects were divided into 2 groups according to the frequency of colorectal cancer in their families. A shift of the compartment of proliferating epithelial cells toward the lumenal surface of colonic crypts was seen in the group of subjects with a stronger family history of colorectal cancer, with significant differences in the numbers of proliferative cells in the upper and the lower crypt compartments (P < 0.05) and in the fraction of proliferative cells at the highest compartment at the lumenal surface of the crypts (P < 0.05). Cell proliferation patterns in normal-appearing mucosa of the 2 groups revealed no difference in whole crypt [3H]thymidine labeling index. Colonoscopic examination of the 56 subjects revealed an overall prevalence of adenomas of 21%; when stratified by frequency of colorectai cancer in their families, 3 of 22 subjects (14%) with a weaker family history had adenomas, while 9 of 34 (26%) with a stronger family history had adenomas. Thus, parallel abnormalities of colonic epithelial cell proliferation and neoplasia were seen in individuals with a family history of colorectal cancer, both of which were more pronounced with increasing strength of family history. This observation provides further evidence of relationships among these factors in the etiology of "sporadic" colorectal cancer. I N T R O D U C T I O N The appearance of colorectal cancer in patients with FAP 5 and HNPCC follows a classical autosomal dominant Mendelian pattern of inheritance. In both syndromes, the adenoma is believed to be the precursor lesion, with hundreds to thousands of colorectal adenomas occurring in FAP, and few in HNPCC. The gene for FAP has now been localized to the long arm of chromosome 5, and studies are in progress to identify the function of this gene as well as mechanisms leading to cancer (1-4). Recent studies o f sporadic colorectal cancer in the general population have also suggested that inheritance has a role in its development (5, 6). Familial clustering with approximately a 3-fold increase in colorectal cancer incidence has been observed in families having first degree relatives affected by colon cancer (7-9). Individuals at risk for colorectal cancer by virtue of their family history have had abnormal proliferation of colonic epithelial cells Received 8/17/92; accepted 10/29/92. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. To whom requests for reprints should be addressed, at Memorial Sloan-Kettering Cancer Center, Box 408, 1275 York Avenue, New York, NY 10021. 2 Current address: 120 Summit Avenue, P.O. Box 1005, Summit, NJ 07902. 3 Current address: Maimonides Medical Center, 4802 10th Avenue, Brooklyn, NY 11219. 4 Current address: North Shore University Hospital, 300 Community Drive, Manhasett, NY 11030. 5 The abbreviations used are: FAP, familial adenomatous polyposis; HNPCC, hereditary nonpolyposis colorectal cancer; dThd, thymidine; FICC, familial index of colorectal cancer. (10-15), resulting in an expanded size of the normal colonic crypt zone of cell proliferation, a phenotypic abnormality preceding the development of adenomas and carcinomas. However, no studies have been carried out on relatives of individuals with "sporadic" colon cancer to specifically examine relationships between cell proliferation, the occurrence of adenomas, and the strength of the family history. A study of this type could clarify whether relatives in "sporadic" colon cancer families possess proliferative patterns similar to members of FAP and HNPCC families, whether the phenotype is inherited, and whether it parallels the presence of adenoma formation and colon cancer. The present study investigates the expression of both colonic epithelial cell proliferation and adenomatous polyps in relatives of individuals with "sporadic" colorectal cancer. Both of these findings are potential biomarkers of an underlying tumor suppressor gene, which, like the genes responsible for FAP and HNPCC, could lead to an individual 's having increased susceptibility for the development o f colorectal cancer. M A T E R I A L S AND M E T H O D S Subjects with one or more relatives affected with colorectal cancer were studied. Family histories were obtained from probands to determine the presence of colorectal cancer in first, second, and third degree relatives. Verification was obtained from hospital records, death certificates, and physician reports. All subjects included had no personal history or symptoms of colorectal neoplasia or other cancer and no history of inflammatory bowel disease, and were in good general health. All subjects had a total colonoscopy performed following a 2-day liquid diet, citrate of magnesia, and tap water enemas. All identified polyps were removed and processed for histological examination. Slides of removed polyps were reviewed by one pathologist (C. U.) without knowledge of the subject's family history, and polyps were classified as either hyperplastic, tubular, tubulovillous, villous, or other (normal mucosa, inflammation, etc.). At the time of colonoscopy, biopsies from normal-appearing colonic mucosa were also obtained from the rectum for the study of mucosal proliferation. These biopsies were incubated with [3H]dThd according to methods described previously and were processed for microautoradiography (10). Mucosal specimens sectioned longitudinally from the base of colonic crypt to the lumen were analyzed by light microscopy. The total number of cells per crypt column was counted with each side of the crypt column being counted separately, and number and position of [3H]dThd-labeled cells were counted and scored. Measurements were performed without knowledge of the individual subject's family history. The height-distribution patterns for labeled cells were determined as described previously (10, 16), and the location of [3H]dThd-labeled and unlabeled epithelial cells in colonic crypts of individuals in each of the 2 groups of subjects studied was analyzed by computer program (16). For the entire crypt column, and for each crypt compartment [crypt divided equally into 5 compartments: 1 (base) to 5 (surface)], the following were measured: (a) the total number of epithelial cells; (b) the number of [3H]dThd-labeled epithelial cells; and (c) the fraction of [3H]dThd-labeled epithelial cells (labeling indices). Statistical comparisons were made using the 2-tailed Student's t test for comparison of means and the X 2 statistic for comparison of outcomes. Parents, siblings, and children of a given individual were scored as first degree relatives by convention. Grandparents, aunts, and uncles were scored as