A follow-up study of colonic epithelial proliferation as a biomarker ina Native-American family with hereditary nonpolyposis colon cancer

Regional differences in colorectal cancer incidence, stage, and subsite among American Indians and Alaska Natives, 1999-2004

BACKGROUND

Colorectal cancer (CRC) is a leading cause of cancer morbidity and mortality for American Indians and Alaska Natives (AI/ANs), but misclassification of race causes underestimates of disease burden.

METHODS

The authors compared regional differences in CRC incidence, stage at diagnosis, and anatomic distribution between AI/ANs and non-Hispanic whites (NHWs). To reduce misclassification, data from the National Program of Cancer Registries; the Surveillance, Epidemiology, and End Results Program; and the Indian Health Service (IHS) were linked. The analysis was limited to the 56% of AI/AN who live in IHS Contract Health Service Delivery Areas.

RESULTS

From 1999 to 2004, the overall incidence rate (per 100,000 persons per year) of CRC was 9% lower in the AI/AN population (46.3) than in the NHW population (50.8). However, AI/AN CRC incidence rates varied nearly 5-fold regionally, from 21 in the Southwest to 102.6 in Alaska. Compared with NHW rates, AI/AN rates were significantly higher in Alaska (rate ratio [RR], 2.03), the Northern Plains (RR, 1.39), and the Southern Plains (RR, 1.16) but were lower in the Pacific Coast (RR, 0.80), the East (RR, 0.65), and the Southwest (RR, 0.45). AI/ANs were diagnosed more often with advanced CRC than with localized CRC (RR, 1.92) compared with NHWs (RR, 1.48). Females more often had proximal CRC among both the AI/AN population (females, 40.1%; males, 33.5%) and the NHW population (females, 50.1%; males, 40.3%), although AI/ANs had a higher proportion of distal cancers overall.

CONCLUSIONS

CRC incidence rates in AI/AN populations varied dramatically between regions. Efforts are needed to make CRC screening a priority, overcome barriers to endoscopic screening, and to engage AI/AN communities in culturally appropriate ways to participate in prevention and early detection programs.

A Monotonous Population of Elongated Cells (MPECs) in Colorectal Adenoma Indicates a High Risk of Metachronous Cancer

Accurate predictors for metachronous colorectal cancer (CRC) development after polypectomy are lacking. We evaluated the prognostic value of classical clinicopathologic features and a monotonous population of elongated cells (MPECs) in colorectal adenomas from 171 consecutively selected population-based patients with long-term follow-up. Quantitative image analysis, and univariate and multivariate regression analysis were applied. Ten of 171 adenomas (5.8%) developed metachronous CRC (defined as >24 mo interval and >5 cm from the index adenoma to the cancer). Median follow-up of adenomas with metachronous CRC was 68.4 and without cancer 149.7 months (range: 25 to 192 and 25 to 256, respectively). The most prognostic classical features were the localization of the marker adenoma as proximal (ie, in the cecum through transverse colon) versus distal from the transverse colon [P=0.0003, hazard ratio (HR)=8] and the number of polyps found during colonoscopy (<or=2 vs.>2, P=0.002, HR=6). Quantitative features of the MPECs included the longest nuclear axis and variance of the number of nuclei with 2 neighbors (higher and lower in cancer cases, respectively). Of the 171 adenomas, 50 (29%) had MPECs, of which 9 (18%) patients developed metachronous CRC at follow-up, contrasting 1/121 (0.8%) without MPECs (P=0.0003, HR=23). MPECs occurred in both low-grade and high-grade dysplasia, and in tubular and (tubulo) villous adenomas. MPECs had the strongest predictive value for metachronous CRC development. Adenomas proximally located had additional value but only if they were MPEC positive (which only occurred in 5 adenomas, 3 of which (60%) developed cancer). Having more than 2 polyps also had additional prognostic value but only in MPEC-negative adenomas [10 cases; 1 (10%) developed cancer]. Dysplasia grade and histologic growth pattern had no additional value. Thus, colorectal adenomas with subsequent metachronous cancer development can be identified more accurately with MPECs than with classical prognostic factors.

Inherited predisposition to cancer: a historical overview

The hereditary predisposition to cancer dates historically to interest piqued by physicians as well as family members wherein striking phenotypic features were shown to cluster in families, inclusive of the rather grotesque cutaneous findings in von Recklinghausen's neurofibromatosis, which date back to the sixteenth century. The search for the role of primary genetic factors was heralded by studies at the infrahuman level, particularly on laboratory mouse strains with strong susceptibility to carcinogen-induced cancer, and conversely, with resistance to the same carcinogens. These studies, developed in the 19th and 20th centuries, continue today. This article traces the historical aspects of hereditary cancer dealing with identification and ultimate molecular genetic confirmation of commonly occurring cancers, particularly of the colon in the case of familial adenomatous polyposis and its attenuated form, both due to the APC germline mutation; the Lynch syndrome due to mutations in mismatch repair genes, the most common of which were found to be MSH2, MLH1, and MSH6 germline mutations; the hereditary breast-ovarian cancer syndrome with BRCA1 and BRCA2 germline mutations; the Li-Fraumeni (SBLA) syndrome due to the p53 mutation; and the familial atypical multiple mole melanoma in association with pancreatic cancer due to the CDKN2A (p16) germline mutation. These and other hereditary cancer syndromes have been discussed in some detail relevant to their characterization, which, for many conditions, took place in the late 18th century and, in the more modern molecular genetic era, during the past two decades. Emphasis has been placed upon the manner in which improved cancer control will emanate from these discoveries.

Development of a genetics education workshop curriculum for Native American college and university students

The long-term goal of Genetic Education for Native Americans (GENA), a project funded by the National Human Genome Research Institute (NHGRI), is to provide a balance of scientific and cultural information about genetics and genetic research to Native Americans and thereby to improve informed decision making. The project provides culturally sensitive education about genetic research to Native American medical students and college and university students. Curriculum development included focus groups, extensive review of available curricula, and collection of information about career opportunities in genetics. Special attention was focused on genetic research to identify key concepts, instructional methods, and issues that are potentially troublesome or sensitive for Native Americans. Content on genetic research and careers in genetics was adapted from a wide variety of sources for use in the curriculum. The resulting GENA curriculum is based on 24 objectives arranged into modules customized for selected science-related conference participants. The curriculum was pretested with Native American students, medical and general university, health care professionals, and basic scientists. Implementation of the curriculum is ongoing. This article describes the development and pretesting of the genetics curriculum for the project with the expectation that the curriculum will be useful for genetics educators working in diverse settings.

Genetic counseling in a Navajo hereditary nonpolyposis colorectal cancer kindred

BACKGROUND

Cross-cultural genetic counseling was provided to an extended Navajo Indian family in which the MLH1 gene mutation for hereditary nonpolyposis colorectal cancer (HNPCC) had been identified. The family had been observed by the authors since 1983 and over the years had been provided with intensive education regarding the natural history of HNPCC as well as recommendations for cancer surveillance and management that was responsive to this natural history.

METHODS

Following identification of the MLH1 mutation, DNA from family members was evaluated by a reference laboratory (OncorMed, Gaithersburg, MD), where sequences were checked in both the forward and reverse directions against the published sequence for MLH1. The 4bp deletion beginning at the first nucleotide of codon 727 was easily visualized in the heterozygous condition in both affected and predispositional individuals. The family was reeducated as a group and then provided further education individually during genetic counseling sessions, at which time they were appraised of potential penalties, such as insurance and employer discrimination, and psychological sequelae that could result from knowledge of the MLH1 mutation. Strict confidentiality of this information was assured.

RESULTS

DNA testing was performed on 51 family members. Twenty-three individuals were counseled, seven of whom were positive for MHL1. Reactions ranged from full acceptance of the genetic implications to traditional Navajo reasoning such as the family had been cursed.

CONCLUSIONS

DNA-based genetic counseling requires comparison and empathy, coupled with intensive preeducation regarding potential penalties and advantages that might emanate from this knowledge. Special care must be given to patients' culture, beliefs, and traditions.

Colorectal cancer and noncancer patients have similar labeling indices by microscopy and computed image analysis

The labeling index (LI), a microscopic measurement of proliferative activity in colonic crypts, is proposed as an indicator of colonic cancer risk. Computed image analysis of proliferative regions is less labor intensive and more objective than is direct microscopy but has not been validated for labeling indices by direct comparison. The authors compared colonic crypt proliferation in 26 cancer and 13 noncancer patients by using Ki-67 monoclonal antibody (McAb) labeling of flat mucosa obtained from surgically removed, frozen specimens. In cancer patients, the mucosa specimen was excised 10 cm away from the tumor, and the LI was determined microscopically for the whole crypt, the upper two thirds, and the upper one third of 15 crypts. Nuclear antigen levels of 15 whole crypts were determined by using the CAS-200 computed image analyzer (Cell Analysis Systems, Elmhurst, IL). Cancer and noncancer specimens were compared as were microscopically determined LI and stained nuclei specimens by using image analysis. No statistically significant difference in proliferative activity of whole crypts, or the upper two thirds of crypts, was observed between cancer specimens and noncancer specimens from using either technique. However, a significant correlation existed between microscopic analysis and computed image analysis of labeled nuclei. Computed image analysis using Ki-67 McAb labeling can be used instead of microscopy to determine crypt LI, but neither method can be used to distinguish cancer specimens from noncancer specimens.

Evolution of hereditary bowel cancer

Familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC) are both inherited as autosomal dominant conditions in which the mutation gives rise to a tendency to produce precancerous adenomas. However these two forms of hereditary bowel cancer show important differences at the clinical, pathological and molecular genetic levels. It is argued that the first tissue manifestation of FAP is the unicryptal adenoma. The existence of a preceding field change characterised by diffuse hyperproliferation and various altered phenotypes does not stand up to critical scrutiny. The processes of neoplastic evolution in FAP and HNPCC are compared in detail. It is suggested that an understanding of the function of the FAP and HNPCC genes will lead to the development of cancer prevention strategies aimed at blocking the earliest stages of neoplastic development.

Genetics, natural history, tumor spectrum, and pathology of hereditary nonpolyposis colorectal cancer: an updated review

Hereditary nonpolyposis colorectal cancer (HNPCC) dates to Warthin's description of family G, which he began studying in 1895. Warthin's observations were not fully appreciated until 1966 when two families with an autosomal dominant inheritance pattern of nonpolyposis colorectal cancer (CRC) and endometrial cancer were described. This condition was first termed the "cancer family syndrome" and was later renamed HNPCC. Some have proposed that HNPCC consists of at least two syndromes: Lynch syndrome I, with hereditary predisposition for CRC having early (approximately 44 years) age of onset, a proclivity (70%) for the proximal colon, and an excess of synchronous and metachronous colonic cancers and Lynch syndrome II, featuring a similar colonic phenotype accompanied by a high risk for carcinoma of the endometrium. Transitional cell carcinoma of the ureter and renal pelvis and carcinomas of the stomach, small bowel, ovary, and pancreas also afflict some families. Current estimates indicate that HNPCC may account for as much as 6% of the total CRC burden. There are no known premonitory phenotypic signs or biomarkers of cancer susceptibility in the Lynch syndromes. This report will summarize current knowledge, with emphasis on the manner in which this knowledge can be employed effectively for diagnosis and management of HNPCC.

Rectal epithelial cell proliferation patterns as predictors of adenomatous colorectal polyp recurrence

To determine whether proliferative patterns in flat rectal mucosal samples can predict the recurrence of adenomatous colorectal polyps, after polypectomy, biopsy specimens from normal looking rectal mucosa were obtained at endoscopy from 55 patients diagnosed for the first time as having adenomatous colorectal polyps. Epithelial cell proliferation was assessed in biopsy specimens through 3H-thymidine autoradiography. After polypectomy, patients were followed for 24 months and underwent complete colonoscopy every 6 months to detect and remove any metachronous lesions. In 40 patients second biopsy specimens were taken during one of the follow up colonoscopies to evaluate the stability of proliferative indices over time. The ratio of labelled (S phase) to total cells (labelling index) for the entire crypt, as well as ratios for each of the five equal compartments into which the crypt had been divided longitudinally, was calculated for each patient. Mean labelling indices for upper crypt compartments 3 and 4 + 5 in the 22 patients in whom polyps recurred were significantly higher (respectively p < 0.05 and p < 0.01) than those of the 33 without recurrence suggesting that an upward shift of the crypt's replicative compartment is associated with polyp recurrence. Labelling indices remained essentially unchanged in those patients who underwent biopsy twice. Reproducible kinetic parameters such as these might be useful in planning follow up of patients with adenomatous polyps after polypectomy.

Ulex europaeus agglutinin-1 binding in hereditary bowel cancer

Ulex europaeus agglutinin-1 (UEA-1) binds specifically to alpha-L-fucose, the terminal sugar of blood group substances H2 and Ley the expression of which is confined mainly to the proximal colon. The aim of the study was to determine whether there is neo-expression of alpha-L-fucose in the normal appearing mucosa of the distal bowel in subjects with or at risk of hereditary bowel cancer. UEA-1 binding was investigated by means of a direct lectin-peroxidase technique in tissues derived from patients with familial adenomatous polyposis (9) and affected (16) or at risk of (14) hereditary non-polyposis colorectal cancer. Control tissues were obtained from normal subjects and patients with sporadic bowel cancer and no family history of the condition. There was increased expression of alpha-L-fucose in some adenomas (mosaic pattern), in most carcinomas (diffuse), in hyperplastic polyps (crypt base), but not in normal appearing mucosa or transitional mucosa (adjacent to carcinoma) in any of the groups of patients examined. In view of the negative findings for normal-appearing mucosa, the suggestion that there is a pre-neoplastic field change in subjects at risk of hereditary bowel cancer may be unfounded.