Molecular genetic changes in benign colorectal tumors synchronous with microsatellite unstable carcinomas do not support a field defect.

Background: A colorectal cancer may develop through a particular molecular genetic pathway, raising the question of whether the particular molecular changes are random, or are unique to the particular segment of colon. We wanted to determine whether molecular changes found within a colorectal cancer might also be detected in separate adenomas and polyps removed from the same area of colon at surgery. Microsatellite instability was chosen as a marker for a pathway of colon carcinogenesis.

GNAS gene mutation may be present only transiently during colorectal tumorigenesis.

Mutations of the gene GNAS have been shown to activate the adenylate cyclase gene and lead to constitutive cAMP signaling. Several preliminary reports have suggested a role for GNAS gene mutations during colorectal carcinogenesis, particularly mucinous carcinomas. The aim of this study was to clarify the incidence of GNAS mutations in adenomas (tubular, tubulovillous, and villous), carcinomas with residual adenoma, and carcinomas, and to relate these findings to mutations of the KRAS gene and to the mucinous status of the tumors.

Copy number of the Adenomatous Polyposis Coli gene is not always neutral in sporadic colorectal cancers with loss of heterozygosity for the gene.

Background: Changes in the number of alleles of a chromosome may have an impact upon gene expression. Loss of heterozygosity (LOH) indicates that one allele of a gene has been lost, and knowing the exact copy number of the gene would indicate whether duplication of the remaining allele has occurred. We were interested to determine the copy number of the Adenomatous Polyposis Coli (APC) gene in sporadic colorectal cancers with LOH.

Colorectal Cancers with the Uncommon Findings of KRAS Mutation and Microsatellite Instability.

Sporadic colorectal cancers with microsatellite instability (MSI) frequently contain a mutation of the BRAF gene. Additionally, it has been shown that BRAF mutations in colorectal cancers are mutually exclusive of KRAS mutation. We evaluated 14 cases of colorectal cancer with MSI that were BRAF wild type but demonstrated a KRAS mutation.

Strong correlation between molecular changes in endometrial carcinomas and concomitant hyperplasia.

Objective: Endometrial cancer (EC) results from the accumulation of numerous genetic abnormalities contributing to the progression from hyperplasia to EC. Information on these various genetic changes has been primarily derived from studying groups of either hyperplasias or cancers.We evaluated both hyperplastic and EC tissue obtained from the same surgical specimens for KRAS mutations, microsatellite instability (MSI), and mismatch repair gene methylation, and results were correlated between the paired hyperplastic tissue and EC.

Colorectal tumors from APC*I1307K carriers principally harbor somatic APC mutations outside the A8 tract.

Purpose: APC*I1307K (c.3920T>A) is an inherited variant associated with colorectal tumour risk found almost exclusively in those of Ashkenazi Jewish ancestry. A single nucleotide substitution creates an oligo-adenine tract (A8) that appears to be inherently prone to further mis-pairing and slippage.

Detailed molecular genetics of the APC*E1317Q mutation in tumor tissue suggest it may not be pathologically significant.

APC*E1317Q is a low-penetrance variant of the APC gene suggested as a risk for the development of colorectal adenomas and carcinomas. There is very little in the literature describing the molecular details of APC*E1317Q in tumor tissue. We provide information about the molecular genetics of 3 patients with APC*E1317Q.

Similarities of molecular genetic changes in synchronous and metachronous colorectal cancers are limited and related to the cancers' proximities to each other.

Synchronous and metachronous colorectal cancers are distinct primary neoplasms diagnosed either simultaneously or sequentially in the same patient. Because they arise in a common genetic and environmental background, they offer a unique opportunity to study molecular genetic changes occurring during carcinogenesis. We evaluated tumors from 50 patients with synchronous and five additional patients with metachronous cancers for loss of heterozygosity of the genes APC and DCC, KRAS and BRAF gene mutations, and microsatellite instability and methylation.

KRAS gene mutations are more common in colorectal villous adenomas and in situ carcinomas than in carcinomas.

We have evaluated the frequency of KRAS gene mutations during the critical transition from villous adenoma to colorectal carcinoma to assess whether the adenomas contain a KRAS mutation more frequently than carcinomas. We analyzed sporadic villous and tubulovillous adenomas, in situ carcinomas, and primary colorectal carcinomas from multiple patients. The cancers were further evaluated for mucinous status and microsatellite instability.

Ki-ras gene mutations are invariably present in low-grade mucinous tumors of the vermiform appendix.

Objective: Low-grade mucinous tumors of the appendix appear to have a simple histological structure. Paradoxically, reports have suggested a greater frequency of Ki-ras gene mutation in these lesions than in more complex lesions such as benign colonic adenomas and carcinomas. We assessed several molecular genetic changes, including Ki-ras gene mutations, in a large series of low-grade mucinous tumors of the appendix.

Microsatellite instability and DNA methylation of endometrial tumors and clinical features in young women compared with older women.

Introduction: Molecular genetic changes in endometrial cancers are important to identify possible family cancer syndromes and thus, to facilitate appropriate screening. Most studies in this regard have focused primarily on young women. We have assayed cancers for microsatellite instability (MSI) and DNA methylation from a large group of patients younger than 50 years and a comparable group of older women.

Adequacy of colonoscopic biopsy specimens for molecular analysis: a comparative study with colectomy tissue.

Molecular analyses of tumors are increasingly useful for prognosis and for guiding therapy. Colonoscopic biopsy provides the first source of tissue for most cases of colorectal carcinoma and therefore might become an important source for molecular analyses. We have addressed the question whether molecular analyses of colonoscopic biopsy yield results similar to the findings from the surgical specimen.

Clinical and genetic findings in an Ashkenazi Jewish population with colorectal neoplasms.

Background: The authors evaluated the frequency of the carrier status of three ancestral colorectal neoplasm-associated mutations (APC:I1307K, BLM(Ash), and MSH2*1906G>C) found in the Jewish population among a case series with documented colorectal neoplasms. They further compared family and personal histories plus environmental exposures of the carriers and noncarriers of the I1307K mutation and examined clinical differences with regard to the colorectal neoplasms and the specific molecular genetic changes in these lesions.

Methods: Analyses were performed on tissue from stored paraffin-embedded blocks for the three germline mutations plus the KRAS mutation and APC loss of heterozygosity (LOH) and APC gene sequencing.

The Adenomatous Polyposis Coli (APC) gene microsatellite marker D5S1385 is equally informative for loss of heterozygosity as the marker D5S346.

Molecular analyses for loss of heterozygosity (LOH) at a gene locus are used to identify genomic imbalance in tumor tissue. A frequently utilized microsatellite marker for the Adenomatous Polyposis Coli (APC) gene is denoted D5S346. However, when an individual has two identical forms of this microsatellite, then a second microsatellite, also near the APC gene, is needed.

The characterization of somatic APC mutations in colonic adenomas and carcinomas in Ashkenazi Jews with the APC I1307K variant using linkage disequilibrium.

Mutations of the adenomatous polyposis coli (APC) gene play a critical role in the development of colorectal neoplasms. A novel mechanism involves a germline variant, at codon 1307 of the APC gene. The mutation is thought to create an unstable segment of DNA, which facilitates the development of somatic mutations.