Genetic alterations in DNA diploid, aneuploid and multiploid colorectal carcinomas identified by the crypt isolation technique

Abstract

Loss of heterozygosity (LOH) and microsatellite instability (MSI) commonly occur in colorectal carcinomas. However, the role of these genetic alterations in determining DNA ploidy status of tumors (diploid, aneuploid and multiploid) remains unclear. In the present study, we attempted to clarify the relationship between genetic alterations and DNA ploidy status. Crypt isolation coupled with DNA cytometric sorting and polymerase chain reaction assay (17 microsatellite markers) were used to study allelic losses and MSI in 59 colorectal carcinomas (diploid, 15; aneuploid, 10 and multiploid, 34). Of the 15 diploid carcinomas, 6 exhibited MSI in which allelic losses were rarely found. The other 9 diploid tumors mostly exhibited allelic losses, but none displayed MSI status. Whereas allelic losses frequently occurred in the aneuploid carcinomas and the aneuploid populations of multiploid carcinomas, they were rarely detected in the diploid populations of multiploid carcinomas. MSI status was not observed in aneuploid carcinomas nor in either population of multiploid carcinomas. Although multiploid carcinomas genetically resemble aneuploid carcinomas in the expression of the severe LOH phenotype, the genetic alterations seen in the diploid populations of multiploid carcinomas may differ from those of diploid carcinomas. Furthermore, all diploid, aneuploid and both the diploid and aneuploid fractions of the multiploid tumors that were non‐MSI exhibited a high rate of LOH, suggesting that LOH is independent of the tumor's ploidy status. Int. J. Cancer 88:614–619, 2000. © 2000 Wiley‐Liss, Inc.

Analysis of allelic imbalances at multiple cancer‐related chromosomal loci and microsatellite instability within the same tumor using a single tumor gland from colorectal carcinomas

“…In fact, in previous studies, this marker was commonly used to study allelic imbalance in gastrointestinal tumors. 12,23 To our knowledge, the extensive analysis of LOH within the same tumor using multiple sets of 10 single tumor glands to examine intratumoral heterogeneity of colorectal carcinomas has not been previously studied. In addition, our results showed a high frequency of genetic intratumoral heterogeneity (27/30; 90%).…”

Three independent genetic profiles based on mucin expression in early differentiated-type gastric cancers—a new concept of genetic carcinogenesis of early differentiated-type adenocarcinomas

“…These microsatellite markers have been reported frequently in gastric 18 or colorectal carcinomas. 19,20 Microsatellite markers on 1p, 8p and 22q that are used for analysis of LOH in colorectal carcinomas were examined, since the histological appearance of differentiated-type carcinoma of the stomach resembles that of colorectal carcinomas. In addition, a variable number of tandem repeat polymorphisms at the DCC locus were tested.…”

“…For quantitative detection of the allelic loss at each locus, PCR-LOH (loss of heterozygosity) analysis was performed as described previously. 19,20 A 1-ml aliquot of the PCR product was added to 3-ml formamide and a 0.5-ml TAMRA 500 size standard (Applied Biosystems, CA, USA), loaded on a 6% polyacrylamide-8-M urea gel, and run for 2-6 h in a 373A Automated Sequencer (Applied Biosystems, CA, USA) at a constant power of 30 W.…”

“…MSI-positive colorectal carcinomas were used as controls in the study and were divided into two groups, those with high-level instability (ie, MSI at^33% of loci) and those with low-level instability (ie, MSI at %17% of loci), as described previously. 20,21 However, tumors with only one alteration of the marker examined using the above criteria, and those were previously categorized as MSI low, were considered MSI-negative tumors in this study.…”

Molecular Validation of the Modified Vienna Classification of Colorectal Tumors

“…These changes characterize the chromosomal instability (CIN) or LOH genotype, which is often associated with DNA aneuploidy. [7][8][9] Aneuploidy is well known as an indicator used to predict the malignant potential of colorectal adenomas. Most sporadic colorectal carcinomas arising in Western countries are believed to arise from adenoma 10 and belong genetically to the LOH genotype.…”