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

Abstract

Genetic changes related to colorectal carcinomas are accumulated in individual tumor glands during disease progression. Microsatellite allelic analysis of individual tumor glands from 30 colorectal carcinomas using a polymerase chain reaction (PCR) assay coupled with crypt isolation was used to detect intratumoral genetic heterogeneity, the sequence of allelic imbalances (AIs) and the microsatellite instability status of single tumor glands during neoplastic progression. In addition, the CpG islands methylated phenotype (CIMP) status was examined using a methylation-specific PCR method. The specimens were divided into 2 groups: a pooled gland sample, which was composed of more than 50 tumor glands, and a single tumor gland sample. The latter consisted of 10 single tumor glands, which were obtained from the same tumor separately. Most colorectal carcinomas (27 of 30 tumors) examined were heterogeneous for at least one genetic alteration, with from 2 to 7 genotypically different subclones detected per tumor. In 12 of the 27 heterogeneous tumors, it was possible to define the order of genetic alterations during the tumor progression. By analyzing multiple single tumor glands within the same tumor, we found that various subclonal expansions were seen within the same tumors.

DNA methylation of interferon regulatory factors in gastric cancer and noncancerous gastric mucosae

“…RNA was also obtained from normal stomach glands using the crypt isolation technique as described previously. (30) Gene expression analysis. Real-time PCR was carried out using TaqMan Gene Expression Assays (Applied Biosystems, Foster City, CA, USA) and a 7900HT Fast Real-Time PCR System (Applied Biosystems) according to the manufacturer's instructions.…”

Microsatellite instability in colorectal cancer

“…It is believed that the adenoma-carcinoma sequence underlies the development of colorectal cancer in most patients, and two distinct pathways have been identified -the microsatellite instability (MSI) and the chromosomal instability (CIN) pathways 2 -6 . Discovery of these two pathways has led to the paradigm of colorectal cancer as a genetically heterogeneous disease 2,5,7 . Colorectal cancer with MSI has a better prognosis than stage-matched microsatellitestable cancer 8 -12 .…”

Molecular analysis of single isolated glands in gastric cancers and their surrounding gastric intestinal metaplastic mucosa

“…It has long been established that gastric cancers develop from a single gland cell that undergoes an accumulation of genetic changes (1), and which eventually results in a malignant tumor with monoclonal character (2,3). Recent molecular genetic evidence also supports this concept (1).…”

“…According to established theory, these accumulated genetic alterations can be identified by loss of heterozygosity (LOH) at many chromosomal loci within the tumor (4). It is also true that differences between tumor glands are thought to cause genetic heterogeneity within the same tumor (1)(2)(3), and some studies stated that genetic heterogeneity is frequently found in individual gastric cancers (5)(6)(7). Such genetic heterogeneity within the same tumor complicates the development of a tumor-treatment strategy based on tumor pathogenesis (8,9).…”

“…Such genetic heterogeneity within the same tumor complicates the development of a tumor-treatment strategy based on tumor pathogenesis (8,9). Analyzing the accumulation of multiple genetic alterations in a single tumor gland is thought to be useful for assessing genetic differences among the cells of a single tumor (2,3).…”