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

Abstract

Abstract. The biological properties and underlying genetics of gastric cancer and gastric intestinal metaplasia evolve with neoplastic progression from the genetics of the original gland cell. PCR assay with crypt isolation was used in tumors from 20 patients to examine microsatellite alterations (allelic imbalance at 17p, 5q, 18q, 3p, 4p, and 9p, and microsatellite instability) in glands from each tumor and from intestinal metaplastic lesions. Tumor specimens were processed as either pooled-gland samples or single-gland samples. Pooled gland sample was composed of 10-20 tumor glands, intestinal metaplastic glands, or nonmetaplastic glands. Single gland sample was 10 tumor glands from tumor and single gland sample was 5 gastric intestinal metaplastic and 5 nonmetaplastic glands from its surrounding metaplastic mucosa. Multiple genetic alterations were found in individual tumor glands, with various subclonal expansions seen within the same tumor. Although microsatellite instability was found in 2 of 20 tumor single-gland samples, none was detected in metaplastic single-gland samples. Most cancers appear to have a heterogeneous composition. On the other hand, microsatellite alterations were also detected within the nonmetaplastic as well as intestinal metaplastic single-gland samples.In conclusion, the present data on tumor and corresponding intestinal metaplastic and nonmetaplastic glands suggest that genetic alterations already occur within the surrounding of the noncancerous mucosa.

Spatially defined microsatellite analysis reveals extensive genetic mosaicism and clonal complexity in intestinal metaplastic glands

“…found that the incidence of genetic instability [including microsatellite instability (MSI) and loss of heterozygosity (LOH)] was 48% in IM with concurrent gastric cancer and 21% in IM with gastritis only . More recent studies of randomly dissected IM glands suggest that localized alteration in the MSs might have occurred, even though they were undetectable with bulk samples …”

“…11 More recent studies of randomly dissected IM glands suggest that localized alteration in the MSs might have occurred, even though they were undetectable with bulk samples. 12 Since the acquisition of the ability to generate genomic mutations or tolerate accelerated genomic changes is a critical step in the development of malignancy, 13 highly localized and stochastic genomic alterations would have provided an important annotation for the importance of the IM tissues in the cascade toward malignancy.…”

“…Therefore, we have systematically analyzed alterations to well established MS markers (BAX, BAT‐25, D2S123 and D5S346) previously found as sensitive indicators of MSI in IM and gastric cancer in spatially defined IM glands. Using laser capture microdissection (LCM) to isolate IM tissues, we are able to show that there is extensive length heterogeneity as measured by the MS markers not only between individual IM glands, regardless of whether or not they are in close proximity, but also within individual glands.…”

Case of gastric neuroendocrine carcinoma showing an interesting tumorigenic pathway

“…PCR-allelic imbalance (AI) analyses were performed using a thermal cycler (GeneAmp PCR System 9600; Perkin-Elmer, CA, United States) according to previously reported procedures[3]. AIs on chromosomes 1p, 3p, 4p, 5q, 8p, 9p, 13q, 17p, 18p, and 22q were examined using 22 highly pleomorphic microsatellite markers (D1S228, D1S548, D3S2402, D3S1234, D4S2639, D4S1601, D5S107, D5S346, D5S299, D5S82, D8S201, D8S513, D8S532, D9S171, D9S1118, D13S162, TP53, D18S487, D18S34, D22S274, D22S1140, and D22S1168).…”

Complex clonal mosaicism within microdissected intestinal metaplastic glands without concurrent gastric cancer

“…A recent study of IM tissues from the periphery of resected cancer tissues found that there was considerable genomic instability at this stage 5 6. However, since these tissues coinhabit the same microenvironment as cancer and presumably over a prolonged period time, it is critical to determine whether such pervasive genetic instability is an inherent and early property of IM tissue alone.…”