Fractional allelic loss in gastric carcinoma correlates with growth patterns

Abstract

To gain an insight into the genetic events underlying morphological phenotypes, we analysed 58 gastric carcinoma tissues for the genome-wide allelotype study using microsatellite markers. Based on a binomial distribution, loss of heterozygosity (LOH) that was significantly more frequent than expected (P<0.05) thus interpreted as nonrandom LOH selected during tumorigenesis. The overall extent of chromosomes undergoing LOH i.e. fractional allelic loss (FAL, the ratio of LOH-positive markers to the total number of informative markers) was measured in each tumor patient. Nonrandom LOH was found on 17p (48.0%), 18q (38.4%), 13q (38.1%) and 9p (36.4%). Overall, there were no significant phenotypes correlated with allelic loss on specific chromosome regions. Based on a bimodal distribution of FAL values with two peaks bordered by a mean of 0.233, tumors were classified into LOH-related (>0.233) and LOH-unrelated (<0.233) types. Among 24 patients with LOH-related tumors, increase in the infiltrative type of growth pattern was found to correspond with a significant trend of increasing FAL values. This study shows that the growth pattern of gastric carcinoma is correlated with FAL, suggesting that a malignant phenotype is influenced by LOH event.