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Clinical epigenetics

Genetic and epigenetic alterations of netrin-1 receptors in gastric cancer with chromosomal instability.


PMID 26207151

Abstract

The gene expressions of netrin-1 dependence receptors, DCC and UNC5C, are frequently downregulated in many cancers. We hypothesized that downregulation of DCC and UNC5C has an important growth regulatory function in gastric tumorigenesis. In the present study, a series of genetic and epigenetic analyses for DCC and UNC5C were performed in a Japanese cohort of 98 sporadic gastric cancers and corresponding normal gastric mucosa specimens. Loss of heterozygosity (LOH) analyses and microsatellite instability (MSI) analysis was applied to determine chromosomal instability (CIN) and MSI phenotypes, respectively. More than 5xa0% methylation in the DCC and UNC5C promoters were found in 45xa0% (44/98) and 32xa0% (31/98) gastric cancers, respectively, and in 9xa0% (9/105) and 5xa0% (5/105) normal gastric mucosa, respectively. Overall, 70xa0% (58 of 83 informative cases) and 51xa0% (40 of 79 informative cases) of gastric cancers harbored either LOH or aberrant methylation in the DCC and UNC5C genes, respectively. In total, 77xa0% (51 of 66 informative cases) of gastric cancers showed cumulative defects in these two dependence receptors and were significantly associated with chromosomal instability. Both DCC and UNC5C were inactivated in 97xa0% of CIN-positive gastric cancers and in 55xa0% of CIN-negative gastric cancers. Defect in netrin receptors is a common feature in gastric cancers. DCC alterations are apparent in the early stages, and UNC5C alterations escalate with the progression of the disease, suggesting that the cumulative alterations of netrin-1 receptors was a late event in gastric cancer progression and emphasizing the importance of this growth regulatory pathway in gastric carcinogenesis.