MYC insertions in diffuse-type gastric adenocarcinoma.

BACKGROUND: MYC is important in gastric carcinogenesis. A few studies reported MYC translocation or insertion associated with gastric cancer. MATERIALS AND METHODS: MYC copy number and its insertion, as well as the chromosomes in which MYC was inserted, were evaluated by fluorescence in situ hybridization assay in interphase and metaphase cells of 12 diffuse-type gastric cancer samples. MYC protein expression was evaluated by immunohistochemistry. RESULTS: The presence of 3 MYC signals was the most frequent alteration. All cases also presented 4 and 5 MYC signals. In all samples, we observed chromosome 8 trisomy with MYC copies and MYC insertion into the chromosomes 2, 7, 14, 17, 18 and 22. All samples presented nucleic and cytoplasmic immunoreactivity. CONCLUSION: MYC cytoplasmic immunoreactivity can be the result of MYC insertion with the breakpoints within or close to the regions that are able to target the nucleus. MYC insertion and cytoplasmatic immunoreactivity may be a common characteristic of diffuse-type gastric cancer.

Interrelationship between chromosome 8 aneuploidy, C-MYC amplification and increased expression in individuals from northern Brazil with gastric adenocarcinoma.

AIM: To investigate chromosome 8 numerical aberrations, C-MYC oncogene alterations and its expression in gastric cancer and to correlate these findings with histopathological characteristics of gastric tumors. METHODS: Specimens were collected surgically from seven patients with gastric adenocarcinomas. Immunostaining for C-MYC and dual-color fluorescence in situ hybridization (FISH) for C-MYC gene and chromosome 8 centromere were performed. RESULTS: All the cases showed chromosome 8 aneuploidy and C-MYC amplification, in both the diffuse and intestinal histopathological types of Lauren. No significant difference (P < 0.05) was observed between the level of chromosome 8 ploidy and the site, stage or histological type of the adenocarcinomas. C-MYC high amplification, like homogeneously stained regions (HSRs) and double minutes (DMs), was observed only in the intestinal-type. Structural rearrangement of C-MYC, like translocation, was observed only in the diffuse type. Regarding C-MYC gene, a significant difference (P < 0.05) was observed between the two histological types. The C-MYC protein was expressed in all the studied cases. In the intestinal-type the C-MYC immunoreactivity was localized only in the nucleus and in the diffuse type in the nucleus and cytoplasm. CONCLUSION: Distinct patterns of alterations between intestinal and diffuse types of gastric tumors support the hypothesis that these types follow different genetic pathways.