Analysis of MYC and chromosome 8 copy number changes in gastrointestinal cancers by dual-color fluorescence in situ hybridization.

We performed dual (two-color) fluorescence in situ hybridization (FISH) by using direct fluorescent labeling probes for C-MYC and chromosome 8 in six gastrointestinal (three stomach and three colon) cancers. There are several reports of increased C-MYC copy numbers in solid tumors. To date, however, genetic rearrangements including those of the C-MYC gene have not actually been detected by FISH. Metaphase FISH demonstrated the C-MYC gene on other chromosomes (i.e., in addition to chromosome 8) in one gastric cancer. Somatic mutations such as chromosome translocation or insertion including the C-MYC gene are assumed to have occurred in this case. Our results suggest that genetic rearrangements, in addition to an increased C-MYC copy number, may be a mechanism of MYC oncogene activation in solid tumors.