Oncogene amplification in solid tumors.

The term gene amplification refers to the selective increase of the gene copy number and is better designated as DNA amplification. It should not be confused with elevated gene expression, although amplification generally does result in enhanced levels of the products encoded by the amplified gene. Amplification is one of the mechanisms by which cells can meet the demand for synthesis of specific gene products in amounts exceeding the transcriptional capacity of a single copy gene. Cytogenetic studies of human and animal tumor cells have provided evidence for mysterious chromosomal abnormalities including double minutes (DMs), C-bandless chromosomes (CMs) or homogeneously staining chromosomal regions (HSRs) diagnostic for amplified DNA. MYCN has been the first oncogene found amplified in direct preparations of solid tumors, the group of oncogenes undergoing amplification has considerably expanded since. Today amplification of oncogenes is recognized as a major player in the development of many solid tumors in humans and at the same time is a reflection of the genetic instability of solid tumor cells.