ABSTRACT
Amplification of many different genes has been described in the literature. The genes that confer drug resistance are particularly amenable to study, and as such they have been used extensively to attempt to unravel the molecular basis of gene amplification. Cells are plated and exposed to the selective agent, and the surviving cells that grow to form colonies are counted. This relative plating efficiency (normalized to the number of surviving cells in the nonselected population) estimates the incidence of drug resistance. The clonogenic assay and Luria–Delbrück fluctuation analysis were also used to measure amplification in nontumorigenic cells. The tumorigenic phenotype is believed to arise through a multistep accumulation of genetic changes. In neuroblastomas, the frequency and extent of N-myc amplification is reported to be a better prognostic indicator than any other determinant.
