CYCLIN-DEPENDENT KINASE-6 (CDK6) AMPLIFICATION IN HUMAN GLIOMAS IDENTIFIED USING 2-DIMENSIONAL SEPARATION OF GENOMIC DNA

DNA amplification is a common mechanism invoked by many human tumors t o elicit overexpression of genes whose products are involved in drug r esistance or cell proliferation, Although amplified regions in tumor D NA may exceed several megabases in size, segments of amplicons with a high probability of containing gene sequences may be amenable to detec tion by restriction landmark genomic scanning (RLGS), a high-resolutio n DNA analysis that separates labeled NotI fragments in two dimensions , Here, we tested this by applying RLGS to matched samples of glioma a nd normal brain DNA and found tumor-specific amplification of the gene encoding cyclin-dependent kinase 6 (CDK6), an observation not previou sly reported in human tumors, The CDK6 gene has been localized to chro mosome 7q21-22, but in the gliomas studied here, it was not coamplifie d with either the syntenic MET (7q31) or epidermal growth factor recep tor (7p11-p12) genes, suggesting that this may be part of a novel ampl icon in gliomas, We then corroborated this finding by identifying both amplification-associated and amplification-independent increases in C DK6 protein levels in gliomas relative to matched normal brain samples , These data implicate the CDK6 gene in genomic amplification and illu strate the potential of RLGS for the more general identification and c loning of novel genes that are amplified in human cancer.