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Figure 79-8 A cDNA array experiment. RNA is prepared from cells, reverse transcribed to cDNA, and labeled with fluorescent dyes (typically green for normal cells and red for cancer cells). The fluorescent probes are mixed and hybridized to the cDNA array. Each spot on the array is a cDNA fragment that represents a different gene. The image is then captured with a fluorescence camera; red spots indicate higher expression in tumor compared with reference while green spots represent the opposite. Yellow signals indicate equal expression levels in normal and tumor specimens. After clustering analysis of multiple arrays, the results are. | Chapter 079. Cancer Genetics Part 10 Figure 79-8 Normij Cancer Tissues Préparé ÇÜNA. fabel Data analysis from I Hlullipli arrays I Hybridize Capture image Sourc Faun ftsr K p r Öl. Br un ld E H ur rSL Longo DLj J m ror JL Loscalco Ji Harrisatt r PrirKipl c Intarnai Hadiapa 17th Edrtiom http v . fimtdi na.com Copyright tho Mc 3r w-Hilt Cjmp.nni Int Adi rlghtr rtl ru d. A cDNA array experiment. RNA is prepared from cells reverse transcribed to cDNA and labeled with fluorescent dyes typically green for normal cells and red for cancer cells . The fluorescent probes are mixed and hybridized to the cDNA array. Each spot on the array is a cDNA fragment that represents a different gene. The image is then captured with a fluorescence camera red spots indicate higher expression in tumor compared with reference while green spots represent the opposite. Yellow signals indicate equal expression levels in normal and tumor specimens. After clustering analysis of multiple arrays the results are typically represented graphically using Treeview software which shows for each sample a color-coded representation of gene expression for every gene on the array. In addition with the completion of the Human Genome Project and advances in sequencing technologies large-scale mutational profiling of the cancer genome has become possible. Hundreds of genes from a given pathway MAPK pathway for example or from a gene family can be systematically sequenced in a large number of cancers in order to identify genes that are crucial to human oncogenesis. This approach has been used to identify several novel targets in various cancers. For example B-RAF mutations were identified in a large fraction of melanomas and PIK3CA mutations were identified in large fractions of colon breast and hepatocellular cancers. Most recently this approach has been applied to an unbiased set of genes including about two-thirds of all those known to encode proteins. Hundreds of genes not previously implicated in cancers .
