In the group's initial scan of tumor samples, researchers identified gene mutations that would increase RTK/RAS/RAF pathway activity in 62 percent of the samples. The affected genes are oncogenes, or genes that have the potential to cause cancer when mutated or expressed at high levels. Consequently, these tumor samples were classified as oncogene-positive.
To identify additional alterations, the investigators looked at DNA copy number changes, or changes in gene number resulting from the deletion or amplification (multiplication) of sections of DNA in the genome. In doing so, they detected amplification of two oncogenes, ERBB2 and MET, which are part of the RTK/RAS/RAF pathway. Gene amplification usually leads to increased expression of the encoded protein in cells.
Now that these amplifications have been identified, clinicians may be able to treat patients whose tumors have specific gene changes with drugs currently available or under development.
"It is quite striking that we have now identified an actionable mutation in over 75 percent of patients with lung adenocarcinoma, a significant improvement from a decade ago," said Matthew Meyerson, M.D., Ph.D., Harvard Medical School, Dana-Farber Cancer Institute, The Broad Institute, and one of the lead investigators on the project.
Additional analysis identified other genes that may play important roles in lung cancer development. Mutations in one of these genes, NF1, had previously been reported in lung cancer; NF1 is a known tumor suppressor gene that regulates the RTK/RAS/RAF pathway. Mutations in NF1 also put the pathway into overdrive. Another mutated gene, RIT1, is also part of the RTK/RAS/RAF pathway, and this is the first study to associate mutation of this gene with lung cancer.
"This most recent TCGA stu
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NIH/National Cancer Institute