At a Glance
Why Get Tested?
When to Get Tested?
A sample of tumor tissue
Test Preparation Needed?
The Test Sample
What is being tested?
This test detects specific mutations in the KRAS gene in the DNA of cancer cells and tissue. The presence of these mutations may indicate that certain drugs will not be effective in treating the cancer.
KRAS is a short name for the gene v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog. It is one of a group of genes involved in a pathway called the epidermal growth factor receptor (EGFR) pathway. This complex signaling pathway involves numerous components that relay signals from outside of the cell to within the cell to help regulate cell growth, division, survival and death.
In many normal cells, binding of epidermal growth factor (EGF) to its receptor (EGFR) on the surface of the cell is an important signal to cell growth and division. Other signals in the pathway involve a class of proteins called tyrosine kinase (TK) enzymes and a protein produced by the KRAS gene. Normally, the components of the pathway interact in the regulation of cell growth and division and do not individually stimulate cell proliferation.
However, in some cancers, EGFR becomes active even in the absence of EGF, leading to uncontrolled cell growth and division. Drugs that inhibit EGFR or tyrosine kinase enzymes are often helpful for treating such cancers. Some of these cancers, though, have a mutation in the KRAS gene that produces an abnormal K-Ras protein. The abnormal protein is always active and can stimulate cell growth even in the absence of signals from EGFR and TK. In such cancers, drugs that inhibit EGFR or TK will not be effective.
KRAS mutations are found in many different types of cancers but have been most extensively studied in colon cancer and non-small cell lung cancer. Approximately 40% of colon cancers and 20% of lung cancers will have KRAS mutations.
There are several different methods of testing for KRAS mutations, but all of them involve evaluating the KRAS gene in tumor tissue.
How is the sample collected for testing?
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
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Franklin, W. et. al. (2012 January). KRAS Mutation Comparison of Testing Methods and Tissue Sampling Techniques in Colon Cancer. J Mol Diagn. v 12(1): 43–50. [On-line information]. Available online at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2797717/ through http://www.ncbi.nlm.nih.gov. Accessed May 2012.
Anderson, S. (2011 August 15). Laboratory Methods for KRAS Mutation Analysis. Medscape Today News from Expert Rev Mol Diagn. v 11(6):635-642 [On-line information]. Available online at http://www.medscape.com/viewarticle/746638 through http://www.medscape.com. Accessed May 2012.
Markman, M. (Updated 2012 March 28). Colorectal Cancer and KRAS/BRAF. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/1690010-overview through http://emedicine.medscape.com. Accessed May 2012.
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Chowdhuri, S. et. al. (2012 May 8). EGFR and KRAS Mutation Analysis in Cytologic Samples of Lung Adenocarcinoma Enabled by Laser Capture Microdissection. Medscape Today News from Modern Pathology. v 25(4):548-555 [On-line information]. Available online at http://www.medscape.com/viewarticle/763033 through http://www.medscape.com. Accessed May 2012.
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