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Thursday, December 6, 2012

Detecting breast cancer via methylation levels

Epigenetics, and specifically DNA methylation, is in the news quite a lot. I’ve explained DNA methylation before (here and here). Suffice it to say that this ‘after-factory’ alteration does not affect the sequence of DNA but does affect the expression of that DNA, often by inactivating the genes involved. However, you may be asking, ‘when is this new field of study going to yield anything useful?’ If you or someone you know is at risk for developing breast cancer, that day may be sooner than you think.

Researchers from various German universities and research hospitals compared methylation levels in ten breast cancer tumors (two from pre-invasive tumors and eight from invasive cancers) and ten normal controls. Overall, they found over 200 sites that were significantly hypermethylated in the tumor samples. In particular, they found nine genes that were already significantly hypermethylated in the pre-invasive tumors. In fact, methylation levels did not differ much between pre-invasive and invasive tumors or between different tumor subtypes. This finding suggests that methylation can be used as a tool for the early detection of breast cancer tumors.

If you consider that the five-year survival rate for breast cancer can increase to nearly 100% (depending on the type of cancer) if the disease is detected early enough, the importance of this finding cannot be overstated. The next step is to figure out whether the extreme methylation is a cause or an effect of the tumorigenesis. Interestingly, many of the genes that are hypermethylated, and thus inactivated, in breast cancer samples are homeobox genes (genes that are involved in embryonic development). The authors speculate that this may indicate that the breast cancer tumor cells originated as stem cells.

Faryna, M., Konermann, C., Aulmann, S., Bermejo, J., Brugger, M., Diederichs, S., Rom, J., Weichenhan, D., Claus, R., Rehli, M., Schirmacher, P., Sinn, H., Plass, C., & Gerhauser, C. (2012). Genome-wide methylation screen in low-grade breast cancer identifies novel epigenetically altered genes as potential biomarkers for tumor diagnosis The FASEB Journal DOI: 10.1096/fj.12-209502