Cancer clinicians currently classify breast cancer into three basic therapeutic groups: oestrogen receptor (ER) positive, HER2 (breast cancer that tests positive for a protein called Human Epidermal growth factor Receptor 2), and triple negative, or basal-like, breast cancer. Each group varies in prevalence, and has different treatment options and predicted outcomes.
A recent study in the journal Nature described four main breast cancer classes, or subtypes, breaking down these three groups even further. Each subtype is caused by different subsets of genetic and epigenetic (environment driven) abnormalities.
Understanding Cancer Genomics
The DNA in your cells is packaged into two sets of chromosomes. This is your genome. Chromosomes are composed of six billion individual DNA letters. Genomics studies the sequence of these letters and how each string of letters passes along information to help cells function properly.
The study of the cancer genome helps scientists discover which letter changes cause a cell to become a cancer cell. It also helps them distinguish one type of cancer from another. Changes in DNA can cause cells to produce the wrong amount of a certain protein, or to make a misshapen protein that doesn't work as it should. In cancer, these DNA changes cause cells to survive and grow out of control and damage surrounding tissue.
Breast Cancer Subtypes
Understanding the subtle differences among cancers is important because even patients with the same general type of cancer may have different treatment responses.
The four subtypes outlined in the Nature study are another way to characterize the molecular architecture of breast cancer. Integrating these analyses of cancers help scientists produce a comprehensive catalog of likely genomic drivers of the most common breast cancer subtypes.
Genomic characteristics also provide clues for targets for potential new drug therapies. Fortunately, the Cancer Genomics Atlas is charting genomic changes in more than 20 cancer types, including breast cancer.
Scientists have identified these four subtypes of breast cancers before, says Rajiv Datta, MD, Medical Director of Gertrude & Louis Feil Cancer Center, Oceanside, NY. "This study analyses them in further details with molecular markers. At the current time, there is no immediate implication for breast cancer patients. It will be a few years before this data can be transferred into clinical practice. The future of breast cancer is basically heading towards personalizing breast cancer treatment, and this study takes it one step closer."
Rajiv V. Datta, MD, FACS, FRCS, FICS, reviewed this article.
Sources:
Perou, Charles M., Ellis, Matthew J., and Parker, C. Joel S. "Comprehensive Molecular Portraits of Human Breast Tumours." Journal name: Nature Volume: 490 (2012): Pages: 61-70. Web. 23 September 2012.
http://www.nature.com/nature/journal/v490/n7418/full/nature11412.html
The Cancer Genome Atlas. "What is Cancer Genomics?" Web.
http://cancergenome.nih.gov/cancergenomics/whatisgenomics/whatis
The Cancer Genome Atlas. "Cancer Genomics: What Does It Mean for You?" Web. July 2010.
http://cancergenome.nih.gov/PublishedContent/Files/pdfs/1.1.0_CancerGenomics_TCGA-Genomics-Brochure-508.pdf
The Cancer Genome Atlast. "Breast Ductal Carcinoma." Web. 12 October 2012.
http://cancergenome.nih.gov/cancersselected/breastductal
National Institutes of Health. "Study Reveals Genomic Similarities Between Breast and Ovarian Cancers." Press Release. Web. 24 September 2012.
http://www.cancer.gov/newscenter/newsfromnci/2012/TCGAbreast
