Research from the US has given scientists a better understanding of the genetic and molecular defects inside breast cancer cells.

International researchers working as part of the Cancer Genome Atlas (TCGA) project have completed the genetic mapping of 800 breast tumours, giving researchers a clearer view into the defects behind each sub-type of breast cancer, as well as providing pointers towards new treatments.

The study, published in Nature, also identified a molecular similarity between one sub-type of breast cancer - known as 'Basal-like' - and a hard-to-treat form of ovarian cancer.

The researchers looked at the 800 tumours in vast detail, examining their genetic defects, and other aspects of their biology, such as the degree to which different genes and pathways were switched on, and whether their DNA was chemically modified ('epigenetics').

They compared these analyses to four previously known sub-types of breast cancer: HER2-enriched, Luminal A, Luminal B and Basal-like.

"This comprehensive new analysis of 800 breast tumours is a welcome addition to the wealth of new information about the underlying biology of breast cancer, and will be a precious and valuable resource for cancer researchers," said Professor Carlos Caldas, a breast cancer expert for Cancer Research UK, who was not involved in the study.

"This will allow us to further refine understanding of the disease, with the ultimate aim of improving things for those who matter most - people diagnosed with breast cancer."

Professor Caldas added that the study corroborated the findings of the Cancer Research UK-funded METABRIC study, which revealed breast cancer to be ten separate diseases.

Dr Charles Perou, from the University of North Carolina, and one of the paper's authors, said the study represented "a near complete framework for the genetic causes of breast cancer, which will significantly impact clinical medicine in the coming years."

The mapping project gave scientists a better picture of the genetic causes behind the most common form of breast cancer, known as Estrogen-Receptor positive/Luminal A disease.

The researchers found that this sub-type had the widest range of genetic alterations, some of which could be targeted by drugs currently in clinical development.

The striking similarity between basal-like breast tumours, which are often hard-to-treat 'triple-negative' breast cancers, and ovarian tumours suggests a common origin and the future possibility of treatments that would be effective for both diseases, the researchers said.

"The molecular similarity of one of the principal subtypes of breast cancer to that found in ovarian cancer gives us additional leverage to compare treatments and outcomes across these two cancers," said Professor Harold Varmus, director of the US's National Cancer Institute, which funded the study.

"This treasure trove of genetic information will need to be examined in great detail to identify how we can use it functionally and clinically."

Source: CRUK