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New Breast Cancer Gene Associations Found

By Stephen Luntz

The Peter MacCallum Cancer Centre has discovered two genes with variations associated with an increased risk of breast cancer.

The FANCC and BLM gene variations identified in a PLOS Genetics paper appear to be associated with just 1% of breast cancers. While this figure is small, lead author Dr Ella Thompson says: “If it is your family that has it, it’s very important to you. The other encouraging aspect is that this study makes us confident other genes can be found the same way.”

Thompson adds that it is likely that future discoveries of variations associated with breast cancer will be responsible for similarly small proportions of cancers. “It’s quite surprising that so many genes are all contributing to the same disease,” she says. “We can’t say why, but this is what the data is showing us. What is interesting is that these genes are involved with a common pathway with the BRCA genes: DNA repair.”

In the two decades since the identification of the importance of the BRCA1 and BRCA2 genes in breast cancer, genetic research has bounded ahead yet the genetic risk factors for breast cancer remain largely obscure. Thompson says this is in part because the rarity of other mutations, or their weak association with cancer, make them harder to identify.

“Events that are so rare need really large validation cohorts to prove associations – beyond the cohort size most labs have in their own collections – so they require collaborations across sites,” Thompson says. The need for such collaborations is being addressed through Complexo, a program to share data between cancer researchers, with the Peter MacCallum Cancer Centre as a leading contributor.

Thompson adds that the BRCA1 and BRCA2 genes are associated with roughly 20% of breast cancers yet have other features that make them easier to identify than the FANCC and BLM genes. BRCA1 is also associated with ovarian cancer, and BRCA2 is associated with breast cancer in men.

“There have been lots of attempts to do linkage studies on families with breast cancers and these didn’t come up with clear peaks, which is a clue that more than one gene is involved,” Thompson says.

While the association between FANCC and BLM alterations and breast cancer has been established, Thompson says little is known about how common they are, and therefore just how high the risk of getting cancer is for a woman with the mutated form.