Scientists have found that DNA errors associated with an increased risk of breast cancer affect five times more genes than previously known.
The researchers found 352 errors that they believe with "reasonable confidence" hit 191 genes, less than a fifth of which were previously recognized.
The international study – published in the journal Nature Genetics – compared the DNA of 109,900 breast cancer patients with about 88,937 healthy controls.
He found that one-third of the discovered genetic variants increase the likelihood that women will develop hormone-responsive breast cancer.
This affects about four out of five breast cancer patients and can be treated with hormone treatments such as tamoxifen.
Fifteen percent of the variants found by experts predispose women to the rarer "estrogen receptor-negative" breast cancer, while the other variants are linked to both types.
Breast cancer is a polygenic disease, meaning it is not caused by a single genetic variant or gene, but is more likely when a combination is present.
The study found 352 DNA "errors" associated with an increased risk of developing breast cancer. File photo
Previous research has found 150 areas in the genome that contain genetic alterations that affect the risk of breast cancer, but experts are rarely able to identify the specific variants and genes involved.
Each variant alone increases the risk of developing the disease by a small amount.
But all in all, they give women a clearer picture of their genetic risk and the best strategies to prevent their onset, the researchers said.
Alison Dunning of Cambridge University said: "This incredible batch of newly discovered breast cancer genes provides us with many more genes to work with, most of which have not been studied before.
"This will help us build a much more detailed picture of how breast cancer arises and develops. But the sheer number of genes now known to play a role emphasizes the complexity of the disease."
Cancer Research UK says 11,371 women died of breast cancer in 2017
Following a separate study – conducted by a team from University College London (UCL) – a group of cells that play a role in the body's immune response may be the key to "more effective" cancer treatments.
Scientists found that "T cells" – a subset of white blood cells – are activated to kill cancer cells after an experimental mouse immunotherapy study.
Immunotherapy is a form of cancer treatment that utilizes the power of the body's immune system to prevent, control and get rid of the disease.
Although T cells are good at finding and killing infected cells, they don't recognize most cancers because tumors develop from body tissue and look normal to T cells.
The main challenge of T-cell immunotherapy is finding ways to target T cells to attack cancer cells.
Professor Sergio Quezada of the UCL Cancer Institute, co-author of the study, said: "We knew that these immune cells were able to proactively kill cancer cells with incredible potency, but to maximize their potential, we needed to know how this mechanism was possible. enabled. "
The study, funded by Cancer Research UK, is published in the journal Immunity.