The findings may ultimately help scientists understand who's at risk for breast cancer and what to do about it.
Doctors already know that variations in the BRCA1 and BRCA2 genes make breast cancer and ovarian cancer more likely. But experts have long suspected that other genes also affect breast cancer.
Now, researchers say they've found four genes that affect breast cancer risk. But the new findings don't explain all cases of breast cancer. A complex mix of genetic and lifestyle factors likely affect breast cancer risk.
Breast Cancer Genetics
In three new studies, scientists compared the genes of women with breast cancer with women without breast cancer.
The first study, published online in Nature, comes from researchers including Douglas Easton, PhD, professor of genetic epidemiology at England's University of Cambridge.
Easton's team screened the genes of nearly 4,400 women with breast cancer and 4,300 women without breast cancer. They checked their results in more than 44,400 other women, roughly half of whom had breast cancer.
Four genes -- the FGFR2, TNRC9, MAP3K1, and LSP1 genes -- had variations that were more common in women with breast cancer than in women without breast cancer, the study shows.
The other two studies, published online in Nature Genetics, echo some of Easton's findings.
In one study, researchers screened the genes of 1,776 women with breast cancer and 2,072 women without breast cancer. Four variations in the FGFR2 gene were more common in the women with breast cancer than in the women without breast cancer.
The FGFR2 gene suppresses tumors. Mutations in that gene may mar tumor suppression.
"This finding opens up new avenues of research into the causes and prevention of breast cancer," states researcher David Hunter, MBBS, ScD, in a Harvard news release.
Hunter works in Boston in the medicine department of Harvard Medical School and Brigham and Women's Hospital.
In the other study, researchers in Iceland compared genes of more than 4,550 women with breast cancer and more than 17,570 women without breast cancer. Certain DNA variations -- including a spot near the TNRC9 gene -- were more common in the breast cancer patients.
The findings varied "markedly" among different ethnic groups, write the scientists, who included Simon Stacey, PhD, of Decode Genetics in Reykjavik, Iceland.
Genetic tests for the BRCA1 and BRCA2 genes are already in use for certain high-risk patients.
But it may be too soon to start screening for the four new breast cancer genes, since the findings need to be confirmed in other studies.
"It is premature to recommend screening women for these gene variants," states Hunter, referring to his team's findings about the FGFR2 gene variations.