A gene that leads to one of the most drug-resistant forms of breast cancer has been discovered by an international group of researchers in Manhattan, raising hope of developing new methods to treat younger women with higher risk of developing breast cancer.
In their research, published online in the journal Nature Genetics, scientists said that they have identified a major reason why women with a mutated version of BRCA1 breast cancer gene are at high risk of developing the disease.
It is already known that women carrying a defective copy of the BRCA1 gene have up to an 85 percent lifetime risk of developing the disease. Now, scientists at Columbia University, collaborating with a team in Sweden have discovered at least one fundamental reason why BRCA1, if mutated, may increase a woman’s risk of developing deadly type of breast cancer.
The scientists said that BRCA1 inactivates a tumor suppressor gene called PTEN. This tumor suppressor gene PTEN is a result of the failed DNA repair in a breast cell containing the mutant gene BRCA1, said lead investigator Dr Ramon Parsons of Columbia University Medical Centre, New York, and colleagues.
PTEN has instructions to produce a protein that stops the uncontrolled cell growth of cancer, but BRCA1 prevents PTEN from doing its work, the scientists reported. Defects in PTEN probably account for 50 percent of breast cancers in women who inherit a mutated BRCA1 gene, they said.
"These findings are exciting because ever since the link was established between BRCA1 and breast cancer more than 10 years ago, we have been frustrated by our lack of understanding about how mutations in this gene cause breast cancer," said Dr Parsons
"We have been stymied by our limited resources to treat these cancers, which are associated with very poor prognoses. Now that we know that PTEN is involved, we finally have a target for therapy for these cancers."
PTEN is a human gene that acts as a tumor suppressor gene, which means that the protein encoded by this gene helps regulate the cycle of cell division by keeping cells from growing and dividing too rapidly or in an uncontrolled way.
But, mutations in BRCA1 cause the PTEN gene to make a protein that does not function properly or does not work at all. The defective protein is unable to stop cell division or signal abnormal cells to die, which can lead to tumor growth, particularly in the breast, thyroid or uterus.
Researchers now hope to find an effective way to treat the disease by replacing the missing PTEN.
Breast cancer is the most common tumor in women. It is a malignant form of tumor spreading quickly to the bones, hips, lungs and in some, the brain. One in ten women is likely to develop breast cancer and almost 75% would do so after menopause. Besides hereditary or genetic factors, some other causes of this form of tumor are early puberty, late menopause, not having a child or having a first child after age 30. Risk is considerably lowered if one has short menstrual life, large family or first child before the age of 18.
BRCA1 and BRCA2 are the two most familiar breast cancer genes, which cause a quarter of hereditary cases. Besides accounting for 15% of all breast cancer, BRCA1 and BRCA2 mutations are associated with increased risk of variety of other cancer including ovarian cancer.
The risk of development of breast cancer in women carrying BRCA2 mutations are similar to the risk of BRCA1 carriers, however the risk of development of ovarian cancer is lower in BRCA2 mutation carriers compared to BRCA1 mutation carriers.
According to Geneva-based World Health Organization (WHO) data, breast cancer engulfs 500,000 lives a year globally.