US researchers have demonstrated that a protein called alphaB-crystallin, which normally protects cells from stress damage, triggers events that may cause breast cancer when overactive.

Breast cancer is the most common cancer in women and is responsible for over 400,000 deaths annually in women throughout the world.

The majority of these deaths are the result of aggressive breast tumors that often fail to respond to current treatments.

The researchers found that women whose breast tumors express the alphaB-crystallin protein have a shorter survival, suggesting that alphaB-crystallin may be a useful molecular marker to identify women with aggressive breast cancer and to develop new targeted cancer therapies.

"Basically, breast cancer cells have hijacked alphaB-crystallin, a protein that normally protects cells against stress injury and death, and used it to promote their uncontrolled growth," said lead researcher Vincent Cryns.

"Currently, we don’t have any targeted treatments like tamoxifen or Herceptin for the aggressive type of breast tumors that express alphaB-crystallin.

"Our results suggest that these tumors may respond to drugs that block this important pathway activated by alphaB-crystallin."

The study is published in the Journal of Clinical Investigation.