Using human breast cancer cells and the protein that causes
fireflies to glow, a Johns Hopkins team has shed light on why
some breast cancer cells become resistant to the anticancer
effects of the drug tamoxifen. The key is a discovery of two
genetic "dimmer switches" that apparently control how a breast
cancer gene responds to the female hormone estrogen. In a report
published online July 7 by Human Molecular Genetics, the
scientists show how a gene known as RET in breast cancer cells
responds to estrogen by dialing up the manufacture of a
signaling protein that instructs cells to divide and causes
tumors to become aggressive through the escape from estrogen
dependence. Scientists have long known that breast cancers are
either estrogen-receptor positive or estrogen-receptor negative.
The positive subset, generally associated with better outcomes
for patients, is sensitive to the drug tamoxifen, which blunts
aggressive tumor growth through estrogen receptor inhibition,
according to Zachary E. Stine, the resea