A natural compound derived from the herb feverfew may prevent or curtail resistance to tamoxifen, the go-to drug prescribed for breast cancer patients.

Why are cancer researchers so interested in the feverfew derivative parthenolide? Of the 70 percent of the newly diagnosed cases of breast cancer that are classified as estrogen receptor positive (ER+), half of them don't respond to tamoxifen, a drug designed to block estrogen from binding to a cell's protein receptor.

Based on previous research, tamoxifen resistance is governed by the overexpression of the protein complex nuclear factor kappa B (NF-kB) in ER+ breast cancer cases. After conducting a battery of tests, researchers discovered parthenolide blocked the action of NF-kB, making cells more sensitive to tamoxifen.

Despite their success, scientists still don't understand the "hideously complex process" that enables the overexpression of NF-kB or any other cellular adaptations to trigger the resistance of tamoxifen.

Nevertheless, it's encouraging to discover something as natural and ubiquitous to our lives and environment as a member of the sunflower family can have such a powerful effect on the drugs we take to battle cancer.

The FASEB Journal February 12, 2010

Georgetown University Medical Center February 15, 2010