Adding a Second Drug Boosts Tamoxifen's Effectiveness

Ivanhoe Newswire
Tuesday, January 2, 2007; 12:00 AM

(Ivanhoe Newswire) -- Taking a second drug with tamoxifen may help the breast cancer medication retain its full strength indefinitely.

Tamoxifen has been widely used since the 1970s to treat certain types of breast cancer and to prevent recurrence after surgery. Over time, patients develop resistance to the drug, and it loses its effectiveness.

Researchers from the National Cancer Institute tested a compound called disulfide benzamide or DIBA in mice and in cell cultures. They found DIBA fully restored tamoxifen's effectiveness, reducing tumor growth by nearly 50 percent.

"Exposure to DIBA causes certain physical changes to occur between the estrogen receptor and the biological machinery that stimulates cell division," reports lead author Li Hua Wang, Ph.D. "By coincidence, these changes also restore the estrogen receptor to a form that makes it vulnerable once again to tamoxifen."

Tamoxifen is used in women who have estrogen receptor-positive cancers in which cancer cell growth is strongly influenced by estrogen. When estrogen binds to the estrogen receptor, it triggers a series of events that promote cells to divide. If it is a breast cancer cell, it can lead to tumor growth.

Tamoxifen blocks the effects of estrogen on breast tissue, which initially slows or stops tumor growth altogether.

Researchers say the study's results in mice are exciting and look promising to try in humans. They are now trying to produce DIBA in a water-soluble form, so it could be taken as a pill and used in preclinical studies.

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SOURCE: Cancer Cell, 2006;10:487