Vitamin A May Be Key to Better Breast Cancer Drugs

STUDY FINDINGS:

• A form of retinoic acid, a vitamin A derivative, could lead to a new drug combination for breast cancer treatment.

A recent study from the University of Chicago may lead to new treatments for common breast cancers that don’t respond to traditional therapies. Using cells taken from patients with estrogen-related breast cancers, researchers at the Institute for Genomics and System Biology compared how the receptors of estrogen and retinoic acid, a derivative of vitamin A, affected the genes involved in breast cancer. (Receptors, often described as the ears or antennae on a cell, can send signals for breast cancer cells to grow.)

The results, reported in the June 26 issue of the journal Cell, found that the estrogen receptor and the retinoic acid receptor appeared to compete with each other to activate or repress many of the same genes, according to Kevin White, director of the institute and one of the study’s authors. “What we found was not only that these receptors target many of the same breast cancer genes, but also that they have an antagonistic relationship,” he says. Estrogen can send signals that tell breast cancer cells to grow, while retinoic acid seems to inhibit cellular growth. “We call it a yin yang effect,” White says.

Retinoic acid has been approved for the treatment of promyelocytic leukemia, but it can be quite toxic. The goal is to develop a retinoic acid derivative with similar structure and function but with a much lower toxicity that could be used in combination with standard drugs like tamoxifen, or to develop new anticancer drugs. “These studies suggest that combining drugs that target the retinoic acid pathway with those targeting the estrogen receptor pathway might prove more fruitful in treatment of breast cancer,” says Harold Burstein, M.D., a breast cancer specialist at the Dana-Farber Cancer Institute in Boston.

Cathie Gandel is a freelance writer who covers health and science.