Tamoxifen is a selective estrogen receptor modulator (SERM), with tissue-specific antagonistic or agonistic effects. Receptor activation leads to the formation of homo- and hetero-dimers, which in turn interact with accessory proteins to regulate gene transcription. Tamoxifen is commonly used to activate Cre-ER in transgenic conditional models.

CELL LINE DEVELOPMENT
· Used in transgenic models to induce Cre-mediated recombination in conjunction with Cre-ER, a fusion protein consisting of Cre recombinase and a mutant form of the estrogen receptor hormone-binding domain that specifically binds tamoxifen but not estrogen (Feil et al.; Zhang et al.).

CANCER RESEARCH
· Inhibits growth in the human breast cancer cell line, MCF-7 (Katzenellenbogen et al.).
· Antagonist of estrogen receptor action in breast tissue and breast cancer cells (Abe et al.; Horwitz et al.).