Previous studies indicate that the
triterpene glycoside actein from the herb black cohosh inhibits growth of human
breast cancer cells. This study seeks to identify genes altered in human
breast cancer cells by treatment with
actein, using gene expression analysis. We treated MDA-MB-453 human
breast cancer cells with
actein at 2 doses, 20 or 40 microg/mL, for 6 or 24 hr. We identified 5 genes that were activated after each of the treatments that are known to play a role in cellular responses to diverse stresses, including the DNA damage and unfolded protein responses. In addition, four genes that mediate the integrated stress response (ISR), including
activating transcription factor 4, were induced under at least one of the 4 treatment conditions. We used hierarchical clustering to define clusters comprising patterns of gene expression. Two ISR genes,
activating transcription factor 3 (ATF3) and DNA damage- inducible transcript 3, and
lipid biosynthetic genes were activated after exposure to
actein at 40 microg/mL for 6 hr, whereas the cell cycle genes
cyclin E2 and cell division cycle 25A were repressed. Our results suggest that
actein induces 2 phases of the ISR, the survival phase and the apoptotic phase, depending on the dose and
duration of treatment. We confirmed the results of gene expression analysis with real-time RT-PCR for 18 selected genes and Western blot analysis for ATF3. Since
actein activated
transcription factors that enhance apoptosis, and repressed cell cycle genes, it may be useful in the prevention and
therapy of
breast cancer.