4-Hydroxyphenylretinamide (4HPR) derivatives regulate aromatase activity and expression in breast cancer cells.

Recent studies exhibit that 4-hydroxyphenylretinamide (4HPR) decreases aromatase activity in breast and placental cells. The effect of synthetic 4HPR analogs on aromatase and expression was examined in three breast cancer cell lines. Most derivatives did not decrease cellular aromatase activity. Two of the analogs even stimulated aromatase activity at the transcriptional level. Only one derivative significantly decreased aromatase in all three breast cancer cell lines and also suppressed CYP19 gene expression in one of the cell line. Placental microsomal aromatase assay rule out the possibility that this compound directly inhibits the aromatase enzyme. A non-genomic mechanism in suppression of cellular aromatase activity of this compound is proposed.