RARA and breast cancer: Since the effect of depleting RARα1 occurs through a different gene regulatory program compared with retinoid agonists, and since RARα1 is genetically redundant and appears to be the only RARα subtype in breast tumor cell lines and possibly the major subtype in clinical tumors, this new approach (rather than the use of RAR agonists) to enhancing hormonal adjuvant therapy in breast cancer may be clinically more acceptable.