RARA and breast cancer: To examine the relationship between the patients’ prognoses and the changes in RAR and ERK signaling, we classified breast cancer patients into four categories (RA-ND/ERK-NI, RA-ND/ERK-I, RA-D/ERK-NI, and RA-D/ERK-I), based on expression profiles of the RA-dependent and ERK-dependent upregulated genes.