Treatment with a demethylating agent rescues hCRBP expression in MCF-7 clone B and ZR75-1 cells. A. RT-PCR Southern blot analysis of hCRBP expression in MDA-MB-468 and MCF-7 clone B cells treated as indicated, demonstrating different sensitivity to endogenous (serum) retinoids. RA, 1 μM all-trans RA; TSA, 100 nM trichostatin A (24 h treatment). B. RT-PCR Southern analysis of hCRBP expression in MCF-7 clone A and ZR75-1 cells treated as indicated, demonstrating that a demethylating agent is required for CRBP reexpression. AzaC, 5 μM 5-azacytidine (72 h pretreatment, 96 h total); RA and TSA as above (present during last 24 h).