PGR and breast cancer: To further confirm that the expression of iRFP713 in p(ERE)2-(PRE)2iRFP713 is specifically regulated by intracellular ER/PR in breast cancer cells, we used antagonists of ER and PR to silence the respective targeted proteins in cells transfected with p(ERE)2-(PRE)2iRFP713 or pNLSiRFP713.