PGR and breast cancer: To identify the molecular subtypes of tumors, we measured expression of Esr1, Pgr, and Erbb2. All five mammary tumors from Trp53wm-R172H/+ mice (Ad-Cre plus IR) exhibited minimal level of the Esr1 and Pgr transcripts, and only one of these tumors showed higher expression of Erbb2, making them predominantly triple negative (80%, Fig. 3f, g).