ESR1 and breast cancer: To extend the human disease relevance of our findings in rat models, we evaluated ANGPTL7 mRNA by RNA-ISH from seven tumor sections from six different human breast cancer patient-derived xenografts (PDXs) each derived from high-grade invasive ductal carcinomas, and each triple-negative (ER-negative, PR-negative, HER2-negative receptor status) by PDX tumor histology (Fig. 6A).