Progesterone signals through PGR, a nuclear hormone receptor that directly induces transcription of downstream effector genes.45 In addition to its function as a nuclear hormone receptor, PGR can activate the proto-oncogene tyrosine kinase SRC rapidly in the cytoplasm of breast cancer and mammary epithelial cells upon progesterone stimulation.46–48. Here, NR0B1 is linked to breast carcinoma.