As previously reported, possible mechanisms for HR expression shift in breast cancer cells caused by chemotherapy were as follows: First, chemotherapy induced the regression to a positive hormone receptor status, since all cells originally derived from well-differentiated hormone receptor positive breast cancer cells[8]; Another explanation would be selection of tumor cells clone during treatment, with selective disappearance of either HR-positive or HR-negative tumor cells. The gene discussed is NR4A1; the disease is neoplasm.