To examine if endogenous ERα interacts with endogenous Hsp70-1/Hsc70 and determine the subcellular site where the ERα-Hsp70-1/Hsc70 interactions occur in ERα-positive breast cancer cells, we performed IPs using cytosolic and nuclear proteins of human breast cancer MCF7 cells as starting materials, respectively. The gene discussed is HSPA8; the disease is breast cancer.