EP1 receptor (or PTGER1) is a receptor or prostaglandin E2 (PGE2). The receptor may play a role in the smooth muscle contractile response to PGE2 in various tissues. EP1 receptor transactivates EGFR thus activating Akt, while activation of EGFR by its cognate ligand EGF increased COX-2 expression and PGE2 production. This crosstalk between EP1 and EGFR signaling synergistically promotes cancer cell growth and invasion. Some EP1-specific antagonists inhibit osteoclast formation induced by RANKL from the early stage of osteoclastogenesis. This cell line expresses EP1 cDNA that is identical to GenBank NM_000955.2 except for 1 sense mutation, Thr→Ala at position 70. It has been reported as a natural variant.