111In-labeled 1,4,7,10-tetraazacyclododecane- N,N′,N″,N‴-tetraacetic acid-Lys8-vasotocin: A new powerful radioligand for oxytocin receptor-expressing tumors

We developed a radioactive ligand for tumors expressing oxytocin receptors (OTRs) by linking the chelating agent 1,4,7,10-tetraazacyclododecane. N,N′,N″,N‴-tetraacetic acid (DOTA) to Lys⁸-vasotocin (LVT), an analogue of oxytocin with high affinity for OTRs. The new reagent (DOTA-LVT) retained high affinity for human OTRs, as proved by in vitro affinity binding to cells endogenously expressing OTRs, such as MCF7 breast carcinoma and MOG-U-V-W glioblastoma cells lines, as well as to transiently transfected COS7 cells. In in vivo experiments, DOTA-LVT carrying ¹¹¹In showed specific binding activity to OTR-positive TS/A mouse mammary tumors. The present study opens new perspectives for imaging and, possibly, therapy of OTR-positive human tumors such as breast and endometrial carcinomas, neuroblastomas, and glioblastomas.