Tumorreduction by atosiban was unexpected since it was thought to be anOTR antagonist; further studies, however, demonstrated atosiban tobe a biased ligand, selectively activating Gi signalingwhile blocking Gq signaling.140 In another study that used BALB/c mice bearing MC4-L2 mouse mammaryadenocarcinomas, treatment with OT for 42 days reduced tumor growthrate and tumor size (∼82%).137 Treatmentwith atosiban was also studied; however, no significant changes intumor growth or size were observed. This evidence concerns the gene GNAI1 and neoplasm.