TNFRSF18 and neoplasm: Consistently, a true GITR signaling elicited by a recombinant pentameric GITR-L led only to a transient inhibition of MC38 tumor growth which was due to an enhancement of naïve Treg proliferation on the one hand, and on the other hand to a gradual accumulation of activated Tregs, which are insensitive to GITR mediated suppression (Kim et al. 2015).