TNFRSF9 and neoplasm: However, in multiple tumor models, the study of Zhang et al. showed that stealth (PEGylated) immunoliposomes, whose surface is conjugated with IL-12 and anti-CD137, had equivalent immunostimulatory effects compared to that of the “free” drugs, but with a nearly complete absence of systemic toxicity in a murine melanoma model [54].