45 showed that IL-22 gene knockouts allowed fewer tumors in ApcMin/+ mice, whereas knockouts of IL-22-binding protein caused more (in the colon). Further work is needed to determine if these functions of dendritic cells explain tumor suppression by PGD2. Identification of mechanisms involving PGD2 and PTGDR may suggest molecular targets for tumor prevention studies. This evidence concerns the gene PTGDS and neoplasm.