CASP8 and neoplasm: Biochemical analysis confirmed that while macrophages inhibited TRAIL-induced activation of caspase 8 and caspase-9 and cleavage of PARP and β-catenin, treatment with vitamin D3 promoted TRAIL-mediated activation of the apoptotic cascade in tumor cells that were grown in the presence of WT, but not VDR deficient macrophages (Fig. 4B).