(A) Tumor spheroids isolated from eGFP mice exposed to CM-DiI-labeled liposomes or PBS show eGFP-expressing stromal cells (green fluorescence), cells that have endocytosed CM-DiI-labeled liposomes (red fluorescence), and a subpopulation of host stromal cells that uptake liposomes (yellow or orange fluorescence, arrows). (B) Tumor spheroids from C57Bl/6 mice exposed to CM-DiI-labeled liposomes or PBS and labeled for expression of the macrophage marker CD68 (green fluorescence) show colocalization of CM-DiI andCD68 (yellow or orange fluorescence, arrows). (C) Spheroids exposed as described in (B) and labeled for the dendritic cell marker CD11c (green fluorescence, arrows) show no colocalization. D. CM-DiI-labeled or unlabeled macrophages were treated with CLIP or PLIP and the conditioned medium was transferred to cultures of mesothelioma cells. Cells incubated in conditioned medium from CM-DiI-labeled CLIP-treated macrophages (left, arrows); cells incubated in conditioned medium from CM-DiI-labeled, PLIP-treated macrophages (middle) or unlabeled, CLIP-treated macrophages (right). All cells were counterstained with DAPI (blue nuclear fluorescence). For details, see Miselis et al. in this issue.