Differentiation of Human Tumour‐associated Dendritic Cells into Endothelial‐like Cells: An Alternative Pathway of Tumour Angiogenesis

Abstract

Until recently, the only accepted mechanism of tumour vascularization was the sprouting of endothelial cells (EC) from pre-existing vessels, while recent studies suggest the contribution of stem cell-derived endothelial progenitors as well as cells from the myeloid lineage. Here, we show a new way of endothelial differentiation that involves the specific modulation of monocytes by the tumour environment. The tumour milieu is characterized by the presence of cytokines and lactate which induce the differentiation of tumour-invading monocytes into tumour-associated dendritic cells (DC). Additional incubation of tumour-associated DC with pro-angiogenic factors, such as vascular endothelial growth factor and oncostatin M, led to transdifferentiation into endothelial-like cells. The cells showed strong expression of von Willebrand factor and VE-Cadherin, both classical EC markers, while leukocytic markers were reduced. In addition, they were able to form network-like structures on matrigel, which could be blocked by the DNA-based drug Defibrotide. This finding may be of great therapeutic relevance for tumour therapy.

VEGF-A not Ang2 mediates endothelial-like differentiation of immature DCs by ERK1/2 signaling in the microenvironment of human colon adenocarcinoma

“…Tumor-associated DCs (TADCs) incubated additionally with VEGF and oncostatin M could trans-differentiate into endothelial-like cells (ELCs), which might be an alternative pathway of tumor angiogenesis (6). These reports show that DC progenitor or DCs can trans-differentiate into ELCs, possibly contributing to vasculogenesis in the adult.…”

“…Addition of conditioned medium of murine Lewis lung carcinoma cells was used to investigate the CD34 + cells' differentiation (5). It has been shown that the tumor microenvironment characterized by the presence of cytokines and lactate can induce monocytes to transdifferentiate into ELCs in the presence of pro-angiogenic mediators (6,9). These methods can simulate the tumor microenvironment to some extent.…”

“…Peripheral blood mononuclear cells (PBMCs) were harvested from healthy adult volunteers by density gradient centrifugation over Ficoll (6) and seeded in 24-well plates at 2x10 9 /l for 3 h. The adherent cells (monocytes) were induced toward DCs with rhGM-CSF 100 µg/l (Amoytop), rhIL-4, 5 µg/l (PeproTech). SW620 supernatant (40%) was added at the end of day 2.…”

“…Cells with green fluorescent particles in the cytoplasm were counted as having positive expression. DiI-Ac-LDL and India ink uptake assay (6,11). The induced cells and control were seeded in 96-well plates and incubated for 36 h, then, 10 µg/ml DiI-Ac-LDL (Biomedical Technologies Inc.) was added and the cells were further incubated at 37˚C for 4 h. The medium containing DiI-Ac-LDL was removed, and washed 3 times with PBS, then 10 µl/ml India ink was added into the medium and the cells were incubated at 37˚C for another 4 h. The India ink medium was removed and the cells were washed 3 times with PBS.…”

Generation and Labeling of Murine Bone Marrow-derived Dendritic Cells with Qdot Nanocrystals for Tracking Studies

“…Although DCs are cells specialized in triggering immune responses, they have been shown to participate in pathological conditions such as cancer and atherosclerosis 4,15,16 . They have been also claimed to participate in angiogenic process 17,18 , even suggested as structurally participating in the developing of new vessels 19,20 . Thus, methods that allow for DC tracking in vivo, and determining their geographical localization in different tissues 4,21,22 are very valuable.…”