Cannabinoids inhibit
tumor neovascularization as part of their tumorregressive action. However, the underlying mechanism is still under debate. In the present study the impact of
cannabinoids on potential
tumor-to-endothelial cell communication conferring anti-angiogenesis was studied. Cellular behavior of human umbilical vein endothelial cells (HUVEC) associated with angiogenesis was evaluated by Boyden chamber, two-dimensional tube formation and
fibrin bead assay, with the latter assessing three-dimensional sprout formation. Viability was quantified by the WST-1 test.
Conditioned media (CM) from A549
lung cancer cells treated with
cannabidiol, Δ(9)-tetrahydrocannabinol,
R(+)-methanandamide or the CB2 agonist
JWH-133 elicited decreased migration as well as tube and sprout formation of HUVEC as compared to CM of vehicle-treated
cancer cells. Inhibition of sprout formation was further confirmed for
cannabinoid-treated A549 cells co-cultured with HUVEC. Using antagonists to
cannabinoid-activated receptors the antimigratory action was shown to be mediated via
cannabinoid receptors or transient receptor potential vanilloid 1.
SiRNA approaches revealed a
cannabinoid-induced expression of tissue inhibitor of matrix metalloproteinases-1 (TIMP-1) as well as its upstream trigger, the
intercellular adhesion molecule-1, to be causally linked to the observed decrease of HUVEC migration. Comparable anti-angiogenic effects were not detected following direct exposure of HUVEC to
cannabinoids, but occurred after addition of recombinant
TIMP-1 to HUVEC. Finally, antimigratory effects were confirmed for CM of two other
cannabinoid-treated
lung cancer cell lines (H460 and H358). Collectively, our data suggest a pivotal role of the anti-
angiogenic factor TIMP-1 in intercellular
tumor-endothelial cell communication resulting in anti-angiogenic features of endothelial cells.