Enhanced tumor cell adhesion to the subendothelial matrix resulting from 12(S)‐HETE‐induced endothelial cell retraction

Abstract

A 12-lipoxygenase metabolite of arachidonic acid, 12(S)-hydroxyeicosatetraenoic acid (12[S]-HETE), which is produced by platelets and tumor cells, was tested for its ability to induce retraction of endothelial cell monolayers. The induction of endothelial cell retraction is a critical step in tumor cell metastasis. Endothelial cells demonstrated reversible retraction in response to 12(S)-HETE, but did not respond to the stereoisomer 12(R)-HETE or to unrelated 5-lipoxygenase (i.e., 5[S]-HETE) or 15-lipoxygenase (i.e., 15[S]-HETE) metabolites. Endothelial cells did not demonstrate loss of viability in response to 12(S)-HETE. The induction of retraction was both dose and time dependent. Scanning electron microscopy confirmed that 12(S)-HETE induced endothelial cell retraction and revealed collapsed filopodia on their surface, the appearance of spaces between endothelial cells and the underlying subendothelial matrix, in addition to large gaps between adjacent endothelial cells. Tumor cell adhesion to endothelial cell monolayers was enhanced 1 h after pretreatment of monolayers with 12(S)-HETE but not after pretreatment with other lipoxygenase metabolites. Tumor cell adhesion to endothelial cell monolayers 36 h after pretreatment with 12(S)-HETE was not different from adhesion to untreated monolayers. Therefore we suggest that 12(S)-HETE generated during tumor cell-platelet-endothelial cell interactions may induce reversible endothelial cell retraction, allowing tumor cell access to the subendothelial matrix, which is a critical step in their eventual extravasation from the microvasculature during hematogenous metastasis.

Synthetic curcuminoids modulate the arachidonic acid metabolism of human platelet 12-lipoxygenase and reduce sprout formation of human endothelial cells

“…Surface expression of integrin a v h 3 , a tumor-induced angiogenic vasculature -related endothelial cell integrin, is up-regulated by 12(S)-HETE, promoting integrin translocation from intracellular pools (13). Furthermore, 12(S)-HETE can induce endothelial cell cytoskeletal rearrangement, resulting in endothelial cell retraction (14), a necessary step for tumor cell extravasations. In addition, 12(S)-HETE can stimulate tumor cell motility (15) and augment the invasive potential of AT2.1 rat prostate tumor cells (16).…”

Characterization of human 12-lipoxygenase genes.

“…Although these are the most abundant products of arachidonate metabolism formed in platelets (2), their biological function remains unclear. One possibility is that 12-lipoxygenase products modulate the transformation of the membrane glycoprotein lIb/IIIa complex that occurs with platelet activation, revealing cryptic binding sites for fibrinogen (3,4). Synthetic 12-HETE has been reported to regulate the expression of this complex in a stereospecific manner in tumor cells (5), and the platelet enzyme has been reported to translocate (6), in a calcium-dependent manner, from the cytosol to the cell membrane.…”

Molecular cloning, primary structure, and expression of the human platelet/erythroleukemia cell 12-lipoxygenase.

“…The products also displayed UV spectra identical to those of the standard compounds (data not shown analysis using the 32P-labeled PL12lx clone (Fig. 4) endothelial cell retraction (25) (Fig. 5).…”