12(S)-HETE increases intracellular Ca2+ in lymph-endothelial cells disrupting their barrier function in vitro; stabilization by clinical drugs impairing calcium supply

Secretion of 12(S)-HETE by breast cancer emboli provokes “circular chemorepellent induced defects” (CCIDs) in the adjacent lymphatic vasculature facilitating their intravasation and lymph node metastasis which determines prognosis. Therefore, elucidating the mechanism of lymph endothelial cell (LEC) wall disintegration may provide cues for anti-metastatic intervention. The role of intracellular free Ca2+ for CCID formation was investigated in LECs using MCF-7 or MDA-MB231 breast cancer cell spheroids in a three-dimensional cell co-culture model. 12(S)-HETE elevated the Ca2+ level in LEC by activating PLC/IP3. Downstream, the Ca2+-calmodulin kinase MYLK contributed to the phosphorylation of Ser19-MLC2, LEC contraction and CCID formation. Approved clinical drugs, lidoflazine, ketotifen, epiandrosterone and cyclosporine, which reportedly disturb cellular calcium supply, inhibited 12(S)-HETE-induced Ca2+ increase, Ser19-MLC2 phosphorylation and CCID formation. This treatment strategy may reduce spreading of breast cancer through lymphatics.