Cysteinyl leukotriene 2 receptor promotes endothelial permeability, tumor angiogenesis, and metastasis.

Cysteinyl leukotrienes (cys-LTs) are proinflammatory mediators that enhance vascular permeability through distinct receptors (CysLTRs). We found that CysLTR regulates angiogenesis in isolated mouse endothelial cells (ECs) and in Matrigel implants in WT mice and enhances EC contraction and permeability via the Rho-dependent myosin light chain 2 and vascular endothelial (VE)-cadherin axis. Since solid tumors utilize aberrant angiogenesis for their growth and metastasis and their vessels exhibit vascular hyperpermeability, we hypothesized that CysLTR, via its actions on the endothelium, might regulate tumor growth. Both tumor growth and metastases of adoptively transferred syngeneic Lewis lung carcinoma (LLC) cells are significantly reduced in CysLTR-null mice () compared with WT and CysLTR-null mice (). In WT recipients of LLC cells, CysLTR expression is significantly increased in the tumor vasculature, compared with CysLTR. Further, the tumor vasculature in recipients exhibited significantly improved integrity, as revealed by increased pericyte coverage and decreased leakage of i.v.-administered Texas Red-conjugated dextran. Administration of a selective CysLTR antagonist significantly reduced LLC tumor volume, vessel density, dextran leakage, and metastases in WT mice, highlighting CysLTR as a VEGF-independent regulator of the vasculature promoting risk of metastasis. Thus, both genetic and pharmacological findings establish CysLTR as a gateway for angiogenesis and EC dysregulation in vitro and ex vivo and in an in vivo model with a mouse tumor. Our data suggest CysLTR as a possible target for intervention.