Roles of prostaglandin E2-EP3/EP4 receptor signaling in the enhancement of lymphangiogenesis during fibroblast growth factor-2-induced granulation formation

Thromboxane A₂ receptor signaling facilitates tumor colonization through P-selectin-mediated interaction of tumor cells with platelets and endothelial cells

Thromboxane A(2) (TXA(2) ) is a prostanoid formed by thromboxane synthase using the cyclooxygenase product, prostaglandin H(2), as the substrate. TXA(2) was shown to enhance tumor metastasis, but the underlying mechanism remains unclear. B16F1 melanoma cells were intravenously injected into TXA(2) receptor (TP) knockout mice (TP(-/-) ) and wild-type littermates (WT). TP(-/-) showed a reduction in B16F1 lung colonization and mortality rate, which were associated with a decreased number of platelets. Platelet activation as assessed by P-selectin expression was suppressed in TP(-/-) . A selective P-selectin neutralizing antibody decreased the lung colonization in WT mice, but not in TP(-/-) . The expression of P-selectin glycoprotein ligand-1 in B16F1 and HUVEC were enhanced by treatment with U46619, a thromboxane analog. The plasma levels of vascular endothelial growth factor (VEGF) and stromal-derived factor (SDF)-1 were lower in TP(-/-) . In TP(-/-) , the mobilization of progenitor cells expressing CXCR4(+) VEGFR1(+) from bone marrow and the recruitment of those cells to lung tissues were suppressed. These results suggest that TP signaling plays a critical role in tumor colonization through P-selectin-mediated interactions between platelets-tumor cells and tumor cells-endothelial cells through the TP signaling-dependent production of VEGF and SDF-1, which might be involved in the mobilization of VEGFR1(+) CXCR4(+) cells. Blockade of TP signaling might be useful in the treatment of tumor metastasis.

Modulation of lymphangiogenesis: a new target for aspirin and other nonsteroidal anti-inflammatory agents? A systematic review

Recent studies have implicated that lymphangiogenesis plays a role in the development of metastasis in experimental cancer models and in certain types of human tumors. Epidemiological and laboratory data suggest that non steroidal anti-inflammatory agents (NSAIDs) have antitumor activities, although the mechanisms have not been elucidated. This systematic review aimed to synthesize data on the effect of aspirin and other NSAIDs on lymphangiogenesis. In particular, an answer was attempted to be found for the following primary questions: Is there an effect of aspirin and NSAIDs on lymphangiogenesis? If yes, is this effect mediated through COX-II inhibition or through COX-II-independent mechanisms? Electronical databases were searched with the appropriate search terms for the period from 1966 up to and including February 2011. The few identified experimental trials indicated that aspirin and other NSAIDs inhibit lymphangiogenesis, with a potential decrease in metastatic spread, possibly through COX-II-dependent regulation of VEGF-C expression. COX-II-independent mechanisms of inhibition of lymphangiogenesis by salicylates and the other NSAIDs have not been investigated. Although further research validation is needed, this proposed effect of NSAIDs might have therapeutic implications in chemoprevention, adjuvant chemotherapy, and treatment of metastatic disease.