Eicosapentaenoic acid suppresses angiogenesis via reducing secretion of IL-6 and VEGF from colon cancer-associated fibroblasts

Eicosapentaenoic acid (EPA) improves interleukin (IL)-6 hypercytokinemia in patients with advanced cancer due to its anti-inflammatory effects. This EPA mechanism has been revealed to lead to several anticancer effects. While the effects of EPA on cancer cells have been investigated, particularly in terms of angiogenesis, its effects on the tumor stroma remain unclear. In the present study, the authors clarified the role of EPA in cancer angiogenesis against colon cancer-associated fibroblasts (CAFs) from the colon stroma. With established human CAFs and normal fibroblasts from colon stroma (NFs), the authors evaluated IL-6 and vascular endothelial growth factor (VEGF) secretion with or without EPA treatment using ELISA. The signal inhibition of mitogen-activated protein kinase (ERK) in CAFs by EPA was evaluated using western blotting. In vitro anti-angiogenesis effects were evaluated by the angiogenesis assay on Matrigel using human umbilical vein endothelial cells (HUVECs) cultured with the supernatant obtained from CAF cultures with or without EPA. IL-6 secretion was greater from CAFs compared with that from NFs and stimulation with lipopolysaccharide (LPS) resulted in greater IL-6 secretion from the two fibroblast types compared with that from fibroblasts without LPS stimulation. While LPS stimulation increased VEGF secretion from the two fibroblast types, EPA decreased IL-6 and VEGF secretion from CAFs. Western blotting revealed that the addition of 30 mu M EPA inhibited the ERK phosphorylation signal in CAFs. Furthermore, the angiogenesis assay with Matrigel revealed that the CAF culture supernatants treated with EPA suppressed tubular formation in HUVECs. These reductions may have been caused by the inhibition of ERK phosphorylation by EPA. Thus, EPA reduces cancer angiogenesis associated with CAFs. Additional studies will be needed to clarify the continuous anti-angiogenetic effect of chemotherapy using angiogenesis inhibitors (e.g. bevacizumab and aflibercept) in conjunction with or without EPA, and the clinical usage of EPA in conjunction with chemotherapy in vivo.