We previously demonstrated anti-angiogenic activity of pyridoxal 5'-phosphate (PLP) and pyridoxal (PL) using in vitro and ex vivo angiogenesis models and anti-colon tumor effect of vitamin B6 in mice. There is growing evidence that endothelial progenitor cells (EPCs) in circulation contribute to tumor-induced angiogenesis. It is of importance to clarify whether EPC differentiation is involved in the mechanism of anti-angiogenic effect of vitamin B6. In this study, we investigated the effect of vitamin B6 on angiogenesis in embryonic stem cell-derived embryoid bodies (EBs). PLP suppressed angiogenesis in EBs at ≥100 µM. Among the vitamin B6 compounds at the concentration of 200 µM, PL, as well as PLP, was the most effective suppressor of vasculogenesis, while pyridoxine was inactive. These results were consistent with their effects in rat aorta and endothelial cell assays. Interestingly, pyridoxamine (PM), which had no effect in rat aorta and endothelial cell assays, also exerted a significant suppressive effect in this model. This study demonstrated an inhibitory effect of PM on vasculogenesis in this EB model as well as PLP and PL, and suggests that suppression of EPC differentiation is at least in part responsible for the mechanism of the anti-angiogenesis effect of vitamin B6.

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