MFTZ-1 reduces constitutive and inducible HIF-1alpha accumulation and VEGF secretion independent of its topoisomerase II inhibition.

J Cell Mol Med. 2009 Jun 16; Dai M, Miao ZH, Ren X, Tong LJ, Yang N, Li T, Lin LP, Shen YM, Ding JAbstract The macrolide compound MFTZ-1 has been identified as a novel topoisomerase II (Top2) inhibitor with potent in vitro and in vivo anti-tumor activities. In this study, we further examined the effects of MFTZ-1 on hypoxia-inducible factor-1alpha (HIF-1alpha) accumulation, vascular endothelial growth factor (VEGF) secretion and angiogenesis. MFTZ-1 reduced HIF-1alpha accumulation driven by hypoxia or growth factors in human cancer cells. Mechanistic studies revealed that MFTZ-1 did not affect the degradation of HIF-1alpha protein or the level of HIF-1alpha mRNA. By contrast, MFTZ-1 apparently inhibited constitutive and inducible activation of both phosphatidylinositol-3-kinase (PI3K)-Akt and p42/p44 mitogen-activated protein kinase (MAPK) pathways. Further studies revealed that MFTZ-1 abrogated the HIF-1alpha-driven increase in VEGF mRNA and protein secretion. MFTZ-1 also lowered the basal level of VEGF secretion. The results reveal an important feature that MFTZ-1 can reduce constitutive, HIF-1alpha-independent VEGF secretion and concurrently antagonize inducible, HIF-1alpha-dependent VEGF secretion. Moreover, MFTZ-1 disrupted tube formation of human umbilical vein endothelial cells (HUVECs) stimulated by hypoxia with low-concentration serum or by serum at normoxia, and inhibited HUVECs migration at normoxia. MFTZ-1 also prevented microvessel outgrowth from rat aortic ring. These data reflect the potent anti-angiogenesis of MFTZ-1 under different conditions. Furthermore, using specific small interfering RNA targeting Top2alpha or Top2-defective HL60/MX2 cells, we showed that MFTZ-1 affected HIF-1alpha accumulation and HUVECs tube formation irrelevant to its Top2 inhibition. Taken together, our data collectively reveal that MFTZ-1 reduces constitutive and inducible HIF-1alpha accumulation and VEGF secretion possibly via PI3K-Akt and MAPK pathways, eliciting anti-angiogenesis independently of its Top2 inhibition.