Vasculogenic Mimicry of HT1080 Tumour Cells In Vivo: Critical Role of HIF-1α-Neuropilin-1 Axis

Abstract

HT1080 - a human fibrosarcoma-derived cell line – forms aggressive angiogenic tumours in immuno-compromised mice. In spite of its extensive use as a model of tumour angiogenesis, the molecular event(s) initiating the angiogenic program in these cells are not known. Since hypoxia stimulates tumour angiogenesis, we examined the hypoxia-induced events evoked in these cells. In contrast to cells grown under normoxic conditions, hypoxia-primed (1% O2) HT1080 cells formed robust tubules on growth factor-reduced matrigel and formed significantly larger tumours in xenograft models in a chetomin-sensitive manner, indicating the role of HIF-1α-mediated transcription in these processes. Immuno-histochemical analyses of tumours formed by GFP-expressing HT1080 cells clearly showed that the tumour cells themselves expressed various angiogenic markers including Neuropilin-1 (NRP-1) and formed functional vessels containing red blood cells, thereby unambiguously demonstrating the vasculogenic mimicry of HT1080 cells in vivo. Experiments performed with the HT1080 cells stably transfected with plasmid constructs expressing shNRP-1 or full-length NRP-1 clearly established that the HIF1α-mediated up-regulation of NRP-1 played a deterministic role in the process. Hypoxia-exposure resulted in an up-regulation of c-Myc and OCT3/4 and a down-regulation of KLF4 mRNAs, suggesting their involvement in the tumour formation and angiogenesis. However, silencing of NRP-1 alone, though not affecting proliferation in culture, was sufficient to abrogate the tumour formation completely; clearly establishing that the hypoxia-mediated HIF-1α-dependent up-regulation of NRP-1 is a critical molecular event involved in the vasculogenic mimicry and tumor formation by HT1080 cells in vivo.

Mammalian target of rapamycin signaling is involved in the vasculogenic mimicry of glioma via hypoxia-inducible factor-1α

“…Various molecules involved in VM formation have been investigated in different tumors, including HIF-1α (14,35), VE-cadherin (36,37), EphA2 (37,38), MMP-14 (39), MMP-2 (39) and Ln-5-γ2 chain (40). Following the identification of the above-described molecules involved in VM, a classical model of the signaling cascade implicated in VM was suggested (reviewed in ref.…”

A new perspective of vasculogenic mimicry: EMT and cancer stem cells (Review)

“…In addition to tumor angiogenesis, HIF-1a is closely associated with VM formation (4,110–112). Recently, Misra et al (113) found that hypoxia-exposure resulted in an upregulation of c-Myc and OCT3/4, and contributed to VM formation. Hypoxia was also recognized as an important regulator of CSCs and EMT through NF-κB, PI3K/Akt/mTOR, Notch, Wnt/β-catenin and Hedgehog signaling pathways (114,115).…”

Desmoglein 2 promotes vasculogenic mimicry in melanoma and is associated with poor clinical outcome

“…Furthermore, the presence of histologically-detected VM networks in primary tumors is predictive of poor survival and increased metastasis in patients with melanoma [10–14] and other cancers [3, 4, 15]. Similarly, in animal models, inhibiting VM in solid cancers leads to improved survival [16, 17], and a recent study found that breast cancer clones with the highest capacity to enter the vasculature and establish metastasis were those most efficient at generating VM networks [18]. Together, these findings highlight the biological and clinical significance of VM.…”