The present results are consistent with our previous research, demonstrating that ND and microwave-radiofrequency carbon allotrope decreased the vascular selleck chemicals llc network in glioblastoma tumour and, consequently, their volume and weight. Moreover, diamond nanoparticles decreased the mRNA level of the main pro-angiogenic factors selleck compound VEGFA and bFGF . ND also affected the transcription level of the human stress-responsive genes of cells exposed to stress (heat shock, cytotoxic and oxidative stress). It has been demonstrated that although ND did not show toxic effects on leukaemia cell line HL-60, it up-regulates the expression of the gene SOD1, responsible for the defence mechanism against
reactive oxygen species, and down-regulates the genes JUN, GADD45A and FRAP1, responsible for protection against genotoxic and cellular stress . Moreover, the anti-angiogenic activity of nanoparticles has been related to their inhibitory effects on pro-angiogenic factors. Gold nanoparticles specifically
bind to VEGFA and bFGF and inhibit their interaction with cell membrane receptors [23, 24]. Among all the tested nanoparticles, only MWNT and more significantly ND showed anti-angiogenic activity. Nanomaterials with graphite structure (NG and GNS) did not alter blood vessel development. There are only a few studies on the biological activity of GNS. Wang et al.  showed that GNS oxide exhibited A-1210477 low toxicity in mice and human fibroblast cells. Furthermore, GNS displayed
low cytotoxicity in erythrocytes and fibroblasts , which together with our results suggests that GNS is highly biocompatible with the vascular system. Similarly, NG had no effect on CAM angiogenesis, although they have the same shape and similar size and are produced in the same way (but under different conditions) as ND , which had the strongest anti-angiogenic activity (Table 1). The strongest inhibition of vessel growth by ND may be linked to the inhibition of VEGF receptor (KDR) expression. VEGF is a major pro-angiogenic factor essential selleckchem for the development of the blood vessel network. It is controlled by the release of growth factors dependent on the oxygen level, with HIF-1 being one of the most important . Hypoxia leads to the up-regulation of VEGF and, thus, the formation of new blood vessels, which consequently normalises the oxygen status. In tumours, high activity and fast divisions of tumour cells lead to oxygen deficiency that enhances vessel growth. KDR is also regulated by various signalling molecules in response to changes in oxygen concentration [28, 29]. Hypoxia leads to KDR up-regulation and activation of the angiogenic signalling cascade [30, 31]. Down-regulation of KDR by ND may decrease hypoxia-mediated angiogenesis and exert efficient and long-lasting anti-angiogenic effects. Moreover, chronic hypoxia can lead to further down-regulation of KDR .