NOX-A12 shows inhibition of SDF-1 mediated CXCR7 internalization dose dependently with an IC50of 3

NOX-A12 shows inhibition of SDF-1 mediated CXCR7 internalization dose dependently with an IC50of 3.0 0.9 nM (Fig.1B). dependent on both drug dose and duration of treatment. In addition we treated tumors only when they were visible by MRI and exhibited complete regression of the tumors that was not achieved by irradiation alone or with the addition of temozolomide. ZM-447439 == Conclusions == Inhibition of SDF-1 following tumor irradiation is usually a powerful way of improving tumor response of glioblastoma multiforme. Keywords:angiogenesis, CXCL12, Thy1 CXCR4, CXCR7, ENU-induced tumors, glioblastoma, irradiation, NOX-A12, SDF-1, vasculogenesis Radiotherapy is an important component of the treatment of glioblastoma multiforme (GBM), but despite the high radiation doses used and the combination of anticancer brokers and targeted therapies, the tumors invariably recur, leading to the demise of more than 75% of the patients by 2 years. Importantly, most of the recurrences occur within the radiation field.14Thus any method of improving local control of the primary tumor would improve the curability of GBM patients. We recently proposed a novel paradigm for the treatment of solid tumors with radiotherapy with a particular emphasis on GBM.5This was based on our previous finding that doses of radiation in the therapeutic range abrogate local angiogenesis,6forcing the tumor to rely on the vasculogenesis pathway. Vasculogenesis entails de novo growth of blood vessels from circulating cells for the restoration of the tumor vasculature, thereby allowing tumor recurrence. We exhibited both with the subcutaneously transplanted FaDu human head and neck tumor7and with the intracranially implanted U251 human GBM5that tumor recurrence could be markedly reduced or even prevented by inhibition of irradiation-induced recruitment of the pro-angiogenic CD11b+ myelomonocytes. This could be achieved either with anti-CD11b antibodies7or by inhibiting the conversation of stromal cell derived factor1 (SDF-1, CXCL12) with its chemokine receptor CXCR4,5which is usually highly expressed on CD11b+ monocytes. Kozin and colleagues8have also shown that tumor irradiation induces uptake of CD11b+ monocytes into the tumors and that the SDF-1/CXCR4 inhibitor AMD3100 delivered for ZM-447439 21 days after irradiation enhances the antitumor efficacy of radiation. Except in the ZM-447439 case of the highly radiosensitive U251, post-irradiation treatment with AMD3100, however, only prolonged the radiation-induced growth delay, and the tumors eventually recurred in the 2 2 studies pointed out. Although CD11b+ monocytes facilitate vasculogenesis by tissue remodeling requiring matrix metalloproteinase9,6they do not form blood vessels themselves.5,8Therefore, we hypothesized that other circulating cells, such as endothelial cells (ECs) or endothelial progenitor cells (EPCs),9as well as possibly pericytes, may be needed to restore the irradiated vasculature. Since ECs in solid tumors, including GBM, have been shown to express high levels of CXCR7,1012the more recently discovered second receptor for SDF-1,13,14we hypothesized that the most effective strategy for preventing post-irradiation vasculogenesis in GBM would be to block both SDF-1 receptors, CXCR4 and CXCR7. A logical way to achieve concomitant inhibition would be to target the shared ligand SDF-1.15 A modality fulfilling these requirements is the PEGylated mirror-image RNA oligonucleotide (a so-called Spiegelmer) NOX-A12 that binds with high affinity to SDF-1. NOX-A12 consists of 45l-enantiomeric RNA nucleotides and carries a 40-kDa polyethylene glycol (PEG) modification at its 5-end in order to increase plasma residence time. The 45l-nucleotides of the oligonucleotide form a structural scaffold that recognizes SDF-1 with.