SDF-1 Blockade Enhances Anti-VEGF Therapy of Glioblastoma and Can Be Monitored by MRI.

Despite the approval of antiangiogenic therapy for glioblastoma multiforme (GBM) patients, survival benefits are still limited. One of the resistance mechanisms for antiangiogenic therapy is the induction of hypoxia and subsequent recruitment of macrophages by stromal-derived factor (SDF)-1α (CXCL-12). In this study, we tested whether olaptesed pegol (OLA-PEG, NOX-A12), a novel SDF-1α inhibitor, could reverse the recruitment of macrophages and potentiate the antitumor effect of anti-vascular endothelial growth factor (VEGF) therapy. We also tested whether magnetic resonance imaging (MRI) with ferumoxytol as a contrast agent could provide early information on macrophage blockade. Orthotopic human G12 glioblastomas in nude mice and rat C6 glioblastomas were employed as the animal models. These were treated with bevacizumab or B-20, both anti-VEGF antibodies. Rats were MR imaged with ferumoxytol for macrophage detection. Tumor hypoxia and SDF-1α expression were elevated by VEGF blockade. Adding OLA-PEG to bevacizumab or B-20 significantly prolonged the survival of rodents bearing intracranial GBM compared with anti-VEGF therapy alone. Intratumoral CD68+ tumor associated macrophages (TAMs) were increased by VEGF blockade, but the combination of OLA-PEG + VEGF blockade markedly lowered TAM levels compared with VEGF blockade alone. MRI with ferumoxytol as a contrast agent noninvasively demonstrated macrophage reduction in OLA-PEG + anti-VEGF-treated rats compared with VEGF blockade alone. In conclusion, inhibition of SDF-1 with OLA-PEG inhibited the recruitment of TAMs by VEGF blockage and potentiated its antitumor efficacy in GBM. Noninvasive MRI with ferumoxytol as a contrast agent provides early information on the effect of OLA-PEG in reducing TAMs.

Inhibiting vasculogenesis after radiation: a new paradigm to improve local control by radiotherapy.

Tumors are supported by blood vessels, and it has long been debated whether their response to irradiation is affected by radiation damage to the vasculature. We have shown in preclinical models that, indeed, radiation is damaging to the tumor vasculature and strongly inhibits tumor angiogenesis. However, the vasculature can recover by colonization from circulating cells, primarily proangiogenenic CD11b+ monocytes or macrophages from the bone marrow. This secondary pathway of blood vessel formation, known as vasculogenesis, thus acts to restore the tumor vasculature and allows the tumor to recur following radiation. The stimulus for the influx of these CD11b+ cells into tumors following irradiation is the increased levels of hypoxia-inducible factor-1 in the tumor due to induced tumor hypoxia secondary to blood vessel loss. This increases tumor levels of the chemokine stromal cell-derived factor-1, which has chemokine receptors CXCR4 and CXCR7 on monocytes and endothelial cells thereby capturing these cells in the tumors. The increase in CD11b+ monocytes in tumors following irradiation can be prevented using antibodies or small molecules that inhibit hypoxia-inducible factor-1 or the interaction of stromal cell-derived factor-1 with its receptors. We show that the effect of inhibiting these chemokine-chemokine receptor interactions is a marked increase in the radiation response of transplanted or chemically induced tumors in mice and rats. This strategy of inhibiting vasculogenesis following tumor irradiation is a new paradigm in radiotherapy and suggests that higher levels of local control of tumors in several sites would be achievable with this strategy.

Mature results from a randomized Phase II trial of cisplatin plus 5-fluorouracil and radiotherapy with or without tirapazamine in patients with resectable Stage IV head and neck squamous cell carcinomas.

BACKGROUND: The objective of this article was to report the results from a randomized trial that evaluated the efficacy and toxicity of adding tirapazamine (TPZ) to chemoradiotherapy in the treatment of patients with head and neck squamous cell carcinomas (HNSCC). METHODS: Sixty-two patients with lymph node-positive, resectable, TNM Stage IV HNSCC were randomized to receive either 2 cycles of induction chemotherapy (TPZ, cisplatin, and 5-fluorouracil [5-FU]) followed by simultaneous chemoradiotherapy (TPZ, cisplatin, and 5-FU) or to receive the same regimen without TPZ. Patients who did not achieve a complete response at 50 Grays underwent surgical treatment. Stratification factors for randomization included tumor site, TNM stage, and median tumor oxygen tension. The primary endpoint was complete lymph node response. RESULTS: The addition of TPZ resulted in increased hematologic toxicity. There was 1 treatment-related death from induction chemotherapy. The complete clinical and pathologic response rate in the lymph nodes was 90% and 74% for the standard treatment arm and the TPZ arm, respectively (P = .08) and 89% and 90% at the primary site in the respective treatment arms (P = .71). The 5-year overall survival rate was 59%, the cause-specific survival rate was 68%, the rate of freedom from recurrence was 69%, and the locoregional control rate was 77% for the entire group. There was no difference with regard to any of the outcome parameters between the 2 treatment arms. The significant long-term toxicity rate also was found to be similar between the 2 arms. CONCLUSIONS: The addition of TPZ increased hematologic toxicity but did not improve outcomes in patients with resectable, Stage IV HNSCC using the protocol administered this small randomized study. The combination of induction and simultaneous chemoradiotherapy resulted in excellent survival in these patients.