Synergy of nab-paclitaxel and bevacizumab in eradicating large orthotopic breast tumors and preexisting metastases.

INTRODUCTION: Patients with metastatic disease are considered incurable. We previously showed that nabpaclitaxel (nanoparticle albumin-embedded paclitaxel) combined with anti-vascular endothelial growth factor A (VEGF-A) antibody, bevacizumab, eradicates orthotopic small-sized breast tumors and metastasis. Here, we assessed this therapy in two models of advanced (450-600 mm(3)) breast tumors and delineated VEGF-A-dependent mechanisms of tumor resistance.
METHODS: Mice with luciferase-tagged advanced MDA-MB-231 and MDA-MB-435 tumors were treated with saline, nab-paclitaxel (10 or 30 mg/kg), bevacizumab (4 mg/kg), or combined drugs. Lymphatic and lung metastases were measured by luciferase assay. Proinflammatory and survival pathways were measured by ELISA, Western blot and immunohistochemistry.
RESULTS: Nab-paclitaxel transiently suppressed primary tumors by 70% to 90% but had no effect on metastasis. Coadministration of bevacizumab increased the response rate to 99%, including 71% of complete responses in MDA-MB-231-bearing mice treated concurrently with 30 mg/kg of nab-paclitaxel. This combinatory regimen significantly reduced or eliminated preexisting lymphatic and distant metastases in MDA-MB-231 and MDA-MB-435 models. The mechanism involves paclitaxel-induced NF-κB pathway that upregulates VEGF-A and other tumor prosurvival proteins.
CONCLUSIONS: Bevacizumab prevents tumor recurrence and metastasis promoted by nab-paclitaxel activation of NF-κB pathway. Combination therapy with high-dosed nab-paclitaxel demonstrates the potential to eradicate advanced primary tumors and preexisting metastases. These findings strongly support translating this regimen into clinics.