Nab-paclitaxel Efficacy in the Orthotopic Model of Human Breast Cancer Is Significantly Enhanced By Concurrent Anti–Vascular Endothelial Growth Factor A Therapy

Nab-paclitaxel is an albumin-bound 130-nm particle form of paclitaxel that has shown an improved efficacy in experimental tumor models and clinical studies compared with solvent-based paclitaxel. Anti–vascular endothelial growth factor A (VEGF-A) antibody bevacizumab is known to enhance antitumor activity of cytotoxic drugs. This study evaluated the effects of combined nab-paclitaxel and bevacizumab therapy on growth and metastatic spread of orthotopic breast tumors. Cytotoxic and clonogenic assays measured VEGF-A–dependent modulation of nabpaclitaxel toxicity on cultured tumor cells. Antitumor effects were assessed in mice with luciferase-tagged, wellestablished MDA-MB-231 tumors (250–310 mm3) treated with one, two, or three cycles of nab-paclitaxel (10 mg/ kg, daily for five consecutive days), bevacizumab (2–8 mg/kg, twice a week), or with combination of both drugs. VEGF-A protected MDA-MB-231 cells against nab-paclitaxel cytotoxicity, whereas bevacizumab sensitized cells to the effect of the drug. Combined bevacizumab and nab-paclitaxel treatment synergistically inhibited tumor growth and metastasis resulting in up to 40% of complete regressions of well-established tumors. This therapy also decreased the incidence of lymphatic and pulmonary metastases by 60% and 100%, respectively. The significant increase in the cure of tumor-bearing mice in the nab-paclitaxel/bevacizumab combined group compared with mice treated with single drugs strongly advocates for implementing such strategy in clinics.