rNAPc2, a Novel Inhibitor of Tissue Factor/Factor VIIa Complex, Suppresses Lung Metastasis and Synergizes with 5-FU or Bevacizumab in Mouse Models of Colorectal Cancer.

Recombinant nematode anticoagulant protein c2 (rNAPc2) is a specific inhibitor of tissue factor (TF)/factor VIIa complex with novel anti-metastasis, anti-angiogenesis, and anti-thrombosis activities. rNAPc2 has been previously shown to inhibit both the primary growth and metastasis of murine B16 melanoma and Lewis lung carcinoma in mice. TF is highly expressed in human colorectal tumors and the level of TF expression positively correlates with the progression of malignancy. To explore the therapeutic potential of rNAPc2 during tumor growth and progression, we tested rNAPc2 efficacy in experimental colorectal cancer in mice. Both primary and metastatic colorectal tumor models were used in the current study and rNAPc2 was given to mice via daily intraperitoneal injections. Administration of rNAPc2 inhibited pulmonary metastasis in mice systemically disseminated with CT26 murine colon carcinoma cells in a dose-dependent fashion, as measured by either number of lung surface metastases or lung mass. While rNAPc2 treatment alone moderately reduced primary tumor growth, combining rNAPc2 with the cytotoxic agent 5-fluorouracil (5-FU) resulted in synergistic growth inhibition of HCT116 human colorectal tumor xenografts in nude mice. Likewise, rNAPc2 further reduced tumor growth in HCT116 human colorectal tumor xenograft-bearing mice receiving bevacizumab (humanized anti-vascular endothelial growth factor monoclonal antibody). The doses and dosing regimens of rNAPc2 used in these murine models of colorectal cancer were well tolerated by recipient mice without major complications of hemorrhage or any other adverse effects. In conclusion, the synergistic tumor inhibitory activity of rNAPc2 in pre-clinical colorectal cancer models suggests that rNAPc2 may be an effective anti-tumor agent in human colorectal cancer patients to potentiate chemo- or anti-angiogenic therapies.