Dual-color imaging of nascent angiogenesis and its inhibition in liver metastases of pancreatic cancer.

As previously shown, the stem cell marker nestin is expressed in nascent blood vessels in transgenic nestin-driven green fluorescent protein (ND-GFP) nude mice. This mouse model was recently utilized to evaluate angiogenesis in primary tumors in an orthotopic model of pancreatic cancer. In the present study, nascent angiogenesis of pancreatic cancer liver metastasis in the ND-GFP transgenic nude mice after splenic injection of low-passage xPA-1 human pancreatic cancer cells expressing red fluorescent protein (RFP) was visualized by dual-color fluorescence imaging. ND-GFP was highly expressed in proliferating endothelial cells and nascent blood vessels in the growing liver metastasis. Immunohistochemical staining showed that CD31 co-localized in ND-GFP-expressing nascent blood vessels. The density of nascent blood vessels in the tumor was readily quantitated. Gemcitabine significantly decreased the mean nascent blood vessel density in the pancreatic liver metastases. In conclusion, the dual-color model of the ND-GFP nude mouse with RFP-expressing pancreatic cancer liver metastases, enabled the simultaneous visualization and quantitation of nascent angiogenesis and its response to angiogenesis inhibitors. This model will be useful for understanding the mechanism of angiogenesis of pancreatic cancer liver metastasis and for the discovery of effective new inhibitors of this process.