In Vivo Imaging of Pancreatic Cancer with Fluorescent Proteins in Mouse Models

In this chapter, we describe protocols for clinically-relevant, metastatic orthotopic mouse models of pancreatic cancer, made imageable with genetic reporters. These models utilize human pancreatic-cancer cell lines which have been genetically engineered to selectively express high levels of green fluorescent protein (GFP) or red fluorescent protein (RFP). Tumors with fluorescent genetic reporters are established subcutaneously in nude mice by injection of the GFP- or RFP-expressing pancreatic cancer cell lines, and fragments of the subcutaneous tumors are then surgically transplanted onto the pancreas of additional nude mice. Loco-regional tumor growth and distant metastasis of these orthotopic tumors occurs spontaneously and rapidly throughout the abdomen in a manner consistent with clinical human disease. Highly-specific, high-resolution, real-time quantitative fluorescence imaging of tumor growth, and metastasis is achieved in vivo without the need for contrast agents, invasive techniques, or expensive imaging equipment. Transplantation of RFP-expressing tumor fragments onto the pancreas of GFP- or cyan fluorescent protein (CFP)-expressing transgenic nude mice was used to facilitate visualization of tumor–host interaction between the pancreatic cancer cells and host-derived stroma and vasculature. Such in vivo models have enabled us to visualize in real time and acquire images of the progression of pancreatic cancer in the live animal. These models can demonstrate the real-time antitumor and antimetastatic effects of novel therapeutic strategies on pancreatic malignancy. These fluorescent models are therefore powerful and reliable tools with which to investigate metastatic human pancreatic cancer and novel therapeutic strategies directed against it.