Detection and measurement of in vitro gene transfer by gamma camera imaging

The purpose of this work was to develop a high capacity method to image gen e transfer to cancer cells growing as monolayers in cell culture plates. A sensitive and high capacity nuclear-imaging method for detection of gene tr ansfer in vitro will allow rapid validation of vectors in different cell li nes under various conditions. Human cancer cell lines (A-427 non-small cell lung, SKOV3.ip1 ovarian, MDA-MB-468 breast, and BxPC-3 pancreatic) were in fected with a replication-incompetent adenoviral vector encoding the human type 2 somatostatin receptor (Ad-hSSTr2). Expression of the hSSTr2 reporter protein in cells was detected by imaging an internalized Tc-99m-labeled, h SSTr2 binding peptide (P2045, Diatide, Inc.). Imaging provided an accurate measure of internally bound Tc-99m as evidenced by equivalence of results f or imaging region of interest (ROI) analyses and gamma counter measurements . Internally bound Tc-99m-P2045 was linearly correlated (R-2 = 0.98) with t he percentage of hSSTr2-positive cells following gene transfer. Excess P204 5 blocked binding and internalization of the Tc-99m-P2045, indicating the s pecificity of the technique. Up to four 96-well plates could be imaged simu ltaneously, thereby demonstrating the high capacity of the system. This nov el in vitro approach provides a new method to test enhanced gene transfer a s new vectors are developed.