FIG. 6.

Immunofluorescence imaging of luciferase protein as a reporter of hybrid formation. Entire primary tumor and lung sections were imaged via tile scanning, and each image of the scan was carefully analyzed to confirm or refute positive staining for luciferase. The luciferase signal was considered a positive signal if it was above background levels associated with negative controls and corresponded to the cytoplasm of a cell with a nucleus. Rare luciferase-positive cells were detected in the primary tumors. Most red signal was not in the cytoplasm of cells associated with nuclei and, therefore, considered nonspecific [insets (a), (c)]. The lungs containing metastases on the other hand [(b), (d)] contained a large number of bona fide luciferase-positive cells corresponding to fusion products. Scale bars on slide scans = 100 μm. Scale bars on 40× inset = 25 μm.