Evidences of antitumor efficacy of AD55-Apoptin in vivo. The pathologic detection by H.E, IHC and TUNEL staining assay were performed. Subcutaneous Huh-7 tumors receiving various treatments were harvested on the 4th day after infection with viruses. Tumor sections were treated as described above methods and materials. A. H.E staining assay. partial area of necrosis have been detected in the sections treated with ONYX-015, AD55, AD55-Apoptin (indicated with the black arrows), compared to the PBS group(×100, original magnification). B. The adenovirus hexon protein as an indicator of adenovirus in vivo was detected by IHC analysis as described above methods and materials. (×400, original magnification). Hexon expression was positive (arrows indicated) in three groups treated with ONYX-015 or AD55 or AD55-Apoptin, respectively. C. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay for detection of apoptotic cells in tumor sections treated with PBS or the above various recombinant viruses (×400, original magnification). The black arrows indicated the obvious apoptotic cells in the AD55-Apoptin treated group than that of AD55, ONYX-015 or PBS treated group.