Histological examinations of NCIH460 tumors treated by different conditions. The hematoxylin-eosin stain of NCIH460 tumors treated by different conditions, PBS plus GCV treated (A); Ad.null treated (B); Ad.hTERT-E1A-TK alone treated (C). Ad.hTERT-E1A-TK plus GCV treated (D). The necrosis is barely seen in control groups (A and B), while there are obvious necrotic areas and numerous apoptotic bodies in the tumor tissues treated by Ad.hTERT-E1A-TK alone or Ad.hTERT-E1A-TK plus GCV treated (C and D). Original magnification ×400.