Apoptosis analysis using TUNEL (a–d) and Hoechst 33 258 staining (e–h). Tumor tissue preparation and procedure for TUNEL and Hoechst 33 258 staining were described in ‘Materials and methods’. Pyknotic or fragmented nuclei emitting an intense fluorescent staining (e–g) were considered apoptotic in comparison with smooth, round-shaped nuclei emitting low fluorescence (h). Representative sections from Meth A tumor tissue are shown as pBLAST45-msFLK-1 plus DDP (a, e), pBLAST45-msFLK-1 (b, f), DDP (c, g), N.S. (d, h) severally. Columns represented apoptotic index within tissue from H22 (solid columns) and Meth A (open columns) (i). The apoptotic index was calculated as a ratio of the apoptotic cell number to the total cell number, which showed systemic therapy with pBLAST45-msFLK-1 plus DDP resulted in significant increment of apoptotic index versus N.S. controls (**P<0.01), pBLAST45-msFLK-1 or DDP alone versus N.S. control (* P<0.05).