IFN-β–induced apoptosis is associated with induction of the Jak-Stat pathway and the proapoptotic mediators Bak and TRAIL. (a) Upper left panel: Cell counts. Lower left panel: Cell death detection ELISA. Right panel: In situ TUNEL staining. (b) Western blot and Northern analyses of downstream mediators of IFN-β/receptor binding. Protein immunoblot analysis of signal transducers and activators of transcription (Stat) proteins, Stat1, Stat2, and ISGF3γ, in whole cell extracts from colorectal cell line KM12L4 48 hours after treatment with PBS, Adβ-gal, or AdhIFN-β (10 pfu). RNA analysis of Stat1, Stat2, ISGF3γ, and IRF1 in treated KM12L4 cells 48 hours after treatment. Equal loading of mRNA is demonstrated on Northern blot by GADPH. (c) Protein immunoblot analysis of Waf1, bcl-2, bcl-X, bak, and bax in whole cell extracts (50 mg) from colorectal cell line KM12L4 48 hours after treatment. Messenger RNA analysis of colorectal cell line KM12L4 48 hours after treatment for the bcl-2 family apoptosis-related genes using the multiprobe RNase Protection Assay (RPA) system. Gel band intensities were quantified with the UN-Scan-It program (Silk Scientific Corp., Orem, Utah, USA) and presented as ratio of AdhIFN-β/PBS band intensity after normalization with the housekeeping gene L32. (d) Messenger RNA analysis of the colorectal cell line KM12L4 48 hours after treatment for the death receptor family apoptosis-related genes using the multiprobe RPA system. Gel band intensities were quantified with the UN-Scan-It program and presented as ratio of AdhIFN-β/PBS band intensity after normalization with the housekeeping gene L32.