Induction of Apoptosis in Cultured Colon Cancer Cells by Transfection with Human Interferon β Gene

The growth of SW480 colon cancer cells following the transfection with the human interferon β (hIFNβ) gene entrapped in cationic multilamellar liposomes was effectively inhibited, but not that of the cells transfected with the gene from which the secretion signal sequence ofhIFNβhad been deleted. The amount of hIFNβ secreted in the medium from SW480 cells transfected withhIFNβgradually increased and became maximum 3 days after the transfection, but no hIFNβ was detected in the medium of the cells transfected with the secretion signal-deletedhIFNβ. These findings indicate that the growth inhibition of SW480 cells after the transfection withhIFNβwas caused by hIFNβ secreted from the transfected cells. At that time, SW480 cells were induced to undergo apoptosis, which was identified by morphological aspects, viz., chromatin condensation, nuclear segmentation, and nucleosomal DNA fragmentation. The hIFNβ-induced apoptosis was found to be linked to the activation of caspases 3 and 8 as evidenced by immunoblot, enzymological, and cell death inhibition analyses.