Induction of apoptosis in oral cancer cells by an anti-bcl-2 ribozyme delivered by an adenovirus vector

Human oral cancer cells may have any of several genetic changes, but the ro le of the bcl-2 oncogene is relatively unexplored. To find out if this gene plays a significant role and whether it could act as a target for gene the rapy of oral cancer, we have examined the effects of an anti-bcl-2 ribozyme on the phenotype of oral cancer cells. A hammerhead ribozyme was designed to cleave the bcl-2 transcript after nucleotide 279 and was confirmed to be effective against a synthetic bcl-2 transcript. A gene encoding the ribozy me was cloned into an adenovirus vector and transferred to the human oral c ancer cell lines 686LN, 1483, and Tu183, Over a 6-day period, the growth of each cancer cell line was reduced, whereas growth of the fibroblast cell l ine FS7 was less inhibited. Inhibition of the oral cancer cells could be at tributed to apoptosis, as indicated by the detection of histone-associated DNA fragments in an immunoassay. Northern blots showed no detectable reduct ion in the level of bcl-2 mRNA of Tu183 cells, but Western blots showed a r eduction of Bcl-2 protein at 24 h after infection with the ribozyme-express ing adenovirus vector. The results imply that (a) expression of the bcl-2 o ncogene is necessary for the survival of oral cancer cells, (b) the bcl-2 g ene transcript presents a target for gene therapy by ribozymes, and (c) an adenovirus vector is a suitable method for transfection of the ribozyme-exp ressing gene.