Down-Regulation of Bcl-2 Protein Sensitizes NCI-H460 Cells to Radiotherapy-Induced Apoptosis

OBJECTIVE To determine whether Bcl -2 protein down -regulation can render NCI -460 cells more susceptible to gamma radiation -induced apoptosis by treatment with antisense oligonucleotide (ASODN) against the coding region of Bcl-2 mRNA. METHODS Cell survival was determined using the trypan blue dye exclusion. Expression of the Bcl-2 protein was assayed using immunofluo-rescence labeling with fluoresce isothiocyanate. Apoptosis was determined by Giemsa staining and flow cytomertry. RESULTS It was found that Bcl-2 ASODN combined with radiation significantly reduced the number of viable cells (P<0.05). There was no difference in cell survival between a nonsense oligodeoxynucleotide/radia-tion combination and cells treated with radiation alone. Bcl -2 ASODN combined with radiation significantly inhibited expression of the Bcl -2 protein in the NCI-H460 cells (P<0.05). Using Giemsa staining, cells treated with Bcl -2 ASODN combined with radiation at 72 h displayed classic apoptotic changes. Apoptotic rates of the NCI-H460 cells treated with Bcl-2 ASODN combined with radiation significantly increased (P< 0.05), compared with either a nonsense oligodeoxynucleotide/radiation combination or radiation-treatment cells alone. CONCLUSION ASODN against the coding region of Bcl-2 mRNA increases radiation-induced apoptosis in NCI-H460 cells.