bcl-2 over-expression delays radiation-induced apoptosis without affecting the clonogenic survival of human prostate cancer cells.
In this study we evaluated the effect of over-expression of the bcl-2 gene, a potent apoptosis suppressor, on radiation-induced apoptotic cell death in 2 human prostate cancer cell lines, androgen-independent PC-3 cells and androgen-sensitive LNCaP cells. Cells were transfected with the bcl-2 gene and bcl-2 transfectant clones isolated under neomycin selection; bcl-2 gene integration and level of mRNA and protein expression in the cloned transfectants were examined by Southern, Northern and Western blot analyses, respectively. Parental, neo control and bcl-2-expressing cells were exposed to single or fractionated doses of ionizing irradiation, and the cellular response to radiation was determined at 24, 48 and 72 hr post-irradiation, on the basis of: (i) loss of cell viability, (ii) clonogenic survival and (iii) induction of apoptotic DNA fragmentation. At 24 hr post-irradiation all cell lines, i.e., parental and bcl-2 transfectants, failed to form colonies, though the majority of bcl-2-expressing cells did not exhibit apoptotic morphology; bcl-2 over-expression in both cell lines reduced apoptosis 48 hr post-irradiation from 20-25% to 5% at a dose of 2,000 cGy. By 72 hr, bcl-2 over-expression afforded a 3-fold protection from radiation-induced apoptosis. There was no significant difference, however, in the clonogenic survival of the parental and bcl-2-expressing cells. Furthermore, there was a 24 hr delay in induction of the apoptosis marker gene SGP-2/TRPM-2 in the bcl-2-expressing cells, co-incidental with the delay in apoptotic DNA fragmentation.
Kyprianou
N
N
Department of Surgery, University of Maryland School of Medicine, Baltimore 21201, USA.
King
E D
ED
Bradbury
D
D
Rhee
J G
JG
D017209:Apoptosis / Q000235:genetics / Q000528:radiation effects*; D002455:Cell Division / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D051152:Clusterin; D053938:DNA Fragmentation; D019254:Genes, bcl-2; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D008297:Male; D018832:Molecular Chaperones; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D011829:Radiation Dosage; D014162:Transfection; D014410:Tumor Stem Cell Assay
C495242:CLU protein, human; D051152:Clusterin; D006023:Glycoproteins; D018832:Molecular Chaperones; D019253:Proto-Oncogene Proteins c-bcl-2