bcl‐2 over‐expression delays radiation‐induced apoptosis without affecting the clonogenic survival of human prostate cancer cells

• Published in: International journal of cancer 1997-01, Vol.70 (3), p.341-348
• Main Authors: Kyprianou, Natasha, King, Edward D., Bradbury, David, Rhee, Juong G.
• Format: Article
• Language: English
• Subjects: Apoptosis - genetics; Apoptosis - radiation effects; Biological and medical sciences; Cell Division - radiation effects; Cell Survival - radiation effects; Clusterin; DNA Fragmentation; Genes, bcl-2; Glycoproteins - metabolism; Humans; Male; Medical sciences; Molecular Chaperones; Prostatic Neoplasms - genetics; Prostatic Neoplasms - metabolism; Prostatic Neoplasms - pathology; Proto-Oncogene Proteins c-bcl-2 - metabolism; Radiation Dosage; Radiation therapy and radiosensitizing agent; Transfection; Treatment with physical agents; Treatment. General aspects; Tumor Stem Cell Assay; Tumors
• ISSN: 0020-7136; 1097-0215
• DOI: 10.1002/(SICI)1097-0215(19970127)70:3<341::AID-IJC16>3.0.CO;2-I

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. Int. J. Cancer, 70:341–348, 1997. © 1997 Wiley‐Liss, Inc.