Antisense Bcl-2 sensitizes prostate cancer cells to radiation.
BACKGROUND
Bcl-2 is anti-apoptotic and overexpression is associated with prostate tumor aggressiveness. We hypothesized that Bcl-2 has a role in prostate cancer radiation (RT) response. The relationship of Bcl-2 expression in four prostate cancer cell lines, and the effect of modulating expression with a Bcl-2 antisense oligonucleotide (G3139, Genasense, oblimersen sodium, Genta Incorporated), to RT was examined.


METHODS
The four cell lines studied were LNCaP (wild type-p53), PC3 (p53 null), Bcl-2 stably transfected LNCaP (LNCaP-BST), and Bcl-2 stably transfected PC3 (PC3-BST) cells. Cells were treated with antisense (AS) Bcl-2 alone or with RT (2-6 Gy). Following RT, cells were processed at 3-6 hr for Western blots, 18 hr for Annexin V staining and flow cytometric analysis, 24 hr for caspases 3+7 quantification by fluorometric assay, and immediately for clonogenic survival.


RESULTS
AS caused a significant reduction in Bcl-2 expression in all cell lines. P53 expression was elevated following RT treatment in LNCaP and LNCaP-BST cells. P21 was increased by RT treatment in all cell lines. AS caused a significant increase in caspase 3+7 activity over the mismatch (MM) controls in all cell lines. When AS was combined with RT, caspase 3+7 activity was further increased significantly over all other groups in all cell lines. Moreover, AS+RT resulted in significantly reduced clonogenic survival over MM+RT, which was dampened in the Bcl-2 overexpressing lines.


CONCLUSIONS
To our knowledge, these data demonstrate for the first time that a Bcl-2 specific AS oligonucleotide sensitizes prostate cancer cells to RT. p53 is not required for this effect.
Mu
Zhaomei
Z
Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
Hachem
Paul
P
Pollack
Alan
A
D017209:Apoptosis / Q000235:genetics / Q000528:radiation effects; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases / Q000096:biosynthesis; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000276:immunology; D016373:DNA, Antisense / Q000235:genetics*; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics*; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis
D050759:Cyclin-Dependent Kinase Inhibitor p21; D016373:DNA, Antisense; D019253:Proto-Oncogene Proteins c-bcl-2; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C505407:CASP3 protein, human; C505520:CASP7 protein, human; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases