Downregulation of BCL-2 induces downregulation of carbonic anhydrase IX, vascular endothelial growth factor, and pAkt and induces radiation sensitization.
OBJECTIVE
Our group previously demonstrated that expression of the oncogene, Bcl-2, was associated with radiation resistance. The aim of the present study was to determine whether Bcl-2 expression in radiation-resistant tumors was associated with expression of carbonic anhydrase IX (CAIX), vascular endothelial growth factor (VEGF), and pAkt and whether downregulation of Bcl-2 could modulate the expression of CAIX, VEGF, and pAkt.


METHODS
Two prostate cancer cell lines, PC-3-Bcl-2 and PC-3-Neo, were injected into the subcutaneous flanks of 192 athymic male nude mice; 96 received PC-3 Bcl-2 and 96 PC-3-Neo. The mice were then treated with antisense Bcl-2 oligodeoxynucleotide (ASODN), reverse control ODN, or vehicle only (mock treatment) with or without irradiation (4 Gy). The tumors were monitored for growth (ie, volume) over time, resected at various points, and processed and sectioned for protein analyses.


RESULTS
Bcl-2 ASODN treatment was associated with downregulation of Bcl-2, VEGF, pAkt, and CAIX. PC-3-Bcl-2 and PC-3-Neo prostate tumor xenografts in mice treated with the combination of Bcl-2 ASODN and irradiation were significantly (ie, one third) smaller than those in mice treated with reverse control ODN alone, Bcl-2 ASODN alone, irradiation alone, or reverse control ODN plus irradiation (P = 0.0001). An increased tumor response to the combined therapy was associated with decreased expression of Bcl-2, VEGF, and pAkt proteins.


CONCLUSIONS
These findings have demonstrated an intimate relationship among CAIX, VEGF, pAkt, and Bcl-2 in prostate tumors. Thus, CAIX might prove effective as a potential marker of tumor radiation resistance. Downregulation of CAIX might lead to radiation sensitization. Consequently, the combination of CAIX reduction and radiotherapy warrants further consideration as a new strategy for therapy.
Anai
Satoshi
S
Division of Urology, University of Florida College of Medicine, Jacksonville, USA.
Shiverick
Kathleen
K
Medrano
Theresa
T
Nakamura
Kogenta
K
Goodison
Steve
S
Brown
Bob D
BD
Rosser
Charles J
CJ
D000818:Animals; D000951:Antigens, Neoplasm / Q000378:metabolism*; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases / Q000378:metabolism*; D045744:Cell Line, Tumor; D015536:Down-Regulation; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D020320:Oligoribonucleotides, Antisense / Q000494:pharmacology; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D011836:Radiation Tolerance; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
D000951:Antigens, Neoplasm; D020320:Oligoribonucleotides, Antisense; D019253:Proto-Oncogene Proteins c-bcl-2; D042461:Vascular Endothelial Growth Factor A; D051057:Proto-Oncogene Proteins c-akt; C089226:CA9 protein, human; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases