Ribozyme minigene-mediated RAD51 down-regulation increases radiosensitivity of human prostate cancer cells.
The strand transferase RAD51 is a component of the homologous recombination repair pathway. To examine the contribution of RAD51 to the genotoxic effects of ionising radiation, we have used a novel ribozyme strategy. A reporter gene vector was constructed so that expression of an inserted synthetic double-stranded ribozyme-encoding oligonucleotide would be under the control of the cytomegalovirus immediate-early gene enhancer/promoter system. The prostate tumour cell line LNCaP was transfected with this vector or a control vector, and a neomycin resistance gene on the vector was used to create geneticin-resistant stable cell lines. Three stable cell lines were shown by western blot analysis to have significant down-regulation of RAD51 to 20-50% of the levels expressed in control cell lines. All three cell lines had a similar increased sensitivity to gamma-irradiation by 70 and 40%, respectively, compared to normal and empty vector-transfected cells, corresponding to dose-modifying factors of approximately 2.0 and 1.5 in the mid-range of the dose-response curves. The amount of RAD51 protein in transfected cell lines was shown to strongly correlate with the alpha parameter obtained from fitted survival curves. These results highlight the importance of RAD51 in cellular responses to radiation and are the first to indicate the potential use of RAD51-targeted ribozyme minigenes in tumour radiosensitisation.
Carcinogenesis Group and Experimental Radiation Oncology Group, Cancer Research Campaign, Paterson Institute for Cancer Research, Wilmslow Road, Manchester M20 4BX, UK.
S J
SJ
Collis
A
A
Tighe
S D
SD
Scott
S A
SA
Roberts
J H
JH
Hendry
G P
GP
Margison
D001483:Base Sequence; D002455:Cell Division / Q000235:genetics / Q000528:radiation effects; D003587:Cytomegalovirus / Q000235:genetics; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics*; D004307:Dose-Response Relationship, Radiation; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D049452:Green Fluorescent Proteins; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D011401:Promoter Regions, Genetic / Q000235:genetics; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000473:pathology; D016337:RNA, Catalytic / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051135:Rad51 Recombinase; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects
D004268:DNA-Binding Proteins; D017874:Immediate-Early Proteins; D008164:Luminescent Proteins; D016337:RNA, Catalytic; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; C495153:RAD51 protein, human; D051135:Rad51 Recombinase