TY - JOUR
T1 - Hypoxia down-regulates DNA double strand break repair gene expression in prostate cancer cells
AU - Meng, Alice X.
AU - Jalali, Farid
AU - Cuddihy, Andrew
AU - Chan, Norman
AU - Bindra, Ranjit S.
AU - Glazer, Peter M.
AU - Bristow, Robert G.
PY - 2005/8
Y1 - 2005/8
N2 - Background and purpose: Intratumoral hypoxia has been correlated with poor clinical outcome in prostate cancer. Prostate cancer cells can be genetically unstable and have altered DNA repair. We, therefore, hypothesized that the expression of DNA double-strand break (DNA-dsb) repair genes in normal and malignant prostate cultures can be altered under hypoxic conditions. Methods and materials: The expression of homologous recombination (HR) and non-homologous recombination (NHEJ) genes following gas hypoxia (0.2%) or exposure to HIF1α-inducing agent, CoCl2 (100 μM), was determined for normal diploid fibroblasts (GM05757) and the pre-malignant and malignant prostate cell lines, BPH-1, 22RV-1, DU145 and PC3. RNA and protein levels were determined using RT-PCR and Western blotting. Additionally, p53 genotype and function, the level of hypoxia-induced apoptosis, and cell cycle distribution, were determined to correlate to changes in DNA-dsb gene expression. Results: Induction of hypoxia was confirmed using HIF1α and VEGF expression in gas- and CoCl2-treated cultures. Hypoxia (48-72 h of 0.2% O2) decreased RNA expression of a number of HR-related genes (e.g. Rad51, Rad52, Rad54, BRCA1, BRCA2) in both normal and malignant cultures. Similar decreases in RNA pertaining to the NHEJ-related genes (e.g. Ku70, DNA-PKcs, DNA Ligase IV, Xrcc4) were observed. In selected cases, hypoxia-mediated decreases in RNA expression led to decreased DNA-dsb protein expression. CoCl2-treated cultures did not show decreased DNA-dsb protein expression. The ability of hypoxia to down-regulate Rad51 and other HR-associated genes under hypoxia was not correlated to c-Abl or c-Myc gene expression, p53 genotype or function, propensity for hypoxia-mediated apoptosis, or specific changes in cell cycle distribution. Conclusions: Hypoxia can down-regulate expression of DNA-dsb repair genes in both normal and cancer cells. If associated with a functional decrease in DNA-dsb repair, this observation could provide a potential basis for the observed genetic instability within tumor cells exposed to hypoxia.
AB - Background and purpose: Intratumoral hypoxia has been correlated with poor clinical outcome in prostate cancer. Prostate cancer cells can be genetically unstable and have altered DNA repair. We, therefore, hypothesized that the expression of DNA double-strand break (DNA-dsb) repair genes in normal and malignant prostate cultures can be altered under hypoxic conditions. Methods and materials: The expression of homologous recombination (HR) and non-homologous recombination (NHEJ) genes following gas hypoxia (0.2%) or exposure to HIF1α-inducing agent, CoCl2 (100 μM), was determined for normal diploid fibroblasts (GM05757) and the pre-malignant and malignant prostate cell lines, BPH-1, 22RV-1, DU145 and PC3. RNA and protein levels were determined using RT-PCR and Western blotting. Additionally, p53 genotype and function, the level of hypoxia-induced apoptosis, and cell cycle distribution, were determined to correlate to changes in DNA-dsb gene expression. Results: Induction of hypoxia was confirmed using HIF1α and VEGF expression in gas- and CoCl2-treated cultures. Hypoxia (48-72 h of 0.2% O2) decreased RNA expression of a number of HR-related genes (e.g. Rad51, Rad52, Rad54, BRCA1, BRCA2) in both normal and malignant cultures. Similar decreases in RNA pertaining to the NHEJ-related genes (e.g. Ku70, DNA-PKcs, DNA Ligase IV, Xrcc4) were observed. In selected cases, hypoxia-mediated decreases in RNA expression led to decreased DNA-dsb protein expression. CoCl2-treated cultures did not show decreased DNA-dsb protein expression. The ability of hypoxia to down-regulate Rad51 and other HR-associated genes under hypoxia was not correlated to c-Abl or c-Myc gene expression, p53 genotype or function, propensity for hypoxia-mediated apoptosis, or specific changes in cell cycle distribution. Conclusions: Hypoxia can down-regulate expression of DNA-dsb repair genes in both normal and cancer cells. If associated with a functional decrease in DNA-dsb repair, this observation could provide a potential basis for the observed genetic instability within tumor cells exposed to hypoxia.
KW - DNA repair
KW - Genetic instability
KW - Hypoxia
KW - Prostate cancer
KW - Rad51
UR - http://www.scopus.com/inward/record.url?scp=28444478320&partnerID=8YFLogxK
U2 - 10.1016/j.radonc.2005.06.025
DO - 10.1016/j.radonc.2005.06.025
M3 - Article
C2 - 16026872
AN - SCOPUS:28444478320
SN - 0167-8140
VL - 76
SP - 168
EP - 176
JO - Radiotherapy and Oncology
JF - Radiotherapy and Oncology
IS - 2
ER -
