RNA-seq profiling of a radiation resistant and radiation sensitive prostate cancer cell line highlights opposing regulation of DNA repair and targets for radiosensitization

Abstract

BackgroundRadiotherapy is a chosen treatment option for prostate cancer patients and while some tumours respond well, up to 50% of patients may experience tumour recurrence. Identification of functionally relevant predictive biomarkers for radioresponse in prostate cancer would enable radioresistant patients to be directed to more appropriate treatment options, avoiding the side-effects of radiotherapy.MethodsUsing an in vitro model to screen for novel biomarkers of radioresistance, transcriptome analysis of a radioresistant (PC-3) and radiosensitive (LNCaP) prostate cancer cell line was performed. Following pathway analysis candidate genes were validated using qRT-PCR. The DNA repair pathway in radioresistant PC-3 cells was then targeted for radiation sensitization using the PARP inhibitor, niacinimide.ResultsOpposing regulation of a DNA repair and replication pathway was observed between PC-3 and LNCaP cells from RNA-seq analysis. Candidate genes BRCA1, RAD51, FANCG, MCM7, CDC6 and ORC1 were identified as being significantly differentially regulated post-irradiation. qRT-PCR validation confirmed BRCA1, RAD51 and FANCG as being significantly differentially regulated at 24 hours post radiotherapy (p-value =0.003, 0.045 and 0.003 respectively). While the radiosensitive LNCaP cells down-regulated BRCA1, FANCG and RAD51, the radioresistant PC-3 cell line up-regulated these candidates to promote cell survival post-radiotherapy and a similar trend was observed for MCM7, CDC6 and ORC1. Inhibition of DNA repair using niacinamide sensitised the radioresistant cells to irradiation, reducing cell survival at 2 Gy from 66% to 44.3% (p-value =0.02).ConclusionsThese findings suggest that the DNA repair candidates identified via RNA-seq hold potential as both targets for radiation sensitization and predictive biomarkers in prostate cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2407-14-808) contains supplementary material, which is available to authorized users.

MicroRNA-21 modulates radiation resistance through upregulation of hypoxia-inducible factor-1α-promoted glycolysis in non-small cell lung cancer cells

“…To investigate the association between miR-21 expression and radiation sensitivity, a radiation-resistant non-small cell lung cancer cell line was generated using A549 parental cells, according to a previous study (22). The cells were treated with increasing doses of radiation for 4 months, in order to generate resistant cells.…”

X-Ray Induced Mutation Frequency at the <i>Hypoxanthine Phosphoribosyltransferase</i> Locus in Clinically Relevant Radioresistant Cells

“…Several reports suggest that radioresistance is associated with the enhanced repair of radiation-induced DNA damage [1] [7] [18] [19]. Our previous study also showed that X-ray-induced phosphorylated histone H2AX (γH2AX) foci disappear more rapidly in HepG2-8960-R than in parental HepG2 [1].…”

Common variation in BRCA1 may have a role in progression to lethal prostate cancer after radiation treatment

“…(25) Alternatively, SNPs in other DNA-repair genes have also been associated with an increased risk of radiation-induced toxicity in patients treated for prostate cancer. (26) However, few studies have evaluated radiosensitivity and survival outcomes in prostate cancer.…”