DNA methylation changes following DNA damage in prostate cancer cells

Abstract

Many cancer therapies operate by inducing double-strand breaks (DSBs) in cancer cells, however treatment-resistant cells rapidly initiate mechanisms to repair damage enabling survival. While the DNA repair mechanisms responsible for cancer cell survival following DNA damaging treatments are becoming better understood, less is known about the role of the epigenome in this process. Using prostate cancer cell lines with differing sensitivities to radiation treatment, we analysed the DNA methylation profiles prior to and following a single dose of radiotherapy (RT) using the Illumina Infinium HumanMethylation450 BeadChip platform. DSB formation and repair, in the absence and presence of the DNA hypomethylating agent, 5-azacytidine (5-AzaC), were also investigated using γH2A.X immunofluorescence staining. Here we demonstrate that DNA methylation is generally stable following a single dose of RT; however, a small number of CpG sites are stably altered up to 14 d following exposure. While the radioresistant and radiosensitive cells displayed distinct basal DNA methylation profiles, their susceptibility to DNA damage appeared similar demonstrating that basal DNA methylation has a limited influence on DSB induction at the regions examined. Recovery from DSB induction was also similar between these cells. Treatment with 5-AzaC did not sensitize resistant cells to DNA damage, but rather delayed recruitment of phosphorylated BRCA1 (S1423) and repair of DSBs. These results highlight that stable epigenetic changes are possible following a single dose of RT and may have significant clinical implications for cancer treatment involving recurrent or fractionated dosing regimens.

Methylation of the Suppressor Gene p16INK4a: Mechanism and Consequences

“…In a precise time frame following DNA repair, transcription further remodels the methylation landscape, generating polymorphic methylation profiles that are transmitted to daughter cells. This association between DNA damage, repair, and methylation has been validated in several biological systems and cells [8][9][10].…”

“…between DNA damage, repair, and methylation has been validated in several biological systems and cells [8][9][10].…”

Accumulation of DNA methylation alterations in paediatric glioma stem cells following fractionated dose irradiation

“…DNA methylation response following radiation treatment has previously been reported but not for stem cells or paediatric tumour cells [27][28][29]. DNA methylation in prostate cancer cells was recently reported to be stable following a single dose of irradiation with few stably altered CpG sites up to 14 days following exposure [30].…”

Epigenetics and DNA Repair in Cancer

“…Hinrichsen et al [71] found that increased methylation in the promoters of MLH1, MSH2, PMS2, and p16 genes are correlated to an advanced stage in hepatocellular carcinoma. Epigenetic marks and DDR are crucial points to understand if changes in DNA methylation can contribute to resistance of cancer treatment, particularly by radiotherapy [72].…”