An Epigenetic Reprogramming Strategy to Resensitize Radioresistant Prostate Cancer Cells

Cancer Res. 2016 May 1;76(9):2637-51. doi: 10.1158/0008-5472.CAN-15-2116. Epub 2016 Mar 16.

Abstract

Radiotherapy is a mainstay of curative prostate cancer treatment, but risks of recurrence after treatment remain significant in locally advanced disease. Given that tumor relapse can be attributed to a population of cancer stem cells (CSC) that survives radiotherapy, analysis of this cell population might illuminate tactics to personalize treatment. However, this direction remains challenging given the plastic nature of prostate cancers following treatment. We show here that irradiating prostate cancer cells stimulates a durable upregulation of stem cell markers that epigenetically reprogram these cells. In both tumorigenic and radioresistant cell populations, a phenotypic switch occurred during a course of radiotherapy that was associated with stable genetic and epigenetic changes. Specifically, we found that irradiation triggered histone H3 methylation at the promoter of the CSC marker aldehyde dehydrogenase 1A1 (ALDH1A1), stimulating its gene transcription. Inhibiting this methylation event triggered apoptosis, promoted radiosensitization, and hindered tumorigenicity of radioresistant prostate cancer cells. Overall, our results suggest that epigenetic therapies may restore the cytotoxic effects of irradiation in radioresistant CSC populations. Cancer Res; 76(9); 2637-51. ©2016 AACR.

MeSH terms

  • Aldehyde Dehydrogenase 1 Family
  • Animals
  • Blotting, Western
  • Cell Line, Tumor
  • Chromatin Immunoprecipitation
  • Comparative Genomic Hybridization
  • DNA Methylation / radiation effects
  • Epigenesis, Genetic / radiation effects*
  • Flow Cytometry
  • Gene Expression Regulation, Neoplastic / radiation effects*
  • Heterografts
  • Histones / genetics
  • Histones / radiation effects
  • Humans
  • Male
  • Mice
  • Mice, Nude
  • Microscopy, Fluorescence
  • Oligonucleotide Array Sequence Analysis
  • Promoter Regions, Genetic / genetics
  • Promoter Regions, Genetic / radiation effects
  • Prostatic Neoplasms / genetics*
  • Radiation Tolerance / genetics*
  • Radiotherapy
  • Retinal Dehydrogenase / genetics*
  • Retinal Dehydrogenase / radiation effects

Substances

  • Histones
  • Aldehyde Dehydrogenase 1 Family
  • ALDH1A2 protein, human
  • Retinal Dehydrogenase