Demethylating drugs as novel analgesics for cancer pain

Clin Cancer Res. 2014 Sep 15;20(18):4882-4893. doi: 10.1158/1078-0432.CCR-14-0901. Epub 2014 Jun 24.


Purpose: In this study, we evaluated the analgesic potential of demethylating drugs on oral cancer pain. Although demethylating drugs could affect expression of many genes, we focused on the mu-opioid receptor (OPRM1) gene pathway, because of its role in pain processing. We determined the antinociceptive effect of OPRM1 re-expression in a mouse oral cancer model.

Experimental design: Using a mouse oral cancer model, we determined whether demethylating drugs produced antinociception through re-expression of OPRM1. We then re-expressed OPRM1 with adenoviral transduction and determined if, and by what mechanism, OPRM1 re-expression produced antinociception. To determine the clinical significance of OPRM1 on cancer pain, we quantified OPRM1 methylation in painful cancer tissues and nonpainful contralateral normal tissues of patients with oral cancer, and nonpainful dysplastic tissues of patients with oral dysplasia.

Results: We demonstrated that OPRM1 was methylated in cancer tissue, but not normal tissue, of patients with oral cancer, and not in dysplastic tissues from patients with oral dysplasia. Treatment with demethylating drugs resulted in mechanical and thermal antinociception in the mouse cancer model. This behavioral change correlated with OPRM1 re-expression in the cancer and associated neurons. Similarly, adenoviral-mediated OPRM1 re-expression on cancer cells resulted in naloxone-reversible antinociception. OPRM1 re-expression on oral cancer cells in vitro increased β-endorphin secretion from the cancer, and decreased activation of neurons that were treated with cancer supernatant.

Conclusion: Our study establishes the regulatory role of methylation in cancer pain. OPRM1 re-expression in cancer cells produces antinociception through cancer-mediated endogenous opioid secretion. Demethylating drugs have an analgesic effect that involves OPRM1.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analgesics, Opioid / pharmacology*
  • Animals
  • Antineoplastic Agents / pharmacology
  • Azacitidine / analogs & derivatives
  • Azacitidine / pharmacology
  • Carcinoma, Squamous Cell / complications*
  • Cytidine / analogs & derivatives
  • Cytidine / pharmacology
  • DNA Methylation
  • Decitabine
  • Disease Models, Animal
  • Heterografts
  • Humans
  • Immunohistochemistry
  • In Situ Hybridization
  • Mice
  • Mouth Neoplasms / complications*
  • Neurons / metabolism
  • Pain / drug therapy*
  • Pain / etiology*
  • Receptors, Opioid, mu / genetics*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transduction, Genetic
  • Trigeminal Ganglion / metabolism


  • Analgesics, Opioid
  • Antineoplastic Agents
  • OPRM1 protein, human
  • Receptors, Opioid, mu
  • Cytidine
  • Decitabine
  • pyrimidin-2-one beta-ribofuranoside
  • Azacitidine