Inhibiting DNA Methylation Causes an Interferon Response in Cancer via dsRNA Including Endogenous Retroviruses

Cell. 2015 Aug 27;162(5):974-86. doi: 10.1016/j.cell.2015.07.011.

Abstract

We show that DNA methyltransferase inhibitors (DNMTis) upregulate immune signaling in cancer through the viral defense pathway. In ovarian cancer (OC), DNMTis trigger cytosolic sensing of double-stranded RNA (dsRNA) causing a type I interferon response and apoptosis. Knocking down dsRNA sensors TLR3 and MAVS reduces this response 2-fold and blocking interferon beta or its receptor abrogates it. Upregulation of hypermethylated endogenous retrovirus (ERV) genes accompanies the response and ERV overexpression activates the response. Basal levels of ERV and viral defense gene expression significantly correlate in primary OC and the latter signature separates primary samples for multiple tumor types from The Cancer Genome Atlas into low versus high expression groups. In melanoma patients treated with an immune checkpoint therapy, high viral defense signature expression in tumors significantly associates with durable clinical response and DNMTi treatment sensitizes to anti-CTLA4 therapy in a pre-clinical melanoma model.

Publication types

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

MeSH terms

  • Animals
  • Azacitidine / pharmacology
  • Cell Line, Tumor
  • DNA Methylation / drug effects*
  • DNA Modification Methylases / antagonists & inhibitors
  • Endogenous Retroviruses / genetics
  • Female
  • Humans
  • Immunotherapy
  • Interferon Type I / immunology*
  • Lung Neoplasms / drug therapy
  • Lung Neoplasms / immunology
  • Melanoma / immunology*
  • Melanoma / therapy*
  • Mice
  • Mice, Inbred C57BL
  • Ovarian Neoplasms / immunology
  • Ovarian Neoplasms / therapy
  • RNA, Double-Stranded / metabolism

Substances

  • Interferon Type I
  • RNA, Double-Stranded
  • DNA Modification Methylases
  • Azacitidine