Loss of PHF8 induces a viral mimicry response by activating endogenous retrotransposons

Nat Commun. 2023 Jul 15;14(1):4225. doi: 10.1038/s41467-023-39943-y.

Abstract

Immunotherapy has become established as major treatment modality for multiple types of solid tumors, including colorectal cancer. Identifying novel immunotherapeutic targets to enhance anti-tumor immunity and sensitize current immune checkpoint blockade (ICB) in colorectal cancer is needed. Here we report the histone demethylase PHD finger protein 8 (PHF8, KDM7B), a Jumonji C domain-containing protein that erases repressive histone methyl marks, as an essential mediator of immune escape. Ablation the function of PHF8 abrogates tumor growth, activates anti-tumor immune memory, and augments sensitivity to ICB therapy in mouse models of colorectal cancer. Strikingly, tumor PHF8 deletion stimulates a viral mimicry response in colorectal cancer cells, where the depletion of key components of endogenous nucleic acid sensing diminishes PHF8 loss-meditated antiviral immune responses and anti-tumor effects in vivo. Mechanistically, PHF8 inhibition elicits H3K9me3-dependent retrotransposon activation by promoting proteasomal degradation of the H3K9 methyltransferase SETDB1 in a demethylase-independent manner. Moreover, PHF8 expression is anti-correlated with canonical immune signatures and antiviral immune responses in human colorectal adenocarcinoma. Overall, our study establishes PHF8 as an epigenetic checkpoint, and targeting PHF8 is a promising viral mimicry-inducing approach to enhance intrinsic anti-tumor immunity or to conquer immune resistance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Histone Demethylases / genetics
  • Histone Demethylases / metabolism
  • Histones* / metabolism
  • Humans
  • Methyltransferases / metabolism
  • Mice
  • Retroelements
  • Transcription Factors* / metabolism

Substances

  • Transcription Factors
  • Histones
  • Retroelements
  • Histone Demethylases
  • Methyltransferases
  • PHF8 protein, human
  • PHF8 protein, mouse