Molecular correlates of sensitivity to PARP inhibition beyond homologous recombination deficiency in pre-clinical models of colorectal cancer point to wild-type TP53 activity

EBioMedicine. 2020 Sep;59:102923. doi: 10.1016/j.ebiom.2020.102923. Epub 2020 Aug 13.

Abstract

Background: PARP inhibitors are active in various tumour types beyond BRCA-mutant cancers, but their activity and molecular correlates in colorectal cancer (CRC) are not well studied.

Methods: Mutations and genome-wide mutational patterns associated with homologous recombination deficiency (HRD) were investigated in 255 primary CRCs with whole-exome sequencing and/or DNA copy number data. Efficacy of five PARP inhibitors and their molecular correlates were evaluated in 93 CRC cell lines partly annotated with mutational-, DNA copy number-, and/or gene expression profiles. Post-treatment gene expression profiling and specific protein expression analyses were performed in two pairs of PARP inhibitor sensitive and resistant cell lines.

Findings: A subset of microsatellite stable (MSS) CRCs had truncating mutations in homologous recombination-related genes, but these were not associated with genomic signatures of HRD. Eight CRC cell lines (9%) were sensitive to PARP inhibition, but sensitivity was not predicted by HRD-related genomic and transcriptomic signatures. In contrast, drug sensitivity in MSS cell lines was strongly associated with TP53 wild-type status (odds ratio 15.7, p = 0.023) and TP53-related expression signatures. Increased downstream TP53 activity was among the primary response mechanisms, and TP53 inhibition antagonized the effect of PARP inhibitors. Wild-type TP53-mediated suppression of RAD51 was identified as a possible mechanism of action for sensitivity to PARP inhibition.

Interpretation: PARP inhibitors are active in a subset of CRC cell lines and preserved TP53 function may increase the likelihood of response.

Keywords: Colorectal cancer; PARP inhibition; RAD51; TP53; gene expression; homologous recombination deficiency; mutational signatures.

MeSH terms

  • Animals
  • Antineoplastic Agents / pharmacology
  • Cell Line, Tumor
  • Colorectal Neoplasms / diagnosis
  • Colorectal Neoplasms / drug therapy
  • Colorectal Neoplasms / etiology
  • Colorectal Neoplasms / metabolism*
  • DNA Copy Number Variations
  • Gene Expression Profiling
  • Homologous Recombination*
  • Humans
  • Mice
  • Mutation
  • Neoplasm Staging
  • Poly(ADP-ribose) Polymerase Inhibitors / pharmacology*
  • Poly(ADP-ribose) Polymerases / metabolism*
  • Prognosis
  • Transcriptome
  • Tumor Suppressor Protein p53 / genetics
  • Tumor Suppressor Protein p53 / metabolism*
  • Whole Exome Sequencing

Substances

  • Antineoplastic Agents
  • Poly(ADP-ribose) Polymerase Inhibitors
  • TP53 protein, human
  • Tumor Suppressor Protein p53
  • Poly(ADP-ribose) Polymerases