Coinhibition of topoisomerase 1 and BRD4-mediated pause release selectively kills pancreatic cancer via readthrough transcription

Sci Adv. 2023 Oct 13;9(41):eadg5109. doi: 10.1126/sciadv.adg5109. Epub 2023 Oct 13.

Abstract

Pancreatic carcinoma lacks effective therapeutic strategies resulting in poor prognosis. Transcriptional dysregulation due to alterations in KRAS and MYC affects initiation, development, and survival of this tumor type. Using patient-derived xenografts of KRAS- and MYC-driven pancreatic carcinoma, we show that coinhibition of topoisomerase 1 (TOP1) and bromodomain-containing protein 4 (BRD4) synergistically induces tumor regression by targeting promoter pause release. Comparing the nascent transcriptome with the recruitment of elongation and termination factors, we found that coinhibition of TOP1 and BRD4 disrupts recruitment of transcription termination factors. Thus, RNA polymerases transcribe downstream of genes for hundreds of kilobases leading to readthrough transcription. This occurs during replication, perturbing replisome progression and inducing DNA damage. The synergistic effect of TOP1 + BRD4 inhibition is specific to cancer cells leaving normal cells unaffected, highlighting the tumor's vulnerability to transcriptional defects. This preclinical study provides a mechanistic understanding of the benefit of combining TOP1 and BRD4 inhibitors to treat pancreatic carcinomas addicted to oncogenic drivers of transcription and replication.

MeSH terms

  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Cell Line, Tumor
  • DNA Topoisomerases, Type I / metabolism
  • Humans
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Pancreatic Neoplasms* / drug therapy
  • Pancreatic Neoplasms* / genetics
  • Proto-Oncogene Proteins p21(ras) / genetics
  • Proto-Oncogene Proteins p21(ras) / metabolism
  • Transcription Factors* / genetics
  • Transcription Factors* / metabolism
  • Transcription, Genetic

Substances

  • BRD4 protein, human
  • Cell Cycle Proteins
  • Nuclear Proteins
  • Proto-Oncogene Proteins p21(ras)
  • Transcription Factors
  • TOP1 protein, human
  • DNA Topoisomerases, Type I