Cell Reports (Sep 2020)

SFPQ Depletion Is Synthetically Lethal with BRAFV600E in Colorectal Cancer Cells

  • Kathleen Klotz-Noack,
  • Bertram Klinger,
  • Maria Rivera,
  • Natalie Bublitz,
  • Florian Uhlitz,
  • Pamela Riemer,
  • Mareen Lüthen,
  • Thomas Sell,
  • Katharina Kasack,
  • Bastian Gastl,
  • Sylvia S.S. Ispasanie,
  • Tincy Simon,
  • Nicole Janssen,
  • Matthias Schwab,
  • Johannes Zuber,
  • David Horst,
  • Nils Blüthgen,
  • Reinhold Schäfer,
  • Markus Morkel,
  • Christine Sers

Journal volume & issue
Vol. 32, no. 12
p. 108184

Abstract

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Summary: Oncoproteins such as the BRAFV600E kinase endow cancer cells with malignant properties, but they also create unique vulnerabilities. Targeting of BRAFV600E-driven cytoplasmic signaling networks has proved ineffective, as patients regularly relapse with reactivation of the targeted pathways. We identify the nuclear protein SFPQ to be synthetically lethal with BRAFV600E in a loss-of-function shRNA screen. SFPQ depletion decreases proliferation and specifically induces S-phase arrest and apoptosis in BRAFV600E-driven colorectal and melanoma cells. Mechanistically, SFPQ loss in BRAF-mutant cancer cells triggers the Chk1-dependent replication checkpoint, results in decreased numbers and reduced activities of replication factories, and increases collision between replication and transcription. We find that BRAFV600E-mutant cancer cells and organoids are sensitive to combinations of Chk1 inhibitors and chemically induced replication stress, pointing toward future therapeutic approaches exploiting nuclear vulnerabilities induced by BRAFV600E.

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