Glycogen Synthase Kinase-3 Inhibition Sensitizes Pancreatic Cancer Cells to Chemotherapy by Abrogating the TopBP1/ATR-Mediated DNA Damage Response

Clin Cancer Res. 2019 Nov 1;25(21):6452-6462. doi: 10.1158/1078-0432.CCR-19-0799. Epub 2019 Sep 18.


Purpose: Pancreatic ductal adenocarcinoma (PDAC) is a predominantly fatal common malignancy with inadequate treatment options. Glycogen synthase kinase 3β (GSK-3β) is an emerging target in human malignancies including PDAC.Experimental Design: Pancreatic cancer cell lines and patient-derived xenografts were treated with a novel GSK-3 inhibitor 9-ING-41 alone or in combination with chemotherapy. Activation of the DNA damage response pathway and S-phase arrest induced by gemcitabine were assessed in pancreatic tumor cells with pharmacologic inhibition or siRNA depletion of GSK-3 kinases by immunoblotting, flow cytometry, and immunofluorescence.

Results: 9-ING-41 treatment significantly increased pancreatic tumor cell killing when combined with chemotherapy. Inhibition of GSK-3 by 9-ING-41 prevented gemcitabine-induced S-phase arrest suggesting an impact on the ATR-mediated DNA damage response. Both 9-ING-41 and siRNA depletion of GSK-3 kinases impaired the activation of ATR leading to the phosphorylation and activation of Chk1. Mechanistically, depletion or knockdown of GSK-3 kinases resulted in the degradation of the ATR-interacting protein TopBP1, thus limiting the activation of ATR in response to single-strand DNA damage.

Conclusions: These data identify a previously unknown role for GSK-3 kinases in the regulation of the TopBP1/ATR/Chk1 DNA damage response pathway. The data also support the inclusion of patients with PDAC in clinical studies of 9-ING-41 alone and in combination with gemcitabine.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenocarcinoma / drug therapy*
  • Adenocarcinoma / genetics
  • Adenocarcinoma / pathology
  • Animals
  • Apoptosis / drug effects
  • Ataxia Telangiectasia Mutated Proteins / genetics*
  • Carcinoma, Pancreatic Ductal / drug therapy*
  • Carcinoma, Pancreatic Ductal / genetics
  • Carcinoma, Pancreatic Ductal / pathology
  • Carrier Proteins / genetics*
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Checkpoint Kinase 1
  • DNA Damage / drug effects
  • DNA-Binding Proteins / genetics*
  • Deoxycytidine / analogs & derivatives
  • Deoxycytidine / pharmacology
  • Flow Cytometry
  • Gene Expression Regulation, Neoplastic / drug effects
  • Glycogen Synthase Kinase 3 beta / antagonists & inhibitors
  • Glycogen Synthase Kinase 3 beta / genetics*
  • Humans
  • Indoles / pharmacology
  • Maleimides / pharmacology
  • Mice
  • Nuclear Proteins / genetics*
  • Phosphorylation / drug effects
  • Protein Kinase Inhibitors / pharmacology
  • Signal Transduction / drug effects


  • 3-(5-fluorobenzofuran-3-yl)-4-(5-methyl-5H-(1,3)dioxolo(4,5-f)indol-7-yl)-pyrrole-2,5-dione
  • Carrier Proteins
  • DNA-Binding Proteins
  • Indoles
  • Maleimides
  • Nuclear Proteins
  • Protein Kinase Inhibitors
  • TOPBP1 protein, human
  • Deoxycytidine
  • gemcitabine
  • ATR protein, human
  • Ataxia Telangiectasia Mutated Proteins
  • Checkpoint Kinase 1
  • Glycogen Synthase Kinase 3 beta