Target Deconvolution of a Multikinase Inhibitor with Antimetastatic Properties Identifies TAOK3 as a Key Contributor to a Cancer Stem Cell-Like Phenotype

Mol Cancer Ther. 2019 Nov;18(11):2097-2110. doi: 10.1158/1535-7163.MCT-18-1011. Epub 2019 Aug 8.


Pancreatic cancer remains an incurable condition. Its progression is driven, in part, by subsets of cancer cells that evade the cytotoxic effects of conventional chemotherapies. These cells are often low-cycling, multidrug resistant, and adopt a stem cell-like phenotype consistent with the concept of cancer stem cells (CSC). To identify drugs impacting on tumor-promoting CSCs, we performed a differential high-throughput drug screen in pancreatic cancer cells cultured in traditional (2D) monolayers versus three-dimensional (3D) spheroids which replicate key elements of the CSC model. Among the agents capable of killing cells cultured in both formats was a 1H-benzo[d]imidazol-2-amine-based inhibitor of IL2-inducible T-cell kinase (ITK; NCGC00188382, inhibitor #1) that effectively mediated growth inhibition and induction of apoptosis in vitro, and suppressed cancer progression and metastasis formation in vivo An examination of this agent's polypharmacology via in vitro and in situ phosphoproteomic profiling demonstrated an activity profile enriched for mediators involved in DNA damage repair. Included was a strong inhibitory potential versus the thousand-and-one amino acid kinase 3 (TAOK3), CDK7, and aurora B kinases. We found that cells grown under CSC-enriching spheroid conditions are selectively dependent on TAOK3 signaling. Loss of TAOK3 decreases colony formation, expression of stem cell markers, and sensitizes spheroids to the genotoxic effect of gemcitabine, whereas overexpression of TAOK3 increases stem cell traits including tumor initiation and metastasis formation. By inactivating multiple components of the cell-cycle machinery in concert with the downregulation of key CSC signatures, inhibitor #1 defines a distinctive strategy for targeting pancreatic cancer cell populations.

Publication types

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

MeSH terms

  • Animals
  • Cell Culture Techniques
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Drug Screening Assays, Antitumor
  • Female
  • Gene Expression Regulation, Enzymologic / drug effects
  • Gene Expression Regulation, Neoplastic / drug effects
  • High-Throughput Screening Assays
  • Humans
  • Imidazoles / administration & dosage*
  • Imidazoles / chemistry
  • Imidazoles / pharmacology
  • Mice
  • Neoplastic Stem Cells / cytology
  • Neoplastic Stem Cells / drug effects*
  • Neoplastic Stem Cells / enzymology
  • Pancreatic Neoplasms / drug therapy*
  • Pancreatic Neoplasms / enzymology
  • Protein Kinase Inhibitors / administration & dosage*
  • Protein Kinase Inhibitors / chemistry
  • Protein Kinase Inhibitors / pharmacology
  • Protein Serine-Threonine Kinases / metabolism*
  • Spheroids, Cellular / cytology
  • Spheroids, Cellular / drug effects
  • Xenograft Model Antitumor Assays


  • Imidazoles
  • Protein Kinase Inhibitors
  • Protein Serine-Threonine Kinases
  • TAOK3 protein, human