Synthesis and properties of a selective inhibitor of homeodomain-interacting protein kinase 2 (HIPK2)

PLoS One. 2014 Feb 24;9(2):e89176. doi: 10.1371/journal.pone.0089176. eCollection 2014.


Homeodomain-interacting protein kinase 2 (HIPK2) is a Ser/Thr kinase controlling cell proliferation and survival, whose investigation has been hampered by the lack of specific inhibitors able to dissect its cellular functions. SB203580, a p38 MAP kinase inhibitor, has been used as a tool to inhibit HIPK2 in cells, but here we show that its efficacy as HIPK2 inhibitor is negligible (IC₅₀>40 µM). In contrast by altering the scaffold of the promiscuous CK2 inhibitor TBI a new class of HIPK2 inhibitors has been generated. One of these, TBID, displays toward HIPK2 unprecedented efficacy (IC₅₀ = 0.33 µM) and selectivity (Gini coefficient 0.592 out of a panel of 76 kinases). The two other members of the HIPK family, HIPK1 and HIPK3, are also inhibited by TBID albeit less efficiently than HIPK2. The mode of action of TBID is competitive with respect to ATP, consistent with modelling. We also provide evidence that TBID is cell permeable by showing that HIPK2 activity is reduced in cells treated with TBID, although with an IC₅₀ two orders of magnitude higher (about 50 µM) than in vitro.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Apoptosis / drug effects
  • Carrier Proteins / antagonists & inhibitors*
  • Cell Line, Tumor
  • Cell Membrane Permeability / drug effects
  • Hep G2 Cells
  • Humans
  • Protein Kinase Inhibitors / chemical synthesis*
  • Protein Kinase Inhibitors / pharmacology*
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors*


  • Carrier Proteins
  • Protein Kinase Inhibitors
  • Adenosine Triphosphate
  • HIPK2 protein, human
  • Protein-Serine-Threonine Kinases

Grant support

This work was supported by grants from the European Commission (ProkinaseResearch, Contract LSHB-CT-2004-503467, to L.A.P. and C.K.), AIRC (Associazione Italian per la Ricerca sul Cancro) Project IG10312, Italian Miur (PRIN 2008, LAP). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.