Inhibition of PI3K by ZSTK474 suppressed tumor growth not via apoptosis but G0/G1 arrest

Biochem Biophys Res Commun. 2009 Jan 30;379(1):104-9. doi: 10.1016/j.bbrc.2008.12.015. Epub 2008 Dec 16.


Phosphoinositide 3-kinase (PI3K) is a potential target in cancer therapy. Inhibition of PI3K is believed to induce apoptosis. We recently developed a novel PI3K inhibitor ZSTK474 with antitumor efficacy. In this study, we have examined the underlying mode of action by which ZSTK474 exerts its antitumor efficacy. In vivo, ZSTK474 effectively inhibited the growth of human cancer xenografts. In parallel, ZSTK474 treatment suppressed the expression of phospho-Akt, suggesting effective PI3K inhibition, and also suppressed the expression of nuclear cyclin D1 and Ki67, both of which are hallmarks of proliferation. However, ZSTK474 treatment did not increase TUNEL-positive apoptotic cells. In vitro, ZSTK474 induced marked G(0)/G(1) arrest, but did not increase the subdiploid cells or activate caspase, both of which are hallmarks of apoptosis. These results clearly indicated that inhibition of PI3K by ZSTK474 did not induce apoptosis but rather induced strong G(0)/G(1) arrest, which might cause its efficacy in tumor cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Female
  • G1 Phase / drug effects*
  • Humans
  • Mice
  • Mice, Inbred BALB C
  • Neoplasms / enzymology*
  • Neoplasms / pathology
  • Phosphoinositide-3 Kinase Inhibitors*
  • Protein Kinase Inhibitors / pharmacology*
  • Resting Phase, Cell Cycle / drug effects*
  • Triazines / pharmacology*
  • Xenograft Model Antitumor Assays


  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase Inhibitors
  • Triazines
  • ZSTK474