Hippo/Mst1 stimulates transcription of the proapoptotic mediator NOXA in a FoxO1-dependent manner

Cancer Res. 2011 Feb 1;71(3):946-54. doi: 10.1158/0008-5472.CAN-10-2203. Epub 2011 Jan 18.

Abstract

The proapoptotic protein Noxa, a member of the BH3-only Bcl-2 protein family, can effectively induce apoptosis in cancer cells, although the relevant regulatory pathways have been obscure. Previous studies of the cytotoxic effects of α-tocopheryl succinate (α-TOS) on cancer cells identified a mechanism whereby α-TOS caused apoptosis requiring the Noxa-Bak axis. In the present study, ab initio analysis revealed a conserved FoxO-binding site (DBE; DAF-16 binding element) in the NOXA promoter, and specific affinity of FoxO proteins to this DBE was confirmed by fluorescence anisotropy. FoxO1 and FoxO3a proteins accumulated in the nucleus of α-TOS-treated cells, and the drug-induced specific FoxO1 association with the NOXA promoter and its activation were validated by chromatin immunoprecipitation. Using siRNA knockdown, a specific role for the FoxO1 protein in activating NOXA transcription in cancer cells was identified. Furthermore, the proapoptotic kinase Hippo/Mst1 was found to be strongly activated by α-TOS, and inhibiting Hippo/Mst1 by specific siRNA prevented phosphorylation of FoxO1 and its nuclear translocation, thereby reducing levels of NOXA transcription and apoptosis in cancer cells exposed to α-TOS. Thus, we have demonstrated that anticancer drugs, exemplified by α-TOS, induce apoptosis by a mechanism involving the Hippo/Mst1-FoxO1-Noxa pathway. We propose that activation of this pathway provides a new paradigm for developing targeted cancer treatments.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / physiology
  • Carcinoma, Non-Small-Cell Lung / genetics
  • Carcinoma, Non-Small-Cell Lung / metabolism
  • Carcinoma, Non-Small-Cell Lung / pathology
  • Carcinoma, Non-Small-Cell Lung / therapy
  • Cell Line, Tumor
  • Forkhead Box Protein O1
  • Forkhead Transcription Factors / genetics
  • Forkhead Transcription Factors / metabolism*
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Jurkat Cells
  • Lung Neoplasms / genetics
  • Lung Neoplasms / metabolism
  • Lung Neoplasms / pathology
  • Lung Neoplasms / therapy
  • Lymphoma, T-Cell / genetics
  • Lymphoma, T-Cell / metabolism
  • Lymphoma, T-Cell / pathology
  • Lymphoma, T-Cell / therapy
  • Promoter Regions, Genetic
  • Protein Serine-Threonine Kinases / antagonists & inhibitors
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins c-bcl-2 / biosynthesis*
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • RNA, Small Interfering / administration & dosage
  • RNA, Small Interfering / genetics
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction
  • Transcription, Genetic
  • alpha-Tocopherol / pharmacology*

Substances

  • FOXO1 protein, human
  • Forkhead Box Protein O1
  • Forkhead Transcription Factors
  • Intracellular Signaling Peptides and Proteins
  • PMAIP1 protein, human
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Small Interfering
  • STK4 protein, human
  • Protein Serine-Threonine Kinases
  • alpha-Tocopherol