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PBK/TOPK interacts with the DBD domain of tumor suppressor p53 and modulates expression of transcriptional targets

F Hu1, R B Gartenhaus, D Eichberg

  • 1Marlene and Stewart Greenebaum Cancer Center, University of Maryland, Baltimore, MD 21201, USA.

Oncogene
|July 13, 2010
PubMed

Insights

PDZ-binding kinase (PBK/TOPK) interacts with tumor suppressor p53, downregulating its function. PBK/TOPK knockdown increases apoptosis and cell cycle arrest, suggesting PBK/TOPK as a cancer therapy target.

Area of Science:

  • Oncology
  • Molecular Biology
  • Biochemistry

Background:

  • PDZ-binding kinase (PBK/TOPK) is a serine-threonine kinase overexpressed in various tumors.
  • The precise role of PBK/TOPK in oncogenesis is not fully understood.
  • p53 is a critical tumor suppressor protein involved in cell cycle regulation and apoptosis.

Purpose of the Study:

  • To investigate the interaction between PBK/TOPK and p53.
  • To elucidate the functional consequences of this interaction on p53 activity and cancer cell behavior.
  • To evaluate PBK/TOPK as a potential therapeutic target in cancer.

Main Methods:

  • Co-immunoprecipitation and yeast two-hybrid assays to confirm PBK/TOPK-p53 interaction.
  • PBK/TOPK knockdown experiments using RNA interference.
  • Analysis of p53 target gene expression (e.g., p21) and cell cycle progression.
  • Cell viability, apoptosis, and growth rate assays in knockdown cell lines.
  • Gene microarray analysis to identify differentially regulated genes.

Main Results:

  • PBK/TOPK physically interacts with the DNA-binding domain of p53 in colorectal carcinoma cells.
  • PBK/TOPK knockdown leads to upregulation of p53 target genes, including p21, especially after genotoxic stress.
  • Stable knockdown of PBK/TOPK in cancer cell lines (HCT116, MCF-7) results in increased apoptosis, G2/M arrest, and reduced cell growth.
  • Microarray analysis reveals differential regulation of additional p53 target genes involved in apoptosis and cell cycling upon PBK knockdown.

Conclusions:

  • PBK/TOPK interacts with and downmodulates the transactivation function of p53.
  • Elevated PBK/TOPK levels may promote tumor development by suppressing p53 activity and reducing cell-cycle regulators like p21.
  • PBK/TOPK represents a potential therapeutic target for antineoplastic kinase inhibitors to enhance chemotherapy efficacy.

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