Related Experiment Video

Updated: Jun 23, 2026

Identification of Transcription Factor Regulators using Medium-Throughput Screening of Arrayed Libraries and a Dual-Luciferase-Based Reporter
11:32

Identification of Transcription Factor Regulators using Medium-Throughput Screening of Arrayed Libraries and a Dual-Luciferase-Based Reporter

Published on: March 27, 2020

The transcriptional induction of PIK3CA in tumor cells is dependent on the oncoprotein Y-box binding protein-1

A Astanehe1, M R Finkbeiner, P Hojabrpour

  • 1Laboratory for Oncogenomic Research, Departments of Pediatrics and Experimental Medicine, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada.

Oncogene
|May 12, 2009
PubMed

Insights

The oncogenic transcription factor Y-box binding protein-1 (YB-1) induces PIK3CA expression, a key gene in cancer. Silencing YB-1 reduces PIK3CA levels, PI3K signaling, and cellular invasion in breast cancer models.

Area of Science:

  • Molecular Biology
  • Oncology
  • Cancer Genetics

Background:

  • The PIK3CA gene, encoding the p110alpha subunit of phosphatidylinositol-3-kinase (PI3K), is a known oncogene.
  • While PIK3CA's role in cancer is established, the mechanisms driving its expression in tumor cells remain largely unknown.
  • Previous research indicated that the tumor suppressor protein p53 transcriptionally silences the PIK3CA promoter.

Purpose of the Study:

  • To investigate the role of the oncogenic transcription factor Y-box binding protein-1 (YB-1) in regulating PIK3CA expression.
  • To identify the functional elements within the PIK3CA promoter responsive to YB-1.
  • To elucidate the downstream signaling pathways affected by YB-1-mediated PIK3CA induction and its impact on cancer cell behavior.

Main Methods:

  • Chromatin immunoprecipitation (ChIP) assays to identify YB-1 binding sites on the PIK3CA promoter.
  • Electrophoretic mobility shift assays (EMSAs) to confirm YB-1-DNA interactions.
  • siRNA-mediated silencing of YB-1 in basal-like breast cancer models.
  • Western blotting to assess protein levels (p110alpha, downstream signaling molecules).
  • Assessment of PI3K activity, urokinase plasminogen activator (uPA) production, and cellular invasion.

Main Results:

  • Three YB-1-responsive elements were identified on the PIK3CA promoter.
  • Silencing YB-1 reduced p110alpha protein levels and PI3K activity in various PIK3CA contexts (wild type, amplified, mutated).
  • YB-1 silencing suppressed downstream signaling (p90 ribosomal S6 kinase, S6 ribosomal protein), cellular invasion, and uPA production.
  • The suppressive effects of YB-1 silencing on invasion and uPA were reversible upon introduction of constitutively active PIK3CA.

Conclusions:

  • Y-box binding protein-1 (YB-1) is the first identified oncogene that transcriptionally induces PIK3CA expression.
  • YB-1 regulates PIK3CA promoter activity, impacting PI3K signaling and cellular invasion.
  • Targeting YB-1 may represent a therapeutic strategy for cancers driven by PIK3CA dysregulation.

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