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Identification of Inositol Phosphate or Phosphoinositide Interacting Proteins by Affinity Chromatography Coupled to Western Blot or Mass Spectrometry
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Identification of Inositol Phosphate or Phosphoinositide Interacting Proteins by Affinity Chromatography Coupled to Western Blot or Mass Spectrometry

Published on: July 26, 2019

Inositol polyphosphate 4-phosphatase II regulates PI3K/Akt signaling and is lost in human basal-like breast cancers

Clare G Fedele1, Lisa M Ooms, Miriel Ho

  • 1Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.

Proceedings of the National Academy of Sciences of the United States of America
|December 4, 2010
PubMed

Insights

Inositol polyphosphate 4-phosphatase-II (INPP4B) acts as a tumor suppressor in breast cancer by regulating cell growth via the PI3K/Akt pathway. Loss of INPP4B indicates aggressive basal-like breast carcinomas.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cell Signaling

Background:

  • Inositol polyphosphate 4-phosphatase-II (INPP4B) regulates the phosphoinositide 3-kinase (PI3K) pathway and is a known tumor suppressor in epithelial cancers.
  • Loss of heterozygosity (LOH) for INPP4B is observed in some breast cancers, but its protein expression across subtypes and in normal breast tissue remains largely uncharacterized.

Purpose of the Study:

  • To investigate the expression patterns of INPP4B protein in normal breast tissue and various breast cancer subtypes.
  • To elucidate the functional role of INPP4B in regulating breast cancer cell proliferation and signaling pathways.
  • To determine the clinical significance of INPP4B loss in primary human breast carcinomas.

Main Methods:

  • Immunohistochemical analysis of INPP4B protein expression in normal breast tissue and human breast cancer samples.
  • In vitro studies involving INPP4B knockdown and reconstitution in ER-positive and ER-negative breast cancer cell lines.
  • Assessment of Akt activation, cell proliferation, and anchorage-independent growth.
  • Correlation analysis between INPP4B expression, clinical parameters (grade, tumor size, hormone receptor status), and PTEN status.

Main Results:

  • INPP4B is expressed in normal ER-positive breast cells and ER-positive cancer cell lines; its expression is lost in ER-negative lines.
  • INPP4B knockdown enhances Akt activation and proliferation in ER-positive cells; INPP4B reconstitution suppresses these in ER-negative cells.
  • Loss of INPP4B protein is frequent in primary breast carcinomas, associated with high grade, larger tumors, loss of hormone receptors, and PTEN-null status.
  • INPP4B loss is most common in aggressive basal-like breast carcinomas.

Conclusions:

  • INPP4B functions as a tumor suppressor by inhibiting mammary epithelial cell proliferation through the PI3K/Akt pathway.
  • Loss of INPP4B protein expression is a significant biomarker for aggressive basal-like breast carcinomas.
  • INPP4B status may inform prognosis and therapeutic strategies for specific breast cancer subtypes.

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