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PIK3CA cooperates with other phosphatidylinositol 3'-kinase pathway mutations to effect oncogenic transformation

Katsutoshi Oda1, Jennifer Okada, Luika Timmerman

  • 1Cancer Research Institute, Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, California, USA. katsutoshi-tky@umin.ac.jp

Cancer Research
|October 3, 2008
PubMed

Insights

Mutant PIK3CA often co-occurs with upstream mutations in cancers, indicating it’s a late-stage event. Targeting the PI3K pathway’s p110alpha isoform offers a promising therapeutic strategy for these late-stage tumors.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cancer Genetics

Background:

  • Cancer mutations often occur in different pathways, but PIK3CA mutations frequently co-occur with upstream mutations (Ras, ERBB2/3, PTEN) in colon, breast, and endometrial cancers.
  • PIK3CA mutations are predominantly found in invasive tumors, suggesting they are late-stage events that enhance PI3K pathway activation.

Purpose of the Study:

  • To investigate the role of PIK3CA mutations in conjunction with upstream alterations in cancer development and PI3K pathway activation.
  • To determine the specific PI3K isoform responsible for downstream signaling in cancers with co-occurring mutations.

Main Methods:

  • Analysis of co-occurring mutations in PIK3CA and upstream genes (Ras, ERBB2/3, PTEN) in various cancer types.
  • Experimental validation of PIK3CA's effect on PI3K pathway signaling (p-AKT levels) in the presence of mutant Ras or PTEN knockdown.
  • Soft agar assays to assess anchorage-independent growth modulated by PIK3CA and Ras mutations.

Main Results:

  • Mutant PIK3CA significantly amplifies p-AKT signaling induced by mutant Ras or PTEN knockdown.
  • PIK3CA mutations dramatically enhance anchorage-independent growth driven by mutant Ras.
  • In cancers with combined PIK3CA and upstream mutations, PI3K pathway signaling to Akt is exclusively mediated by the p110alpha isoform.

Conclusions:

  • PIK3CA mutations act as a late-stage driver, augmenting PI3K pathway activation when co-occurring with upstream mutations.
  • The p110alpha isoform is the primary mediator of PI3K pathway signaling in tumors with multiple pathway component mutations.
  • Selective inhibition of the p110alpha isoform represents a potential therapeutic strategy for late-stage cancers with co-occurring PI3K pathway mutations.

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