Double PIK3CA mutations in cis increase oncogenicity and sensitivity to PI3Kα inhibitors

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Activating mutations in PIK3CA are common in breast cancer.
• Phosphoinositide 3-kinase alpha (PI3Kα) inhibitors are approved therapies for certain cancers.
• Understanding PIK3CA mutation status is crucial for predicting treatment response.

Purpose of the Study:

• To investigate the prevalence and functional impact of multiple PIK3CA mutations.
• To identify determinants of sensitivity to PI3Kα inhibitors.
• To compare the effects of single versus double PIK3CA mutations.

Main Methods:

• Genomic analysis of PIK3CA-mutant cancer samples.
• Biochemical assays to assess PI3K activity and signaling.
• Evaluation of cell proliferation and tumor growth.
• Comparison of sensitivity to PI3Kα inhibitors based on mutation status.

Main Results:

• 12-15% of analyzed cancers harbor multiple PIK3CA mutations, predominantly double mutations on the same allele (in cis).
• Double PIK3CA mutations lead to increased PI3K activity, enhanced downstream signaling, and accelerated cell proliferation and tumor growth.
• Biochemical mechanisms involve disrupted p110α/p85α binding and increased p110α membrane lipid binding.
• Double PIK3CA mutations are associated with increased sensitivity to PI3Kα inhibitors compared to single-hotspot mutations.

Conclusions:

• Multiple PIK3CA mutations represent a significant oncogenic event.
• The presence of double PIK3CA mutations enhances oncogenic signaling and tumor growth.
• Patients with double PIK3CA mutations demonstrate heightened sensitivity to PI3Kα inhibitors, suggesting potential therapeutic stratification.