Precision Targeting of Mutant PI3Kα in Cancer by Selective Degradation

Area of Science:

• Oncology
• Molecular Biology
• Pharmacology

Background:

• The PIK3CA gene encodes the p110α catalytic subunit of PI3Kα, a frequently activated kinase in solid tumors.
• PI3Kα pathway dysregulation is a common driver in various cancers, including breast cancer.
• Targeting PI3Kα is a promising therapeutic strategy, but drug resistance remains a challenge.

Purpose of the Study:

• To investigate the mechanism of action of PI3Kα inhibitors taselisib and inavolisib in breast cancer.
• To determine if these inhibitors affect the stability of the mutant p110α protein.
• To explore strategies for overcoming feedback-mediated drug resistance in PI3Kα-driven cancers.

Main Methods:

• Utilized breast cancer cell lines with HER2 receptor tyrosine kinase (RTK) positivity.
• Administered PI3Kα inhibitors taselisib and inavolisib.
• Assessed the degradation of the mutant p110α protein.
• Investigated receptor tyrosine kinase (RTK)-dependent mechanisms.

Main Results:

• Taselisib and inavolisib induced the degradation of the mutant p110α protein in HER2-positive breast cancer cells.
• This degradation was dependent on the activity of receptor tyrosine kinases (RTKs).
• The observed effect suggests a mechanism to limit feedback-mediated drug resistance.

Conclusions:

• PI3Kα inhibitors can trigger RTK-dependent degradation of mutant p110α.
• This finding offers a potential strategy to overcome drug resistance in PI3Kα-mutant cancers.
• The study may lead to an improved therapeutic index for PI3Kα inhibitors in HER2-positive breast cancer.