Decrease in phosphorylated ERK indicates the therapeutic efficacy of a clinical PI3Kα-selective inhibitor CYH33 in...

Area of Science:

• Oncology
• Molecular Biology
• Pharmacology

Background:

• Phosphoinositide 3-kinases (PI3Ks) are frequently hyperactivated in breast cancer, driving tumor growth.
• Targeting the PI3K pathway, particularly PI3Kα, shows promise but exhibits variable responses in patients.
• CYH33 is a novel, selective PI3Kα inhibitor currently in phase I clinical trials.

Purpose of the Study:

• To evaluate the efficacy of CYH33 in preclinical breast cancer models.
• To identify potential predictive biomarkers for CYH33 response.
• To understand the molecular mechanisms underlying CYH33 sensitivity.

Main Methods:

• In vivo studies using human breast cancer cell xenografts and transgenic mouse models (R26-Pik3ca^H1047R;MMTV-Cre).
• In vitro proliferation assays on a panel of human breast cancer cell lines.
• Analysis of correlations between CYH33 sensitivity and genetic mutations (PIK3CA, HER2 amplification), subtypes (HER2-enriched, luminal, basal-like), cell cycle phase, and signaling pathway activation (Akt, ERK).
• Assessment of phosphorylated ERK levels in patient-derived xenografts.

Main Results:

• CYH33 potently inhibited tumor growth in both xenograft and transgenic mouse models.
• Sensitivity to CYH33 varied across different breast cancer cell lines.
• Activating PIK3CA mutations, HER2 amplification, and HER2-enriched or luminal subtypes correlated with increased sensitivity.
• CYH33 induced G1 phase arrest and inhibited both Akt and ERK phosphorylation.
• Decreased ERK phosphorylation in patient-derived xenografts correlated positively with CYH33 sensitivity.

Conclusions:

• CYH33 demonstrates significant preclinical efficacy as a PI3Kα inhibitor for breast cancer.
• Biomarkers such as PIK3CA mutations, HER2 status, and decreased ERK phosphorylation may predict response to CYH33.
• These findings provide valuable insights for the rational design of ongoing clinical trials involving CYH33.