Phenotypic changes of HER2-positive breast cancer during and after dual HER2 blockade

Area of Science:

• Oncology
• Molecular Biology
• Genomics

Background:

• HER2-enriched (HER2-E) subtype of HER2-positive (HER2+) breast cancer is highly dependent on the HER2 pathway.
• A significant proportion (20-60%) of HER2+/HER2-E tumors exhibit resistance to standard anti-HER2 therapies.

Purpose of the Study:

• To investigate the molecular and phenotypic changes in HER2+/HER2-E breast cancer following dual HER2 blockade.
• To explore the therapeutic implications of observed subtype switching, particularly in relation to CDK4/6 inhibition.

Main Methods:

• Analysis of gene expression data from HER2+/HER2-E tumors and cell lines before, during, and after neoadjuvant treatment with lapatinib and trastuzumab (PAMELA trial).
• In vitro modeling to assess phenotypic changes and drug sensitivity.

Main Results:

• Dual HER2 blockade induces a shift towards a low-proliferative Luminal A phenotype in HER2-E tumors and cell lines.
• This phenotypic switch is more pronounced in hormone receptor-positive (HR+) HER2+ disease.
• The induced Luminal A phenotype correlates with increased sensitivity to CDK4/6 inhibition.
• Discontinuation or resistance to anti-HER2 therapy results in the restoration of the original HER2-E phenotype.

Conclusions:

• Dual HER2 blockade can reprogram the HER2-E subtype towards a more treatable phenotype.
• Maintenance anti-HER2 therapy may be beneficial.
• Targeting subtype switching with CDK4/6 inhibitors represents a promising therapeutic strategy for overcoming resistance in HER2-E breast cancer.