Charting the multilevel molecular response to palbociclib in ER-positive breast cancer

Area of Science:

• Oncology
• Molecular Biology
• Genomics

Background:

• Hormone receptor-positive, HER2-negative (HR+/HER2-) breast cancer (BC) treatment has improved with CDK4/6 inhibitors combined with endocrine therapy.
• Variable patient responses and acquired resistance to CDK4/6 inhibitors present significant clinical challenges.

Purpose of the Study:

• To define the comprehensive molecular response to palbociclib, a widely used CDK4/6 inhibitor, in breast cancer cells.
• To identify molecular mechanisms underlying response and resistance to CDK4/6 inhibition.

Main Methods:

• Global gene expression profiling
• Protein abundance analysis
• Splicing analysis
• Chromatin accessibility assays

Main Results:

• CDK4/6 inhibition induced broad molecular changes, including gene expression, protein levels, and chromatin accessibility.
• Identified unexpected feedback between CDK4/6 and estrogen-response signaling pathways.
• Discovered a widespread alternative splicing program impacting protein function.
• Co-targeting CDK7 with CDK4/6 inhibitors showed additive effects on cell fitness.

Conclusions:

• CDK4/6 inhibition elicits a complex, multitiered molecular response in breast cancer cells.
• The identified molecular changes and feedback loops have significant clinical implications for therapeutic strategies.
• Findings nominate combination therapies, such as targeting CDK7, to overcome resistance and enhance treatment efficacy.