Cell cycle plasticity underlies fractional resistance to palbociclib in ER+/HER2- breast tumor cells

Area of Science:

• Oncology
• Cell Biology
• Cancer Therapeutics

Background:

• Palbociclib, a CDK4/6 inhibitor, is effective against ER+/HER2- breast tumors but exhibits fractional resistance.
• Fractional resistance, where a subset of tumor cells persists during treatment, is a critical factor influencing patient outcomes.
• Understanding the mechanisms of fractional resistance is vital for improving breast cancer therapy.

Purpose of the Study:

• To investigate the cellular mechanisms underlying fractional resistance to palbociclib in ER+/HER2- breast cancer.
• To identify specific cell cycle regulators and pathways involved in conferring resistance to CDK4/6 inhibitors.
• To explore therapeutic strategies targeting cell cycle plasticity to overcome fractional resistance.

Main Methods:

• Utilized multiplex, single-cell imaging to identify fractionally resistant cells in both cell cultures and patient-derived tumor samples.
• Analyzed the expression and accumulation of key cell cycle regulators (e.g., E2F1, retinoblastoma protein, CDK2) in resistant cells.
• Employed trajectory inference methods to model cell cycle dynamics and identify alternative cell cycle pathways.

Main Results:

• Identified fractionally resistant cells exhibiting premature accumulation of G1 cell cycle regulators.
• Demonstrated that resistant cells are sensitive to pharmacological inhibition of CDK2.
• Revealed cell cycle plasticity as a mechanism enabling tumor cells to escape palbociclib therapy through alternate cell cycle paths.

Conclusions:

• Cell-to-cell variability in core cell cycle regulators drives fractional resistance to palbociclib.
• Targeting cell cycle plasticity and eliminating resistant cell cycle pathways holds promise for enhanced breast cancer treatment.
• Further research into the drivers of cell cycle plasticity could lead to improved therapeutic strategies for fractionally resistant breast tumors.