Hyperthermia Selectively Destabilizes Oncogenic Fusion Proteins

Area of Science:

• Oncology
• Molecular Biology
• Biophysics

Background:

• Acute promyelocytic leukemia (APL) is driven by the PML/RARα fusion protein.
• Standard therapies targeting PML/RARα are effective but can lead to relapse and drug resistance.
• Drug-resistant mutations in PML/RARα pose a significant clinical challenge.

Purpose of the Study:

• To investigate the effect of thermal stress on the PML/RARα fusion protein, including drug-resistant mutants.
• To elucidate the mechanism by which hyperthermia affects PML/RARα.
• To explore the synergistic potential of hyperthermia with existing APL therapies.

Main Methods:

• Treatment of cells and patient samples with mild hyperthermia.
• Analysis of protein stability, aggregation, and degradation pathways (ubiquitination, SIAH2 E3 ligase).
• In vivo studies in mouse models and testing in refractory APL patient samples.

Main Results:

• Thermal stress destabilizes PML/RARα, including drug-resistant variants, and other oncofusions like AML1/ETO and TEL/AML1.
• Mild hyperthermia induces PML/RARα aggregation with corepressors, leading to degradation via SIAH2.
• Hyperthermia and arsenic therapy exhibit distinct mechanisms and synergistic effects in APL treatment, including refractory cases.

Conclusions:

• Hyperthermia destabilizes oncofusion proteins, offering a therapeutic vulnerability.
• Hyperthermia synergizes with arsenic therapy in APL, improving outcomes in relapsed and refractory disease.
• Targeting heat shock sensitivity of oncofusion proteins presents a novel strategy for cancer therapy.