RSK1 dependency in FLT3-ITD acute myeloid leukemia

Area of Science:

• Oncology
• Molecular Biology
• Hematology

Background:

• Internal tandem duplications (ITD) in fms-like tyrosine kinase 3 (FLT3) are the most frequent genetic alteration in de novo acute myeloid leukemia (AML).
• FLT3-ITD mutations drive leukemogenesis and confer resistance to therapy.

Purpose of the Study:

• To identify novel dependencies in FLT3-ITD AML.
• To elucidate the regulatory mechanisms governing FLT3-ITD activity.
• To evaluate the therapeutic potential of targeting identified dependencies.

Main Methods:

• Cell line experiments involving RSK1 perturbation and inhibition.
• Biochemical assays including cycloheximide, MG-132, and ubiquitination assays.
• Analysis of patient data for prognostic markers.
• In vivo studies using xenograft and syngeneic leukemia models.

Main Results:

• RSK1 was identified as a core dependency in FLT3-ITD AML, with its inhibition inducing apoptosis and abrogating FLT3 signaling.
• RSK1 regulates FLT3-ITD activity and stability via the deubiquitinase USP1, a second identified dependency.
• Elevated RPS6KA1 and USP1 expression correlated with poor prognosis in AML patients.
• RSK1 inhibition with PMD-026 reduced leukemic burden in preclinical models.

Conclusions:

• RSK1 and USP1 are critical for FLT3-ITD AML survival and represent promising therapeutic targets.
• Targeting RSK1, particularly with inhibitors like PMD-026, demonstrates significant preclinical efficacy.
• RPS6KA1 and USP1 expression may serve as predictive biomarkers for patient survival and treatment response.