CKS1-dependent proteostatic regulation has dual roles combating acute myeloid leukemia whilst protecting normal hematopoiesis

Abstract

Acute myeloid leukemia (AML) is an aggressive hematological disorder comprising a hierarchy of quiescent leukemic stem cells (LSCs) and proliferating blasts with limited self-renewal ability. AML has a dismal prognosis, with extremely low two-year survival rates in the poorest cytogenetic risk patients, primarily due to the failure of intensive chemotherapy protocols unable to deplete LSCs, which reconstitute the disease in vivo, and the significant toxicity towards healthy hematopoietic cells. Whilst much work has been done to identify genetic and epigenetic vulnerabilities in AML LSCs, little is known about protein dynamics and the role of protein degradation in drug resistance and relapse. Here, using a highly specific inhibitor of the SCFSKP2-CKS1 complex, we report a dual role for CKS1-dependent protein degradation in reducing AML blasts in vivo, and importantly depleting LSCs. Whilst many AML LSC targeted therapies show significant toxicity to healthy hematopoiesis, inhibition of CKS1-dependent protein degradation has the opposite effect, protecting normal hematopoietic cells from chemotherapeutic toxicity. Together these findings demonstrate CKS1-dependent proteostasis is key for normal and malignant hematopoiesis. Significance CKS1-dependent protein degradation is a specific vulnerability in AML LSCs. Specific inhibition of SCFSKP2-CKS1 is lethal to CKS1Bhigh AML blasts and all AML LSCs. Normal hematopoiesis is protected from chemotherapeutic toxicity by inhibition of CKS1-dependent protein degradation, substantiating a dual role for CKS1-dependent protein degradation in clinical treatment of AML.