PSTK inhibition activates cGAS-STING, precipitating ferroptotic cell death in leukemic stem cells.

Abstract

Differentiation arrest and dependence on oxidative metabolism are features shared among genetically diverse acute myeloid leukemias (AML). A phenotypic CRISPR-Cas9 screen in AML identified dependence on phosphoseryl-tRNA kinase (PSTK), an atypical kinase required for the biosynthesis of all selenoproteins. In vivo, PSTK inhibition (PSTKi) impaired AML cell growth and leukemic stem cell self-renewal. Notably, timed pharmacologic PSTKi effectively targeted chemo-resistant AML in murine and patient-derived xenograft models, showing selectivity for malignant cells over normal hematopoietic cells. Mechanistically, PSTKi-induced reactive oxygen species (ROS) triggering mitochondrial DNA release into the cytosol and activated cGAS-STING. This activation in turn disrupted iron metabolism augmenting ROS generation and amplifying ferroptosis. Together, these findings reveal a self-reinforcing PSTK-cGAS-STING-ROS loop culminating in an oxidative crisis and ferroptotic cell death of leukemic stem cells. The data highlight the potential for augmenting standard cancer chemotherapies using timed metabolic intervention to eliminate chemopersisting cells and thereby impede disease relapse.