A quiescence/TGF-β1 CRISPRi screen reveals drug uptake transporters as secondary targets of kinase inhibitors in AML

Acute myeloid leukemia (AML) relapse is driven by leukemia cells that survive treatment. Since standard chemotherapy targets cycling cells, various forms of dormancy, including quiescence, may allow them to evade therapy and trigger relapse. However, the role of quiescence in AML therapy remains unclear. Here, we show that quiescence in AML is strongly associated with poor patient outcomes. It coincides with active TGF-β signaling, and treatment of AML cells with TGF-β1 induces a G0 arrest. A drug-focused CRISPRi screen identified TGFBR1 inhibitors as effective in preventing quiescence. However, although treatment with the TGF-β inhibitor vactosertib prevents quiescence, it completely abolishes cytarabine-induced cell death. Further investigation, combining a second CRISPRi screen with LC-MS/MS and in silico analyses, uncovered that vactosertib targets the nucleoside transporter SLC29A1 (ENT1), reducing intracellular cytarabine levels. Importantly, we found that this drug interaction is not unique to TGFBR1 inhibitors, but extends to other clinically important kinase inhibitors. These findings may have important implications for optimizing combination therapies in the future.

Publication History

Article published online:
09 May 2025