Synergistic Targeting of Protein Translation and Inhibition of NOTCH Signaling in T-ALL

Oncogenic NOTCH signaling is a major driver of T-cell transformation in T-cell acute lymphoblastic leukemia (T-ALL). However, clinical studies testing the efficacy of NOTCH1 inactivation with γ-secretase inhibitors (GSIs) have shown limited antileukemic activity for these drugs as single agents. Here we used an expression-based virtual screening approach and network perturbation analyses to identify and functionally characterize new highly active antileukemic drugs synergistic with NOTCH1 inhibition in T-ALL. Gene expression profiling studies have shown a prominent gene expression signature dominated by genes involved in growth and metabolism downstream of NOTCH1 in T-ALL. Notably, loss of the PTEN tumor suppressor gene confers resistance to GSI therapy and effectively rescues the gene expression signature induced by NOTCH1 inhibition in T-ALL. We hypothesized that drugs inducing transcriptional programs overlapping with those driven by NOTCH1 inhibition and antagonizing those resulting from PTEN loss could have synergistic antileukemic effects with GSIs in PTEN wild type and PTEN null leukemia cells. To address this question we generated gene expression signatures from Pten conditional-inducible knockout NOTCH1-driven leukemias in basal condition, upon NOTCH1 inhibition by GSI treatment and upon deletion of Pten. Connectivity Map (cMAP) analysis in this series identified 17 high scoring compounds as candidate antileukemic drugs ( p in vivo . To address the mechanisms mediating the antileukemic effects of withaferin A we performed a detailed analysis of the gene expression signatures induced by this drug in T-ALL lymphoblasts. These studies revealed a strong enrichment of downregulated genes involved in translation regulation in T-ALL cells upon treatment with withaferin A ( p Disclosures Califano: Therasis Inc: Employment; Cancer Genetics Inc: Consultancy; Ipsen pharmaceuticals: Consultancy; Thermo Fischer Scientific: Consultancy.