A therapeutically targetable NOTCH1-SIRT1-KAT7 axis in T-cell Leukemia.

T-cell Acute Lymphoblastic Leukemia (T-ALL) is a NOTCH1-driven disease in need of novel therapies. Here, we identified a NOTCH1-SIRT1-KAT7 link as a therapeutic vulnerability in T-ALL, in which the histone deacetylase SIRT1 is overexpressed downstream of a NOTCH1-bound enhancer. SIRT1 loss impaired leukemia generation, while SIRT1 overexpression accelerated leukemia and conferred resistance to NOTCH1 inhibition in a deacetylase-dependent manner. Moreover, pharmacological or genetic inhibition of SIRT1 resulted in significant antileukemic effects. Global acetyl-proteomics upon SIRT1 loss uncovered hyperacetylation of KAT7 and BRD1, subunits of a histone acetyltransferase complex targeting H4K12. Metabolic and gene expression profiling revealed metabolic changes together with a transcriptional signature resembling KAT7 deletion. Consistently, SIRT1 loss resulted in reduced H4K12ac, and overexpression of a non-acetylatable KAT7 mutant partly rescued SIRT1 loss-induced proliferation defects. Overall, our results uncovered novel therapeutic targets in T-ALL and revealed a circular feedback mechanism balancing deacetylase/acetyltransferase activation with potentially broad relevance in cancer.