Data from Mechanisms of <i>NT5C2</i>-Mediated Thiopurine Resistance in Acute Lymphoblastic Leukemia

Abstract

<div>Abstract<p>Relapse remains a formidable challenge for acute lymphoblastic leukemia (ALL). Recently, recurrent mutations in <i>NT5C2</i> were identified as a common genomic lesion unique in relapsed ALL and were linked to acquired thiopurine resistance. However, molecular mechanisms by which <i>NT5C2</i> regulates thiopurine cytotoxicity were incompletely understood. To this end, we sought to comprehensively characterize the biochemical and cellular effects of <i>NT5C2</i> mutations. Compared with wild-type NT5C2, mutant proteins showed elevated 5′-nucleotidase activity with a stark preference of thiopurine metabolites over endogenous purine nucleotides, suggesting neomorphic effects specific to thiopurine metabolism. Expression of mutant NT5C2 mutations also significantly reduced thiopurine uptake <i>in vitro</i> with concomitant increase in efflux of 6-mercaptopurine (MP) metabolites, plausibly via indirect effects on drug transporter pathways. Finally, intracellular metabolomic profiling revealed significant shifts in nucleotide homeostasis induced by mutant NT5C2 at baseline; MP treatment also resulted in global changes in metabolomic profiles with completely divergent effects in cells with mutant versus wild-type NT5C2. Collectively, our data indicated that <i>NT5C2</i> mutations alter thiopurine metabolism and cellular disposition, but also influence endogenous nucleotide homeostasis and thiopurine-induced metabolomic response. These complex mechanisms contributed to <i>NT5C</i>2-mediated drug resistance in ALL and pointed to potential opportunities for therapeutic targeting in relapsed ALL.</p></div>