Clonal evolution mechanisms in NT5C2 mutant-relapsed acute lymphoblastic leukaemia

Abstract

Relapsed acute lymphoblastic leukemia (ALL) is associated with chemotherapy resistance and poor prognosis1. Gain-of-function mutations in the 5′-nucleotidase, cytosolic II (NT5C2) gene induce resistance to 6-mercaptopurine (6-MP) and are selectively present in relapsed ALL2,3. Yet, the mechanisms involved in NT5C2 mutation-driven clonal evolution during leukemia initiation, disease progression and relapse remain unknown. Using a conditional inducible leukemia model, we demonstrate that expression of Nt5c2 p.R367Q, a highly prevalent relapsed-ALL NT5C2 mutation, induces resistance to chemotherapy with 6-MP at the cost of impaired leukemia cell growth and leukemia-initiating cell activity. The loss of fitness phenotype of Nt5c2+/R367Q mutant cells is associated with excess export of purines to the extracellular space and depletion of the intracellular purine nucleotide pool. Consequently, blocking guanosine synthesis via inosine-5′-monophosphate dehydrogenase (IMPDH) inhibition induced increased cytotoxicity against NT5C2-mutant leukemia lymphoblasts. These results identify NT5C2 mutation-associated fitness cost and resistance to chemotherapy as key evolutionary drivers shaping clonal evolution in relapsed ALL and support a role for IMPDH inhibition in the treatment of ALL.

NOTCH1 pathway activating mutations and clonal evolution in pediatric T‐cell acute lymphoblastic leukemia

“…Furthermore, we identified the acquisition of NT5C2 and BRAF mutations in cases of “switched” clones, respectively. NT5C2 mutation involves in clonal evolution during disease progression and relapse with induction of resistance to 6‐mercaptopurine . Mutations in MAPK pathway, including BRAF , were frequently observed in LCH .…”

Can one target T-cell ALL?

“…Consequently, expression of relapse-associated NT5C2 mutations in ALL cell lines induces resistance to thiopurine chemotherapy [48,49]. This resistance phenotype was formally verified in patient-derived xenografts and in vivo in a mouse conditional-and-inducible knock-in leukemia model with expression of the highly prevalent Nt5c2 p.R367Q allele [52]. Clonal evolution dynamic analyses in this model revealed positive selection of the Nt5c2 mutation under 6-MP chemotherapy and progression under therapy [52].…”

“…This resistance phenotype was formally verified in patient-derived xenografts and in vivo in a mouse conditional-and-inducible knock-in leukemia model with expression of the highly prevalent Nt5c2 p.R367Q allele [52]. Clonal evolution dynamic analyses in this model revealed positive selection of the Nt5c2 mutation under 6-MP chemotherapy and progression under therapy [52]. However, 6-MP resistance comes at the cost of impaired leukemia cell growth and leukemia-initiating cell activity as result of mutation-driven enhancement of purine degradation and excess export of purines [52].…”

“…Clonal evolution dynamic analyses in this model revealed positive selection of the Nt5c2 mutation under 6-MP chemotherapy and progression under therapy [52]. However, 6-MP resistance comes at the cost of impaired leukemia cell growth and leukemia-initiating cell activity as result of mutation-driven enhancement of purine degradation and excess export of purines [52]. In addition, the leak of purines to the media results in increased dependence on purine biosynthesis and cells harboring NT5C2 mutations show increased sensitivity to mizoribine, an inhibitor of IMPDH, a central enzyme responsible for the production of IMP downstream of both the de novo and salvage purine biosynthetic pathways [52].…”

Clonal evolution analysis of paired anaplastic and well‐differentiated thyroid carcinomas reveals shared common ancestor

“…The present study investigates the possible genomic evolution in 5 patients with coexisting ATC/well‐differentiated thyroid carcinoma (WDTC) pairs. Moreover, extensive clonality‐based evolutionary analysis was performed in this study using validated bioinformatics tools and strategies, providing additional detail into the relationship between these tumors …”