Tzoneva et al. [43], using a knock-in mouse model for expression of mutant cN-II-(R367Q), the most frequent of the 32 different cN-II mutant alleles to date described in relapse-ALL, demonstrated that this gain-of-function mutant induced resistance to 6-MP both in vitro and in vivo. Here, NT5C2 is linked to acute lymphoblastic leukemia.