Driver mutations in Janus kinases in a mouse model of B-cell leukemia induced by deletion of PU.1 and Spi-B

Abstract

Precursor B-cell acute lymphoblastic leukemia (B-ALL) is associated with recurrent mutations that occur in cancer-initiating cells. There is a need to understand how driver mutations influence clonal evolution of leukemia. The E26-transformation-specific (ETS) transcription factors PU.1 and Spi-B (encoded by Spi1 and Spib) execute a critical role in B-cell development and serve as complementary tumor suppressors. Here, we used a mouse model to conditionally delete Spi1 and Spib genes in developing B cells. These mice developed B-ALL with a median time to euthanasia of 18 weeks. We performed RNA and whole-exome sequencing (WES) on leukemias isolated from Mb1-CreΔPB mice and identified single nucleotide variants (SNVs) in Jak1, Jak3, and Ikzf3 genes, resulting in amino acid sequence changes. Jak3 mutations resulted in amino acid substitutions located in the pseudo-kinase (R653H, V670A) and in the kinase (T844M) domains. Introduction of Jak3 T844M into Spi1/Spib-deficient precursor B cells was sufficient to promote proliferation in response to low IL-7 concentrations in culture, and to promote proliferation and leukemia-like disease in transplanted mice. We conclude that mutations in Janus kinases represent secondary drivers of leukemogenesis that cooperate with Spi1/Spib deletion. This mouse model represents a useful tool to study clonal evolution in B-ALL.

Janus Kinase Mutations in Mice Lacking PU.1 and Spi-B Drive B Cell Leukemia through Reactive Oxygen Species-Induced DNA Damage

“…Mb1 ϩ/Cre Spi1 lox/lox Spib Ϫ/Ϫ mice (shortened to Mb1-CreΔPB mice) develop precursor B cell acute lymphoblastic leukemia (B-ALL) at 100% incidence with a median time to euthanasia of 18 weeks (18). Mb1-CreΔPB leukemias invariably express interleukin-7 receptor on their surface, have a pro-B/pre-B phenotype, and are either clonal or oligoclonal with respect to immunoglobulin (Ig) heavy chain and Ig rearrangements (18). In this study, we sought to determine if there are recurrent secondary driver mutations associated with Mb1-CreΔPB leukemias.…”

“…These mice, called Mb1-CreΔPB, to indicate that PU.1 and Spi-B are deleted in the B cell lineage, have a profound block to B cell development starting at the small pre-B cell stage, demonstrating a requirement for PU.1 and Spi-B in B cell development (17). Importantly, 100% of Mb1-CreΔPB mice develop B-ALL by 18 weeks of age (18). Previous work suggests that secondary driver mutations cooperate with PU.1/Spi-B deletion to induce leukemia (18).…”

“…Importantly, 100% of Mb1-CreΔPB mice develop B-ALL by 18 weeks of age (18). Previous work suggests that secondary driver mutations cooperate with PU.1/Spi-B deletion to induce leukemia (18). However, it is unclear whether secondary driver mutations are recurrent and, if so, what the mechanism(s) of mutagenesis is.…”

IRF4 deficiency vulnerates B progeny for leukemogenesis via Jak3 mutations resembling Ph-like B-ALL in humans

“…Some of these SNVs are already known from other leukemia mouse models. 37 To clarify the significance of the mutations for IL-7 signaling, we cloned the JAK3 R653H and JAK3 T844M mutants into a retroviral (RV) expression plasmid, which labels transduced cells with Thy1.1. We then transduced IL-7 dependent, Eµ-Myc transgene driven murine preB-leukemia cells 38,39 with these RVs and cultured them with or without IL-7.…”

Comparative Analysis of Systemic and Tumor Microenvironment Proteomes From Children With B-Cell Acute Lymphocytic Leukemia at Diagnosis and After Induction Treatment

“…The clonal rise of leukemia cells is mainly associated with cumulative mutations that directly affect the panel of proteins that are secreted in the tumor microenvironment ( 3 ). Some of these proteins are responsible for cellular events in the leukemic niche that control disease spread ( 4 ) and can result from systemic transcriptional changes related to disease prognosis ( 5 ).…”