https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(12)62187-4.pdf

Acute lymphoblastic leukaemia.

A large number of cytokines signal through the JAK–STAT pathway. Abnormal function of this pathway may lead to a variety of diseases. Targeting the defects in this signaling pathway has already led to treatment advances, and further advances are likely.

JAKs and STATs in Immunity, Immunodeficiency, and Cancer

Genetic alterations that activate NOTCH1 signaling and T cell transcription factors, coupled with inactivation of the INK4/ARF tumor suppressors, are hallmarks of T-lineage acute lymphoblastic leukemia (T-ALL), but detailed genome-wide sequencing of large T-ALL cohorts has not been carried out. Using integrated genomic analysis of 264 T-ALL cases, we identified 106 putative driver genes, half of which had not previously been described in childhood T-ALL (for example, CCND3, CTCF, MYB, SMARCA4, ZFP36L2 and MYCN). We describe new mechanisms of coding and noncoding alteration and identify ten recurrently altered pathways, with associations between mutated genes and pathways, and stage or subtype of T-ALL. For example, NRAS/FLT3 mutations were associated with immature T-ALL, JAK3/STAT5B mutations in HOXA1 deregulated ALL, PTPN2 mutations in TLX1 deregulated T-ALL, and PIK3R1/PTEN mutations in TAL1 deregulated ALL, which suggests that different signaling pathways have distinct roles according to maturational stage. This genomic landscape provides a logical framework for the development of faithful genetic models and new therapeutic approaches.

/pdf/the-genomic-landscape-of-pediatric-and-young-adult-t-lineage-4lj166zvr1.pdf

The genomic landscape of pediatric and young adult T-lineage acute lymphoblastic leukemia

Genetic Alterations Activating Kinase and Cytokine Receptor Signaling in High-Risk Acute Lymphoblastic Leukemia

The translational control of oncoprotein expression is implicated in many cancers. Here we report an eIF4A RNA helicase-dependent mechanism of translational control that contributes to oncogenesis and underlies the anticancer effects of silvestrol and related compounds. For example, eIF4A promotes T-cell acute lymphoblastic leukaemia development in vivo and is required for leukaemia maintenance. Accordingly, inhibition of eIF4A with silvestrol has powerful therapeutic effects against murine and human leukaemic cells in vitro and in vivo. We use transcriptome-scale ribosome footprinting to identify the hallmarks of eIF4A-dependent transcripts. These include 5′ untranslated region (UTR) sequences such as the 12-nucleotide guanine quartet (CGG)4 motif that can form RNA G-quadruplex structures. Notably, among the most eIF4A-dependent and silvestrol-sensitive transcripts are a number of oncogenes, superenhancer-associated transcription factors, and epigenetic regulators. Hence, the 5′ UTRs of select cancer genes harbour a targetable requirement for the eIF4A RNA helicase. The translation of many messenger RNAs that encode important oncogenes and transcription factors depends on the eIF4A RNA helicase to resolve G-quadruplex structures, implying eIF4A inhibition as an effective cancer therapy. The expression of some oncoproteins is regulated at the translational level. Hans-Guido Wendel and colleagues show that a subset of oncoprotein- and transcription factor-encoding mRNAs that are dependent on the translation initiation factor eIF4A contain a G-quadruplex-forming structure in their 5′ untranslated regions. These findings explain why silvestrol, a plant-derived anticancer agent that targets eIF4A-dependent translation, is not generally toxic but can be well tolerated except in cancer cells which are dependent on the activities of these proteins. In a separate study in this issue, Stephan Vagner and colleagues show that inhibition of eIF4F cooperates with BRAF inhibitors in reducing the growth of melanomas linked to BRAF mutations.

RNA G-quadruplexes cause eIF4A-dependent oncogene translation in cancer

Interleukin 7 (IL-7) and its receptor, formed by IL-7Rα (encoded by IL7R) and γc, are essential for normal T-cell development and homeostasis Here we show that IL7R is an oncogene mutated in T-cell acute lymphoblastic leukemia (T-ALL) We find that 9% of individuals with T-ALL have somatic gain-of-function IL7R exon 6 mutations In most cases, these IL7R mutations introduce an unpaired cysteine in the extracellular juxtamembrane-transmembrane region and promote de novo formation of intermolecular disulfide bonds between mutant IL-7Rα subunits, thereby driving constitutive signaling via JAK1 and independently of IL-7, γc or JAK3 IL7R mutations induce a gene expression profile partially resembling that provoked by IL-7 and are enriched in the T-ALL subgroup comprising TLX3 rearranged and HOXA deregulated cases Notably, IL7R mutations promote cell transformation and tumor formation Overall, our findings indicate that IL7R mutational activation is involved in human T-cell leukemogenesis, paving the way for therapeutic targeting of IL-7R-mediated signaling in T-ALL

Julia Tritapoe

Papers

Oncogenic IL7R gain-of-function mutations in childhood T-cell acute lymphoblastic leukemia.