SCIENTIFIC PROGRAMME
SESSION I
BIOLOGY OF B-CELL
PRECURSOR ALL
SESSION II
BIOLOGY OF T-CELL ALL
SESSION III
MINIMAL RESIDUAL
DISEASE MONITORING
SESSION IV
INDIVIDUALIZED
MANAGEMENT OF ALL
SESSION V
NEW ADVANCES IN ALL
SESSION VI
CAR T-CELLS &
ALLOGENEIC HSCT
SESSION VII
FRONTLINE
INCORPORATION OF
BITES AND ADCS
SESSION VIII
T-CELL ALL AND
LYMPHOBLASTIC
LYMPHOMA
SESSION IX
PH AND PH-LIKE ALL
SELECTED ABSTRACTS
FOR AN ORAL
PRESENTATION
SELECTED ABSTRACTS
AS E-POSTERS
DISCLOSURES
IL7R GAIN-OF-FUNCTION MUTATION IS SUFFICIENT TO INITIATE B-CELL ACUTE
LYMPHOBLASTIC LEUKEMIA IN VIVO WITH FEATURES OF PAX5 P80R AND PH-LIKE ALL
Afonso R.M. Almeida1, Joao L. Neto1, Ana Cachucho1, Mayara Euzebio1,2, Xiangu Meng3, Rathana Kim4, Marta B.
Fernandes1, Beatriz Raposo1, Mariana Oliveira1, Daniel Ribeiro1, Rita Fragoso1, Priscilla P. Zenatti2, Tiago Soares1,
Mafalda R. de Matos1, Juliana Ronchi Correa1,2, Mafalda Duque1, Kathryn G. Roberts5, Zhaohui Gu5, Chunxu Qu5,
Susan Pyne6, Nigel J. Pyne6, Vasco M. Barreto7, Isabelle Bernard-Pierrot3, Emmanuelle Clappier8, Charles G.
Mullighan5, Ana R. Grosso9, J. Andres Yunes2 and João T. Barata1
((1)Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal, (2)Centro
Infantil Boldrini, Campinas, SP, Brazil, (3)Institut Curie, PSL Research University, CNRS, UMR144, Equipe Labellisée
Ligue contre le Cancer, Paris, France, (4)4Hematology Laboratory, Saint-Louis Hospital, AP-HP, Paris, France, and
Saint-Louis Research Institute, Université de Paris, INSERM U944/Centre National de la Recherche Scientifique
(CNRS) Unité Mixte de Recherche (UMR) 7212, Paris, France, (5)Pathology, St. Jude Children's Research Hospital,
Memphis, TN, (6)Strathclyde Institute of Pharmacy and Biomedical Sciences (SIPBS), University of Strathclyde,
Glasgow, Scotland, United Kingdom, (7)NOVA Medical School - Faculdade de Ciências Médicas, Universidade
NOVA de Lisboa, Lisboa, Portugal, (8)INSERM U944/CNRS UMR7212, Institut Universitaire d'Hématologie, Paris,
France, (9)UCIBIO, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade NOVA
de Lisboa, Caparica, Portugal
Objectives:Interleukin-7 (IL-7) and IL-7 receptor α (encoded by IL7R) are essential for normal lymphoid
development. IL7R gain-of-function mutations were identified in acute lymphoblastic leukemia (ALL)
and IL7R is a bona fide lymphoid oncogene. We aimed to determine whether IL7R gain-of-function
mutations alone can initiate leukemia.
Methods: We generated conditional Il7rflCPT knock-in animals that were characterized for disruption of
lymphoid development. We analyzed immunophenotype by FACS, transcriptome by RNAseq, and
proteome by LC-MS. Tumor mutational profiling was performed by WES. Further methodologies
included Sanger sequencing, qRT-PCR, immunoblotting, immunohistochemistry, drug treatment, self-renewal
transplant experiments, viral transduction of BM precursors, and cell sorting.
Results: We show that physiological levels of expression of mutant IL7R in lymphoid precursors lead
to a pre-leukemia stage in which B-cell precursors display self-renewal ability. This is followed by the
development of highly penetrant precursor B-ALL that resembles PAX5 P80R or Ph-like human
leukemia. Leukemia establishment associates with transcriptional upregulation of oncogenes such as
Myc or Bcl2, downregulation of tumor suppressors such as Ikzf1 or Arid2, and mutations in Pax5
(precisely P80R) or in signaling genes, such as Kras, Flt3l, Limk1 or Cdc42bpb. Transduction of
hematopoietic precursors with a Kras mutant and subsequent transplantation to lethally irradiated
recipient mice shows that Kras upregulates IL7R expression and cooperates in providing a selective
advantage to IL-7R mutant-expressing B-cell precursors. In agreement, leukemia establishment
associates with striking IL-7R signaling upregulation. This is reflected in the activation of key
downstream targets, such as STAT5, MYC and mTOR. Importantly, leukemia cell viability relies on the
maintenance of high IL-7R-mediated signaling, as shown by inhibition of JAK1, STAT5 or PI3K/mTOR
signaling. To further demonstrate the importance of high IL-7R signaling levels in promoting
leukemogenesis, we generated homozygous IL7R mutant animals, which display maximal signaling.
We find that they display fully-penetrant early leukemia onset. Interestingly, we identify 2
transcriptional subgroups in mouse Ph-like tumors and provide evidence of their existence in human
Ph-like ALL. One of the mouse Ph-like ALL subgroups is transcriptionally-enriched in antifolate
resistance and JAK-STAT signaling pathways and presents mutations in regulators of chromatin
remodeling and transcription, whereas the other shows enrichment for Wnt and Hippo signaling
pathways and displays Cdkn2a deletions, Kras mutations and Gins2 gains. Finally, we sought to identify
therapeutic vulnerabilities in IL-7R-driven B-ALL. Because IL7R mutant leukemias exhibit clear
upregulation of mTOR signaling, we administered the clinical-grade dual PI3K and mTOR inhibitor