In vivo leukemogenic potential of the mutant IL-7R

Author(s)

Mayara Ferreira Euzébio

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2019-09-10

Examining board members

José Andrés Yunes; Sara Teresinha Olalla Saad; Marcelo Alves Mori

• Advisor: José Andrés Yunes

Abstract

Acute lymphoid leukemia (ALL) is an aggressive cancer characterized by high production and accumulation of immature lymphoid precursors, which proliferate and replace healthy bone marrow cells. Several mutations have been described in genes related to regulation of lymphoid development, cell cycle, tumor suppression and ALL signal transduction. Studies from our research group found gain of function mutations in the IL-7R gene in 9% of T-ALL cases. Most of the mutations result in the introduction of a cysteine that allows homodimer formation between two IL-7Ralpha chains by cysteine disulfide bonds. Chain homodimerization confers constitutive activation to the pathways downstream of the receptor, such as JAK-STAT and PI3K/AKT, independently of IL7 and the ?c chain. In vitro studies show that cells transduced with mutant IL-7R show increased survival and proliferation in the absence of growth factors, and when transplanted into healthy mice, these cells result in tumor development and organ infiltration, indicating the leukemogenic potential mutant IL-7R. Therefore, the aim of this study was to evaluate whether mutant IL-7R, under the control of its own promoter, was capable of causing the development of leukemia in mice. Our research group has developed a strain of knockin mice, B6-IL7RCPT, which contains a specific locus mutation in the IL-7Ralpha gene, inserted as an inverted exon 6 and flanked by Cre, LoxP and Lox511 recombinase recognition sequences. Activation of the mutation depends on exon inversion, which can only occur through the Flex-switch system, which is promoted by the action of Cre recombinase. Breeding of Vav1-cre and CD2-icre strains with the B6-IL7RCPT strain allowed the exon inversion in hematopoietic stem cells (HSCs) and the common lymphoid progenitors (CLPs), respectively, resulting in offspring that express the mutant receptor. We found that the IL-7Ralpha mutant was able to generate lymphoproliferative disorder, with prevalence increase in B-cells and decrease in T-cells, as well as B-type lymphoid leukemia in 35% or 80% of cases, depending on the stage (HSC or CLP, respectively) in that the mutant IL-7R was beginning to be transcribed. The leukemias found presented pre-B to late pro-B immunophenotypes and showed intermediate or no expression of CD45, resembling human ALL. We also found that the oncogenic mutation in IL7R? did not result in myeloproliferative disorders or myeloid leukemias. These results show that the IL-7R mutant has leukemogenic potential when expressed under its own promoter in an animal model, and also mutations in IL-7R may be driver mutations (AU)

• FAPESP's process: 16/07724-2 - In vivo leukemogenic potential of the mutant IL-7R
• Grantee: Mayara Ferreira Euzébio
• Support Opportunities: Scholarships in Brazil - Master