One of the hallmarks of acute lymphoblastic leukemia (ALL) is the presence of chromosomal and genetic abnormalities. In a previous study we described for the first time oncogenic gain-of-function mutations in the alpha chain of IL-7 receptor (IL7Ra), restricted to T-cell ALL (T-ALL) in 9% of patients. Although some genetic mutations are important 'drivers' of oncogenesis, in most cases it is a sum of several mutations that result in fully cell transformation and progression to cancer. Accordingly, several mutations have been shown to act collaboratively in promoting leukemogenesis. In a first line of investigation, we will address whether the IL7Ra mutation, as the first oncogenic event, is sufficient to initiate leukemia and which other mutations are necessary to evolve to a fully leukemia phenotype. A conditional IL7Ra point-mutant mouse line will be developed (third party) and monitored for the occurrence of 'spontaneous' leukemia and defects on thymocytes development. Recurrent association between specific mutations in different patients suggest their functional collaboration. In our previous study, mutations in the IL7Ra were found associated to HOXA genes alterations. In a recent whole genome sequencing study on T-ALL, IL7Ra mutations were found associated with GATA3 mutations and with presence of the SET-NUP214 fusion transcription factor implicated in HOXA aberrant expression. In the present study, ex vivo functional assays will be performed to test the relevance of GATA3 defects and SET-NUP214 expression in term of enhancing the proliferative and survival advantages driven by IL7Ra mutations. Finally, to identify new genetic mutations associated with the mutant IL7Ra defect we aim to sequence the whole exome of our five T-ALL cases positive for the IL7Ra mutation. In a second line of investigation, we aim to study the mechanism and subcellular location of mutant IL7R signalling. In most cases, these IL7Ra mutations introduce an unpaired cysteine in the extracellular juxtamembrane-transmembrane region of the receptor, allowing de novo formation of intermolecular disulfide bonds between mutant IL7Ra subunits, thereby driving constitutive signaling via JAK1/STAT5, and promoting cell survival and proliferation, typical of oncogenic transformation. In this study we aim to delete or insert cysteines at different positions in the extracellular region of the mutant IL7Ra receptor, investigating their effect on dimer/oligomers formation and on downstream signaling capability. Moreover, we aim to identify the subcellular compartment(s) where the mutant IL7Ra is functional. Finally, since in normal cells the IL7R is a heterodimer formed by the IL7Ra and IL2Rg chains, it is possible that the mutant IL7Ra-IL7Ra homodimer could serve as a leukemia-specific antigen, a fact that will be exploited in this study for the development of monoclonal antibodies, as one possible approach to develop new therapeutics for these patients. (AU)
Articles published in Agência FAPESP Newsletter about the research grant:
DA SILVA, RODRIGO FERNANDES;
CARDOZO, DANIELA MAIRA;
LIBANIO RODRIGUES, GISELE OLINTO;
DE SOUZA-ARAUJO, CAROLINE NATANIA;
MIGITA, NATACHA AZUSSA;
LUCCI DE ANGELO ANDRADE, LILIANA APARECIDA;
YUNES, JOSE ANDRES;
CAISMOV24, a new human low-grade serous ovarian carcinoma cell line.
NOV 13 2017.
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