Abstract #5611: Identification of new genes sustaining Bcr-Abl oncogenic signalling and CML progression through a genetic tool based on human Bcr-Abl transgenic Drosophila melanogaster (Dm)
Authors: Francesca Messa, Roberto Bernardoni, Francesca Arruga, Monica Pradotto, Chiara Maffè, Enrico Bracco, Cristina Panuzzo, Emanuela Messa, Ilaria Iacobucci, Sonia Carturan, Marco Leone, Antonia Rotolo, Elisabetta Greco, Giovanni Martinelli, Michele Baccarani, Giuseppe Saglio, Daniela Cilloni
Journal: Cancer Research (2009)

AACR Annual Meeting-- Apr 18-22, 2009; Denver, CO

Despite the role of Bcr-Abl in the pathogenesis of Chronic Myeloid Leukaemia (CML) is well established, the mechanisms responsible for CML progression are largely unknown. The aims of the study were to perform a genetic screening to identify new genes and pathways leading to CML progression and to provide a tool allowing a wide screening of drugs. We developed a genetic model based on transgenic human p210 Bcr-Abl Dm. We generated two fly lines expressing either h-p210 wt or carrying the T315I mutation, in a tissue specific manner such as fly eyes or lymph gland, which is the Dm haematopoietic system. A wide modifier screening was performed using 300 fly stocks carrying well characterized chromosome deletions within the whole genome. The resulting progeny was first screened using eye phenotype as read-out system. As second step, each deletion responsible for phenotype changes was analyzed either by expressing it into lymph gland in order to analyzed their function into a haematopoietic background or by crossing hBcr-Abl Dm with loss of function mutants of each gene included in the identified regions. The expression of both wt and mutated hBcr-Abl result into a severe eye glazed phenotype strictly dependant on p210 protein amount. The analysis of eye-phenotype in the progeny obtained from screening crosses shows a first group of flies (38%) displaying a more aggressive phenotype since they lack genes encoding for Bcr-Abl negative regulators and a second group (32%) showing a mild phenotype due to the absence of genes involved in the oncogenic signalling. Among these genes, PI3K loss of function strongly modifies Bcr-Abl phenotype thus supporting the tool effectiveness while its constitutively activation results into eye overgrowth, corresponding to disrupted proliferation. We have now identified a list of genes responsible for phenotype changes, including Fax, Dab and Pros. Loss of function mutations of these genes induced a worse eye phenotype suggesting their role as enhancers of Bcr-Abl signalling. Further confirmation of their involvement in human disease comes from the analysis of their role in 35 CML patients at diagnosis and during progression in which these genes result highly down-regulated. Moreover, transfection of CML cell line with gain of function constructs reduced proliferation and induced apoptosis. By contrast, loss of function of ENA, the CRKL hortologous, didn\#8217;t induce phenotype changes. Finally, a drug screening was performed by feeding flies with drugs and by testing their effectiveness on wt and T315I/Bcr-Abl phenotypes rescue. In conclusion Fax, Dab and Pros seem to be crucial for human Bcr-Abl oncogenic signalling thus supporting the idea that Dm is a powerful genetic tool which allows the identification either of genes involved in CML progression and Imatinib resistance or of drugs active on wt and T315I/ Bcr-Abl

Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 5611.