Abstract 246: Genome-wide screening for dominant modifiers in Drosophila identified new genes involved in BCR-ABL signaling and chronic myeloid leukemia (CML) progression

Abstract

Abstract Despite the role of Bcr-Abl in the pathogenesis of CML is well established, the mechanisms responsible for CML progression remain unknown. The aim of the study was to perform a genome-wide screening to identify new genes and pathways leading to CML progression. We performed the genetic screening using our set-up model of human p210 Bcr-Abl (hBcr-Abl) transgenic Drosophila melanogaster (Dm) in which the tissue specific expression of hBcr-Abl is able to induce a severe eye phenotype or the formation of melanotic tumors, when expressed into the fly lymph gland, the Dm hematopoietic system. The whole fly genome containing 14.000 genes was analyzed using 278 fly stocks carrying well characterized chromosome deletions. The resulting progeny was screened using eye and lymph gland as first and second read-out system respectively. Data obtained from both screens were analyzed using the Gene Ontology software. These results were compared with gene expression signatures of CML from Microarray data. As final point, the identified genes were validated analyzing either BM or PB samples from CML patients and healthy donors. The analysis of eye/lymph gland-phenotypes in the progeny obtained from screen crosses, shows a first group of flies (38%) displaying a more aggressive phenotype since they lack genes encoding for hBcr-Abl negative regulators and a second group (32%) showing a mild phenotype due to the absence of genes involved in the oncogenic signalling. 42% of the 4000 Dm genes mapping in these regions displayed a known human counterpart. Gene Ontology profiles of these genes included oncogenes, tumor suppressors and genes involved in the regulation of transcription, signal transduction, proliferation, differentiation, apoptosis and splicing. Moreover, a computational comparison of our results in fly with gene expression signatures of CML from Microarray data, showed only a partial overlap. Interestingly, the 72% of identified genes was not known to be involved in human leukaemia. However, further confirmation of our findings comes from the validation in human samples in which 1250 genes were found to be associated with CML; among these genes, we found not only an alteration of their expression profiles in CML patients compared to the healthy donors, but also protein alterations such as expression of different splicing forms or misplaced proteins, suggesting that Dm screening is a valid approach to identify not only differentially expressed genes but also specific pathways and genes otherwise altered by hBcr-Abl. In conclusion, the identification of these genes allows identifying of the changes occurring in CML at the genomic level and gives deeper insights into the molecular basis of the disease; moreover this study points to specific gene pathways that might represent new targets for therapy in CML in order to prevent or overcome resistance and progression. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 246.