Untersuchung der Expression des nukleären Onkogens SKI und des Transkriptionsrepressors GFI bei der akuten myeloischen Leukämie

AML is a rare malignant disease of the hematopoietic cell system that affects the older mem-bers of the population. Hematopoiesis is regulated by a complex interaction between the tran-scription factors, oncogenes, tumorsupressors and receptors. Further investigation of these pathways in signal transduction have produced results in new insights of pathogenesis and could point to new possibilities of a new and more specific treatment of AML. These findings have resulted in transcription factors being a central issue in the scientific research of hema-tooncology. Two transcription factors are the oncogene SKI and the transcription re¬pressor GFI-1 that represent important regulators of hematopoiesis. SKI and GFI-1 interact with the same interaction partners and have the same target genes. As a result of the interacting genes and target genes being the same, a possible interaction of the oncogene ski as corepressor for GFI-1 is investigated in this work. First 74 AML patient samples were analyzed for their SKI and GFI 1 expression. The samples were classified in risk groups according to WHO criteria. It was investigated whether there is a connection between the SKI and GFI-1 expression with regard to the survival or the risk classification. The SKI and GFI-1 expression were also tested for correlation in the 74 AML patient samples. The results of the present study show a trend toward a worse survival for patients that express more SKI than the average. In addition, there is a higher expression of SKI in high and intermediate risk group. These results are confirmed within current literature. Regarding the GFI-1 expression; AML patients which had a lower GFI-1 expression than the average, show a shorter survival than patients who express GFI-1 above average (not signifi-cant) and no relationship between the risk group classification and the GFI-1 expression. There was neither a positive nor a negative correlation of SKI and GFI-1 expression in AML patients. The second part of the presented work was functional experiments. SKI expression was sup-pressed by transfection of siRNA against SKI and treatment of HL60 cells with VPA. The GFI 1 expression was then investigated by western blot and RT-PCR. Also the PU.1- and ICSBP expression after SKI suppression by transfection of U937 cells with siRNA against SKI was determined. As expected, SKI was successfully suppressed. There was an overex-pression of GFI-1 even at the slightest SKI suppression. Especially after transfection with larger quantities of siRNA, GFI-1 expression was regressed. Compared to the control the PU.1- and ICSBP expression were unchanged. The results of this study reflect current knowledge as represented in the most recent literature. It can be assumed that there is an interaction of the oncogene SKI with the transcription re-pressor GFI 1, especially in view of a feed-forward loop. Therefore GFI-1 inhibits target genes (e.g. miRNA 21) that regulate SKI expression. In turn SKI interacts directly as a core-pressor with GFI 1 and so may affect its own expression. The importance of the feed-forward loop remains unclear, but a closer examination of this feed-forward loop could be part of fu-ture experiment.