Ets1 Expression Is Upregulated In Chronic Myeloid Leukemia (Cml) And The Ets1 Transcriptional Program Correlates With Disease Progression Towards Blast Crisis

Chronic myeloid leukemia is a clonal myeloproliferative neoplasm characterized by the occurrence of the Ph1 chromosome in a primitive hematopoietic stem cell with a major amplification of myeloid compartment. Despite the major progress obtained by the use of tyrosine kinase inhibitors (TKI), resistances to these drugs occur with progression towards blast crisis (BC) during which there is an increase of BCR-ABL expression. To evaluate the potential targets of BCR-ABL in this context, a gene profiling analysis of the UT7-11 cell line overexpressing BCR-ABL fusion protein was performed using a whole transcriptome microarray. One of the highly upregulated genes was ETS1 with a fold change of +35.86. ETS1 proto-oncogene, the founder member of the ETS-domain family of transcription factors such as TEL and FLI1, is the human homolog of the avian erythroblastosis virus E26. They play a crucial role in stem cell biology, tumorigenesis and ETS1 has been shown to be involved in the regulation of granulocytic differentiation. Its role in CML pathophysiology has not been studied so far. We first showed by Western blots that ETS1 protein was highly increased in UT7-11 cells as compared to parental UT7 cells. Using a DOX-Inducible BCR-ABL system, we have shown that ETS1 expression was downregulated upon inhibition of BCR-ABL expression. ETS1 expression was a tyrosine kinase dependent event as its expression was reduced in the presence of TKI. To determine if ETS1 expression is upregulated in primary leukemic cells, we have analyzed leukemic cells of CML patients at diagnosis (n= 40) as compared to healthy controls (n= 30) showing an increase of ETS1 mRNA expression in primary CML cells in a highly significant manner (p Disclosures No relevant conflicts of interest to declare.