Expression data from conditionally immortalized MLL-AF9 and MLL-ENL hematopoietic progenitor cells following loss of MLL-fusion oncogene. Mus musculus

Chromosomal translocations encoding the MLL-AF9 and MLL-ENL fusion transcription factors are prevalent in infant acute leukaemia and therapy-related leukaemia. In order to conditionally express the MLL-fusion oncogene in primary haematopoietic progenitor cells (HPC), retroviral delivery of the Tet-off expression system was used (Horton et al., Cancer Res, 2005). Treatment of the conditional cells with Doxycycline caused a decrease in MLL-AF9/ENL mRNA and protein expression, and resulted in terminal differentiation of the cells. By analysing global changes in gene expression after treatment of cells with Doxycycline we were able to identify a number of potential transcriptional target genes of the MLL-AF9 and MLL-ENL fusion oncogenes. Overall design: Lineage negative progenitors were purified from murine bone marrow and co-transduced with MSCV-TRE-MLL-AF9 or MSCV-TRE-MLL-ENL and MSCV-tTA retroviral supernatants. Six independent cell lines (MA1, MA3, MA4, ME4, ME5, ME7) with conditional expression of the MLL-AF9 or MLL-ENL oncogene and two independent cell lines (cMA3, cME3) with constitutive MLL-fusion oncogene expression were generated. The immortalised cell lines were characterised to determine their tTA dependent MLL-fusion oncogene expression, morphology, immunophenotype, and cytokine requirements. Total RNA was extracted, using TRIzol reagent, from the cell lines, each of them cultured without or with 2µg/ml Doxycycline for 48 hours and used for hybridisation on Affymetrix microarrays.