Project description:MN1 leukemia is a poor prognosis leukemia occuring as MN1 overexpression or fusion with TEL (MN1-TEL), MN1 and MN1-TEL show different biology in terms of dependence of known self-renewal associated genes in leukemia, c-kit positive murine primary bone marrow cells were retrovirally transduced with MN1, MN1-TEL or MN1-TEL mutant MN1-TELdelDBD showing biological similarity with MN1, after retroviral transformation of cells and 10 d culture RNA was extracted and gene expression profiling was assessed
Project description:Expression of meningioma 1 (MN1) has been proposed to be a negative prognostic molecular marker in adult AML with normal cytogenetics, however its role in pediatric leukemia is unknown. We found elevated MN1 expression in 53 of 88 pediatric leukemia cases: significant amounts of MN1 were found in immature B-cell ALL and most cases of infant leukemia but no MN1 expression was detected in T-cell acute lymphoblastic leukemia (T-ALL). Interestingly 17 of 19 cases harboring MLL-X fusions showed also elevated MN1 expression. Lentiviral siRNA mediated MN1 knock-down resulted in cell cycle arrest and impaired clonogenic growth of 3 MLL-X-positive human leukemia cell lines overexpressing MN1 (THP-1, RS4;11, MOLM13). In a mouse MLL/ENL-induced leukemia MN1 overexpression resulted from retroviral provirus insertion. Strikingly co-expression of MN1 with MLL/ENL resulted in significantly reduced latency for induction of an AML phenotype in mice suggesting functional cooperation. MN1 overexpression in MLL/ENL-carrying cells resulted in expansion of the L-GMP population and facilitated disease induction in secondary recipients. Gene expression profiling allowed to define a number of potential MN1 hematopoietic targets. Up-regulation of CD34, FLT3, HLF, or DLK1 was validated in bone marrow transiently overexpressing MN1, in MN1-induced mouse leukemias, as well as in some cases of pediatric leukemias overexpressing MN1. Taken together, our work suggests that MN1 overexpression is essential for growth of leukemic cells, and that MN1 can act as a cooperating oncogene with MLL-X fusion genes most probably through modification of a distinct gene expression program that leads to expansion of a leukemia initiating cell population. In three independent experiments bone marrow cells were transduced with MSCV-MN1-IRES/YFP or empty vector. 72h after transduction EYFP-positive cells were FACS-sorted and RNA isolated by ion-exchange chromatography with RNAmini (Qiagen) according to the manufacturerâs protocol
Project description:We used Affymetrix microarrays to characterize gene expression profiles that were perturbed in common myeloid progenitor (CMP) cells due to enforced expression of full-length or truncated forms of MN1. Expression profiles of MN1-induced leukemias arising from whole bone marrow transduction were also compared with the profiles obtained from the CMP cells. Lineage negative mouse bone marrow cells were transduced with retroviral vectors expressing full-length or truncated MN1 proteins. After 2 days in culture, cells were FACS-sorted for GFP expression and cultured for a further 3 days in growth media. After 5 days total, RNA was isolated and processed for microarray analysis. RNA was also prepared for microarray analysis from leukemias arising in mice following whole bone marrow transduction with full-lenght MN1.