Gene expression profiling of LMO2 associated T cell lymphoblastic leukemia induced by insertional mutagenesis

Aberrant co-expression of LMO2 and TAL1 is regularly found in T cell acute lymphoblastic leukemia (T-ALL). Here we describe a xenotransplant model for primary T-ALL cells derived from a patient who developed LMO2/TAL1 associated T-ALL after gene therapy for X-SCID (gamma c deficiency) due to insertional activation and a SIL-TAL1 fusion as an additional independent event. We identified a protein complex containing LMO2, TAL1 and E47 in the patients T-ALL cells. This complex functions as a transcription regulation complex in undifferentiated hematopoietic cells. However, its role in T-ALL is not fully understood. By comparative gene expression profiling we identified retinaldehyde dehydrogenase (RALDH2) as one of the genes which was highly up regulated in the primary T-ALL cells; the gene product was N-terminally truncated (RALDH2-T), but enzymatically active. To investigate the interference of LMO2 in RALDH2-T expression as well as the role of RALDH2-T in T-ALL development, LMO1 (analogue of LMO2) was down regulated by RNA interference in the T-ALL cell line Jurkat which led to a decrease of RALDH2-T expression and cell viability, indicating that positive regulation of RALDH2-T through an LMO1 or 2 containing transcription regulation complex might be essential for maintaining the T-ALL phenotype.

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