Gene expression profiling of precursor T-cell lymphoblastic leukemia/lymphoma identifies oncogenic pathways that are potential therapeutic targets

Abstract

We compared the gene expression pattern of thymic tumors from precursor T-cell lymphoblastic lymphoma/leukemia (pre-T LBL) that arose in transgenic mice that overexpressed SCL, LMO1 or NUP98-HOXD13 (NHD13) with that of thymocytes from normal littermates. Only two genes, Ccl8 and Mrpl38, were consistently more than fourfold overexpressed in pre-T LBL from all three genotypes analyzed, and a single gene, Prss16 was consistently underexpressed. However, we identified a number of genes, such as Cfl1, Tcra, Tcrb, Pbx3, Eif4a, Eif4b and Cox8b that were over or under-expressed in pre-T LBL that arose in specific transgenic lines. Similar to the situation seen with human pre-T LBL, the SCL/LMO1 leukemias displayed an expression profile consistent with mature, late cortical thymocytes, whereas the NHD13 leukemias displayed an expression profile more consistent with immature thymocytes. We evaluated two of the most differentially regulated genes as potential therapeutic targets. Cfl1 was specifically overexpressed in SCL-LMO1 tumors; inactivation of Cfl1 using okadaic acid resulted in suppression of leukemic cell growth. Overexpression of Ccl8 was a consistent finding in all three transgenic lines, and an antagonist for the Ccl8 receptor-induced death of leukemic cell lines, suggesting a novel therapeutic approach.

Figure 1.. Hierarchical clustering of murine pre-T LBL gene expression profiles

Hierarchical clustering was determined using the classical Pearson method. The first hierarchical break distinguished a group of the LMO1 and NHD13 tumors from the group of the SCL-LMO1 tumors and normal thymus.

Figure 2.. Chemokine ligand 8 is important for leukemic cell survival

Murine pre-T LBL cell lines were treated with the Ccr3 antagonist, SB328437, at the concentration of 69 µM for 72 hours. #6812 and 1901 are pre-T LBL cell lines established from SCL-LMO1 and NHD13 mice, respectively. #1931 and 1939 are pre-T LBL cell lines established from OLIG2-LMO1 mice. F4–6 is a Friend virus-induced murine erythroleukemia cell line.

Figure 3.. Cofilin1 is important for growth of SCL-LMO1 pre-T LBL

Treatment of the SCL-LMO1 pre-T LBL cell line #6812 with Okadaic acid resulted in the suppression of cell growth and an increased proportion of inactivate phospho-cofilin1.

Figure 4.. Pbx3 is a downstream target of NHD13

Upper panel. A pre-T LBL cell line established from an SCL-LMO1 mouse (#6812) was transfected with an NHD13 expression vector or empty vector (lanes 6812NHD13 and 6812pz respectively). Expression of NHD13 was detected by RT-PCR; RT(+) and RT (−) indicate presence or absence or reverse transcriptase respectively. Lower panel. PBX3 is up-regulated in the sample transfected with the NHD13 expression vector. 2975 and 2413 are two primary NHD13 tumors used as positive controls for PBX3 expression. β-actin amplification is used as an RNA quality control.