A microarray model system identifies potential new target genes of the proto-oncogene HOX11

HOX11 is a homeobox gene originally identified at a chromosomal breakpoint in T-cell acute lymphoblastic leukemia (T-ALL). It is one of the most frequently deregulated genes in T-ALL, although the precise role of HOX11 in leukemogenesis as well as in normal development remains obscure. To gain more insight into the functional role of HOX11, we utilized a microarray model system to characterize the gene expression network that it directs. Using one of our T-ALL cell lines that had been stably transfected to express HOX11 and high-density oligonucleotide HG-U95A arrays, we identified a large number of differentially expressed genes in response to the enforced expression of HOX11. We focused on examining genes found to be up-regulated according to the microarray analysis and selected three putative target genes, NFKB2, SMARCD3, and NR4A3, for further investigation. We could not only confirm the up-regulation of NR4A3 by an independent method in all clones expressing HOX11, but luciferase reporter assays demonstrated that the effect that HOX11 exerted on the proximal promoter of NR4A3 was dependent on the presence of an intact homeodomain, providing support for the idea that HOX11 manifests its regulatory function via its action as a transcription factor.