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We analyzed the kinetics of donor engraftment among various peripheral blood cell subpopulations and their relationship to outcomes among 120 patients with hematologic malignancies given hematopoietic cell transplantation (HCT) after nonmyeloablative conditioning consisting of 2 Gy total body irradiation (TBI) with or without added fludarabine. While patients rapidly developed high degrees of donor engraftment, most remained mixed donor/ host chimeras for up to 180 days after HCT. Patients given preceding chemotherapies and those given granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cell (G-PBMC) grafts had the highest degrees of donor chimerism. Low donor T-cell (P ‫؍‬ .003) and natural killer (NK) cell (P ‫؍‬ .004) chimerism levels on day 14 were associated with increased probabilities of graft rejection. High T-cell chimerism on day 28 was associated with an increased probability of acute graft-versus-host disease (GVHD) (P ‫؍‬ .02). Of 93 patients with measurable malignant disease at transplantation, 41 achieved complete remissions a median of 199 days after HCT; 19 of the 41 were mixed T-cell chimeras when complete remissions were achieved. Earlier establishment of donor NK-cell chimerism was associated with improved progressionfree survival (P ‫؍‬ .02). Measuring the levels of peripheral blood cell subset donor chimerisms provided useful information on HCT outcomes and might allow early therapeutic interventions to prevent graft rejection or disease progression. (Blood.

In order to characterize the specificity of expression of the neurotransmitter biosynthetic gene dopamine beta-hydroxylase (DBH), the identification of proteins that interact with the DB1 enhancer was initiated. A homeobox-containing cDNA was isolated from a PC12 expression cDNA library screened with the DB1 enhancer. The homeodomain is a member of the paired-like class, and is encoded by several nonidentical cDNAs. The cDNAs contain the same sequence in the homeodomain and 3' coding and noncoding sequences, but diverge in sequence 5' to the homeodomain. This family of homeobox-containing cDNAs is named Arix. Arix mRNA transcripts are found only in noradrenergic, DBH-positive tissues, and in cell lines derived from those tissue. The DB1 enhancer contains two binding sites for the Arix homeodomain, and both sites contribute to basal activity of the DBH promoter. When introduced into tissue culture, Arix regulates the transcriptional activity from the DBH promoter, and also from the promoter of the tyrosine hydroxylase gene, encoding the initial enzyme of the catecholamine biosynthetic pathway. The pattern of expression of the Arix transcripts, the presence of the homeodomain, and the transcriptional regulatory properties suggest that this family of proteins may be involved in the specificity of expression of the catecholamine biosynthetic genes.

Transcription of the neurotransmitter biosynthetic genes tyrosine hydroxylase and dopamine ␤-hydroxylase (DBH) is regulated by cell type-specific transcription factors, including the homeoprotein Arix, and second messengers, including cyclic AMP. The cis-acting regulatory sites of the DBH gene which respond to Arix and cAMP lie adjacent to each other, between bases ؊180 and ؊150, in a regulatory element named DB1. Neither Arix nor cyclic AMP analogs alone effectively stimulate transcription from the DBH promoter in nonneuronal cell cultures. However, when Arix is present together with cAMP, transcription is substantially activated. Synergistic transcription from the DBH promoter can also be elicited by cotransfection of Arix with an expression vector encoding the catalytic subunit of protein kinase A. Nuclear extracts from PC12 cells display a cAMP-induced complex binding to the DB1 element, and antisera to transcription factors CREB, CREM, Fos, and Jun indicate that these proteins, or closely related family members, interact with DB1. A dominant negative construct of CREB inhibits the response of the DBH promoter to protein kinase A. These results demonstrate a synergistic interaction between a homeodomain protein and the cAMP signal transduction system and suggest that similar interactions may regulate the tissuespecific expression of neuroendocrine genes.The phenotypic expression of genes encoding neurotransmitter biosynthetic enzymes is influenced by local environmental signals such as growth factors and neurohormones. Expression of genes encoding the catecholamine biosynthetic enzymes tyrosine hydroxylase (TH) 1 and dopamine ␤-hydroxylase (DBH) has been shown to be modulated by extracellular signals, including glucocorticoid hormones (1-4), the neuropeptide vasoactive intestinal peptide (5, 6), nicotine (7,8), and the neurotrophic factors insulin-like growth factor I (9) and acidic fibroblast growth factor (10). In addition, physiological neural stimuli, such as cold or immobilization stress, can modulate expression of these genes (11)(12)(13)(14).These extracellular signals are transduced from the cell surface through second messenger cascades to the nucleus, where they influence transcriptional control mechanisms. The widely studied second messenger systems initiated through elevations of cyclic AMP and diacylglycerols and mediated through protein kinases A and C stimulate transcription from both the TH and DBH promoters (1, 4, 15-17, 19, 20). In the TH gene, separate regulatory elements mediate these responses: elements at Ϫ45 and Ϫ102 are essential for the response to cyclic AMP (19,(22)(23)(24), whereas an AP1 site at Ϫ205 represents the region responsive to phorbol esters (25). The cyclic AMP regulatory element (CRE) at Ϫ45 also mediates the cellular response to calcium (26) and nicotine (8), and contributes to the cell-type specificity of TH expression (19,28). In the DBH gene, a single region, spanning from Ϫ180 to Ϫ150 of the rat gene, (Ϫ189 to Ϫ176 of the human gene), mediates the response to both...

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