The HOXB4 Homeoprotein Differentially Promotes Ex Vivo Expansion of Early Human Lymphoid Progenitors

Abstract

The HOXB4 homeoprotein is known to promote the expansion of mouse and human hematopoietic stem cells (HSCs) and progenitors of the myeloid lineages. However, the putative involvement of HOXB4 in lymphopoiesis and particularly in the expansion of early lymphoid progenitor cells has remained elusive. Based on the ability of the HOXB4 protein to passively enter hematopoietic cells, our group previously designed a long-term culture procedure of human HSCs that allows ex vivo expansion of these cells. Here, this method has been further used to investigate whether HOXB4 could cause similar expansion on cells originating from CD34؉ hematopoietic progenitor cells (HPCs) committed at various levels toward the lymphoid lineages. We provide evidence that HOXB4 protein delivery promotes the expansion of primitive HPCs that generate lymphoid progenitors. Moreover, HOXB4 acts on lymphomyeloid HPCs and committed T/natural killer HPCs but not on primary B-cell progenitors. Our results clarify the effect of HOXB4 in the early stages of human lymphopoiesis, emphasizing the contribution of this homeoprotein in the maintenance of the intrinsic lymphomyeloid differentiation potential of defined HPC subsets. Finally, this study supports the potential use of HOXB4 protein for HSC and HPC expansion in a therapeutic setting and furthers our understanding of the mechanisms of the molecular regulation of hematopoiesis. STEM CELLS 2008;26:312-322 Disclosure of potential conflicts of interest is found at the end of this article.

HOXC4 homeoprotein efficiently expands human hematopoietic stem cells and triggers similar molecular alterations as HOXB4

“…We previously showed that MS-5 cells engineered to secrete HOXB4 had no phenotypic changes. 7,9 In the present study, we extended this observation to HOXC4-transduced MS-5 cells as well. This strongly argues for a direct role of the secreted homeoproteins on human HSC.…”

“…Human immature hematopoietic cell isolation, labeling, culture and cloning assays were performed as already described, [7][8][9] and fully presented in the Online Supplementary Design and Methods section.…”

“…Expanded cells have an enhanced capacity to repopulate in vivo and to maintain their pluripotentiality. [7][8][9] Nevertheless, whatever the technology used, the HOXB4-mediated expansion of HSC and progenitors is always somewhat lower in humans than in mice. We, therefore, decided to examine whether using HOXC4 would improve expansion efficacy.…”

TAT-mediated transduction of NF-Ya peptide induces the ex vivo proliferation and engraftment potential of human hematopoietic progenitor cells

“…Although some success with murine stem and progenitor cells has been achieved, success with human stem cells has proven more elusive. In this study, we sought to take advantage of 3 previous lines of research: (1) several studies have demonstrated that overexpression of HOX4 transcription factors, and especially HOXB4, in mouse HSCs can trigger real HSC expansion, as demonstrated by competitive repopulating assays in congenic mice 1,48,49 ; (2) each of the HOX4 genes, as well as several additional genes important to HSC proliferation, are downstream transcriptional targets of NF-Ya; and (3) TAT-peptide technology offers the potential to directly deliver functional transcription factors to the nucleus of live cells. TAT-peptide technology, if it can be effectively developed, would have the dual advantages of providing a temporary effect without permanent alteration of the stem cell genome.…”

Papel de Notch e NF-kB na regulação de fatores de transcrição durante a diferenciação in vitro de células T a partir de células progenitoras hematopoéticas CD34+

“…Além disso, diversos estudos demonstram que a expressão dos genes HOX varia com a diferenciação das células-tronco (Giannola et al, 2000). O fator HOXB4 tem abundante expressão nas células hematopoéticas primitivas e sua expressão declina com a especificação durante o processo de diferenciação celular, isso ocorre porque o HOXB4 tem papel na regulação do balanço entre a auto-renovação e a diferenciação das células-tronco hematopoéticas, sendo responsável, principalmente, pela manutenção do fenótipo das células-tronco primitivas (Sauvageau et al, 1994;Giampaolo et al, 1994;Moretti et al, 1994;Giannola et al, 2000;Pineault et al, 2002;Haddad et al, 2008;Milson, 2009). Ainda, genes HOX apresentam funções no desenvolvimento dos linfócitos T normais, e na ativação de NK (Lawrence et al, 1996).…”