SALL4 is a robust stimulator for the expansion of hematopoietic stem cells

Abstract

HSCs are rare cells that have the unique ability to self-renew and differentiate into cells of all hematopoietic lineages. The lack of donors and current inability to rapidly and efficiently expand HSCs are roadblocks in the development of successful cell therapies. Thus, the challenge of ex vivo human HSC expansion remains a fertile and critically important area of investigation. Here, we show that either SALL4A-or SALL4B-transduced human HSCs obtained from the mobilized peripheral blood are capable of rapid and efficient expansion ex vivo by >10 000-fold for both CD34 ؉ /CD38 ؊ and CD34 ؉ / CD38 ؉ cells in the presence of appropriate cytokines. We found that these cells retained hematopoietic precursor cell immunophenotypes and morphology as well as normal in vitro or vivo potential for differentiation. The SALL4-mediated expansion was associated with enhanced stem cell engraftment and long-term repopulation capacity in vivo. Also, we demonstrated that constitutive expression of SALL4 inhibited granulocytic differentiation and permitted expansion of undifferentiated cells in 32D myeloid progenitors. Furthermore, a TAT-SALL4B fusion rapidly expanded CD34 ؉ cells, and it is thus feasible to translate this study into the clinical setting. Our findings provide a new avenue for investigating mechanisms of stem cell self-renewal and achieving clinically significant expansion of human HSCs. (Blood. 2011;118(3):576-585)

Stem Cell Gene SALL4 Suppresses Transcription through Recruitment of DNA Methyltransferases

“…For example, knock-out mice studies showed that DNMT1-deficient hematopoietic stem cells lost the ability of self-renewal and are unable to give rise to multilineage hematopoiesis (30). We have recently reported that SALL4 is a robust stimulator for hematopoietic stem/progenitor cell expansion (12,31). It would be interesting to study the profound relationship between SALL4 and DNA methytransferases during stem cell proliferation and multipotency maintenance in the future.…”

“…The cells were infected overnight for 12-15 h and then recovered in culture medium. qRT-PCR was performed as described previously (12). Primers are described in supplemental Table S1.…”

“…EBF1 is such a gene, which drives B cell lineage specification and commitment (22). The SALL4-induced hypermethylation of EBF1 promoter and subsequent gene suppression is supportive of the observed blood stem/progenitor cell expansion by treatment of SALL4 (12,13).…”

“…For this purpose, cells were transduced with GFP control or SALL4-expressing lentiviruses as described under "Experimental Procedures" and in Ref. 12. The ectopic expression of SALL4 protein was confirmed by Western blotting analysis as well as fluorescence microscopic examination (data not shown).…”

“…In embryonic stem cells, SALL4 can activate OCT4 and interact with Nanog, and the SALL4/OCT4/Nanog transcriptional network is essential for the maintenance of cell "stemness" (9 -11). Recently, we have shown that SALL4 can serve as a robust stimulator for the expansion of hematopoietic stem/progenitor cells (12,13). The mechanisms by which SALL4 affects hematopoietic stem/progenitor cell growth and identity include blocking differentiation and permitting proliferation of undifferentiated cells (12,13).…”