LNK (SH2B3) inhibition expands healthy and Fanconi anemia human hematopoietic stem and progenitor cells

Hematopoietic stem cell transplantation (HSCT) remains the only curative treatment for a variety of hematological diseases. Allogenic HSCT requires hematopoietic stem cells (HSCs) from matched donors and comes with cytotoxicity and mortality. Recent advances in genome modification of HSCs have demonstrated the possibility of using autologous HSCT-based gene therapy to alleviate hematologic symptoms in monogenic diseases, such as the inherited bone marrow failure (BMF) syndrome Fanconi anemia (FA). However, for FA and other BMF syndromes, insufficient HSC numbers with functional defects results in delayed hematopoietic recovery and increased risk of graft failure. We and others previously identified the adaptor protein LNK (SH2B3) as a critical negative regulator of murine HSC homeostasis. However, whether LNK controls human HSCs has not been studied. Here, we demonstrate that depletion of LNK via lentiviral expression of miR30-based short hairpin RNAs results in robust expansion of transplantable human HSCs that provided balanced multilineage reconstitution in primary and secondary mouse recipients. Importantly, LNK depletion enhances cytokine-mediated JAK/STAT activation in CD34(+) hematopoietic stem and progenitor cells (HSPCs). Moreover, we demonstrate that LNK depletion expands primary HSPCs associated with FA. In xenotransplant, engraftment of FANCD2-depleted FA-like HSCs was markedly improved by LNK inhibition. Finally, targeting LNK in primary bone marrow HSPCs from FA patients enhanced their colony forming potential in vitro. Together, these results demonstrate the potential of targeting LNK to expand HSCs to improve HSCT and HSCT-based gene therapy.