Pyrimidoindole derivatives are agonists of human hematopoietic stem cell self-renewal.

Fares I, Chagraoui J, Gareau Y, Gingras S, Ruel R, Mayotte N, Csaszar E, Knapp DJHF, Miller P, Ngom M, Imren S, Roy D-C, Watts KL, Kiem H-P, Herrington R, Iscove NN, Humphries KR, Eaves CJ, Cohen S, Marinier A, Zandstra PW, Sauvageau G. Pyrimidoindole derivatives are agonists of human hematopoietic stem cell self-renewal. Science 345: 1509–1512, 2014.

Prepared by: Samantha Hinds, Advance Stem Cell, Fall 2015

 

 

Layman Summary

Hematopoietic stem cell (HSC) transplant is the most viable option to curing hematological disorders. Currently, bone marrow HSCs are easily accessible for treatment. The compatibility of the HLA alleles between the donors and recipients predict the likelihood of immune rejection. Human cord blood (CB) has an immature immune system and a lower risk of chronic graft-versus-host disease. Unfortunately, CB extractions produce insufficient Hematopoietic progenitors (CD34+) cells to effectively treat adult patients. The researchers discovered that a small molecule, UM171, is capable of expanding the number and proliferative potential of CB derived LT-HSC. These researchers utilized mobilized peripheral blood (mPB) in a fed-batch system to screen 5280 drugs’ ability to expand CD34+CD45RA- cells. UM729 most significantly increased the number of CD34+CD45RA-. Furthermore, other drugs with increased expansion of CD34+CD45RA- targeted aryl hydrocarbon receptor (AhR) pathway. For example, StemRegenin 1 (SR1) suppresses AhR to promote the expansion of CD34+ cells. To elucidate the mechanism of UM729, the researchers compared UM171, a more potent analog of UM729, to SR1. The results indicated that UM729/UM171 functions independently of the AhR pathway. To determine whether UM171 antagonized or cooperate with SR1 in their ability to expand CD34+CD45-RA- cells, the authors asked what type of blood cells was generated.The results indicated that UM171 attenuated cell differentiation. Further studies revealed that UM171 did not require SR1 to expand the most primitive stem cells needed for transplantation. In vivo transplantation studies in mice that can retain human cells indicated that the studies in the laboratory (in vitro) could be extended in vivo. Notably, UM171 increased overall reconstitution of hematopoietic cells (CD45+), with a bias towards lymphoid cells and suppressed the differentiation of erythrocytes and megakaryocytes. Molecules like UM171 have the potential to be used in the clinic to expand LT-HSC from small unit of cord blood for transplantation to adults. According to the information available on the Université de Montréal’s website, there should be an ongoing clinical trial with UM171.

 

 

Scientific Summary

Human cord blood (CB) is an excellent alternative to allogenic Hematopoietic stem cell (HSC) transplant. CB has an immature immune system that reduced the risk of chronic graft-versus-host disease. Unfortunately, the small amount of HSCs and progenitor cells available in cord blood limits their use in adults. The authors of this paper identified a family of molecules that can stimulate the hematopoietic cells. The expanded cells were shown to be long-term-repopulating hematopoietic stem cells (LT-HSCs) using immunodeficient mice. Using an automated and large scale system, the authors used a fed-batch culture system to screen 5280 compounds that expanded CD34+CD45RA- cells, resulting in the selection of UM729 for further studies. The authors selected UM729 and then synthesized 300 analogs. Similar screening selected the compound UM171 as the most potent with respect to increased expansion without affecting direct mitogenic activity and rate of cell division. Next, the authors asked if UM171 can synergize with a previously reported StemRegenin1 (SR1). Although, both SR1 and UM171 produced approximately equal amounts of CD34+ cells, CD34+CD45RA- cells were more abundant with UM171 treatment. SR1 enhanced the effect of UM171 by causing 13 fold increase of CD34+ cells. There was no significant difference between co-addition of UM171 and SR1, and UM171 alone. The authors concluded that the cooperativity between UM171 and SR1 was limited to the short-lived progenitors whereas the expansion of LT-HSC could occur with UM171. In order to study the function of the expanded hematopoietic cells, the authors performed serial transplant in NOD/SCID gamma (NSG) mice. The in vivo studies recapitulated the in vitro studies with the UM171-expanded cells. UM171 showed marked upregulation of surface molecules, including PROCR, a marker for mouse LT-HSCs. Although the direct mechanism by which UM171 expanded LT-HSCs remains unclear, the paper conformed that UM171 can expand HSCs from human cord blood. In total, the paper showed UM171’s ability to expand human LT-HSCs, independent of AhR suppression. This study demonstrated the potential for UM171 to expand HSCs from a small amount of cord blood to generate cells for transplantation.

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