“The 89th of Stem Cell Biology and Regenerative Medicine Forum”
Date：Mar 23rd (Wed) 2016
Time : 13:00 〜 14:30
Place：8th floor Hospital Building------------------------------------------------------------------------------------------------------------------------------------（Internal Speaker）
13:00-13:30 Kimihito Cojin Kawabata (Institute of Medical Science, Division of Cellular
Therapy, The University of Tokyo, Tokyo, Japan)
ATP-binding Cassette Transporter G2 (Abcg2) Plays Oncogenic Roles in
Myelodysplastic Syndrome in Mouse BMT Model and Characterizes Advanced
MDS in Clinical Specimens（External Speaker）
13:30-14:30 Susie Nilsson (Office of the Chief Executive Science Leader,Manufacturing, CSIRO)
Therapeutic targeting and rapid mobilization of endosteal HSC using asmall molecule integrin antagonist-------------------------------------------------------------------------------------------------------------------------------------

Hosted by Center for Stem Cell Biology and Regenerative Medicine---Information--＊ Please register attendance at the reception desk.
＊ Next forum（the90th）will be held on Apr 14th 18:00〜19:30.
＊ Please contact tatsu-m@ims.u-tokyo.ac.jp, for Forum speaker recommendations

ATP-binding Cassette Transporter G2 (Abcg2) Plays Oncogenic Roles in
Myelodysplastic Syndrome in Mouse BMT Model and Characterizes
Advanced MDS in Clinical Specimens
Kimihito Cojin Kawabata (Institute of Medical Science, Division of CellularTherapy, The University of Tokyo, Tokyo, Japan)
A histone H3 Lysine 27 (H3K27)-methyltransferase, enhancer of zeste homolog
2(EZH2) is known as a tumor-associated gene. Physiological role of EZH2 is an
enzymatic component of polycomb repressive complex 2 (PRC2) to inhibit
expression of target genes. While EZH2 plays oncogenic roles by repressing theexpression of tumor suppressors in solid tumors and some lymphomas, it plays
rather tumor-suppressive roles in myeloid malignancies. We have generated ashort-form EZH2 that lacks the catalytic SET domain (EZH2-dSET). Using thisEZH2 mutant we could produce serially transplantable MDS-like diseases.
Microarray analysis using the MDS-like bone marrow cells enabled us to identify
novel targets of EZH2 in MDS tumorigenesis, including ATP-binding cassette(ABC) transporters. Either in our clinical specimens or TCGA public database,
ABCG2 high expressions were observed in MDS samples but not in de novo AMLand CML samples. The results from clinical data also indicate a link between
U2AF1 mutations and ABCG2 expression via disrupted EZH2. Intriguingly, withAbcg2 expression alone, primary bone marrow cells could produce an MDS-likecytopenic disease in our BMT model. Those Abcg2-MDS mice had severe
cytopenia due to inefficient hematopoiesis. Using histological, in vivo live imaging,and in vitro analyses of bone marrow, altered microenvironments in Abcg2-MDS
mice were suggested. In conclusion, a short form of EZH2 upregulates Abcg2expression resulting in MDS-like disease in model mice. ABCG2 is a gene specificto advanced MDS in clinical samples, and its overexpression leads to cytopenic
disease showing inefficient hematopoiesis.

Therapeutic targeting and rapid mobilization of endosteal HSC using a small
molecule integrin antagonist
Susie Nilsson (Office of the Chief Executive Science Leader, Manufacturing,CSIRO)
The collection of haematopoietic stem cells (HSC) for bone marrowtransplantation relies on their mobilisation into the peripheral blood (PB).
Traditionally, this has been routinely achieved using granulocyte-colony
stimulating factor (G-CSF). However, G-CSF-based mobilisation requires multiple
doses over a number of days, is known to alter the function of the HSC niche aswell as bone formation, can cause bone pain and spleen enlargement as well asother rare but life threatening complications. Recently the use of small moleculesfor HSC mobilisation has been explored, such as the CXCR4 antagonist AMD3100(Plerixafor/Mozobil). However, clinical mobilisation with AMD3100 is only
effective in combination with G-CSF and the search for rapid, selective and G-CSF
independent mobilisation regimes remains a topic of interest. Recently, we haveshown that inhibiting 9 1/ 4 1 integrins with a small molecule antagonist(N-(Benzene-sulfonyl)-L-prolyl-L-O-(1-Pyrrolidinylcarbonyl)tyrosine;BOP)
rapidly mobilises HSC with long-term multi-lineage engraftment potential.
Additive augmentation of the engraftment of PB HSC was observed when BOP
was co-administered with AMD3100. This combination effectively out-competed
PB HSC mobilised with 4 days of G-CSF treatment in murine competitivetransplant models. Subsequently, we demonstrated enhanced mobilisation using thesmall molecule combination could be recapitulated in humanizedNODSCIDIL2Rγ−/− mice, where a significant increase in PB CD34+ stem andprogenitor cells were observed after treatment with BOP and AMD3100. To assess
the binding activity of this class of integrin antagonists on stem cell populations ex
vivo and in vivo, we synthesized a related fluorescent analogue (R-BC154). Using
R-BC154, we showed that this class of antagonists preferentially bind mouse andhuman HSC via intrinsically activated 9 1/ 4 1 integrins within the endosteal
niche; the region most closely associated with the bone/BM interface. Morerecently, we have applied this concept to the chemosensitisation of acutelymphoblastic leukaemia, whereby quiescent BM leukaemic cells were effectively
dislodged from their protective endosteal BM microenvironment rendering themsusceptible to chemotherapy. The results support the use of dual 9 1/ 4 1 integrin
inhibitors as effective, rapid and transient mobilisation agents with promisingclinical applications in stem cell therapies.