Oral and Poster Abstracts
651. Myeloma: Biology and Pathophysiology, excluding Therapy: Poster I
Diseases, multiple myeloma, smoldering myeloma, B-Cell Lymphoma, Plasma Cell Disorders, Lymphoid Malignancies
(San Diego Convention Center)
We previously established normal B cell-derived induced pluripotent stem cells (BiPSCs; BiPSC13 and MIB2-6). BiPSCs are known to maintain VDJ rearrangement of the IgH gene, and they can be induced by the tet-off system to express activation-induced cytidine deaminase (AID; BiPSC13-AID and MIB2-6-AID) and differentiate into hematopoietic progenitor cells (HPCs) (Scientific Rep, 2017). Using these BiPSCs, we attempted to prove the existence of abnormal B cells, which are thought to be myeloma-initiating cells, originating from mature B cells transformed by reprogramming. We speculated that BiPSCs could develop into myeloma-initiating cells that undergo chromosomal translocation or gain genetic abnormalities during redifferentiation into mature B cells. First, using the comet assay, we confirmed the DNA-damaging effect of AID in BiPSCs-AID. Secondly, we differentiated BiPSC13-AID into CD34+/CD38-/CD43-/CD45- cells by co-culture with stromal cells (mouse embryo cell line: 10T1/2), and we subsequently transplanted the cells into the bone marrow (BM) of immunodeficient NRG mice. The presence of CD34+ cells was still observed in mouse BM 4 months after transplantation; however, no differentiation into B cells was detected. Next, using the CRISPR/Cas9 system, we attempted to make BiPSCs with chromosomal translocation t(11;14); we succeeded in establishing a 293T cell line with t(11;14), then confirmed t(11;14) in MIB2-6-AID, and the clone is now being established. Furthermore, we established BiPSC13-Pax5, which can be induced by the tet-off system to express Pax5, and we then differentiated BiPSC13-Pax5 into CD34+/Pax5+/CD38-/CD43-/CD45- cells by co-culture with stromal cells (10T1/2). We expect that the HPCs or hematopoietic stem cells (HSCs) derived from BiPSCs will further differentiate into B cells due to the expression of Pax5 in the BM of NRG mouse. We also established BiPSC13-AID-p53-/-, in which p53 was deleted using the CRISPR/Cas9 system, and the cells differentiated into HPCs. Interestingly, we detected some CD43+/CD45+ cells among CD34+/CD38- cells after the co-culture of BiPSC13-AID with aorta-gonad-mesonephros-derived stromal cell (AGM-S3) instead of 10T1/2. Therefore, AGM-S3 may promote the differentiation of BiPSCs into cells that are more similar to HSCs. These CD34+ cells differentiated from BiPSCs will be transplanted into the BM of NRG mouse.
*signifies non-member of ASH
Disclosures: Hanamura: CHUGAI PHARMACEUTICAL CO., LTD.: Research Funding; Kyowa Hakko Kirin Company, Limited: Research Funding; Fujimoto Pharmaceutical Corporation: Research Funding; Takeda Pharmaceutical Company Limited.: Other: Lecture fee; Bristol-Myers Squibb: Other: Lecture fee, Research Funding; Celgene: Other: Lecture fee.