Abstract 6347: Immunotherapeutic application of induced pluripotent stem cell technology: Rejuvenated BCMA-specific CD8+T cells for multiple myeloma
Authors: Bae Jooeun , Kitayama Shuichi , Herbert Zach , Daheron Laurence , Munshi Nikhil , Kaneko Shin , Ritz Jerome , Anderson Kenneth 
Published: June 2022

Abstract
T cell regenerative medicine represents an immunotherapeutic approach using antigen-specific induced Pluripotent Stem Cells (iPSC) to rejuvenate CD8+ cytotoxic T lymphocytes (CTL). Here, we report an iPSC-derived therapeutic strategy targeting B-Cell Maturation Antigen (BCMA) to overcome exhaustion of antigen-specific CTL and revitalize them to fully functional antigen-specific memory T cells to target multiple myeloma (MM). First, we established the iPSC by reprogramming IFN-γ producing heteroclitic BCMA72-80 (YLMFLLRKI) peptide-specific CD8+ CTL via Sendai virus transduction of transcription factors, OCT3/4, SOX2, KLF4 and c-MYC. The BCMA-specific iPSC demonstrated high pluripotency potential and ability to differentiate into three key germ layers, as evidenced by expression of stem cell markers (SSEA-4, TRA1-60), germ differentiation markers (SOX-17 on Endoderm, Brachyury on Mesoderm, and Pax-6 on Ectoderm) and alkaline phosphatase. The polarization of iPSC was followed during embryoid body formation into mesoderm development, evidenced by activation of transcriptional regulators SNAI2, TBX3, PLVAP, HAND1 and CDX2. Furthermore, hematopoietic progenitor cells (HPC; CD34+ CD43+/CD14- CD235a-) were sorted and induced to undergo T cell development under feeder-free culture conditions in the presence of rectonectin. Upon differentiation, phenotypic characterization revealed fully mature T cells with high expression (&gt; 95%) of CD3, CD45, TCRαβ and CD8αβ, which were predominantly CD45RO+ memory T cells with high activation (CD38) and costimulatory (CD28) molecule expression, while lacking immune checkpoints (CTLA4, PD1, LAG3, Tim3). This phenotype was aligned with their high proliferative (1,800-fold increase) capacity and effective anti-tumor cytotoxicity and Th1 cytokine (IFN-γ, IL-2, TNF-α) production against MM patients’ tumor cells in antigen-specific and HLA-A2-restricted manner. Their anti-MM activities were specifically directed against the parent heteroclitic BCMA72-80 peptide via a distinct sole T cell receptor clonotype. RNAseq analyses identified specific transcriptional pathways utilized by BCMA-specific HPC during their differentiation into CD8+ CTL, which include upregulation of transcriptional regulators determining CD4/CD8 T cell differentiation ratio, memory CTL formation, NF-kappa-B/JNK pathway activation, as well as downregulation of regulators controlling B and T cell interactions or CD4+ Th cells and inhibitory receptor development. In summary, these results highlight the processes and pathways mediating somatic T cell epigenetic reprogramming and differentiation into rejuvenated BCMA-specific CD8+ CTL with high proliferation and functional anti-MM activities, providing the framework for regenerative medicine as an adoptive immunotherapy to improve patient outcome in MM.
Citation Format: Jooeun Bae, Shuichi Kitayama, Zach Herbert, Laurence Daheron, Nikhil Munshi, Shin Kaneko, Jerome Ritz, Kenneth Anderson. Immunotherapeutic application of induced pluripotent stem cell technology: Rejuvenated BCMA-specific CD8+T cells for multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6347.