Flow Cytometry Based Isolation of HSCs Enables Novel Therapies for Metastatic Breast Cancer
The International Society for Cell & Gene Therapy Conference Annual Meeting (ISCT 2025), held from May 7 to 10 in New Orleans, brought together over 2,500 professionals from academia, industry, and regulatory bodies to explore the latest advancements in cell and gene therapy (CGT). Hosted at the Ernest N. Morial Convention Center, the conference featured a comprehensive program designed to foster collaboration and innovation in the field.
The conference provided a platform for in-depth discussions on pivotal subjects such as induced pluripotent stem cells (iPSCs), exosomes, CAR-T therapies, artificial intelligence, biomanufacturing, and regulatory harmonization. These sessions aimed to tackle pressing practical problems facing the CGT sector and promote collaborative, timely solutions.
At ISCT 2025, Sony Biotechnology was honored to host Prof. Dr. Irving Weissman from Stanford University, a pioneer in hematology and cancer stem cells. Widely recognized as the "father of hematopoiesis," he led the Sony session at the conference.
During his session, Dr. Weissman shared invaluable insights into the development of novel therapies for metastatic breast cancer, specifically using flow cytometry sorted, purified hematopoietic stem cells (HSCs). The flow cytometry-based purification of HSCs eliminates T cells, which are the cause of graft-versus-host disease (GVHD) in allotransplants, since neither mobilized peripheral blood (MPB) nor CD34+ cell preparations are T-cell depleted.
He showed data demonstrating that the HSC allotransplants do not develop GVHD, and the host blood system is largely replaced by donor HSCs. This forms the basis for regenerative medicine when the host blood is genetically defective, depleted, or autoimmune. However, T-cell contaminated transplants give rise to clinical or immunosuppressive subclinical GVHD.
While autologous HSCs can be gene-edited, the ability to perform pure allogeneic HSC transplants from healthy donors presents an alternative option for patients. Pure allogeneic HSCs from organ donors induce transplant tolerance but require ablation of both recipient HSCs and immune T and NK cells. Currently, this ablation is achieved through high-dose chemotherapy or radiotherapy, which induces mutations in all body cells and can lead to secondary lethal diseases.
Dr. Weissman’s team has developed antibodies to deplete HSCs, T cells, and NK cells in vivo, and anti-CD47 antibodies to enable macrophages to assist in cell depletion. In the team’s animal studies, mice became permanently tolerant of HSC donor heart transplants but rejected third-party hearts by day 13.
The session was both inspiring and deeply informative, leaving us with a renewed sense of motivation and many important takeaways.
Dr. Weissman’s labs at Stanford have been among the early adopters of Sony’s next-generation, clinical-grade cell isolation platform, the CGX10 Cell Isolation System, in their groundbreaking work on therapies for metastatic breast cancer patients.
Irving Weissman, MD
Professor of Pathology and Developmental Biology
Stanford University