James Till

James Till co-discovered stem cells through the clonal spleen colony assay, demonstrating that single cells from bone marrow can self-renew and generate multiple blood cell lineages, establishing the stem cell concept that became the foundation for understanding cancer stem cell hierarchies. His quantitative analysis of radiation sensitivity in hematopoietic cells provided the first evidence that stem cells possess unique biological properties distinct from their differentiated progeny. His foundational work enabled the entire fields of stem cell biology, bone marrow transplantation for cancer, and ultimately the cancer stem cell paradigm.