Dr. Clarkson is head of the Laboratory of Hematopoietic Cell Kinetics at Memorial Sloan Kettering Cancer Center. His laboratory has been devoted to understanding the growth and differentiation properties of leukemia cells and progenitor cells. By studying the core biological principles that govern and fuel cancer formation, Dr. Clarkson and his colleagues were among the first to develop and optimize treatment programs for adults with acute leukemias and lymphomas. He has also made significant contributions to the understanding of cancer biology, especially in the area of cancer stem cells. Dr. Clarkson served as the president of the AACR in 1980-81.