On Jun. 17, 1994, the University of Washington and ZymoGenetics scientists reported in Nature the discovery, isolation and cloning of thrombopoietin, the elusive factor that stimulates production of platelets, blood cells crucial to clotting.

TPO is a protein found naturally in the body that stimulates growth of tiny blood cells called platelets, which in turn induce blood clotting. ZymoGenetics hopes use of the protein will one day replace platelet transfusions as a treatment for those undergoing chemotherapy and others with low platelet counts.

The present treatment method isn’t flawless: Often foreign platelets from transfusions are attacked by the patient’s own nervous system. If TPO works for people as it does in the laboratory, the protein has the potential to help as many as 300,000 cancer patients worldwide.