We reformatted each of them as single-chain variable fragments (scFvs), and enforced their heterodimerization by fusing each with complementary acidic and basic leucine zippers (Figure 6C), expressing and purifying them from insect cells, and applying them to the acute megakaryoblastic leukemia Mo7e cells, which are known to express cKit and TpoR. The gene discussed is MPL; the disease is acute megakaryoblastic leukemia.