Platelet-derived growth factor (PDGF) is a mitogen for mesenchyme- and glia-derived cells. PDGF consists of two chains, A and B, which dimerize to form functionally distinct isoforms, PGDF-AA, PDGF-AB and PDGF-BB. These three isoforms bind with different affinities to two receptor types, PDGFR-α and -β, which are endowed with protein tyrosine kinase domains. PDGFR-α can bind to both A and B subunits of PDGF, while PDGFR- PDGF-AA induces the dimerization of αα and αβ and PDGF-BB induces the formation of three types of PDGF-AB induces dimerization of αα and αβ and PDGF-BB induces the formation of three types A dimlist, αα, αβ and ββ. Translocation of the PDGFR-β gene with the Tel gene is linked to chronic myelomonocytic leukemia (CMML), a myelodysplastic syndrome, and demonstrate the oncogenic potential of the PDGF receptors.