A human transforming RET cDNA was isolated from a cDNA library of a THP-1 human monocytic leukemia cell line in which the sequences encoding the last 51 carboxy-terminal amino acids of the ret proto-oncogene were replaced with sequences encoding 9 unrelated amino acids. This cDNA was expressed under the control of the Emu enhancer (Rr150) from the immunoglobulin heavy chain (Igh) gene. (J:276582)