In the 1950s , Cohen worked with Rita Levi-Montalcini at Washington University in St. Louis . He isolated the nerve growth factor and then discovered the epidermal growth factor . Working with Rita Levi-Montalcini ( co-recipient of the Nobel Prize in 1986 ) at Washington University in St. Louis in the 1950s , Cohen isolated nerve growth factor and then went on to discover epidermal growth factor .