Stanley Cohen Biography (1922-)
A pioneer in the study of growth factors--the nutrients that differentiate the development of cells--Stanley Cohen is best known for isolating nerve growth factor (NGF), the first known growth factor, and for subsequently discovering and fully identifying the epidermal growth factor (EGF) . Cohen shared the1986 Nobel Prize for physiology or medicine with his colleague, Italian American neurobiologist Rita Levi-Montalcini, who first discovered NGF. Research on NGF has led to better understanding of such degenerative disordersas cancer and Alzheimer's disease, while studies concerning EGFhave proved useful in exploring alternative burn treatments and skin transplants.
Cohen was born in Brooklyn, New York, in 1922 to Russian immigrant parents. Though his father earned only a modest living as a tailor, both parents, Louisand Fannie (Feitel) Cohen, ensured that their four children received qualityeducations. As a child, Cohen was stricken with polio, imparting himwith a permanent limp. His illness, however, influenced him to pursue intellectual interests. While a student at James Madison High School he earnestly studied science as well as classical music, learning to play the clarinet. Cohen entered Brooklyn College to study chemistry and zoology, graduating in 1943with a B.A. Following his undergraduate studies, Cohen received a scholarship to Oberlin college in Ohio, where he earned an M.A. in zoology in 1945. Hethen attended the University of Michigan on a teaching fellowship in biochemistry, earning his Ph.D. in 1948.
From 1948 until 1952, Cohen worked at the University of Colorado School of Medicine in Denver, holding a research and teaching position in the Departmentof Biochemistry and Pediatrics. There Cohen earned the respect of his peers for his collaborative studies with pediatrician Harry H. Gordon on the metabolic functions of creatinine (a chemical found in blood, muscle tissue, and urine) in newborn infants. Cohen moved to St. Louis, Missouri, in 1952 to work as a postdoctoral fellow in the radiology department at Washington University.The following year, he was asked to become a research associate in the laboratory of renowned zoologist Viktor Hamburger, who was conducting studies on growth processes. Levi-Montalcini, who had been researching nerve cell growthin chicken embryos that had been injected with the tumor cells of male mice,had just returned from Rio de Janeiro, where she had conducted successful tissue culture experiments that definitively proved the existence of NGF. Working at the lab in St. Louis, Levi-Montalcini relied on Cohen's expertise in biochemistry to isolate and analyze NGF.
The collaboration between Levi-Montalcini and Cohen combined two similar personalities. Both scientists have been characterized by their unassuming manners despite their obvious intellectual abilities and perceptive intuitions. Describing her early recollections of Cohen, Levi-Montalcini wrote in her autobiography In Praise of Imperfection, "I had been immediately struck byStan's absorbed expression, total disregard for appearances--as evidenced byhis motley attire--and modesty.... He never mentioned his competence and extraordinary intuition which always guided him with infallible precision in theright direction." Between the years 1953 and 1959, Cohen and Levi-Montalciniconducted intense research, both enthusiastically pursuing thier findings concerning NGF.
By 1956 Cohen had succeeded in extracting NGF from a mouse tumor; however, this proved to be a difficult substance to work with. Upon the suggestion of biochemist Arthur Kornberg, Cohen added snake venom to the extract, hoping to break down the nucleic acids that made the extract too gelatinous. Fortuitously, the snake venom produced more nerve growth activity than the tumor extractitself, and Cohen was able to proceed more rapidly with his studies. In 1958he discovered that an abundant source of NGF could be found in the salivaryglands of male mice--glands not unlike the venom sacs of snakes. Cohen's biochemical advances enabled Levi-Montalcini to study the neurological effects ofNGF in rodents.
At a time when Levi-Montalcini and Cohen were advancing rapidly in their collaborative research, funding for Hamburger's laboratory could no longer support Cohen. Before leaving Washington University, Cohen was able to purify NGF as well as produce an antibody for it; however, its complete chemical structure was not fully determined until 1970 when researchers at Washington University completed analysis of NGF's two identical chains of amino acids. Before departing St. Louis, Cohen also observed an unusual occurrence in newborn rodents that had been injected with unpurified salivary NGF. Unlike control mice,whose eyes opened on the thirteenth or fourteenth day, those injected with the unpurified NGF opened their eyes on the seventh day; they also sprouted teeth earlier than did the control group.
Cohen left Washington University in 1959 to join a research group at Vanderbilt University in Nashville, Tennessee; there he continued his work with growth factors, focusing on identifying the unknown factor in unpurified NGF thathad caused the mice to open their eyes earlier than normal. By 1962, Cohen had extracted the contaminant in these samples of NGF and was able to purify asecond substance, a protein that promoted skin cell and cornea growth which he called epidermal growth factor, or EGF. This protein has found widespread use in treating severe burns; a solution rich in EGF can promote the speedy healing of burned skin, while a skin graft soaked in EGF will quickly bond withdamaged tissue. Cohen also isolated the protein which acted as a receptor for EGF--an important step toward understanding the transmission of signals that stimulate normal and abnormal cell growth--that has been particularly crucial in studying cancer development. Cohen was successful in fully identifyingthe amino acid sequence of EGF by 1972.
Despite his significant contributions, Cohen has never managed a large laboratory, and for many years his work went unacknowledged. He remarked in Science that while the scientific community took little notice of his earlystudies on growth factors, this anonymity proved beneficial. "People left youalone and you weren't competing with the world," he recalled. "The disadvantage was that you had to convince people that what you were working with was real." Cohen's work has subsequently gained wide recognition, and he has received numerous awards in addition to the Nobel, including the Alfred P. Sloan Award in 1982, as well as both the National Medal of Science and the Albert Lasker Award in 1986.