The studies of Rita Levi-Montalcini on the effects of tumor transplantation on the chorioallantoic membrane.

In 1986, Rita Levi-Montalcini and Stanley Cohen were awarded with the Nobel Prize for Physiology and Medicine for the discovery of the nerve growth factor. Among the experimental models used by Levi-Montalcini in the first part of her studies it was the chick embryo chorioallantoic membrane, currently used in the study of tumor growth and angiogenesis. Levi-Montalcini grafted fragments of mouse sarcomas on to the chorioallantoic membranes of 4- to 6-day chick embryos and demonstrated that the tumors infiltrated the host blood vessels. Moreover, the ganglia showed hypertrophy, nerve fibers reaching to the implanted tumors. Levi-Montalcini hypothesized that the effects could have been mediated by a soluble factor, which was later identified as the nerve growth factor.