The gray opossum (Monodelphis domestica): a marsupial model for xenogeneic neoplasms.

Marsupials are born in what is essentially a fetal stage of development and are largely unprotected by endocrine or immune systems during early neonatal life. In this study, gray opossums (Monodelphis domestica) were injected during neonatal life, prepubertally and in adulthood with B16 melanoma from the syngeneic C57BL/6 mouse. Ten days following injection, tumors were found in animals injected on days 4, 6 and 13 of postnatal life but not in prepubertal or adult animals. Because xenogeneic tumors can be grown in it and it is easily maintained and bred in the laboratory, this marsupial species has the potential to become a practical model for cancer research.