Microenvironmental influences on the in vivo behavior of neoplastic lymphocytes.

A transplantable hamster lymphocytic neoplasma of probable monoclonal derivation, induced by the oncogenic DNA simian virus 40, has been adapted to grow in the allogeneic host either as leukemia (characterized by dissemination and poor prognosis) or as lymphoma (characterized by localization and favorable prognosis) [Diamandopoulos, G. Th. (1978) Proc. Natl. Acad. Sci. USA 75, 2011-2015]. In the present experiments the circumstances under which neoplastic lymphocytes that are transplanted in allogeneic animals retain, lose, or regain the capacity for dissemination or localization are assessed. Results indicate that the in vivo behavior of neoplastic lymphocytes is not a stable, irreversible characteristic that is transmitted to the cell progeny. On the contrary, it can be altered by the origin/tissue microenvironment in which the cells proliferate. It is suggested that, whereas neoplastic cell mutation followed by host selection could be responsible for changes in cell behavior, a more likely explanation is that the proliferating neoplastic lymphocytes acquire reversible nonmutational phenotypic characteristics during their interaction with the host microenvironment, which modify their behavior and, as a result, the prognosis of the neoplastic process.