Modulation of tumor incidence by oncofetal products in a syngeneic hepatoma cell-spleen cell model.

An experimental model is described for analysis of cellular and molecular mechanisms involved in the modulation of tumorigenicity by syngeneic lymphoid cells and oncofetal products in vivo. The effect of mouse amniotic fluid (AF) and alpha-fetoprotein (AFP) from this fluid and from serum, free or bound to estrogens, upon the growth of a syngeneic hepatoma was examined in mice transferred with syngeneic spleen cells from hepatoma-bearing donors. Intraperitoneal transfer of spleen cells from hepatoma-bearing into normal syngeneic mice, either tended to stimulate or to inhibit tumor growth in the latter depending on the length of time elapsed between tumor-transplantation in the spleen-cell donor and their sacrifice for spleen excision. For example, only the spleen cells obtained on day 14 and 21 following tumor transplantation protected the recipients from tumor growth. When these protective cells were mixed with hepatoma cells from a low incidence line, and the mixture injected subcutaneously, tumor incidence increased (tumor-promotion effect) rather than the contrary. AF was immunosuppressive inasmuch as it amplified the tumor-promotion effect of the spleen cells. On the other hand, purified AFP from sera of hepatoma bearing mice abolished this tumor-promotion effect.