Untreated female (NZB X NZW)F1 hybrid mice (B/W F1) were found to develop
lymphosarcoma spontaneously as they aged.
Tumor incidence was evaluated in B/W F1 mice immunosuppressed with total
lymphoid irradiation (TLI) and in TLI-conditioned B/W F1 mice reconstituted with 3 X 10(7) BALB/c bone marrow (BM) cells. BALB/C leads to B/W F1 chimerism (79 to 89% BALB/c-type cells) was confirmed by typing peripheral blood lymphocytes with specific alloantisera and
complement by using a microcytotoxicity assay. Chimeras showed no clinical signs of
graft-vs-host disease (GVHD). TLI-treated mice seemed to show a slightly accelerated onset of
lymphosarcoma as compared with untreated controls, but the difference was not significant (p = 0.08). BALB/c leads to B/W F1 chimeras reconstituted at 1 to 3 mo of age (25 mice) developed no
tumors for an observation period of 18 mo after
transplantation. In contrast,
tumors developed in 24/130 of age-matched controls, and in 13/57 of TLI-treated nonreconstituted age-matched B/W F1 mice.
Tumor incidence in BALB/c leads to B/W F1 chimeras transplanted at an older age (9 to 11 mo) was similar to that observed in age-matched TLI-treated B/W F1 mice and age-matched untreated controls. The data suggests that the high naturally occurring incidence of
lymphosarcoma could be reversed by reconstituting TLI-treated mice with BM cells (p = 0.027). Thus, allogeneic BM
transplantation may exert potent graft-vs-tumor effects (GVT) when
tumor susceptible hosts are reconstituted at an early age, whereas GVT is relatively ineffective at an advanced age, which probably correlates with an advanced stage of
tumor development. Allogeneic BM
transplantation should be additionally explored as a potential clinical tool for eradication of certain solid
tumors in adjunct to high-dose
radiochemotherapy, inasmuch as GVT seems to be independent of GVHD.