Transfer of age-associated restrained tumor growth in mice by old-to-young bone marrow transplantation.

B16 melanoma and Lewis lung carcinoma grow more slowly in aged mice. Immunesenescent changes may account for this age-related difference. To test for the effect of immune deficiency on the growth of these tumors, we treated young mice with an immunosuppressive dose of radiation and then observed tumor growth. We also radiated young mice to a higher (lethal) dose and then rescued them with either young or old bone marrow transfusion. Tumors grew more slowly in radiated mice than controls and in those reconstituted with old bone marrow. These findings support the concept of immunesenescent-related reduced tumor growth.