Inhibition of the development of radiation-induced leukemia in mice by reduction of food intake.

We have reported previously that the incidence of tumors induced in Sprague-Dawley rats by total-body gamma-ray irradiation can be considerably reduced by restriction of food intake [Gross, L. & Dreyfuss, Y. (1984) Proc. Natl. Acad. Sci. USA 81, 7596-7598]. In experiments reported here we investigated the influence of reduced food intake on the development of radiation-induced leukemia in C3H(f) mice. The incidence of spontaneous leukemia in mice of this strain does not exceed 0.5%, but it can be considerably increased by total-body x-irradiation. In our study, two groups of C3H(f) mice were submitted to fractionated total-body gamma-irradiation (150 rads, five times at weekly intervals; 1 rad = 0.01 gray). The first group received a full ad lib diet (4.5-5.4 g of Purina Rodent Lab Chow pellets per day, each). In this group 31 out of 58 females (53.4%) and 24 out of 50 males (48%) developed leukemia at an average age of 8 months. In the second group, consisting of sisters and brothers of the first group, and submitted to the same gamma-irradiation but receiving a restricted diet (2 g of Purina Lab Chow pellets each, followed by 3 g on alternate days), only 2 out of 55 females (3.6%), and 1 out of 36 males (2.8%), developed leukemia at an average age of 9 and 12 months, respectively. Leukemia in both groups was predominantly of the lymphatic or lymphoblastic form, the leukemic cells infiltrating most organs, particularly the thymus, mesenteric and peripheral lymph nodes, spleen, liver, kidneys, and bone marrow; in most instances the peripheral blood was also leukemic.