Dietary restriction reduces the incidence of 3-methylcholanthrene-induced tumors in mice: Close correlation with its potentiating effect on host T cell functions

Abstract

All mice treated with 3-methylcholanthrene (MC) suffered with tumor 114 days after treatment. However, 40% dietary restriction caused a great inhibition of tumor incidence. In order to understand the mechanisms by which dietary restriction decreased the occurrence of tumor in mice, we investigated the correlation between tumor incidence and host T cell immune responses. At 114 days after MC administration, the mice were sacrificed and their T cell immune responses were assessed. Flow cytometry studies demonstrated that dietary restriction caused a marked increase of the proportion of Thy 1.2+, L3T4+ T cells in MC-treated diet-restricted mice. Consistent with this result, T cell responses against concanavalin A and interleukin-2 were also potentiated in spleen cells obtained from MC-treated diet-restricted mice, while spleen cells obtained from MC-treated unrestricted mice showed decreased T cell responses because of their tumor burden. Such potentiation of T cell functions by dietary restriction was also observed at earlier stages of MC-induced tumorigenesis. During the course of carcinogenesis, spleen cells obtained from diet-restricted mice showed decreased natural killer activity in vivo. However, in vitro induction of cytotoxic T cells was markedly augmented in MC-treated diet-restricted mice compared with unrestricted mice. These results strongly suggest that the increase of host T cell immune responses might be one of the major causes for the reduction of tumor occurrence by dietary restriction.

Antidiabetic Effects of an Oral Administration of Lactobacillus casei in a Non-Insulin-Dependent Diabetes Mellitus (NIDDM) Model using KK-Ay Mice.

“…Moreover, the mean body weights of the two LCtreated groups were lower than that of the control group but it was not clear why the body weights of the LC-treated mice were lower than those of the control mice, when the food intake did not differ significantly among the groups. It is possible that the host immune response was altered by the dietary restriction as reported [21]. Further studies are required on this point.…”

Effect of Oral Administration ofButyrivibrio fibrisolvensMDT-1, a Gastrointestinal Bacterium, on 3-Methylcholanthrene-Induced Tumor in Mice

“…1). The 3-MC-induced carcinogenesis model has been used in studies of host-mediated cancer control strategies (21,22). Administration of 3-MC yields one of the highest mutation frequencies among various chemical inducers of tumors (23)(24)(25)(26)(27)(28), and 1 unique feature of 3-MC-induced tumors is their high frequency of p53 tumor-suppressor-gene mutations (29)(30)(31).…”

Inhibitory effect of oral administration of Lactobacillus casei on 3-methylcholanthrene-induced carcinogenesis in mice

“…An MC-induced carcinogenesis model has been used in studies of host-mediated cancer prevention strategies [16,17]. MC treatment rapidly induces tumors in mice, which is dierent from the course of development of human tumors.…”