Social isolation stress enhanced liver metastasis of murine colon 26-L5 carcinoma cells by suppressing immune responses in mice.
We investigated the effect of social isolation stress on the formation of experimental liver metastasis resulted from intraportal vein (i.p.v.) injection of colon 26-L5 carcinoma cells in male Balb/c mice, and elucidated some of the underlying mechanism involving the effects of this stress on cellular immunity. Increases in the colony number and tumor burden were observed in the mice socially isolated before and/or after tumor cell challenge, as compared with the group-housed mice. In addition, exposure of mice to 2 weeks of preisolation resulted in decreases in the thymus weight and number of thymocytes by 35.8% and 40.2%, respectively, in comparison with the controls. Reduced proliferative response of splenocytes to various stimuli and suppressed splenic NK activity, as well as decreased macrophage-mediated cytotoxicity, were also found in the mice exposed to social isolation. Thus, these results suggest that social isolation stress enhances tumor metastasis in part via its suppressive effect on the immune system of the host.
Wu
W
W
Department of Pathogenic Biochemistry, Institute of Natural Medicine, Toyama Medical and Pharmaceutical University, Japan.
Yamaura
T
T
Murakami
K
K
Murata
J
J
Matsumoto
K
K
Watanabe
H
H
Saiki
I
I
D000818:Animals; D002277:Carcinoma / Q000276:immunology / Q000473:pathology*; D002452:Cell Count; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D017690:Cell Transplantation; D003110:Colonic Neoplasms / Q000276:immunology / Q000473:pathology*; D007111:Immunity, Cellular / Q000502:physiology*; D007694:Killer Cells, Natural / Q000276:immunology / Q000502:physiology; D008114:Liver Neoplasms, Experimental / Q000276:immunology / Q000473:pathology / Q000556:secondary*; D008264:Macrophages / Q000187:drug effects / Q000276:immunology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D009929:Organ Size / Q000502:physiology; D012934:Social Isolation / Q000523:psychology*; D013154:Spleen / Q000166:cytology / Q000187:drug effects; D013315:Stress, Psychological / Q000276:immunology / Q000473:pathology*