The Effects Of Chronic Emotional Stress On The Mammary Tumor Growth Of C3H/HeJ Mice

Objectives:(l) To determine the effects of chronic emotional stress on the growth of mammary tumor of C3H/HeJ mice. (2) To investigate the potential neuroendocrinology and neuroimmunology mechanisms linking stress and the mammary tumor .Methods: 110 C3H/HeJ female virgin mice were divided into chronic emotional stressed (CES) group which was exposed to drinking-conflict stress and restraint stress and non-treated control(C) group. Mice was decapitated in batches at the end of 0 month (before the exposure of stressors ), 3 months, 6 months or 9 months after being grouped . The parameters measured were the occurrence of mammary tumor , plasma corticosterone level, the production of IL-2 (interleukin-2) from splenocyte and activity of natural killer(NK) cell in spleen.Results: (1) In months 3, 6, mammary tumor morbidity of CES group was significantly higher than that of C group (PO.05). In CES group, tumor morbidity of 3-month, 6-month and 9-month mice increased significantly compared to 0-month mice (P<0.01); In C group, tumor morbidity of 9-month mice was significantly higher than that of 0-month mice (P<0.05). (2) In months 3, 6, and 9, plasma corticosterone levels of CES group were significantly higher than that of C group (P =0.001, 0.022, 0.048 respectively). In CES group, corticosterone levels of 3-month, 6-month and 9-month mice increased significantly compared to 0-month mice (P =0.005, 0.028, 0.007 respectively); In C group, corticosterone levels of 9-month mice were significantly elevated compared to 0-month and 3-month mice (P<0.05). (3) In months 3, 6, the production of IL-2 of CES group was significantly higher than that of C group (P= 0.012 ,0.005 respectively) ; In CES group, the levels of IL-2 of 6-month mice were significantly lower than that of 0-month mice(P<0.05), but in month 9 ,we find they increased again compared to 6-month mice (PO.05); There was no significant difference in differenttime courses of C group. (4) In months 6, 9, NK activity of CES group was lower than that of C group; In CES group, NK activity of 3-month, 6-month and 9-month mice was significantly lowered compared to 0-month mice (PO.01) and that of 3-month mice is higher than 9-month mice (P<0.05) . Interestingly, in C group, NK activity of 9-month unstressed mice is significantly lowered compared to the mice of other time courses.Conclusions: (1) Chronic emotional stress can facilitate the growth of C3H/HeJ mammary tumor and shorten its latent period . (2) Chronic emotional stress can elevate plasma corticosterone level , inhibit the productivity of IL-2 and cause the suppression of NK activity. All these changes companied the accleration of mammary tumor growth, which indicated that these factors may take part in the mediation of the effect of stress on mammary tumor growth . (3) The levels of plasma corticosterone correlated negatively with the production of IL-2, which indicated corticosterone may inhibit the the production of IL-2. But there was no correlation between corticosterone and NK activity , which indicated that the change of NK activity caused by stress may mediated by other mechanisms.