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Temporal Factors Alter Effects of Social Housing Conditions on Responses to Chemotherapy and Hormone Levels in a Shionogi Mammary Tumor Model

From the Departments of Psychology and Biology, Trent University, Peterborough, Ontario, Canada (L.R.K.); the Department of Kinesiology, University College of the Fraser Valley (H.N.A., K.S.S.), Abbotsford, British Columbia, Canada; and the Department of Cellular & Physiological Sciences, Faculty of Medicine, University of British Columbia (J.T.E., J.W.), Vancouver, British Columbia, Canada.

View larger version (23K): [in this window] [in a new window]   Figure 1. Experimental designs.

View larger version (16K): [in this window] [in a new window]   Figure 2. Tumor growth in mice in the drug vehicle treatment condition. Tumor weights (mean ± standard error) from 11 to 18 days after tumor cell injection and formation of social housing conditions (n = 5, II; n = 10, IG; n = 6, GG; n = 5, GI). Tumor growth rates at 16 to 18 days after tumor cell injection and formation of social housing conditions: GI > II = GG > IG (p values <.05).

View larger version (31K): [in this window] [in a new window]   Figure 3. Plasma hormone levels (mean ± standard error) in drug vehicle- (V) or chemotherapy- (C) treated mice at 0, 1, and 5 days after drug vehicle or chemotherapy injection. Significance symbols: treatment (•), group (*), and day (). (A) Corticosterone (CORT): CORT levels were significantly higher at 1 day for C-II than for V-II mice (p < .05; •). (B) Growth hormone (GH): before vehicle/chemotherapy injection (0 days), GH levels did not differ significantly among mice in the housing conditions. At 1 day after drug vehicle injection, GH levels were higher in GI mice compared with all other housing conditions (p values <.05; *). Also, GH levels in GI mice were significantly higher at 1 and 5 days than at 0 days (p values <.05; ). Overall, GH levels were significantly higher in V-GI mice than in C-GI mice (p < .01; •). (C) Testosterone (T): for V mice, significant increases in T levels were seen at 5 days in GG mice compared with IG and GI mice (p values <.05; *). Also for GG mice, T levels were significantly higher at 5 days than those at 1 day (p < .01; ). No significant differences in T levels were seen in C mice or between V and C mice.

View larger version (15K): [in this window] [in a new window]   Figure 4. Tumor growth in mice in the drug vehicle treatment condition. Arrow represents formation of experimental housing conditions. Tumor weights (means ± standard error) from 11 to 18 days after tumor cell injection for drug vehicle-treated mice in the experimental housing conditions (n = 5, II; n = 9, IG; n = 6, GG; n = 6, GI). Tumor growth rates by 18 days after tumor cell injection (4 days after formation of experimental housing conditions): GI = GG > II = IG (p values <.05).

View larger version (32K): [in this window] [in a new window]   Figure 5. Plasma hormone levels (mean ± standard error) in drug vehicle- (V) and chemotherapy- (C) treated mice at 0, 1, and 5 days after drug vehicle or chemotherapy administration. Significance symbols: treatment (•), group (*), and day (). (A) Corticosterone (CORT): at day 0 (1 day after experimental housing condition formation), CORT levels were significantly higher for IG mice than in mice in all other housing conditions (p values <.05; *). Also, CORT levels at day 0 were significantly higher than those at 1 and 5 days in V-IG mice and higher than those at 5 days in C-IG mice (p values <.05; ). Accordingly, CORT levels at 1 day were significantly higher for C-IG than for V-IG mice (p < .01; •). (B) Growth hormone (GH): at day 0, GH levels were significantly higher for GI mice than in mice in all other housing conditions (p values <.01;*) as well as for II than for IG mice (p < .05; *). Also at day 0, GH levels in GI mice were significantly higher than those at 1 or 5 days (p values <.05; ). GH levels at 5 days were significantly higher in C-GI mice than in C-IG mice (p < .05; *). Also, GH levels at 5 days were significantly higher for C-GI than for V-GI mice (p < .05; •). (C) Testosterone (T): for V mice, T levels, overall, were significantly higher in GI than in II mice (p = .01; *) and marginally higher in GI than in IG and GG mice (p = .060 and p = .086, respectively). T levels did not differ significantly for C mice or between the C and V conditions.