Fig. 2. Tumor growth in drug vehicle–treated (TV) mice. Experimental housing conditions were formed (A) immediately after tumor cell injection (experiment 1) or (B) approximately 14 days after tumor cell injection (when tumors weighed approximately 1 g) (experiment 2); arrow represents formation of experimental housing conditions. Tumor weights (mean ± SE) at five measurement times for drug vehicle–treated mice in the three housing conditions of experiment 1 (N = 10 IG, 6 GG, and 8 GI) and the four housing conditions of experiment 2 (N = 12 II, 19 IG, 12 GG, and 14 GI). For experiment 1, tumor growth rates for both days 15 and 17 were significantly faster in both GI and GG mice compared with IG mice (p values < .001). For experiment 2, tumor growth rate by 19 days after tumor cell injection was significantly greater in II mice compared with GG (p < .01) and IG (p < .001) mice.