Objective:
To identify possible hormonal factors involved in the differential responses to
chemotherapy observed in our tumor model, we investigated if the timing among tumor cell injection, rehousing, and
chemotherapy administration differentially affects levels of corticosterone (CORT), growth hormone (GH), and testosterone and tumor and host responses to
chemotherapy.
Methods:
Mice were reared either individually (I) or in groups (G). At 2 to 4 months, mice were injected with tumor cells and retained in their original
housing conditions or rehoused into different experimental groups (GG, IG, II, GI) either immediately (experiment 1) or 14 days later (experiment 2);
chemotherapy was administered when tumors weighed approximately 0.8 g.
Results:
In experiment 1, IG and GG mice had better responses to
chemotherapy than GI mice.
Chemotherapy increased CORT levels in II mice and decreased GH levels in GI mice compared with those of their drug vehicle-treated counterparts. Under the temporal conditions of experiment 2, IG and GG mice lost the advantage seen in experiment 1 in terms of tumor and host responses to
chemotherapy. Before
chemotherapy administration, CORT levels in IG mice and GH levels in GI mice were higher than those in mice in all other
housing conditions. At 1 day after
chemotherapy, CORT levels were higher for
chemotherapy-treated than for drug vehicle-treated IG mice, and at 5 days post
chemotherapy, GH levels were higher in GI than in IG mice.
Conclusions:
Temporal relationships among tumor cell injection, rehousing, and
chemotherapy administration critically influence responses to
chemotherapy; these effects may be mediated, in part, by alterations in hormone levels.
GG = from group to group housing; II = from individual to individual housing; IG = from individual to group housing; GI = from group to individual housing; CORT = corticosterone; GH = growth hormone; T = testosterone; AD = Adriamycin; CY = cyclophosphamide; TGD = tumor growth delay; SC115 = Shionogi carcinoma 115; C = tumor cell-injected, chemotherapy-treated mice; V = tumor cell- injected, drug vehicle-treated mice.
