Temporal factors alter effects of social housing conditions on responses to chemotherapy and hormone levels in a Shionogi mammary tumor model.
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.
Kerr
Leslie R
LR
Departments of Psychology and Biology, Trent University, 1600 West Bank Drive, Peterborough, Ontario, K9J 7B8 Canada. lkerr@trentu.ca
Andrews
Heather N
HN
Strange
Karen S
KS
Emerman
Joanne T
JT
Weinberg
Joanne
J
D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use; D003345:Corticosterone / Q000097:blood; D013006:Growth Hormone / Q000097:blood; D006799:Housing, Animal; D008297:Male; D008325:Mammary Neoplasms, Experimental / Q000097:blood / Q000188:drug therapy* / Q000523:psychology*; D051379:Mice; D008815:Mice, Inbred Strains; D011897:Random Allocation; D013315:Stress, Psychological; D013739:Testosterone / Q000097:blood; D013997:Time Factors
D000970:Antineoplastic Agents; D013739:Testosterone; D013006:Growth Hormone; D003345:Corticosterone