Effects of social isolation on ehrlich tumor growth and tumor leukocyte infiltration in mice: evidence of participation of the submaxillary salivary gland.

OBJECTIVE: Considering previous studies on stress and Ehrlich tumor growth from our laboratory and also known cell growth and behavior-related properties of submaxillary salivary gland products, we studied the effects of stress by social isolation, in combination or not with sialectomy (submaxillary gland ablation), on growth and leukocyte infiltration into Ehrlich adenocarcinomas.
METHODS: 5 x 10(7) tumor cells/ml were inoculated into the footpads of mice and tumor growth was evaluated by measuring paw thickness on alternate days. Ten days after inoculation, tumors were harvested and processed for immunocytochemical analysis of tumor-infiltrating leukocytes (TIL) and nerve-like growth factor (NGF)/epidermal growth factor (EGF)-positive tumor cells. T and B lymphocyte, NK cell and macrophage percentages were calculated.
RESULTS: Sialectomy slightly reduced tumor growth and caused a significant increase in NK cell infiltration of tumors (p < 0.05). Social isolation caused a highly significant enhancement of both tumor growth (p < or = 0.05) and percentage of macrophages infiltrating tumors (p < 0.05). Sialectomized isolated animals showed few significant changes in tumor growth rate (p < or = 0.05), but presented increased percentages of NK cells, macrophages and B lymphocytes (p < 0.05). A reduction in the percentage of NGF+ tumor cells was also observed (p < 0.05). All of these effects were seen only in 8-month-old mice, but not in younger animals.
CONCLUSION: A possible link between salivary gland factors, tumor growth and TIL patterns was considered, suggesting that growth factors may modulate tumor leukocyte infiltration as well as tumor growth rate. Copyright 2002 S. Karger AG, Basel