An immunohistochemical approach for monitoring effects of exercise on tumor stromal cells in old mice.

Epidemiological evidence supports a protective effect of physical activity for breast cancer in older women, but the mechanisms are not well understood. We used 18-month-old BALB/c mice injected in the mammary fat pad with syngeneic 4T1 tumor cells as a model of invasive breast cancer. During the tumor progression phase, there was a significant decrease in labeling for F4/80, a marker for mouse macrophages, and CD34, a marker for vascular endothelial cells, in primary tumors from mice that ran higher average distances compared to mice that ran lower average distances (p≤0.05). These observations suggest that immunohistochemistry can be used to monitor stromal cell populations in tumors from old mice under exercise conditions.