A novel chronic stress-induced shift in the Th1 to Th2 response promotes colon cancer growth.

Epidemiological data have shown that stress and other psychological factors might influence cancer onset and progression. However, to date, the mechanisms are not well understood. In the present study, we used chronic exposure to a scream as a novel form of sound stress to explore the influence of the chronic stress burden on colon cancer progression, and changes in the immune system were observed. Chronic exposure to scream sound stress induced freezing behavior in the mice and decreased the bodyweight gain. It also caused changes in the adrenal gland and increased serum corticosterone and norepinephrine levels. Cytokine microarray analysis showed changes in the levels of Th1 and Th2 cytokines. The chronic scream sound stress caused a shift from the Th1 to the Th2 response both in the circulation and in tumor-infiltrated lymphocytes, and it promoted colon cancer progression significantly. Taken together, chronic scream sound stress can be conveniently used as a novel chronic stress model. Chronic stress contributes to colon cancer progression and induces a Th1/Th2 imbalance in the mouse immune system, which is considered critical during cancer progression.