Chronic stress induces marked progression of breast tumor in BALB/c nude mice. (A), Schematic illustration of the experiment design. (B), Tumor volumes in MCF‐7 tumor‐bearing nude mice with and without exposure to chronic stressors; n = 7 control, n = 7 stress, Mann‐Whitney test for day 7, Welch's t test for days 14 and 21. (C), Bodyweight changes in mice bearing MCF‐7 with and without exposure to chronic stressors; n = 7 control, n = 7 stress, unpaired t test. (D), Tumor volumes in mice bearing MDA‐MB‐231 tumors with and without exposure to chronic stressors; n = 6 control, n = 6 stress, Mann‐Whitney test for day 14, Welch's t test for days 7 and 14. (E), Bodyweight in nude mice bearing MDA‐MB‐231 tumors with and without exposure to chronic stressors; n = 6 control, n = 6 stress, unpaired t test. (F), Representative images of tumors from nude mice bearing MCF‐7 tumors with and without exposure to chronic stressors. (G) ~ (H), Representative images of MCF‐7 breast cancer tissue with and without exposure to chronic stressors. Scale bar, 30 μm. *P < .05, **P < .01, ***P < .001