Figure 1.
Chronic unpredictable stress promoted the metastasis of breast cancer cells. (a) Schematic representation of CUS exposure and tumor cell inoculation. BALB/c mice were exposed to CUS for 5 days and then were orthotopically injected with 4T1 cells on day 6. For the tumor growth model (upper), mice were further stressed from days 7–35 every other day after tumor injection and sacrificed on day 35. For the tumor metastasis model (down), mice were further stressed from days 7–14 every other day after tumor intravenous injection and sacrificed on day 14. (b) Tumor growth curve. n = 8 mice/group. *P < .05, Mann-Whitney test. (c) Representative images of ink-stained lungs. (d) The number of lung nodules per mouse. 4T1 group, n = 13. CUS + 4T1 group, n = 14. **P < .01, unpaired t-test. (e) Representative images of lung H&E staining, arrows indicated metastases. (f) Lung nodule area per mouse using NIH Image J (n = 22 sections/group, two sections per mouse lung tissue, ***P < .001, Mann-Whitney test). (g-j) 5 × 105 4T1 cells were injected intravenously into non-stressed (n = 10) or stressed (n = 12) mice; lung metastasis was evaluated 8 days post-injection. (g) Representative images of ink staining lungs. (h) The number of lung nodules per mouse. ***P < .001, unpaired t-test. (i) Representative images of lung H&E staining, arrows indicate metastases. (j) Lung nodule area per mouse using NIH Image J (n = 20 sections/group, two sections per mouse lung tissue, ***P < .001, Mann-Whitney test)