Figure 1.

Chronic stress promoted colorectal cancer development. (A) Typical locomotion tracks (green lines) of control (Ctrl) mice and mice subjected to chronic stress (Stress) in open field tests (left). Distance moved, rest time, time spent in the center and center entries were compared between control (n=9) and stress (n=9) groups (right). (B) Sucrose preference test was conducted between control and stress groups after completion of the chronic stress paradigm (n=7). (C and D) Chronic stress promotes xenograft tumor growth. MC38 cells were injected subcutaneously into control and stressed C57BL/6 mice to form xenograft tumors (n=6). Tumor growth curve, representative xenograft tumor images (C) and tumor weights (D) are shown, Scale bar, 1 cm. (E) The expression levels of Ki-67 in tumor sections were evaluated by immunohistochemistry and Ki-67 positive cells were indicated as Ki-67 index. Scale bar, 100 μm. (F) Chronic stress education promoted xenograft tumor growth. The xenografts of control and chronic stress groups were dissociated and cultured, then injected subcutaneously into C57BL/6 mice (n=6), representative xenograft tumor images and tumor weights are shown, Scale bar, 1 cm. (G) The levels of epinephrine, norepinephrine and serotonin in control and chronic stress groups were determined by LC-MS. (H-K) Chronic stress promoted colorectal cells proliferation and colony formation. Control and epinephrine (Epi, 10 nM) treated HT-29 cells, cells isolated from control and chronic stress xenografts were subjected to CCK8 assays (H, J) and colony formation assay (I, K). The data are represented as the means ± SEM of at least three independent experiments. *, p < 0.05; **, p < 0.01; ***, p < 0.001.