Hypoxia exposure and colon cancer tumor growth. (A & B) Effect of hypoxia on colon cancer tumor growth (Figure 1C): Four days under normoxia after HCT116 colon cancer cell injection, animals were exposed to hypoxia (10% O2) for 10 days from xenograft model (protocols Figure 1C). (A) Tumor growth curve and (B) Tumor weight. *p < 0.05 as compared with normoxia. n = 6 rats for each group. (C to F) Effect of hypoxia-pretreatment on colon cancer tumor growth: HCT116 cells were cultured in 0.5% hypoxia for 7 days and then harvested for cell proliferation assay and cell progression analysis. In the meantime, the harvested cancer cells were inoculated into nude mice subcutaneously. After 21 days, the animals were sacrificed and the tumors were collected. (C) Cell growth assay and (D) cell cycle progression analysis in vitro (n = 9 for each group); (E) Tumor growth and (F) Tumor weight in mice. n = 5 for each group. *p < 0.05 as compared with normoxia.