Effect of hypoxia on murine colorectal cancer cells growth in vivo

• Main Authors: Wen-Han Chen, 陳玟翰
• Other Authors: Anya Mann-Yuh Lin
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/94290385462288530511

碩士 === 國立陽明大學 === 生理學研究所 === 92 === Hypoxia, frequently found in the center of solid tumor, may modulate tumor growth by altering the expression of genes which encode angiogenic, metabolic and metastatic factors. However, a significant body of studies revealed that hypoxic cells in solid tumors are resistant to chemotherapy and radiotherapy. Hypoxia-inducible factor 1 (HIF-1), the most important transcription factor under hypoxic condition reportedly promotes tumor growth by turning on angiogenic factor gene expression including vascular endothelial growth factor (VEGF). Recent studies have demonstrated that high level expression of HIF-1 is associated with drug resistance in vitro. However, the effect of hypoxic treatment on cancer cells growth in vivo is still unknown. In the present study, three goals were pursued. First, an animal model was established to study the effect of hypoxia on tumor growth in vivo. Secondly, the cellular and biochemical changes in tumors grown in normoxic mice and hypoxic mice were investigated by measuring VEGF levels in tumors and serum as well as CD31, an endothelial cell marker for angiogenesis in tumors. Thirdly, the roles of NF-□B, a transcriptional factor and IL-6, a proinflammatory cytokine in the hypoxia-induced modulation of cancer development were studied. Adult BALB/c male mice were used and murine CT26 colon adenocarcinoma cells were implanted subcutaneously. These mice were divided into two groups: one was under normoxic condition, and the other was subjected to a hypoxic chamber (10% O2、90% N2) for 10 hours/day for 21 days. The averaged body weight of hypoxic mice was not different from that of the normoxic mice. Tumor volume of hypoxic mice was slightly and insignificantly larger than that of normoxic mice. Morphologically, a larger necrotic area was found in tumors grown in the normoxic mice compared with that in hypoxic mice using hematoxylin ＆ eosin staining. No significant difference in serum VEGF was observed in normoxic mice and hypoxic mice using ELISA assay. However, at day 13, higher levels of VEGF gene expression and CD31 positive cells were demonstrated in the tumors grown in hypoxic mice using RT-PCR and immunohistochemistry, respectively. In addition, marked activation of NF-□B and elevation in serum IL-6 were found in hypoxic mice compared with those in normoxic mice by non-radioactive electrophoretic mobility shift assay and ELISA assay, respectively. Furthermore, hypoxic treatment attenuated the sensitivity of tumors to 5-FU 10 mg/kg treatment. In conclusion, our in vivo data found that tumors in the hypoxic mice may turn on VEGF gene expression and result in angiogenesis. Furthermore, elevation in NF-□B activation and IL-6 may contribute to the tumor growth in hypoxic mice. In addition, this animal model may be useful for the in vivo study of drug resistance.