Biological Effect of Irradiation on Adhesion Molecules in Human Colon Cancer Cells and Application to Clinical Medicine

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Nowadays, it is commonly believed that certain cell adhesion molecules play critical roles in cancer metastasis. The adhesion of circulating cancer cells to the vascular endothelium is an important step in the hematogenous metastasis of cancer. Carbohydrate antigens, such as sialyl Lewis^a antigen ( s-Le^a) and sialyl Lewis^x antigen ( s-Le^x), play an important role in cancer metastasis in vitro and in vivo. Especially s-Le^a plays an important role in metastasis to the liver. Currently, preoperative radiotherapy is used for preventing local recurrence of rectal cancer. We investigated the effects of X-ray irradiation on carbohydrate antigens s-Le^a and s-Le^x in vitro.The cell surface expressions of s-Le^a and s-Le^x were determined by flow cytometric analysis at 24 hours after X-ray irradiation of 4 human colon cancer cell lines. s-Le^a and s-Le^x functions were quantitated using a monolayer cell adhesion assay with human umbilical vein endothelial cells ( HUVECs).In this study the expression of s-Le^a decreased significantly at 24 hours after any dose of irradiation in HT 29 and WiDr cells. And X-ray irradiation significantly decreased the cell adhesion capacity of HT 29 and WiDr cells to the HUVECs.These results may indicate the possibility of a reduction of liver metastasis in colon cancer using X-ray irradiation.