大腸癌と大腸正常粘膜細胞の糖脂質の構造解析とその比較

抄録

Malignant transformation is frequently accompanied by a drastic alteration in the structures of oligosaccharides at the cell surface. To understand the nature of the mechanism of alteration of oligosaccharide structures, we have analyzed and compared the structures of glycosphingolipids (GSLs) of colon cancer cells and normal colon epithelial cells from 18 patients. To determine accurate structures of GSLs of colon cancer and normal colon epithelial cells, these cell populations were purified from colon cancer tissues and surrounding normal colon tissues using the epithelial cell marker CD326. GSLs were extracted from the cells and carbohydrate moieties were released by endoglycoceramidase. The oligosaccharides were labeled by pyridylamination, and structurally characterized using a two-dimensional HPLC mapping technique, electrospray ionization tandem mass spectrometry, enzymatic cleavage and methanolysis. This analysis demonstrated that GSLs in normal colon epithelial cells are, in most cases, composed of neutral GSLs having type 1 chains with acidic GSLs being very minor components. The predominant neutral GSL of normal colon epithelial cells is Le^a, together with significant amounts of lactose and Le^b. The expression pattern of GSLs of colon cancers cells are different and vary case to case. However, human colon cancer cells from most cases consist of more various GSLs than normal colon epithelial cells having Le^a, Le^x, LST-c and GM3 as major components, and Le^y, Le^b, sialyl Le^x, sialyl Le^a, IV⁶NeuAcIV²Fuc-nLc₄, VI³NeuAc-nLc₆, and VI⁶NeuAcIII³Fuc-nLc₆ as minor components. These results indicate that levels of GSLs having type 2 chains and sialylated GSLs are elevated in carcinogenesis. Furthermore, we found cancer cells from two patients which presented a variety of sulfated GSLs.