| Cancer, diabetes, and brain or heart vessel diseases are three killers of human health. Among those, tumor disease's cure rate and average living time is the lowest, which can seriously affect patients' living quality. And the malignant degree of tumor disease is decided mainly by the tumor cell's metastasis ability: as we know, benign tumor can not metastasize, and can be cured by surgery resection; and most malignant tumor can occur long distance metastasis, which cause patients suffer from ulcer blooding, perforation, cachexia, and so on, finally cause patients death. Hence, people are more and more pay attention to the mechanism of tumor's metastasis.Tumor's long distance metastasis is a complex progress which involves many steps, and is affected by many factors, mainly including tumor cells shattered from the primary tumor, secreted hydrolase to break down extracellular matrix and basement membrane, penetrated the blood vessel or lymph vessel into stream, then migrated far away to adhere and peneterate them but in other tissue and orgains to form metastatic tumor. During this progress, the key step is tumor cells adhesion to the endothelium of blood or lymph vessels, and lymphatic metastasis frequently occur before hematogenous metastasis, and tumor cells settling in lymph nodes can become a bridgehead for further metastatsis. So study on the mechanism of lymphogenous metastasis is very important.Before tumor cells adhere to wall of lymph vessel, first it moves slowly, and from the axial flow to the marginal flow, then rolling on the free surface of the endothelial cells' surface beneficial to adhere and penetrate, which is similar to white blood cells' peneteration to the inflammation site. During this progress, at least two kinds of adherent molecule participate in interaction of cell adhesion, selectins may be one of them.Sclectin is an animal lectin of C sorts, which has three numbers such as E-, P- and L-selectin.They are specifically expressed adhesion molecular on membranes of activated endothelium, platelets and white blood cells. Among them, L-selectin is continually expressed in the greater number of white blood cells, and is the "homing receptor" of lymph cells.Recently, it has been demonstrated that L-selectin does not merely play in blood system. Olga D. Genbacev et al's studies revealed that surface of embryonic sac can express L-selsctin and the surface of endometrium express the receptor of L-selectin in the implantaion phase which can induce the embryo's implantation. It has been supposed that L-selectin maybe play a key role in the metastasis process of tumor cell to lymph node sincemechanism of tumor to lymph nodeis similar to that of lymph cell's homing, and other facts also support this hypothesis: T cells' hybrid tumor cells which specifically metastasize to lymph node highly express L-selectin; Non-Hodgkin lymphoma cells invading the lymph node is considered to play the key role in metastasis, while those propagated in lymph node frequently express L-selectin and those prefer to propagate in peripheral tissues rarely express L-selectin. Fawn Qian et al demonstrated that L-selectin can facilitated metastasis of tumor cells to lymph node: in transgenic mouse, insulin promoter regulating expression of monkey virus 40T's antigen can induce pancreaticiselet cells specially metasizing to liver without metastasis to lymph node; while coexpression of monkey virus 40T antigen and L-selectin under the regulation of insulin promoter result in specially metastasis of pancreaticislet tumor cells to peripheral lymph nodes', which can be inhibited by L-selectin's antibody. On the contrary, Aviram R et al reported that L-selectin's antibody MEL-14 can not inhibit metastasis of mouse lymphoma cell 38C-13 to lymph node with expression of L-selectin. Hence, more experiments are necessary to determine the L-selectin's function in tumor metastasis.The murin hepatocarcinoma cell line (HCa-F) and its syngeneic cell line (HCa-P) were separated by professor Ling Mao-ying from distant hybri... |
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