Incardona F, Calvo F, Fauvel-Lafeve F, Legrand Y, Legrand C
U 353 INSERM, Protéases et Protéines Adhésives des Cellules Vasculaires et Sanguines, Paris, France.
Int J Cancer. 1993 Sep 30;55(3):471-7. doi: 10.1002/ijc.2910550325.
The attachment of cancer cells to adhesive molecules, such as laminin (LN) and fibronectin (FN) in the extracellular matrix is a critical step in tumor invasion and metastasis. Recent data have suggested a potential role for thrombospondin (TSP), a 420-kDa cyto-adhesive glycoprotein, in the growth and spread of breast cancer. In this study, we have measured the ability of the human breast adenocarcinoma cell line, MDA-MB-231, to synthesize TSP and to use this molecule as an adhesion factor. The level of TSP in cells and secreted into the culture medium were determined by an enzyme-linked immunosorbent assay (ELISA). At pre-confluence, MDA-MB-231 cells were shown to produce a high level of TSP, most of which was retained within the cells. In comparison, FN was almost entirely secreted into the culture medium. An increased secretion of TSP was however measured at low cell density, suggesting that TSP might be required for cell/substratum or cell/cell interactions. As shown by flow cytometry, the cells expressed membrane-bound TSP as well as unoccupied TSP receptors. 125I-TSP bound saturably to 1.2 x 10(6) sites per cell with an apparent dissociation constant of 23 nM. The binding was inhibited by an excess of unlabeled TSP and by heparin, suggesting that the receptor could be a heparan-sulfate proteoglycan or a sulfatide. TSP promoted attachment but not spreading of MDA-MB-231 cells which attached and spread on FN and LN substrates. These results suggest that endogenously synthesized TSP may have a role in the cyto-adherence of tumor cells during the spread of breast cancer.
癌细胞与细胞外基质中的黏附分子（如层粘连蛋白（LN）和纤连蛋白（FN））的附着是肿瘤侵袭和转移的关键步骤。最近的数据表明，血小板反应蛋白（TSP）（一种420 kDa的细胞黏附糖蛋白）在乳腺癌的生长和扩散中可能发挥作用。在本研究中，我们测量了人乳腺腺癌细胞系MDA-MB-231合成TSP并将该分子用作黏附因子的能力。通过酶联免疫吸附测定（ELISA）确定细胞中以及分泌到培养基中的TSP水平。在汇合前，MDA-MB-231细胞显示产生高水平的TSP，其中大部分保留在细胞内。相比之下，FN几乎完全分泌到培养基中。然而，在低细胞密度下测量到TSP的分泌增加，这表明TSP可能是细胞/基质或细胞/细胞相互作用所必需的。如流式细胞术所示，细胞表达膜结合的TSP以及未被占据的TSP受体。125I-TSP以每个细胞1.2×10（6）个位点的饱和结合，表观解离常数为23 nM。未标记的TSP过量和肝素可抑制该结合，这表明该受体可能是硫酸乙酰肝素蛋白聚糖或硫脂。TSP促进MDA-MB-231细胞的附着但不促进其铺展，这些细胞在FN和LN底物上附着并铺展。这些结果表明，内源性合成的TSP可能在乳腺癌扩散过程中肿瘤细胞的细胞黏附中发挥作用。
