Pichon F, Lagarde A E
Division of Cancer and Cell Biology, Mount Sinai Hospital Research Institute, Toronto, Ontario, Canada.
J Cell Physiol. 1989 Aug;140(2):344-58. doi: 10.1002/jcp.1041400221.
MeWo melanoma cells (clone LC1) secrete a potent mitogenic activity susceptible to reinitiate DNA replication in quiescent rodent fibroblasts (CCL39, NRK-49F, NIH-3T3) but not in BHK-21 kidney cells. This activity appears to be closely related to platelet-derived growth factor (PDGF) based on 1) its cationic nature, heat and acid resistance, but sensitivity to reducing agents; 2) its apparent molecular weight (33 kDaltons) as estimated by Biogel filtration, once dissociated from binding proteins by mild acidic treatment; 3) its weak affinity for heparin; and 4) its ability to compete with 125I-PDGF for binding to human and rodent fibroblasts, and to be recognized by anti-PDGF antibodies. Although MeWo cells coexpress the PDGF-A and PDGF-B (c-sis) chain gene transcripts, the secreted product shows reactivity on CCL39 fibroblasts more compatible with the PDGF-BB than with the PDGF-AB isoform. MeWo cell lysates contain activities that bind moderately and strongly to heparin-Sepharose, being eluted with 1.0 and 2.0 M NaCl, respectively. The latter may correspond to basic fibroblast growth factor (basic FGF), consistent with the expression of basic FGF gene mRNAs. The former has not been fully characterized and is probably not the product of the acidic FGF gene. In addition, MeWo cells react positively with the FB2 AH7 antibody, thus indicating that they elaborate material similar to melanoma growth-stimulating activity (MGSA). MeWo cells proliferate in serum-free medium in a cell-density-dependent fashion, both in liquid and semisolid cultures. Their division is modestly enhanced by basic FGF and by human and porcine PDGF but not by the factors that they release. However, the absence of demonstrable 125I-PDGF binding sites on MeWo cells, in conjunction with their lack of sensitivity to suramin growth inhibition, suggests that the secreted PDGF does not act as an autocrine factor. Instead, the autonomous proliferation of MeWo melanoma cells may result from the concerted action of basic FGF and MGSA, which are mostly cell-associated.
MeWo黑色素瘤细胞（克隆LC1）分泌一种强大的促有丝分裂活性物质，这种物质能够使静止的啮齿动物成纤维细胞（CCL39、NRK - 49F、NIH - 3T3）重新启动DNA复制，但对BHK - 21肾细胞却不起作用。基于以下几点，这种活性似乎与血小板衍生生长因子（PDGF）密切相关：1）其阳离子性质、耐热和耐酸性，但对还原剂敏感；2）经温和酸性处理从结合蛋白解离后，通过生物凝胶过滤估计其表观分子量为33千道尔顿；3）其对肝素的亲和力较弱；4）它能够与125I - PDGF竞争结合人和啮齿动物成纤维细胞，并能被抗PDGF抗体识别。尽管MeWo细胞共表达PDGF - A和PDGF - B（c - sis）链基因转录本，但分泌产物在CCL39成纤维细胞上的反应性与PDGF - BB比与PDGF - AB异构体更相符。MeWo细胞裂解物含有与肝素 - 琼脂糖结合程度适中及较强的活性物质，分别用1.0和2.0 M NaCl洗脱。后者可能对应碱性成纤维细胞生长因子（碱性FGF），这与碱性FGF基因mRNA的表达一致。前者尚未完全鉴定，可能不是酸性FGF基因的产物。此外，MeWo细胞与FB2 AH7抗体呈阳性反应，因此表明它们能产生类似于黑色素瘤生长刺激活性（MGSA）的物质。MeWo细胞在无血清培养基中以细胞密度依赖的方式增殖，无论是在液体培养还是半固体培养中。碱性FGF、人及猪的PDGF可适度增强它们的分裂，但它们自身释放的因子却不能。然而，MeWo细胞上未检测到可证明的125I - PDGF结合位点，且它们对苏拉明生长抑制不敏感，这表明分泌的PDGF并非作为自分泌因子起作用。相反，MeWo黑色素瘤细胞的自主增殖可能是由于主要与细胞相关的碱性FGF和MGSA的协同作用。
