de Vries T J, Verheijen J H, de Bart A C, Weidle U H, Ruiter D J, van Muijen G N
Department of Pathology, University Hospital, Nijmegen, The Netherlands.
Cancer Res. 1996 Mar 15;56(6):1432-9.
We recently found that the proteins of the proteolytic system of plasminogen activation emerge in late stages of melanocytic tumor progression. A large body of evidence suggests a role for two proteins, the low-density lipoprotein receptor-related protein (LRP)/alpha(2)-macroglobulin receptor and its receptor-associated protein (RAP), in the internalization of components of the plasminogen activation system. Here, we present data on the presence of these two proteins in human melanoma cell lines which differ in metastatic capacity, their corresponding xenografts, and in cutaneous melanocytic lesions. With flow cytometry, we found surface expression of LRP to be restricted to urokinase plasminogen activator, producing highly metastatic cell lines. These cell lines also produce higher levels of LRP mRNA, whereas RAP mRNA and protein are expressed at equal levels in all cell lines and not expressed at the cell surface. Xenografts of cell lines producing high levels of LRP remarkably contain only a small fraction of LRP-positive tumor cells. Using immunohistochemistry on frozen sections of 107 human melanocytic lesions comprising the various stages of melanocytic tumor progression, we found that expression of both LRP and RAP decreased in tumor progression. Furthermore, we noted that LRP and RAP are coexpressed within the same lesion. Using immunofluorescence double staining, we found that LRP and RAP colocalize in the same cells in the lesions studied and in the same cell structures in the cell lines studied. In conclusion, our results indicate that LRP and RAP are coordinately expressed in a decreased fashion in melanocytic tumor progression. Based on the staining results in xenografts and in human melanocytic lesions, we conclude that a strong correlation between expression of LRP and urokinase-type plasminogen activator seems not to exist in in vivo melanomas.
我们最近发现，纤溶酶原激活蛋白水解系统的蛋白质出现在黑素细胞肿瘤进展的晚期。大量证据表明，两种蛋白质，即低密度脂蛋白受体相关蛋白（LRP）/α2-巨球蛋白受体及其受体相关蛋白（RAP），在纤溶酶原激活系统成分的内化过程中发挥作用。在此，我们展示了这两种蛋白质在转移能力不同的人黑素瘤细胞系、其相应的异种移植物以及皮肤黑素细胞病变中的存在情况。通过流式细胞术，我们发现LRP的表面表达仅限于产生高转移性细胞系的尿激酶型纤溶酶原激活剂。这些细胞系还产生更高水平的LRP mRNA，而RAP mRNA和蛋白质在所有细胞系中的表达水平相同，且在细胞表面不表达。产生高水平LRP的细胞系的异种移植物中，显著仅含有一小部分LRP阳性肿瘤细胞。对107例涵盖黑素细胞肿瘤进展各个阶段的人黑素细胞病变的冰冻切片进行免疫组织化学分析，我们发现LRP和RAP的表达在肿瘤进展过程中均降低。此外，我们注意到LRP和RAP在同一病变中共同表达。通过免疫荧光双重染色，我们发现LRP和RAP在所研究的病变细胞以及所研究的细胞系的相同细胞结构中位于同一细胞内。总之，我们的结果表明，在黑素细胞肿瘤进展过程中，LRP和RAP以协同降低的方式表达。基于异种移植物和人黑素细胞病变中的染色结果，我们得出结论，在体内黑素瘤中，LRP与尿激酶型纤溶酶原激活剂的表达之间似乎不存在强相关性。
