Napoletano Chiara, Rughetti Aurelia, Agervig Tarp Mads P, Coleman Julia, Bennett Eric P, Picco Gianfranco, Sale Patrizio, Denda-Nagai Kaori, Irimura Tatsuro, Mandel Ulla, Clausen Henrik, Frati Luigi, Taylor-Papadimitriou Joyce, Burchell Joy, Nuti Marianna
Department of Experimental Medicine, University of Rome Sapienza, IRCCS San Raffaele Pisana, Rome, Italy.
Cancer Res. 2007 Sep 1;67(17):8358-67. doi: 10.1158/0008-5472.CAN-07-1035.
The type of interaction between tumor-associated antigens and specialized antigen-presenting cells such as dendritic cells (DCs) is critical for the type of immunity that will be generated. MUC1, a highly O-glycosylated mucin, is overexpressed and aberrantly glycosylated in several tumor histotypes. This results in the expression of tumor-associated glycoforms and in MUC1 carrying the tumor-specific glycan Tn (GalNAcalpha1-O-Ser/Thr). Glycopeptides corresponding to three tandem repeats of MUC1, enzymatically glycosylated with 9 or 15 mol of GalNAc, were shown to specifically bind and to be internalized by immature monocyte-derived DCs (iDCs). Binding required calcium and the GalNAc residue and was competed out by GalNAc polymer and Tn-MUC1 or Tn-MUC2 glycopeptides. The macrophage galactose-type C-type lectin (MGL) receptor expressed on iDCs was shown to be responsible for the binding. Confocal analysis and ELISA done on subcellular fractions of iDCs showed that the Tn-MUC1 glycopeptides colocalized with HLA class I and II compartments after internalization. Importantly, although Tn-MUC1 recombinant protein was bound and internalized by MGL, the glycoprotein entered the HLA class II compartment, but not the HLA class I pathway. These data indicate that MGL expressed on iDCs is an optimal receptor for the internalization of short GalNAcs carrying immunogens to be delivered into HLA class I and II compartments. Such glycopeptides therefore represent a new way of targeting the HLA class I and II pathways of DCs. These results have possible implications in designing cancer vaccines.
肿瘤相关抗原与诸如树突状细胞（DCs）等特殊抗原呈递细胞之间的相互作用类型，对于即将产生的免疫类型至关重要。MUC1是一种高度O-糖基化的粘蛋白，在几种肿瘤组织类型中过表达且糖基化异常。这导致肿瘤相关糖型的表达以及MUC1携带肿瘤特异性聚糖Tn（GalNAcα1-O-Ser/Thr）。与MUC1的三个串联重复序列相对应的糖肽，经9或15摩尔GalNAc酶促糖基化后，显示能特异性结合未成熟单核细胞衍生的DCs（iDCs）并被其内化。结合需要钙和GalNAc残基，且被GalNAc聚合物以及Tn-MUC1或Tn-MUC2糖肽竞争抑制。iDCs上表达的巨噬细胞半乳糖型C型凝集素（MGL）受体被证明负责这种结合。对iDCs亚细胞组分进行的共聚焦分析和ELISA表明，内化后Tn-MUC1糖肽与HLA I类和II类区室共定位。重要的是，尽管Tn-MUC1重组蛋白被MGL结合并内化，但该糖蛋白进入了HLA II类区室，而非HLA I类途径。这些数据表明，iDCs上表达的MGL是携带免疫原的短GalNAcs内化的最佳受体，这些免疫原将被递送至HLA I类和II类区室。因此，此类糖肽代表了一种靶向DCs的HLA I类和II类途径的新方法。这些结果在设计癌症疫苗方面可能具有重要意义。
