IntroductionHodgkin lymphoma (HL) is characterized by a minority of neoplastic cells, the Hodgkin and Reed-Sternberg cells (HRS cells), and an extensive inflammatory background. Many studies have documented that HL is associated with disturbed cytokine production. 1 Cytokine and chemokine production may not only promote growth of HRS cells and help to evade immune surveillance, but also cause the characteristic histology and the clinical symptoms of HL. 2 Cross-talk between HRS cells and surrounding lymphocytes has been studied for many years, and this interaction is regarded to be important for the pathogenesis of HL.The application of proteomics techniques has been proven to be a powerful tool for the identification of new biomarkers involved in pathogenesis of many diseases (reviewed by Hanash 3 ). Some studies on hematologic malignancies using proteomics approaches have been reported, 4,5 but application of proteomics technology to HL is still limited. Fujii et al compared HL cell line proteome to anaplastic large cell lymphoma (ALCL) and non-Hodgkin lymphoma (NHL) using a 2-dimensional difference gel electrophoresis approach of total cell lysates. 6,7 HL expressed higher levels of pyridoxine-5Ј-phosphate oxidase, vinculin, dihydropyrimidinase-related protein-2 and NADHubiquinone oxidoreductase compared with ALCL. In comparison to NHL cell lines, HL cell lines showed higher expression of pyridoxine-5Ј-phosphate oxidase, ␥-enolase, vinculin, vimentin, galectin-1, annexin A5, and protein kinase C substrate. 7 Carvalho et al identified changes in the spectrum using quadrupole-time-of-flight hybrid mass spectrometer in serum of HL patients compared with normal controls, but no further protein identification was performed. 8 Overall, only very limited proteomics data are available for HL.To gain more insight into the proteins secreted by HRS cells that might be involved in the cross-talk with infiltrating lymphocytes or might serve as tumor biomarkers, the secretome of HL cell lines was determined in cell culture supernatant. Protein identification was performed by nanoscale reversed-phase liquid chromatography tandem mass spectrometry (LC-MS/MS) after 1D-SDS-PAGE fractionation. Proteins related to immune response were validated in cell culture supernatant and patient plasma by enzyme-linked immunosorbent assay (ELISA) and in tumor tissues by immunohistochemistry.
Methods
Cell lines and cultureThe HL cell lines L1236 and KMH2 were established from HL patients with mixed cellularity subtype, L428 from nodular sclerosis subtype and DEV from nodular lymphocyte predominant HL (NLPHL) subtype. They were cultured in RPMI 1640 medium (Lonza Walkersville, Walkersville, MD) supplemented with fetal calf serum (Lonza Walkersville). For analysis of secreted proteins, to avoid the masking effects of high-abundance serum proteins in the culture medium, the cells were washed 3 times with RPMI 1640 medium to deplete all serum proteins, and cultured in RPMI 1640 medium without serum for 24 hours. Under these conditions, cell via...
