ABSTRACT
Loss of major histocompatibility complex class II (MHC II) expression is associated with poor patient outcome in diffuse large B-cell lymphoma (DLBCL). As MHC II molecules are lost with plasmacytic differentiation in normal cells, we asked whether MHC II loss in DLBCL is associated with an altered differentiation state. We used gene expression profiling, quantum dots, and immunohistochemistry to study the relationship between MHC II and plasma cell markers in DLBCL and plasmablastic lymphoma (PBL). Results demonstrate that MHC II(-) DLBCL immunophenotypically overlap with PBL and demonstrate an inverse correlation between MHC II and plasma cell markers MUM1, PRDM1/Blimp1, and XBP1s. In addition, MHC II expression is significantly higher in germinal center-DLBCL than activated B cell-DLBCL. A minor subset of cases with an unusual pattern of mislocalized punctate MHC II staining and intermediate levels of mRNA is also described. Finally, we show that PBL is negative for MHC II. The results imply a spectrum of MHC II expression that is more frequently diminished in tumors derived from B cells at the later stages of differentiation (with complete loss in PBL). Our observations provide a possible unifying concept that may contribute to the poor outcome reported in all MHC II(-) B-cell tumors.
Subject(s)
Cell Differentiation/genetics , Histocompatibility Antigens Class II/genetics , Lymphoma, Large B-Cell, Diffuse/genetics , Plasma Cells/metabolism , Analysis of Variance , Antigens, CD20/genetics , Antigens, CD20/metabolism , Biomarkers, Tumor/genetics , Biomarkers, Tumor/metabolism , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Gene Expression Profiling , Gene Expression Regulation, Neoplastic , HLA-DR Antigens/genetics , HLA-DR Antigens/metabolism , Histocompatibility Antigens Class II/metabolism , Humans , Immunohistochemistry , Interferon Regulatory Factors/genetics , Interferon Regulatory Factors/metabolism , Lymphoma, B-Cell/genetics , Lymphoma, B-Cell/metabolism , Lymphoma, Large B-Cell, Diffuse/metabolism , Oligonucleotide Array Sequence Analysis , Plasma Cells/pathology , Positive Regulatory Domain I-Binding Factor 1 , Regulatory Factor X Transcription Factors , Repressor Proteins/genetics , Repressor Proteins/metabolism , Transcription Factors/genetics , Transcription Factors/metabolism , X-Box Binding Protein 1ABSTRACT
Prostate cancer is a clinically heterogeneous and multifocal disease. More than 80% of patients with prostate cancer harbor multiple geographically discrete cancer foci at the time of diagnosis. Emerging data suggest that these foci are molecularly distinct consistent with the hypothesis that they arise as independent clones. One of the strongest arguments is the heterogeneity observed in the status of E26 transformation specific (ETS) rearrangements between discrete tumor foci. The clonal evolution of individual prostate cancer foci based on recent studies demonstrates intertumoral heterogeneity with intratumoral homogeneity. The issue of multifocality and interfocal heterogeneity is important and has not been fully elucidated due to lack of the systematic evaluation of ETS rearrangements in multiple tumor sites. The current study investigates the frequency of multiple gene rearrangements within the same focus and between different cancer foci. Fluorescence in situ hybridization (FISH) assays were designed to detect the four most common recurrent ETS gene rearrangements. In a cohort of 88 men with localized prostate cancer, we found ERG, ETV1, and ETV5 rearrangements in 51% (44/86), 6% (5/85), and 1% (1/86), respectively. None of the cases demonstrated ETV4 rearrangements. Mutual exclusiveness of ETS rearrangements was observed in the majority of cases; however, in six cases, we discovered multiple ETS or 5' fusion partner rearrangements within the same tumor focus. In conclusion, we provide further evidence for prostate cancer tumor heterogeneity with the identification of multiple concurrent gene rearrangements.
