Objective: Gene expression profiling of diffuse large B-cell lymphoma (DLBCL) of different immunophenotypes.
Methods: The study included 156 cases of DLBCL, which were subclassified by immunohistochemistry including CD10, bcl-6 and MUM1. Affymetrix U133 plus2.0 oligonucleotide microarrays were used to obtain differential gene expression profiling of 9 DLBCL (3 representative cases from each immunophenotypical group) and 3 tonsils. Clinical stages of all 9 lymphomas were Ann Arbor stage IV.
Results: The immunohistochemistry subclassified 156 cases of DLBCL into 3 groups: CD10(+) and/or bcl-6(+), MUM1(-) (group 1); CD10(+) and/or bcl-6(+), MUM1(+) (group 2); CD10(-) and bcl-6(-), MUM1(+) (group 3). By gene expression array, 9 lymphomas and 3 tonsils were clustered in an unsupervised fashion into 4 groups (A, B, C and D), which were in accordance with the immunophenotypical groups (group 1, 2, 3 and normal). A total of 81 genes were markedly decreased and 86 genes were over-expressed in all DLBCL groups. Although Group B lymphomas showed mixed immunophenotypical features of both germinal center B-cell-like DLBCL (Group A) and activated B-cell-like lymphomas (Group C), gene profile clustering showed that Group B was dissimilar to Group A or Group C, with 45 over-expressed and 27 uniquely expressed genes.
Conclusions: Gene expression profiling indicates that DLBCL can be subgrouped at the molecular level and can be identified by immunophenotyping. The gene expression profile of Group B lymphomas suggests that factors other than the cell-of-origin may contribute to the pathogenesis of DLBCL.