Gene expression study of anaplastic large cell lymphomas: cellular origin, pathogenesis and relation to Hodgkin lymphoma

Anaplastic large cell lymphoma (ALCL) is a main type of T cell lymphomas and comprises three distinct entities: systemic ALK+, systemic ALK- and cutaneous ALK- ALCL. Little is known about their pathogenesis and their cellular origin, and morphological and immunophenotypical overlap exists between ALK- ALCL and classical Hodgkin lymphoma (cHL). We conducted gene expression profiling of microdissected lymphoma cells of ALK+ and ALK- systemic ALCL, cutaneous ALCL and cHL, and of eight subsets of normal T and NK cells. The analysis supports a derivation of ALCL from activated T cells, but the lymphoma cells acquired a gene expression pattern hampering an assignment to a CD4+, CD8+ or CD30+ T cell origin. Indeed, ALCL display a general down-modulation of T cell characteristic molecules. All ALCL types show significant expression of NFB target genes and upregulation of genes involved in oncogenesis (e.g. EZH2). Surprisingly few genes are differentially expressed between systemic and cutaneous ALK- ALCL despite their different clinical behaviour, and between ALK- ALCL and cHL despite their different cellular origin. ALK+ ALCL are characterized by expression of genes regulated by pathways constitutively activated by ALK. This study provides multiple novel insights into the molecular biology and pathogenesis of ALCL.

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Eckerle S, Brune V, Döring C, Tiacci E, Bohle V, Sundström C, Kodet R, Paulli M, Falini B, Klapper W, Chaubert AB, Willenbrock K, Metzler D, Bräuninger A, Küppers R, Hansmann ML