Pathogenesis of Hodgkin's lymphoma.

In Hodgkin's lymphoma (HL), the B cell origin of the tumour cells, the Hodgkin and Reed-Sternberg (HRS) cells, has been disclosed by molecular single cell analysis about 10 yr ago. This finding formed the basis for various studies aimed to better understand the pathogenesis of this peculiar malignancy and the pathophysiology of the HRS cells. Work of our groups in this regard was focussed recently on two main topics, namely the study of differential gene expression in HRS cells and the pathogenesis of composite lymphomas. Composite lymphomas are combinations of HL and B cell non-Hodgkin lymphomas, that turned out to be often clonally related. By molecular analysis of several composite lymphomas for potential transforming events, we identified examples of both shared as well as distinct transforming events. Comparing gene expression profiles of HL-derived cell lines with the corresponding profiles from other B cell lymphomas and normal B cell subsets revealed a global down-regulation of the B cell-specific gene expression signature in HRS cells. Moreover, we identifed aberrant expression and activity of multiple receptor tyrosine kinases in HRS cells of classical and to a lesser extend lymphocyte predominant HL, which appears to be a unique feature of HL, and may offer novel strategies for treatment.