Gene Expression Profiling of Microdissected Hodgkin Reed Sternberg Cells: Molecular Subtypes and Treatment Outcome Correlations

Abstract 268 INTRODUCTION: Classical Hodgkin lymphoma (cHL) is unique among lymphomas due to the scarcity of the malignant Hodgkin Reed Sternberg (HRS) cells, which are derived from clonal germinal center B cells. Investigations using laser capture microdissection permit more detailed analysis of these cells. However, most recent studies were limited by low case numbers and lack of available clinical data. PATIENTS AND METHODS: We studied 29 cases of cHL and the 5 HL lines KMH2, HDLM2, L428, L540, and L1236 by gene expression profiling. All patients were treated at the BC Cancer Agency between 1984 and 2006 and received at least 4 cycles of polychemotherapy and stage-dependent radiotherapy. The cohort also included 5 biopsies taken at relapse. Treatment failure was defined as disease progression or relapse at any time (n=14) after initiation of treatment; treatment success as absence of progression (n=15). We used laser microdissection (Molecular Machines & Industries Cellcut with Nikon Eclipse TE2000-S microscope) to study the enriched HRS cell compartment separately from the microenvironment. RNA extraction was performed on pools of 1000 microdissected HRS cells in each case. Gene expression profiles were generated using Affymetrix HG UA133 2.0 Plus arrays using two-cycle labeling reactions. HRS cell profiles were compared to microdissected germinal centers (GC), and HL cell line profiles compared to enriched tonsillar CD77+ centroblasts (MACS cell separation, Miltenyi). Furthermore, we compared gene expression profiles of treatment failures to those of treatment successes. RESULTS: We identified 1342 differentially expressed probesets (fold change >5, False Discovery Rate (FDR) adjusted p value 5, FDR-adjusted p value DISCUSSION: Using microdissection of HRS cells in a large number of cases we were able to further characterize the unique expression program of HL and refine the data inventory about dysregulated cellular functions and pathways in this disease. Overexpression of genes associated with NFκB, complement and hematopoietic progenitor cells proliferation correlate strongly with treatment failure. Further study using immunohistochemistry is currently ongoing to validate these findings and to develop clinically useful biomarkers. Disclosures: Gascoyne: Roche Canada: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.