Rituximab, a CD20-specific antibody, is used with chemotherapy as a treatment for diffuse large B cell lymphoma (DLBCL). Although many patients benefit from the addition of rituximab to chemotherapy, a favourable response is not achieved in approximately 30% of cases. This sets a prerequisite to better understand the response and resistance mechanisms of rituximab. To do so, we analyzed the gene expression profiles of one rituximab unresponsive and two responsive DLBCL cell lines. In the responsive cells, rituximab affected the expression of genes related to apoptosis, lymphocyte signaling and cytokine response. Our data show rituximab-response to be associated with gene expression in classical signaling cascades involved in cell growth and differentiation, such as previously identified MAPK and completely novel Wnt and TGF-β pathways. Furthermore, our findings support earlier observations that rituximab can induce direct apoptosis and suggest the cell of origin to be associated with the cellular outcome. After validation of cellular results, we used a cohort of 233 R-CHOP treated DLBCL patients and found several of the most differentiating genes to have impact on survival. Together, the results provide an advanced picture of the CD20 mediated signaling of DLBCL cells and may provide new targets in future treatment protocols.

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