ion levels of analysed genes as for e ample MYC or BCL9. Overall, we found that the e pression of most of the analyzed genes affected by IgM treatment is regulated through Erk1 2 activation accompanied by PI3K, TAK1 and partially to lower e tent by IKK2 and JNK. Erk and PI3K signalling is e clusive to the IgM gene module. These pathways are not affected by the other in vitro treat ments Activated NF ��B signalling seems to be less im portant for the IgM gene module. However, the analysis of CD40 mediated e pression of ICAM1, CD58, SLAMF3 or CCR7 revealed a strong involvement of NF ��B signalling. Our analysis sup ports the idea that the MAPK Erk pathway has a major impact on gene e pression in individual DLBCL with a high activation of the IgM gene module.

Therefore, it is reasonable to discuss the use of drugs targeting Erk1 2 for a subgroup of DLBCL characterized by a high activa tion of the IgM driven gene module. In a recent study, a molecular interaction of Erk and CHK2 was shown to affect DNA damage response and apoptosis of DLBCLs. AV-951 The recently described success of using Syk or Btk inhibitors or even mTOR and PKC inhibitors to treat DLBCL might be e plained by the activity of these signalling pathways. We are aware of the limitations of chemical kinase inhibitors to analyse path way elements. However, as comparable compounds are developed for clinical applications, the information drawn from studies integrating in vitro stimulations as pathway surrogates with gene e pression of individual lymphoma patients will provide comprehensive insights into potential targets for therapy.

In the future the uti lized in vitro stimulations can be used in combination with kinase inhibitors to delineate respective pathway interactions as for e ample a link between TAK1 and Erk1 2 or the different branches within PI3K signalling by applying also alternative e perimental approaches. Furthermore, our data indicate that a global investiga tion of kinase inhibitors and their combinations would be useful for a better understanding of gene regulation of global gene e pression changes and their integration with patients data. Conclusions We provide an in vitro model system to investigate path way activations qualitatively and quantitatively. B cell specific stimuli are used to identify gene e pression changes allowing to switch gene e pression from one steady state level characteristic for BL towards that of DLBCLs.

We defined the e tent to which specific signal ling pathways are responsible for differences in gene e pression that distinguish individual DLBCL. Gene modules of IL21, CD40L or IgM discriminate individual DLBCL, from each other, even though derived from different data sets. The greater an individual lymphoma e presses IgM target genes, the greater it will also e press IL21 or CD40L regulated genes. We have shown that mitogen activated protein kinase and phosphoinositide 3 kinase signaling are an import ant part of pathway networks describing difference