1 The CXCR 4-CXCL 12-axis is of prognostic relevance in 2 DLBCL and its antagonists exert pro-apoptotic effects 3 in vitro 4

In tumour cells of more than 20 different cancer types, the CXCR4-CXCL12-axis is 26 involved in multiple key processes including proliferation, survival, migration, invasion, and 27 metastasis. Since data on this axis in diffuse large B cell lymphoma (DLBCL) are inconsistent and 28 limited, we comprehensively studied the CXCR4-CXCL12-axis in our DLBCL cohort as well as the 29 effects of CXCR4 antagonists on lymphoma cell lines in vitro. In DLBCL, we observed a 140-fold 30 higher CXCR4 expression compared to non-neoplastic controls. Interestingly, high expression of 31 CXCR4 was associated with poor clinical outcome. Furthermore, in corresponding bone marrow 32 biopsies, we observed a correlation of CXCL12 expression and lymphoma infiltration rate as well 33 as a reduction of CXCR4 expression in remission of bone marrow involvement after treatment. 34 Furthermore, the niacin derivate of the CXCR4 antagonist AMD070, which was synthesized by us, 35 demonstrated stronger pro-apoptotic effects than AMD070 in vitro and induced expression of 36 certain pro-apoptotic genes in CXCR4 positive lymphoma cell lines. Finally, WK1 treatment 37 resulted in reduced expression of JNK-, ERK1/2and NFκB/BCR-target genes. These data indicate 38 that the CXCR4-CXCL12-axis impacts the pathogenesis of DLBCL and represents a potential 39 therapeutic target in aggressive lymphomas. 40