Abstract
Although the over-expression of angiogenic factors is reported in diffuse large B-cell lymphoma (DLBCL), the poor response to anti-VEGF drugs observed in clinical trials suggests that angiogenesis in these tumours might be driven by VEGF-independent pathways. We show that sphingosine kinase-1 (SPHK1), which generates the potent bioactive sphingolipid sphingosine-1-phosphate (S1P), is over-expressed in DLBCL. A meta-analysis of over 2000 cases revealed that genes correlated with SPHK1 mRNA expression in DLBCL were significantly enriched for tumour angiogenesis meta-signature genes; an effect evident in both major cell of origin (COO) and stromal subtypes. Moreover, we found that S1P induces angiogenic signalling and a gene expression programme that is present within the tumour vasculature of SPHK1-expressing DLBCL. Importantly, S1PR1 functional antagonists, including Siponimod, and the S1P neutralising antibody, Sphingomab, inhibited S1P signalling in DLBCL cells in vitro. Furthermore, Siponimod, also reduced angiogenesis and tumour growth in an S1P-producing mouse model of angiogenic DLBCL. Our data define a potential role for S1P signalling in driving an angiogenic gene expression programme in the tumour vasculature of DLBCL and suggest novel opportunities to target S1P-mediated angiogenesis in patients with DLBCL.
Highlights
To explore the contribution of S1P signalling to angiogenesis in diffuse large B-cell lymphoma (DLBCL), we examined the expression of sphingosine kinase-1 (SPHK1), an enzyme which generates S1P from sphingosine
We found that SPHK1 was present in normal germinal centre (GC) B cells, and in the tumour cells of all 32 cases of DLBCL examined; including cases of both germinal centre B cell (GCB) and non-GCB type defined by the Hans algorithm [29] (Fig. 1c; Supplementary Table 2)
Previous studies have shown that targeting VEGF or its receptors can decrease tumour vascularization and reduce the growth of DLBCL-derived cell lines in vivo, a phase III trial of patients with aggressive NHL receiving RCHOP plus bevacizumab showed cardiotoxicity without improvement in progression-free survival [6]
Summary
There may be therapeutic benefits in targeting angiogenesis in DLBCL, the results of clinical trials of bevacizumab, a monoclonal antibody against VEGFA, have been disappointing. This drug was well tolerated when delivered as a single agent in relapsed DLBCL [4] or in combination with R-CHOP in first-line treatment [5], a phase III study of RA-CHOP (MAIN trial) was stopped due to increased cardiotoxicity in the absence of any significant impact on progression-free survival [6]. One explanation for the limited clinical efficacy of bevacizumab in DLBCL is that angiogenesis in DLBCL does not depend on VEGF; a contention supported by studies showing that VEGF expression does not correlate with micro-vessel density in DLBCL [7, 8]
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