Halting the FGF/FGFR axis leads to anti-tumor activity in Waldenström's Macroglobulinemia by silencing MYD88

The human fibroblast growth factor/fibroblast growth factor-receptor (FGF/FGFR) axis deregulation is largely involved in supporting the pathogenesis of hematologic malignancies, including Waldenström's Macroglobulinemia (WM). WM is still an incurable disease, and patients succumb due to disease progression. Therefore, novel therapeutics designed to specifically target deregulated signaling pathways in WM are required. We aimed to investigate the role of FGF/FGFR system blockade in WM by using a pan-FGF trap molecule (NSC12). Wide-transcriptome profiling confirmed inhibition of FGFR-signaling in NSC12-treated WM cells; unveiling a significant inhibition of MYD88 also confirmed at protein level. Importantly, the NSC12-dependent silencing of MYD88 was functionally active, as it led to inhibition of MYD88-driven pathways, such as BTK and SYK, as well as the MYD88-downstream target HCK. Of note, both canonical and non-canonical NFkB cascades were down-regulated in WM cells upon NSC12 treatment. Functional sequelae exerted by NSC12 in WM cells were studied, demonstrating significant inhibition of WM cell growth, induction of WM cell apoptosis, halting MAPK, JAK/STAT3 and PI3K-Akt pathways. Importantly, NSC12 exerted an anti-WM effect even in the presence of bone marrow microenvironment, both in vitro and in vivo. Our studies provide the evidence for using NSC12 as a specific FGF/FGFR system inhibitor, thus representing a novel therapeutic strategy in WM.