Stefanie A. E. Held

Recurrent genetic and chromosomal aberrations drive multiple myeloma (MM) pathogenesis. Among these, the t(4;14) translocation leads to overexpression of fibroblast growth factor receptor 3 (FGFR3) and is associated with poor prognosis. However, therapeutic approaches directly targeting FGFR3-driven myeloma progression remain limited. Here, we investigated the single-agent activity of ponatinib, a multikinase inhibitor, in MM. KMS18 and U266 myeloma cell lines were treated with ponatinib, and apoptosis induction, as well as VEGF and IL-6 secretion, was assessed. RNA sequencing of MM cells revealed pathway alterations induced by ponatinib treatment, which were subsequently validated by Western blot analysis. In vivo, mice inoculated with 5T33 myeloma cells received ponatinib, and survival was monitored. Notably, ponatinib exerted potent single-agent antimyeloma activity in an FGFR3-dependent manner by inducing apoptosis and suppressing VEGF and IL-6 secretion through inhibition of JAK/STAT, PI3K/AKT, and MAPK signaling. In vivo administration prolonged survival in myeloma-bearing mice. Collectively, our findings demonstrate the therapeutic efficacy of ponatinib in FGFR3-expressing MM beyond selective FGFR3 inhibition, suggesting that concurrent suppression of multiple signaling pathways is a critical mechanism of action. These results highlight the therapeutic potential of combined FGFR3-targeted strategies in multiple myeloma and provide a rationale for further clinical investigation.

Systemic candidiasis is a serious complication in immunocompromised patients, with Candida albicans emerging as the most common opportunistic pathogen. In various therapeutic treatment regimens the immunosuppressive agent Dexamethasone is used. Dexamethasone itself impairs the function of dendritic cells and reduces thereby their capacity for T-cell proliferation through the activation of Dectin-1 by β-glucans. In the present study, we reveal that these tolerogenic dendritic cells (Dex-DCs) have an increased secretion of IL-1ß and IL-18 when stimulated with β-glucans. We show an increased formation of ASC specks, which are crucial for recruiting pro-caspase-1, indicating an elevated inflammasomal activity. In line with this, we were able to show that treatment of tolerogenic dendritic cells with a NLRP3 inhibitor prior to Dectin-1 stimulation normalized the secretion of IL-1ß and IL-18. Furthermore, the addition of Caspase- and Syk-inhibitors led to diminished inflammasome activation as well as to less pyroptosis and apoptosis in response to β -glucan stimulation. Finally, we identified elevated production of reactive oxygen species (ROS) upon β-glucan stimulation in DexDCs as a possible mechanism for apoptosis induction as it can be reversed by the treatment with a specific anti-Dectin-1 antibody. Moreover, the underlying mechanism of the NLRP3 activation seems to be mediated through mitochondrial DNA release induced by mitochondrial ROS. Taken together, the present study demonstrates that Dectin-1 stimulation of tolerogenic DCs can result in severe pro-inflammatory responses due to cytokine release and subsequent NLRP3 inflammasome activation. In conclusion, the application of NLRP3 inflammasome inhibitors to patients treated with corticosteroids like Dexamethasone may significantly improve their outcome as they might be well-protected against local or severe systemic fungal infections.

Excellent pre-analytical stability is an essential precondition for reliable molecular profiling of circulating tumor DNA (ctDNA) in oncological diagnostics. Therefore, in vitro degradation of ctDNA and the additional release of contaminating genomic DNA from lysed blood cells must be prevented. Streck Cell-Free DNA blood collection tubes (cfDNA BCTs) have proposed advantages over standard K₂EDTA tubes, but mainly have been tested in healthy individuals. Blood was collected from cancer patients (n = 53) suffering from colorectal (n = 21), pancreatic (n = 11), and non-small-cell lung cancer (n = 21) using cfDNA BCT tubes and K₂EDTA tubes that were processed immediately or after 3 days (BCTs) or 6 hours (K₂EDTA) at room temperature. The cfDNA isolated from these samples was characterized in terms of yield using LINE-1 qPCR; the level of gDNA contamination; and the mutation status of KRAS, NRAS, and EGFR genes using BEAMing ddPCR. CfDNA yield and gDNA levels were comparable in both tube types and were not affected by prolonged storage of blood samples for at least 3 days in cfDNA BCTs or 6 hours in K₂EDTA tubes. In addition, biospecimens collected in K₂EDTA tubes and cfDNA BCTs stored for up to 3 days demonstrated highly comparable levels of mutational load across all respective cancer patient cohorts and a wide range of concentrations. Our data support the applicability of clinical oncology specimens collected and stored in cfDNA BCTs for up to 3 days for reliable cfDNA and mutation analyses.