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© The Author(s) 2021., [Background]: Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal cancer, requiring novel treatments to target both cancer cells and cancer stem cells (CSCs). Altered splicing is emerging as both a novel cancer hallmark and an attractive therapeutic target. The core splicing factor SF3B1 is heavily altered in cancer and can be inhibited by Pladienolide-B, but its actionability in PDAC is unknown. We explored the presence and role of SF3B1 in PDAC and interrogated its potential as an actionable target. [Methods]: SF3B1 was analyzed in PDAC tissues, an RNA-seq dataset, and publicly available databases, examining associations with splicing alterations and key features/genes. Functional assays in PDAC cell lines and PDX-derived CSCs served to test Pladienolide-B treatment effects in vitro, and in vivo in zebrafish and mice. [Results]: SF3B1 was overexpressed in human PDAC and associated with tumor grade and lymph-node involvement. SF3B1 levels closely associated with distinct splicing event profiles and expression of key PDAC players (KRAS, TP53). In PDAC cells, Pladienolide-B increased apoptosis and decreased multiple tumor-related features, including cell proliferation, migration, and colony/sphere formation, altering AKT and JNK signaling, and favoring proapoptotic splicing variants (BCL-XS/BCL-XL, KRASa/KRAS, Δ133TP53/TP53). Importantly, Pladienolide-B similarly impaired CSCs, reducing their stemness capacity and increasing their sensitivity to chemotherapy. Pladienolide-B also reduced PDAC/CSCs xenograft tumor growth in vivo in zebrafish and in mice. [Conclusion]. SF3B1 overexpression represents a therapeutic vulnerability in PDAC, as altered splicing can be targeted with Pladienolide-B both in cancer cells and CSCs, paving the way for novel therapies for this lethal cancer., This work has been supported by Spanish Ministry of Economy [MINECO; BFU2016–80360-R (to JPC)] and Ministry of Science and Innovation [MICINN; PID2019-105201RB-I00 (to JPC), PID2019-105564RB-I00 (to RML)]. Instituto de Salud Carlos III, co-funded by European Union (ERDF/ESF, “Investing in your future”) [FIS Grants PI17/02287 and PI20/01301 (to MDG), PI18/00757 (to BS,Jr); DTS Grant DTS20/00050 (to RML)); Postdoctoral Grant Sara Borrell CD19/00255 (to AIC); Predoctoral contract FI17/00282 (to EAP)]. Coordinated grant (GC16173694BARB) from the Fundación Asociación Española Contra el Cáncer (AECC) (to BS,Jr). Spanish Ministry of Universities [Predoctoral contracts FPU14/04290 (to SPA); FPU16/06190 (to VHA); FPU18/02275 (to RBE)]. Boehringer Ingelheim Fonds travel grant (EAP). Junta de Andalucía (BIO0139). GETNE2016 and GETNE2019 Research grants (to JPC); and CIBERobn. Associazione Italiana Ricerca Cancro (AIRC 5×1000 n. 12182); Fondazione Italiana Malattie Pancreas – Ministero Salute [FIMPCUP_J38D19000690001]; Fondazione Cariverona: Oncology Biobank Project “Antonio Schiavi” (prot.203885/2017).

Wnt/&beta, catenin signaling has been reported in Acute Myeloid leukemia, but little is known about its significance as a prognostic biomarker and drug target. In this study, we first evaluated the correlation between expression levels of Wnt molecules and clinical outcome. Then, we studied&mdash, in vitro and in vivo&mdash, the anti-leukemic value of combinatorial treatment between Wnt inhibitors and classic anti-leukemia drugs. Higher levels of &beta, catenin, Ser675-phospho-&beta, catenin and GSK-3&alpha, (total and Ser 9) were found in AML cells from intermediate or poor risk patients, nevertheless, patients presenting high activity of Wnt/&beta, catenin displayed shorter progression-free survival (PFS) according to univariate analysis. In vitro, many pharmacological inhibitors of Wnt signalling, i.e., LRP6 (Niclosamide), GSK-3 (LiCl, AR-A014418), and TCF/LEF (PNU-74654) but not Porcupine (IWP-2), significantly reduced proliferation and improved the drug sensitivity of AML cells cultured alone or in the presence of bone marrow stromal cells. In vivo, PNU-74654, Niclosamide and LiCl administration significantly reduced the bone marrow leukemic burden acting synergistically with Ara-C, thus improving mouse survival. Overall, our study demonstrates the antileukemic role of Wnt/&beta, catenin inhibition that may represent a potential new therapeutics strategy in AML.

International audience; In this study, we compared the overall gene and pathway expression profiles of HS-5 and HS-27A stromal cell lines with those of primary bone marrow MSCs to verify if they can be considered a reliable alternative tool for evaluating the contribution of MSCs in tumor development and immunomodulation. Indeed, due to their easier manipulation in vitro as compared to primary MSC cultures, several published studies took advantage of stromal cell lines to assess the biological mechanisms mediated by stromal cells in influencing tumor biology and immune responses. However, the process carried out to obtain immortalized cell lines could profoundly alter gene expression profile, and consequently their biological characteristics, leading to debatable results. Here, we evaluated the still undisclosed similarities and differences between HS-5, HS-27A cell lines and primary bone marrow MSCs in the context of tumor development and immunomodulation. Furthermore, we assessed by standardized immunological assays the capability of the cell lines to reproduce the general mechanisms of MSC immunoregulation. We found that only HS-5 cell line could be suitable to reproduce not only the MSC capacity to influence tumor biology, but also to evaluate the molecular mechanisms underlying tumor immune escape mediated by stroma cells. However, HS-5 pre-treatment with inflammatory cytokines, that normally enhances the immunosuppressive activity of primary MSCs, did not reproduce the same MSCs behavior, highlighting the necessity to accurately set up in vitro assays when HS-5 cell line is used instead of its primary counterpart.