Leukemic Stem/Progenitor Cells and their Microenvironment: The Role of Crucial Inflammatory Factors and Bone Marrow-Derived Mesenspheres

In this thesis, we aimed to investigate the role of inflammation in Myelofibrosis (MF) and the cross-talk between leukemic cells and their microenvironment in Acute Myeloid Leukemia (AML). In MF, we explored how inflammatory stimuli could modulate the malignant clone of HSCs. We observed potent effects of combinations of pro-inflammatory cytokines (IL-1β/ TNF-α/TIMP-1) on survival, clonogenic potential and migration of CD34+ cells isolated from MF patients at diagnosis or without treatment. Our data suggest that the malignant clone is driven not only by intrinsic properties but also by the interplay with the inflammatory microenvironment. In AML, we showed that an inhibitor of metalloproteinases (TIMP-1) could be considered as a ‘bad actor’ in the leukemic context. TIMP-1 modulates different pathways and we highlighted a cytokine function on AML blasts from AML patients at diagnosis. The survival, migration and proliferation of AML blasts was supported by TIMP-1, delineating a signaling pathway mediated through its receptor CD63 and PI3K/Akt/p21. In parallel, in a mouse model of AML MLL-AF9, we also explored the interaction between bone marrow stromal cells (BMSCs) and leukemic blasts. Through a novel system of co-cultures, we demonstrated the supportive/protective role of BMSCs, as non-adherent cells 'mesenspheres'. In this cross-talk we found a reduction of ROS levels and lipid peroxidation in leukemic blasts co-cultured with BMSCs, in stressed conditions. Importantly, we found also chemo-protective role of mesenspheres on leukemic cells mediated by mitochondria transfer. Surprisingly, this interaction could be explained as transfer of sources of anti-oxidants and nutrients between BMSCs and leukemic cells. Through the entire work, we shed new light on mechanisms and networks in haematological malignancies, such as MF and AML, driving toward novel therapeutic strategy to switch off an inflammatory microenvironment and key players of the malignant niches

The tissue inhibitor of metalloproteinases-1 (TIMP-1) promotes survival and migration of acute myeloid leukemia cells through CD63/PI3K/Akt/p21 signaling

We and others have shown that the Tissue Inhibitor of Metalloproteinases-1 (TIMP-1), a member of the inflammatory network exerting pleiotropic effects in the bone marrow (BM) microenvironment, regulates the survival and proliferation of different cell types, including normal hematopoietic progenitor cells. Moreover, TIMP-1 has been shown to be involved in cancer progression. However, its role in leukemic microenvironment has not been addressed. Here, we investigated the activity of TIMP-1 on Acute Myelogenous Leukemia (AML) cell functions. First, we found that TIMP-1 levels were increased in the BM plasma of AML patients at diagnosis. In vitro, recombinant human (rh)TIMP-1 promoted the survival and cell cycle S-phase entry of AML cells. These kinetic effects were related to the downregulation of cyclindependent kinase inhibitor p21. rhTIMP-1 increases CXCL12-driven migration of leukemic cells through PI3K signaling. Interestingly, activation of CD63 receptor was required for TIMP-1's cytokine/chemokine activity. Of note, rhTIMP-1 stimulation modulated mRNA expression of Hypoxia Inducible Factor (HIF)-1a, downstream of PI3K/Akt activation. We then co-cultured AML cells with normal or leukemic mesenchymal stromal cells (MSCs) to investigate the interaction of TIMP-1 with cellular component(s) of BM microenvironment. Our results showed that the proliferation and migration of leukemic cells were greatly enhanced by rhTIMP-1 in presence of AML-MSCs as compared to normal MSCs. Thus, we demonstrated that TIMP-1 modulates leukemic blasts survival, migration and function via CD63/PI3K/ Akt/p21 signaling. As a "bad actor" in a "bad soil", we propose TIMP-1 as a potential novel therapeutic target in leukemic BM microenvironment

Updates on the hematologic tumor microenvironment and its therapeutic targeting.

In this review article, we present recent updates on the hematologic tumor microenvironment following the 3rd Scientific Workshop on the Haematological Tumour Microenvironment and its Therapeutic Targeting organized by the European School of Hematology, which took place at the Francis Crick Institute in London in February 2019. This review article is focused on recent scientific advances highlighted in the invited presentations at the meeting, which encompassed the normal and malignant niches supporting hematopoietic stem cells and their progeny. Given the precise focus, it does not discuss other relevant contributions in this field, which have been the scope of other recent reviews. The content covers basic research and possible clinical applications with the major therapeutic angle of utilizing basic knowledge to devise new strategies to target the tumor microenvironment in hematologic cancers. The review is structured in the following sections: (i) regulation of normal hematopoietic stem cell niches during development, adulthood and aging; (ii) metabolic adaptation and reprogramming in the tumor microenvironment; (iii) the key role of inflammation in reshaping the normal microenvironment and driving hematopoietic stem cell proliferation; (iv) current understanding of the tumor microenvironment in different malignancies, such as chronic lymphocytic leukemia, multiple myeloma, acute myeloid leukemia and myelodysplastic syndromes; and (v) the effects of therapies on the microenvironment and some opportunities to target the niche directly in order to improve current treatments

Bone Marrow Mesenchymal Stem Cells Support Acute Myeloid Leukemia Bioenergetics and Enhance Antioxidant Defense and Escape from Chemotherapy.

Like normal hematopoietic stem cells, leukemic stem cells depend on their bone marrow (BM) microenvironment for survival, but the underlying mechanisms remain largely unknown. We have studied the contribution of nestin+ BM mesenchymal stem cells (BMSCs) to MLL-AF9-driven acute myeloid leukemia (AML) development and chemoresistance in vivo. Unlike bulk stroma, nestin+ BMSC numbers are not reduced in AML, but their function changes to support AML cells, at the expense of non-mutated hematopoietic stem cells (HSCs). Nestin+ cell depletion delays leukemogenesis in primary AML mice and selectively decreases AML, but not normal, cells in chimeric mice. Nestin+ BMSCs support survival and chemotherapy relapse of AML through increased oxidative phosphorylation, tricarboxylic acid (TCA) cycle activity, and glutathione (GSH)-mediated antioxidant defense. Therefore, AML cells co-opt energy sources and antioxidant defense mechanisms from BMSCs to survive chemotherapy.D.F. was supported by Associazione Italiana Ricerca sul Cancro (AIRCFellowship 20930 for Abroad) and scholarships from Società Italiana di Ematologia (SIE) and Associazione "Amici di Beat Leukemia Dr. Alessandro Cevenini ONLUS" and AIL Bologna ODV. A.S.-A. was supported by a European Hematology Association Research Fellowship and C.L.F-C. by a fellowship from Boehringer Foundation. This work was supported by core support grants from the Wellcome Trust (203151/Z/16/Z) and the MRC to the Cambridge Stem Cell Institute, and the Instituto de Salud Carlos III (ISCIII), Ministerio de Ciencia, Innovación y Universidades (MCNU) and Pro CNIC Foundation to CNIC, which is a Severo Ochoa Center of Excellence (SEV-2015-0505). This work was supported by MCNU (Plan Nacional grant SAF-2011-30308 to S.M.-F.; Ramón y Cajal Program grants RYC-2011-09726 to A.S.-A. and RYC-2009-04703 to S.M.-F.); Marie Curie Career Integration Program grants (FP7-PEOPLE-2011-RG-294262/294096) to A.S.-A. and S.M.-F.; Spanish Ministry of Science, Innovation and Universities (BIO2015-67580-P and PGC2018- 097019-B-I00), Carlos III Institute of Health-Fondo de Investigación Sanitaria grant PRB3(IPT17/0019 - ISCIII-SGEFI / ERDF, ProteoRed), Fundació MaratóTV3 (grant 122/C/2015) and “la Caixa” Banking Foundation (project code HR17-00247) to J.V.; the Medical Research Council grant MRC_MC_UU_12022/6 to C.F; an ERC award (COMAL: 647685) and a CRUK Programme Award to B.J.H; the Swiss National Science Foundation (SNF, 31003A_173224/1 & 31003A_173224/1) and the Gertrude von Meissner Foundation (Basel, Switzerland) to J.S.; ISCIII Spanish Cell Therapy Network TerCel, ConSEPOC-Comunidad de Madrid grant (S2010/BMD-2542), National Health Service Blood and Transplant (United Kingdom), European Union’s Horizon 2020 research (ERC- 2014-CoG-648765) and a Programme Foundation Award (C61367/A26670) from Cancer Research UK to S.M.-F., who was also supported in part by an International Early Career Scientist grant of the Howard Hughes Medical Institute

Denatonium as a Bitter Taste Receptor Agonist Modifies Transcriptomic Profile and Functions of Acute Myeloid Leukemia Cells

The contribution of cell-extrinsic factors in Acute Myeloid Leukemia (AML) generation and persistence has gained interest. Bitter taste receptors (TAS2Rs) are G protein-coupled receptors known for their primary role as a central warning signal to induce aversion toward noxious or harmful substances. Nevertheless, the increasing amount of evidence about their extra-oral localization has suggested a wider function in sensing microenvironment, also in cancer settings. In this study, we found that AML cells express functional TAS2Rs. We also highlighted a significant association between the modulation of some TAS2Rs and the poor-prognosis AML groups, i.e., TP53- and TET2-mutated, supporting a potential role of TAS2Rs in AML cell biology. Gene expression profile analysis showed that TAS2R activation with the prototypical agonist, denatonium benzoate, significantly modulated a number of genes involved in relevant AML cellular processes. Functional assay substantiated molecular data and indicated that denatonium reduced AML cell proliferation by inducing cell cycle arrest in G0/G1 phase or induced apoptosis via caspase cascade activation. Moreover, denatonium exposure impaired AML cell motility and migratory capacity, and inhibited cellular respiration by decreasing glucose uptake and oxidative phosphorylation. In conclusion, our results in AML cells expand the observation of cancer TAS2R expression to the setting of hematological neoplasms and shed light on a role of TAS2Rs in the extrinsic regulation of leukemia cell functions

Tamoxifen for the treatment of myeloproliferative neoplasms: a phase II clinical trial and exploratory analysis

Current therapies for myeloproliferative neoplasms (MPNs) improve symptoms but have limited effect on tumor size. In preclinical studies, tamoxifen restored normal apoptosis in mutated hematopoietic stem/progenitor cells (HSPCs). TAMARIN Phase-II, multicenter, single-arm clinical trial assessed tamoxifen’s safety and activity in patients with stable MPNs, no prior thrombotic events and mutated JAK2V617F, CALRins5 or CALRdel52 peripheral blood allele burden ≥20% (EudraCT 2015-005497-38). 38 patients were recruited over 112w and 32 completed 24w-treatment. The study’s A’herns success criteria were met as the primary outcome ( ≥ 50% reduction in mutant allele burden at 24w) was observed in 3/38 patients. Secondary outcomes included ≥25% reduction at 24w (5/38), ≥50% reduction at 12w (0/38), thrombotic events (2/38), toxicities, hematological response, proportion of patients in each IWG-MRT response category and ELN response criteria. As exploratory outcomes, baseline analysis of HSPC transcriptome segregates responders and non-responders, suggesting a predictive signature. In responder HSPCs, longitudinal analysis shows high baseline expression of JAK-STAT signaling and oxidative phosphorylation genes, which are downregulated by tamoxifen. We further demonstrate in preclinical studies that in JAK2V617F+ cells, 4-hydroxytamoxifen inhibits mitochondrial complex-I, activates integrated stress response and decreases pathogenic JAK2-signaling. These results warrant further investigation of tamoxifen in MPN, with careful consideration of thrombotic risk

Tamoxifen for the treatment of myeloproliferative neoplasms: A Phase II clinical trial and exploratory analysis

Current therapies for myeloproliferative neoplasms (MPNs) improve symptoms but have limited effect on tumor size. In preclinical studies, tamoxifen restored normal apoptosis in mutated hematopoietic stem/progenitor cells (HSPCs). TAMARIN Phase-II, multicenter, single-arm clinical trial assessed tamoxifen’s safety and activity in patients with stable MPNs, no prior thrombotic events and mutated JAK2V617F, CALRins5 or CALRdel52 peripheral blood allele burden ≥20% (EudraCT 2015-005497-38). 38 patients were recruited over 112w and 32 completed 24w-treatment. The study’s A’herns success criteria were met as the primary outcome ( ≥ 50% reduction in mutant allele burden at 24w) was observed in 3/38 patients. Secondary outcomes included ≥25% reduction at 24w (5/38), ≥50% reduction at 12w (0/38), thrombotic events (2/38), toxicities, hematological response, proportion of patients in each IWG-MRT response category and ELN response criteria. As exploratory outcomes, baseline analysis of HSPC transcriptome segregates responders and non-responders, suggesting a predictive signature. In responder HSPCs, longitudinal analysis shows high baseline expression of JAK-STAT signaling and oxidative phosphorylation genes, which are downregulated by tamoxifen. We further demonstrate in preclinical studies that in JAK2V617F+ cells, 4-hydroxytamoxifen inhibits mitochondrial complex-I, activates integrated stress response and decreases pathogenic JAK2-signaling. These results warrant further investigation of tamoxifen in MPN, with careful consideration of thrombotic risk

The “Vesicular Intelligence” Strategy of Blood Cancers

Blood cancers are a heterogeneous group of disorders including leukemia, multiple myeloma, and lymphoma. They may derive from the clonal evolution of the hemopoietic stem cell compartment or from the transformation of progenitors with immune potential. Extracellular vesicles (EVs) are membrane-bound nanovesicles which are released by cells into body fluids with a role in intercellular communication in physiology and pathology, including cancer. EV cargos are enriched in nucleic acids, proteins, and lipids, and these molecules can be delivered to target cells to influence their biological properties and modify surrounding or distant targets. In this review, we will describe the “smart strategy” on how blood cancer-derived EVs modulate tumor cell development and maintenance. Moreover, we will also depict the function of microenvironment-derived EVs in blood cancers and discuss how the interplay between tumor and microenvironment affects blood cancer cell growth and spreading, immune response, angiogenesis, thrombogenicity, and drug resistance. The potential of EVs as non-invasive biomarkers will be also discussed. Lastly, we discuss the clinical application viewpoint of EVs in blood cancers. Overall, blood cancers apply a ‘vesicular intelligence’ strategy to spread signals over their microenvironment, promoting the development and/or maintenance of the malignant clone