Hematopoietic Stem Cell Support Research Articles

Intensive salvage chemotherapy with VDTPACE or mCBAD followed by hematopoietic stem-cell support for refractory/relapsed multiple myeloma.

Triple- and quad-refractory multiple myeloma patients usually have an aggressive course and a poor prognosis. Available therapeutic options are scarce. The objective of the current study was to evaluate responses and toxicities of VDTPACE or mCBAD with hematopoietic stem-cell support as a bridge to subsequent therapies in patients with refractory/relapsed multiple myeloma. Thirteen patients were included (11 mCBAD, 2 VDTPACE), and 21 cycles of chemotherapy with hematopoietic stem-cell support were delivered. Mean number of previous therapies was 4.8. Stem cells were infused on a median day 9.9 after chemotherapy. Mean time to neutrophil recovery was 18.2 days in patients receiving the first cycle and 15.9 following subsequent cycles. Before therapy, most patients were in PD (77%), PR (15%), or VGPR (8%). Following treatment, the best responses achieved were PR (46%), VGPR (46%), and CR (8%). Median overall and progression-free survivals were 17 and 9 months. There has been no case of non-relapse mortality. In the 21 cycles, the main complications were infectious. Intensive chemotherapy can decrease disease burden in patients with relapsed/refractory MM, and stem-cell support can successfully decrease toxicities and treatment-related mortality associated with these regimens and may be a good bridging option.

Steady-State Versus Chemotherapy-Based Stem Cell Mobilization in Multiple Myeloma: A Single-Center Study to Analyze Efficacy and Safety.

High-dose chemotherapy followed by autologous hematopoietic stem cell support is recommended in the treatment of eligible multiple myeloma (MM) patients. The aim of this study was to compare the efficacy and safety of steady-state versus chemotherapy-based stem cell mobilization in our Hungarian patient population. The subjects were 210 MM patients who underwent stem cell mobilization procedure between 2018 and 2022. Solo granulocyte colony-stimulating factor (G-CSF) was administered in 104 cases, while 106 patients received chemotherapy which was followed by G-CSF administration. We evaluated the ratio of successful mobilizations, the amount of collected stem cells, the incidence of infections and cost-effectivity in the two groups. In the steady-state group, there was a significantly higher need for plerixafor (45% vs. 13%, P < 0.001), unsuccessful stem cell mobilization was more frequent (11% vs. 3%, P = 0.024) and the mean amount of collected stem cells was lower (6.9 vs. 9.8 × 106, P < 0.001) than in the chemotherapy group. However, infections were less frequent (4% vs. 27%, P < 0.001) and the number of days spent in hospital was significantly lower (6 vs. 14 days, P < 0.001). Plerixafor was more frequently administered in those who had received lenalidomide or daratumumab than in those who had been treated with other regimens (41% vs. 23%, P = 0.007 and 78% vs. 23%, P < 0.001, respectively). Steady-state mobilization is a safe method; however, the higher rate of plerixafor administration and unsuccessful attempts may question its superiority to chemomobilization.

Restrictive versus liberal red blood cell transfusion strategies for people with haematological malignancies treated with intensive chemotherapy or radiotherapy, or both, with or without haematopoietic stem cell support.

Restrictive versus liberal red blood cell transfusion strategies for people with haematological malignancies treated with intensive chemotherapy or radiotherapy, or both, with or without haematopoietic stem cell support.

Cigarette smoke impairs the hematopoietic supportive property of mesenchymal stem cells via the production of reactive oxygen species and NLRP3 activation

BackgroundMesenchymal stem cells (MSCs) play important roles in tissue homeostasis by providing a supportive microenvironmental niche for the hematopoietic system. Cigarette smoking induces systemic abnormalities, including an impeded recovery process after hematopoietic stem cell transplantation. However, the role of cigarette smoking-mediated alterations in MSC niche function have not been investigated.MethodsIn the present study, we investigated whether exposure to cigarette smoking extract (CSE) disrupts the hematopoietic niche function of MSCs, and pathways impacted. To investigate the effects on bone marrow (BM)-derived MSCs and support of hematopoietic stem and progenitor cells (HSPCs), mice were repeatedly infused with the CSE named 3R4F, and hematopoietic stem and progenitor cells (HSPCs) supporting function was determined. The impact of 3R4F on MSCs at cellular level were screened by bulk-RNA sequencing and subsequently validated through qRT-PCR. Specific inhibitors were treated to verify the ROS or NLRP3-specific effects, and the cells were then transplanted into the animal model or subjected to coculture with HSPCs.ResultsBoth direct ex vivo and systemic in vivo MSC exposure to 3R4F resulted in impaired engraftment in a humanized mouse model. Furthermore, transcriptomic profile analysis showed significantly upregulated signaling pathways related to reactive oxygen species (ROS), inflammation, and aging in 3R4F-treated MSCs. Notably, ingenuity pathway analysis revealed the activation of NLRP3 inflammasome signaling pathway in 3R4F-treated MSCs, and pretreatment with the NLRP3 inhibitor MCC950 rescued the HSPC-supporting ability of 3R4F-treated MSCs.ConclusionIn conclusion, these findings indicate that exposure to CSE reduces HSPCs supportive function of MSCs by inducing robust ROS production and subsequent NLRP3 activation.

Identifying Bone Marrow Microenvironmental Populations in Myelodysplastic Syndrome and Acute Myeloid Leukemia.

The bone marrow microenvironment consists of distinct cell populations, such as mesenchymal stromal cells, endothelial cells, osteolineage cells, and fibroblasts, which provide support for hematopoietic stem cells (HSCs). In addition to supporting normal HSCs, the bone marrow microenvironment also plays a role in the development of hematopoietic stem cell disorders, such as myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). MDS-associated mutations in HSCs lead to a block in differentiation and progressive bone marrow failure, especially in the elderly. MDS can often progress to therapy-resistant AML, a disease characterized by a rapid accumulation of immature myeloid blasts. The bone marrow microenvironment is known to be altered in patients with these myeloid neoplasms. Here, a comprehensive protocol to isolate and phenotypically characterize bone marrow microenvironmental cells from murine models of myelodysplastic syndrome and acute myeloid leukemia is described. Isolating and characterizing changes in the bone marrow niche populations can help determine their role in disease initiation and progression and may lead to the development of novel therapeutics targeting cancer-promoting alterations in the bone marrow stromal populations.

Therapeutic Modulation of the Marrow Microenvironment in MDS: A Phase I Trial of Abaloparatide and Bevacizumab

Background: The bone marrow microenvironment (BMME), including mesenchymal stromal cells (MSCs) and osteolineage cells, vascular endothelial growth factor (VEGF) signaling, and marrow angiogenesis, is altered in myelodysplastic syndromes (MDS). BMME manipulation represents a novel therapeutic strategy for MDS. Preclinical studies have demonstrated that parathyroid hormone (PTH) increases MSC and osteoblast support of hematopoietic stem cells and remodels marrow vascularity. This effect can be augmented with the addition of bevacizumab (BEV), which also decreases angiogenesis. Here we report the results of a phase 1 study of abaloparatide (ABL), a PTH-related protein analog, plus BEV in patients with MDS. Methods: Eligible patients were ≥ age 18 with MDS or non-proliferative chronic myelomonocytic leukemia and at least one cytopenia. Those categorized as very-low to intermediate risk per the Revised International Prognostic Scoring System (IPSS-R) who were treatment-naive or had received only prior growth factors were eligible. Patients of all risk categories who had not responded to disease modifying agents were also eligible. Prior therapies were stopped at least 14-days before study start. Patients received one 28-day cycle of ABL (80 mcg/day self-injected) followed by three 28-day cycles of ABL + BEV (5 mg/kg on days 1 and 15). Bone marrow samples were collected at baseline, after cycles 1 and 4, and 3 months after treatment completion. The primary endpoint was the rate of treatment-limiting toxicities (TLTs). Response rates, impact of therapy on BMME cell populations, and effect on health-related quality of life (HRQoL) and geriatric assessment were additional endpoints. Results: Nineteen patients were enrolled and treated. The majority (n=13) received prior therapy, most commonly with an erythropoietin stimulating agent (ESA; 77%). Typical molecular heterogeneity was present and included mutations in SF3B1 (44%), TET2 (33%), ASXL1 (22%), and DNMT3A (22%). No TP53 mutations were noted. Additional baseline characteristics are outlined in Table 1. Three patients (16%) experienced a TLT: a grade 3 infusion-related reaction and grade 2 fatigue with orthostatic hypotension attributed to ABL, and a grade 3 colonic perforation possibly attributed to BEV. There were no other grade 3 events related to treatment (TRAEs). Frequent (≥15%) TRAEs were: back pain (n=6), chills (n=3), and epistaxis (n=3). Analysis of bone marrow samples revealed a significant increase in mean MSC colony forming units (CFU-Fs) after cycle 1 of ABL compared to baseline (20.7 ± 5.8 vs 36.5 ± 6.4 CFU-F per 1x106 cells, p=0.004). This increase was not maintained with the addition of BEV. Of the 17 patients evaluable after at least 2 cycles on study, 15 (88%) had stable disease and 2 (12%) had progression. Five of 6 patients (83%) with MDS with excess blasts 2, prior hypomethylating agents, and/or high to very-high IPSS-R maintained stable disease over 7 months of follow up. The sixth patient achieved a neutrophil response by 2006 International Working Group criteria after 8 weeks of therapy. In the subset of patients with baseline neutropenia (n=4) there was a significant increase in absolute neutrophil count (ANC) after 8 weeks on study (0.89 ± 0.26 vs 1.28 ± 0.32 103 cells/µL, p=0.04). All patients with baseline neutropenia or thrombocytopenia that had improved ANC (n=4) or platelet counts (n=3), respectively, over the first 8 weeks of treatment, had increased CFU-Fs after cycle 1. Three patients (18%) had decreased transfusion needs over the first 8 weeks despite discontinuation of prior ESAs; all 3 also demonstrated increases in CFU-Fs after cycle 1. HRQoL and geriatric assessments were stable throughout the study. Conclusions: ABL + BEV therapy is safe and well-tolerated in MDS. A significant increase in MSCs was noted following single-agent ABL for 4 weeks, suggesting BMME remodeling. This corresponded with significant early improvements in ANC values and transfusion requirements during the first 8 weeks of therapy in some patients. Prolonged stable disease was maintained in a majority of patients, including several with high-risk clinical features. These data suggest successful manipulation of the BMME with effects on hematopoiesis, and warrant further investigation of longer ABL monotherapy as a new treatment paradigm for patients with MDS. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Human NGFR+/VCAM-1+/Mcam+ Bone Marrow-Derived Stromal Cells (NVML) Provide Enhanced Support for Normal Hematopoiesis and Are Disrupted in Myelodysplastic Syndrome

The bone marrow microenvironment (BMME) is indispensable for support of normal and malignant hematopoiesis. Mesenchymal stem/stromal cells (MSCs) give rise to multiple non-hematopoietic components that play a pivotal role in myelodysplastic syndromes (MDS). However, therapeutic targeting of MSCs has been challenging, in part due to the limited definition of the heterogeneity of MSC populations from human bone marrow. Using bone marrow from normal healthy controls obtained through aspirates rather than surgical specimens (normal bone marrow; NBM), we successfully identified two novel distinctive subsets of human MSCs by combining three MSC cell surface markers: CD271/ Nerve Growth Factor Receptor (NGFR), CD106/ Vascular Cell Adhesion Molecule-1 (VCAM-1) and CD146/ Melanoma Cell Adhesion Molecule (MCAM). We first isolated three BM-derived non-endothelial lineage (CD45/CD235ab/CD34-CD31-) cell populations from NBM: CD271+/CD146- (NGFR+/Lineage- cells: NLCs), CD271+/CD146+/CD106+ (NGFR+/VCAM1+/MCAM+/Lineage- NVML cells), and CD271+/CD146+/CD106- (NGFR+/MCAM+/Lineage-; NML cells). Gene profiling by RNA-seq revealed that NLCs and NVML cells represent distinct populations, whereas NML cells are a transitional population. Transcriptional analysis suggested that NVML cells, compared to NLCs, have stem cell characteristics, including quiescence and multipotentiality, and express higher levels of key genes critical for the support of hematopoietic stem and progenitor cells (HSPCs), including CXCL12 (SDF1A), Kit ligand (KITL) and Angiopoietin-1 (ANGPT1). This signature was compatible with BM-derived Leptin receptor+ MSCs with high capacity of supporting HSPCs based on previously reported single cell RNA-seq analysis in mice (Baryawno et al 2019, Cell). Consistent with their transcriptome, functional analysis showed that NVML cells had higher colony forming units (CFU-F) and tri-lineage differentiation capacity compared to NLCs. Normal NLCs or NVML cells were also co-cultured with NBM or human MDS cell line (MDS-L) in the absence of cytokines/chemokines to evaluate the ability of these novel human MSC populations to provide a supportive niche for HSPCs. NVML cells provided increased support for normal hematopoietic progenitors compared to baseline and NLCs (fold increase over baseline 1.78±0.78(NLCs, p<0.05) vs 2.71±1.71(NVML cells, p<0.001), NLCs vs NVML cells, p<0.05). In contrast, NLCs showed increased ability of supporting MDS-L (fold increase over baseline 2.35±1.35 (NLCs, p<0.01) vs 1.5±0.5 (NVML cells, p=0.26), NLCs vs NVML cells, p=0.053). We next profiled the transcriptome of NLCs and NVML cells from 17 patients with MDS in comparison with age-matched healthy controls (n=8, >50 years old). In spite of mutational heterogeneity in this MDS patient cohort, principal component analysis (PCA) revealed a distinctive shift of MDS-derived NVML cells compared to controls. For upregulated transcripts, pathways and gene ontology analyses of differentially expressed genes in NVML cells from MDS compared to controls identified signals related to DNA/RNA processing, while most of the down-regulated transcripts identified cytokines/chemokines critical for HSPCs. When the transcriptional profiles of NVML cells from MDS patients were compared to age-matched NVML controls, critical genes for HSPC support highly expressed in normal NVML (e.g. SDF1A, ANGPT1) were significantly down-regulated. Moreover, the transcriptional signature of NVML cells from MDS patients was similar to that of normal NLCs. Together these data suggest that, in spite of mutational heterogeneity in the hematopoietic clone, MDS may differentially impact these novel human marrow MSC subsets, decreasing normal HSPC support by disrupting NVML cells, which acquired the transcriptional signature of MDS-supportive normal NLCs. These data highlight a novel paradigm to enrich key human niche cells that provide support for HSPCs. Moreover, our data suggest that these human MSC cell subsets are differentially disrupted in MDS. Mutation specific effects are also likely to impact MDS-dependent disruption of the BMME. Therefore, our novel strategy to enrich critical human BM MSC subsets that differentially support normal and malignant hematopoiesis represents a new paradigm to accelerate therapeutic targeting of the BMME in MDS and other hematologic malignancies.

High-Risk Neuroblastoma: Poor Outcomes Despite Aggressive Multimodal Therapy

: Neuroblastoma (NBL) is a highly malignant embryonal tumor that originates from the primordial neural crest cells. NBL is the most common tumor in infants and the most common extracranial solid tumor in children. The tumor is more commonly diagnosed in children of 1-4 years of age. NBL is characterized by enigmatic clinical behavior that ranges from spontaneous regression to an aggressive clinical course leading to frequent relapses and death. Based on the likelihood of progression and relapse, the International Neuroblastoma Risk Group classification system categorized NBL into very low risk, low risk, intermediate risk, and high risk (HR) groups. HR NBL is defined based on the patient's age (&gt; 18 months), disease metastasis, tumor histology, and MYCN gene amplification. HR NBL is diagnosed in nearly 40% of patients, mainly those &gt; 18 months of age, and is associated with aggressive clinical behavior. Treatment strategies involve the use of intensive chemotherapy (CTR), surgical resection, high dose CTR with hematopoietic stem cell support, radiotherapy, biotherapy, and immunotherapy with Anti-ganglioside 2 monoclonal antibodies. Although HR NBL is now better characterized and aggressive multimodal therapy is applied, the outcomes of treatment are still poor, with overall survival and event-free survival of approximately 40% and 30% at 3-years, respectively. The short and long-term side effects of therapy are tremendous. HR NBL carries a high mortality rate accounting for nearly 15% of pediatric cancer deaths. However, most mortalities are attributed to the high frequency of disease relapse (50%) and disease reactiveness to therapy (20%). Newer treatment strategies are therefore urgently needed. Recent discoveries in the field of biology and molecular genetics of NBL have led to the identification of several targets that can improve the treatment results. In this review, we discuss the different aspects of the epidemiology, biology, clinical presentations, diagnosis, and treatment of HR NBL, in addition to the recent developments in the management of the disease.

A Randomized Placebo-Controlled Phase II Study of Clarithromycin or Placebo Combined with VCD Induction Therapy Prior to High-Dose Melphalan with Stem Cell Support in Patients with Newly Diagnosed Multiple Myeloma

▪Background: Uncontrolled studies and a case-matched study indicate that clarithromycin might exert synergistic effects in combination with thalidomide or lenalidomide in the treatment of multiple myeloma. Recent cellular studies have shown that the combination of clarithromycin and bortezomib results in increased cytotoxicity compared to bortezomib alone in myeloma cell lines. A possible mechanism underlying this synergistic effect might be simultaneous inhibition of the ubiquitin-proteasome system by bortezomib and the autophagy-lysosome system by clarithromycin resulting in enhanced endoplasmic reticulum stress-mediated apoptosis in myeloma cells (Moriya et al. Int J Oncol 2013).The Danish Myeloma Study Group (DMSG) initiated the CLAIM trial (NCT02573935), a randomized placebo-controlled phase II study, to investigate the efficacy and safety of clarithromycin in combination with the bortezomib containing VCD regimen.Methods: Patients with newly diagnosed multiple myeloma were randomized (1:1) to receive p.o. clarithromycin 500 mg or a matching placebo tablet twice daily for 63 days in combination with VCD induction therapy. The randomization was stratified according to International Staging System stage. The VCD consisted of 21-day cycles of subcut bortezomib 1.3 mg/sqm days 1, 4, 8, 11, i.v. cyclophosphamide 500 mg/sqm on days 1 and 8, and p.o. dexamethasone 40 mg days 1, 2, 4, 5, 8, 9, 11, 12. After induction treatment the patients proceeded to cyclophosphamide priming (2000 mg/sqm), leukapheresis and high-dose melphalan (200 mg/sqm) with hematopoietic stem cell support (HDT). Patients from six Danish hematology departments participated in the trial. Primary endpoint was to compare rate of very good partial response or better response after three cycles of VCD combined with clarithromycin or placebo. Important secondary end-points were to compare very good partial response or better response two months after HDT, number of stem cells harvested, frequency of infections and safety. The responses were assessed according to the IMWG criteria and analyses were by intention to treat.Results: The study was prematurely stopped for safety reasons after the inclusion of 58 patients (36% of the planned study population). The enrolled patients were randomly assigned to clarithromycin (27) or placebo (31), and the clinical characteristics at baseline were balanced (Table I). VGPR or better response after the VCD induction therapy was obtained in 12 patients (44.4%, (95% CI, [25.5 - 64.7]) and in 16 patients (51.6%, [33.1 - 69.8], P = 0.59) in the clarithromycin group and the control group, respectively. There was no difference in the secondary endpoints between the treatment groups (Table I). A total of 26 serious adverse events were reported in 16 (59.3%) patients in the clarithromycin group and 16 serious adverse events in 10 (32.3%) patients in the control group. Seven patients (25.9%) in the clarithromycin group developed severe gastrointestinal complications (SAE ≥ grade 3) comprising pain, neutropenic enterocolitis, paralytic ileus or peptic ulcer. These complications occurred in only one patient in the control group (Table I). Septicaemia with Gram negative bacteria was observed in 5 patients in the clarithromycin group. By contrast, the only case of septicaemia detected in the control group was pneumococcal sepsis associated with pneumonia. In consequence of this imbalance in occurrence of severe gastrointestinal symptoms and septicaemia the study safety board decided to stop inclusion of new patients and to stop administration of the study drug on 16 September 2016.Conclusion: The study was prematurely stopped due to a number of serious adverse events. Although we only could analyse response data in 58 included patients the data do not suggest any effect of clarithromycin when added to the VCD regimen and our trial does not encourage further clinical studies on the combination of clarithromycin and bortezomib. Surprisingly, our study found an increased frequency of serious adverse events, in particular serious gastrointestinal complications and septicaemia, in the clarithromycin group. It emphasizes the need for controlled studies on the effect of clarithromycin, both in assessment of potential anti-myeloma effects as well as assessment of safety measures. [Display omitted] DisclosuresAbildgaard:Takeda: Research Funding.

Pathological complete response of adding targeted therapy to neoadjuvant chemotherapy for inflammatory breast cancer: A systematic review.

The current use of targeted therapy plus neoadjuvant chemotherapy for inflammatory breast cancer (IBC) is based on data extrapolated from studies in non-IBC. We conducted a systematic review to determine whether neoadjuvant chemotherapy plus targeted therapy results in a higher pathologic complete response (pCR) rate than neoadjuvant chemotherapy alone in patients with IBC. This systematic review was registered in the PROSPERO register with registration number CRD42018089465. We searched MEDLINE & PubMed, EMBASE, and EBSCO from December 1998 through July 2020. All English-language clinical studies, both randomized and non-randomized, that evaluated neoadjuvant systemic treatment with or without targeted therapy before definitive surgery and reported the pCR results of IBC patients. First reviewer extracted data and assessed the risk of bias using the Risk of Bias In Non-randomized Studies of Interventions tool. Second reviewer confirmed the accuracy. Studies were divided into 3 groups according to systemic treatment: chemotherapy with targeted therapy, chemotherapy alone, and high-dose chemotherapy with hematopoietic stem cell support (HSCS). Of 995 screened studies, 23 with 1,269 IBC patients met the inclusion criteria. For each of the 3 groups of studies, we computed a weighted average of the pCR rates across all studies with confidence interval (CI). The weighted averages (95% CIs) were as follows: chemotherapy with targeted therapy, 31.6% (26.4%-37.3%), chemotherapy alone, 13.0% (10.3%-16.2%), and high-dose chemotherapy with HSCS, 23.0% (18.7%-27.7%). The high pCR by targeted therapy group came from anti-HER2 therapy, 54.4% (44.3%-64.0%). Key limitations of this study included no randomized clinical studies that included only IBC patients. Neoadjuvant chemotherapy plus targeted therapy is more effective than neoadjuvant chemotherapy alone for IBC patients. These findings support current IBC standard practice in particular the use of anti-HER2 targeted therapy.

Immunomodulatory and Regenerative Effects of Mesenchymal Stem Cells and Extracellular Vesicles: Therapeutic Outlook for Inflammatory and Degenerative Diseases.

Mesenchymal stem cells (MSCs) are non-hematopoietic, multipotent stem cells derived from mesoderm, which can be easily isolated from many sources such as bone marrow, umbilical cord or adipose tissue. MSCs provide support for hematopoietic stem cells and have an ability to differentiate into multiple cell lines. Moreover, they have proangiogenic, protective and immunomodulatory properties. MSCs have the capacity to modulate both innate and adaptive immune responses, which accompany many diseases, by inhibiting pro-inflammatory reactions and stimulating anti-inflammatory activity. Recent findings revealed that the positive effect of MSCs is at least partly associated with the production of extracellular vesicles (EVs). EVs are small membrane structures, containing proteins, lipids and nuclei acids, which take part in intra-cellular communication. Many studies indicate that EVs contain protective and pro-regenerative properties and can modulate an immune response that is activated in various diseases such as CNS diseases, myocardial infarction, liver injury, lung diseases, ulcerative colitis or kidney injury. Thus, EVs have similar functions as their cells of origin and since they do not carry the risk of cell transplantation, such as tumor formation or small vessel blockage, they can be considered a potential therapeutic tool for cell-free therapy.

The CXCL12 Crossroads in Cancer Stem Cells and Their Niche

Simple SummaryCXCL12 and its receptors have been extensively studied in cancer, including their influence on cancer stem cells (CSCs) and their niche. This intensive research has led to a better understanding of the crosstalk between CXCL12 and CSCs, which has aided in designing several drugs that are currently being tested in clinical trials. However, a comprehensive review has not been published to date. The aim of this review is to provide an overview on how CXCL12 axes are involved in the regulation and maintenance of CSCs, their presence and influence at different cellular levels within the CSC niche, and the current state-of-the-art of therapeutic approaches aimed to target the CXCL12 crossroads.Cancer stem cells (CSCs) are defined as a subpopulation of “stem”-like cells within the tumor with unique characteristics that allow them to maintain tumor growth, escape standard anti-tumor therapies and drive subsequent repopulation of the tumor. This is the result of their intrinsic “stem”-like features and the strong driving influence of the CSC niche, a subcompartment within the tumor microenvironment that includes a diverse group of cells focused on maintaining and supporting the CSC. CXCL12 is a chemokine that plays a crucial role in hematopoietic stem cell support and has been extensively reported to be involved in several cancer-related processes. In this review, we will provide the latest evidence about the interactions between CSC niche-derived CXCL12 and its receptors—CXCR4 and CXCR7—present on CSC populations across different tumor entities. The interactions facilitated by CXCL12/CXCR4/CXCR7 axes seem to be strongly linked to CSC “stem”-like features, tumor progression, and metastasis promotion. Altogether, this suggests a role for CXCL12 and its receptors in the maintenance of CSCs and the components of their niche. Moreover, we will also provide an update of the therapeutic options being currently tested to disrupt the CXCL12 axes in order to target, directly or indirectly, the CSC subpopulation.

Recurrent Crebbp Mutations in Follicular Lymphoma Appear Localized to the Committed B-Cell Lineage

Background: Follicular lymphoma (FL) is genetically characterized by translocations involving the BCL2 locus on chromosome 18q21. However, up to 70% of healthy individuals also carry detectable t(14;18)-positive cells, suggesting BCL2 translocation is critical but not sufficient for FL development. Chromatin modifying genes (CMGs) including KMT2D, CREBBP, EZH2, and EP300 are almost ubiquitously mutated in FL. We previously reported the direct characterization by ultra-deep sequencing of pre-diagnostic blood and tissue specimens from 19 subjects who ultimately developed FL. CREBBP lysine acetyltransferase (KAT) domain mutations were the most commonly observed precursor lesions, detected in blood a median of 7.5 years before diagnosis in patients developing FL (8/19, 42%) but not in healthy adults with or without detected BCL2 translocations (0/13, p=0.01 and 0/20, p&amp;lt;0.001, respectively) (Schroers-Martin et al, ASH Annual Meeting 2017). While the BCL2 translocation is thought to occur in pre-B-cell precursors in the bone marrow, the high prevalence of CMG mutations raises the possibility that, analogous to myeloid age-related clonal hematopoiesis, such early lesions could occur in hematopoietic stem cells (HSCs) rather than in the committed B-cell lineage. Methods: To address this question of mutational hierarchy, we studied blood, bone marrow aspirate, and lymph node samples from 6 patients with CREBBP or KMT2D mutations in their FL tumor. We analyzed flow-sorted purified hematopoietic cell populations by deep sequencing, including isotype-specific mature B-cell, mature T-cell, and precursor populations encompassing HSCs and common lymphoid progenitors (CLPs). Patients additionally underwent routine clinical sequencing of tumor biopsy and marrow specimens. Results: Bulk sequencing of a diagnostic bone marrow aspirate from patient FL002 revealed a CREBBP mutation concordant with FL tumor biopsy. To ascertain the population bearing this mutation, we sorted to high purity viable marrow aspirate cells (Fig. A). The CREBBP mutation was confirmed in the mature B-cell compartment at an AF of 40.3% but was not detected in other cell populations. To validate this finding, a similar sorting strategy was employed on viable bone marrow aspirate or peripheral blood samples from another 4 FL patients bearing CREBBP mutations (Fig B). In each case, CREBBP was absent from the CD34+ precursor population. In patient CIML004 a characteristic KMT2D stop mutation was likewise absent in precursors. An atypical case sheds additional light on the localization of early FL mutations. Patient LYM267 was diagnosed with Grade 1-2 FL bearing CREBBP and NRAS mutations. Eight years into a prolonged remission after chemoimmunotherapy, he developed cutaneous and gingival myeloid sarcoma without radiographic or histopathological evidence of FL recurrence. While the CREBBP mutation was not detected in myeloid sarcoma or bone marrow biopsies, concordant NRAS mutations and clonal VDJ rearrangements were seen in all 3 compartments (Fig. C). This unusual clonal lineage favors the occurrence of the CREBBP mutation later than the branch point between morphologically distinct lymphoid and myeloid tumors, likely in the committed B-cell lineage after pre-BCR rearrangements (Fig D). Conclusions: HSCs are believed to be the cell of origin in several lymphoid leukemias, and mouse models have demonstrated lymphoma development with induced CREBBP lesions in HSCs (Horton et al Nat Cell Bio 2017). However, in sorted hematopoietic cell populations from marrow and peripheral blood, we observed CREBBP mutations in B-cell lineages but never in CD34+/CD20- precursor populations or paired lymphoid/myeloid disease. Our data therefore are not in support of HSCs as a precursor reservoir in FL. Given that cells harboring the t(14;18) translocation in healthy individuals appear derived from the germinal center, recurrent mutations in CREBBP are likely to occur after the pre-B-cell stage. Figure Disclosures Kurtz: Genentech: Consultancy; Foresight Diagnostics: Other: Ownership; Roche: Consultancy. Khodadoust:Kyowa Kirin: Consultancy; Seattle Genetics: Consultancy. Nadel:Innate Pharma: Research Funding; Institut Roche: Research Funding. Diehn:RefleXion: Consultancy; Varian Medical Systems: Research Funding; Illumina: Research Funding; Roche: Consultancy; BioNTech: Consultancy; AstraZeneca: Consultancy. Roulland:Celgene/BMS: Research Funding; Roche: Honoraria. Alizadeh:Pharmacyclics: Consultancy; Genentech: Consultancy; Janssen: Consultancy; Celgene: Consultancy; Chugai: Consultancy; Gilead: Consultancy; Pfizer: Research Funding; Roche: Consultancy.

Caring for older adults with multiple myeloma during the COVID-19 Pandemic: Perspective from the International Forum for Optimizing Care of Older Adults with Myeloma

The novel coronavirus (SARS-CoV-2, COVID-19) was first identified in the province of Wuhan, China in December 2019 [1], following the emergence of new cases of pneumonia of unknown etiology. Since then, the manifestations of COVID-19 infections have ranged from asymptomatic to severe respiratory infections, with increased morbidity in older adults including those with co-morbidities and cancer [2,3]. Presently, global mortality is reported at 4.7%, but this varies widely by location, from 0.7% in Germany to 10.8% in Italy [4]. As of April 13, 2020, the number of infections continues to rise well beyond the 1.9 million cases, and approximately 120,000 COVID-19-related deaths that have already occurred globally [5]. Multiple myeloma (MM) is a malignant plasma cell dyscrasia which predominantly affects older and often frail adults. Although tremendous gains have been made for older adults with MM, infections, including respiratory infections, significantly impact the rate of early mortality in these patients [6,7]. Furthermore, older adults with MM have age-associated vulnerabilities leading to heterogeneity in outcomes [8]. The complexity of caring for older patients have increased substantially during this pandemic, due to concern about their risk of severe morbidity of COVID19 infection. Optimal strategies for these patients will involve staging the malignancy/aging, while simultaneously considering the local prevalence of COVID-19 infection. Herein, we discuss strategies for the risk reduction of COVID-19 transmission, treatment stratification of anti-myeloma therapy and discussion regarding goals of care for older adults with MM during the COVID-19 pandemic.

The Role of Bone Marrow Mesenchymal Stem Cell Derived Extracellular Vesicles (MSC-EVs) in Normal and Abnormal Hematopoiesis and Their Therapeutic Potential.

Mesenchymal stem cells (MSCs) represent a heterogeneous cellular population responsible for the support, maintenance, and regulation of normal hematopoietic stem cells (HSCs). In many hematological malignancies, however, MSCs are deregulated and may create an inhibitory microenvironment able to induce the disease initiation and/or progression. MSCs secrete soluble factors including extracellular vesicles (EVs), which may influence the bone marrow (BM) microenvironment via paracrine mechanisms. MSC-derived EVs (MSC-EVs) may even mimic the effects of MSCs from which they originate. Therefore, MSC-EVs contribute to the BM homeostasis but may also display multiple roles in the induction and maintenance of abnormal hematopoiesis. Compared to MSCs, MSC-EVs have been considered a more promising tool for therapeutic purposes including the prevention and treatment of Graft Versus Host Disease (GVHD) following allogenic HSC transplantation (HSCT). There are, however, still unanswered questions such as the molecular and cellular mechanisms associated with the supportive effect of MSC-EVs, the impact of the isolation, purification, large-scale production, storage conditions, MSC source, and donor characteristics on MSC-EV biological effects as well as the optimal dose and safety for clinical usage. This review summarizes the role of MSC-EVs in normal and malignant hematopoiesis and their potential contribution in treating GVHD.

Salvage treatment for children with relapsed/refractory germ cell tumors: The Associazione Italiana Ematologia Oncologia Pediatrica (AIEOP) experience.

Malignant germ cell tumors (GCTs) are a heterogeneous group of rare neoplasms in children. Optimal outcome is achieved with multimodal therapies for patients with both localized and advanced disease, especially after the introduction of platinum-based chemotherapy regimens. In this respect, data on salvage treatment for children with relapsed or platinum-refractory disease are still limited. Retrospective analysis of data regarding patients affected by malignant GCTs with platinum-refractory or relapsed disease after first-line treatment according to AIEOP TCGM 2004 protocol was conducted. Twenty-one patients, 15 females and 6 males, were considered for the analysis. All 21 patients received second-line conventional chemotherapy (SLCT), two of these immediately after surgery for local relapse removal. Two patients showed a progression of disease during SLCT and died of disease shortly thereafter, whereas 19 patients were in partial remission (PR) or complete remission (CR) after SLCT. Treatment after SLCT consisted in surgery on residual tumor mass (9/19) followed by high dose of chemotherapy (HDCT) with autologous hematopoietic stem cell support (16/19). The overall survival (OS) and event-free survival of the whole populations are 71% and 66.6%, respectively. Platinum-refractory patients OS is 54.5% compared with 91.5% of the relapsed group. There were no treatment-related deaths. SLCT followed or not by HDCT is an effective salvage treatment for children with relapsed/refractory GCTs. However, the role of HDCT following SLCT needs to be further investigated, especially regarding the identification of specific patient subgroups, which can benefit from this more intensive treatment.

Bone Marrow Adipocytes: The Enigmatic Components of the Hematopoietic Stem Cell Niche.

Bone marrow adipocytes (BMA) exert pleiotropic roles beyond mere lipid storage and filling of bone marrow (BM) empty spaces, and we are only now beginning to understand their regulatory traits and versatility. BMA arise from the differentiation of BM mesenchymal stromal cells, but they seem to be a heterogeneous population with distinct metabolisms, lipid compositions, secretory properties and functional responses, depending on their location in the BM. BMA also show remarkable differences among species and between genders, they progressively replace the hematopoietic BM throughout aging, and play roles in a range of pathological conditions such as obesity, diabetes and anorexia. They are a crucial component of the BM microenvironment that regulates hematopoiesis, through mechanisms largely unknown. Previously considered as negative regulators of hematopoietic stem cell function, recent data demonstrate their positive support for hematopoietic stem cells depending on the experimental approach. Here, we further discuss current knowledge on the role of BMA in hematological malignancies. Early hints suggest that BMA may provide a suitable metabolic niche for the malignant growth of leukemic stem cells, and protect them from chemotherapy. Future in vivo functional work and improved isolation methods will enable determining the true essence of this elusive BM hematopoietic stem cell niche component, and confirm their roles in a range of diseases. This promising field may open new pathways for efficient therapeutic strategies to restore hematopoiesis, targeting BMA.

Macrophage-derived oncostatin M contributes to human and mouse neurogenic heterotopic ossifications.

Neurogenic heterotopic ossification (NHO) is the formation of ectopic bone generally in muscles surrounding joints following spinal cord or brain injury. We investigated the mechanisms of NHO formation in 64 patients and a mouse model of spinal cord injury-induced NHO. We show that marrow from human NHOs contains hematopoietic stem cell (HSC) niches, in which mesenchymal stromal cells (MSCs) and endothelial cells provide an environment supporting HSC maintenance, proliferation, and differentiation. The transcriptomic signature of MSCs from NHOs shows a neuronal imprinting associated with a molecular network required for HSC support. We demonstrate that oncostatin M (OSM) produced by activated macrophages promotes osteoblastic differentiation and mineralization of human muscle-derived stromal cells surrounding NHOs. The key role of OSM was confirmed using an experimental model of NHO in mice defective for the OSM receptor (OSMR). Our results provide strong evidence that macrophages contribute to NHO formation through the osteogenic action of OSM on muscle cells within an inflammatory context and suggest that OSM/OSMR could be a suitable therapeutic target. Altogether, the evidence of HSCs in ectopic bones growing at the expense of soft tissue in spinal cord/brain-injured patients indicates that inflammation and muscle contribute to HSC regulation by the brain-bone-blood triad.

Mesenchymal Stromal Cell-Derived Extracellular Vesicles Provide Long-Term Survival After Total Body Irradiation Without Additional Hematopoietic Stem Cell Support

The therapeutic effect of mesenchymal stromal cells (MSC) in tissue regeneration is based mainly on the secretion of bioactive molecules. Here, we report that the radioprotective effect of mouse bone marrow derived mesenchymal stromal cells (mMSC) can be attributed to extracellular vesicles (EV) released from mMSC. The transplantation of mMSC-derived EV into lethally irradiated mice resulted in long-term survival but no improvement in short-term reconstitution of the recipients. Importantly, the radiation rescue was efficient without additional hematopoietic support. In vitro we show a protection by EV of irradiated hematopoietic stem cells but not progenitor cells using stroma-cell cultures and colony-forming assays. After systemic infusion into lethally irradiated recipients, labeled EV traveled freely through the body reaching the bone marrow within 2 hours. We further show that long-term repopulating Sca-1 positive and c-kit low-positive stem cells were directly targeted by EV leading to long-term survival. Collectively, our data suggest EV as an effective first-line treatment to combat radiation-induced hematopoietic failure which might also be helpful in alleviating myelosuppression due to chemotherapy and toxic drug reaction. We suggest the infusion of MSC-derived EV as efficient and immediate treatment option after irradiation injuries. Stem Cells 2017;35:2379-2389.

Efficacy of epirubicin-paclitaxel (EPI-TAX) prior to high-dose chemotherapy (HDCT) in germ cell tumors (GCTs): A 17-year experience.

4557 Background: GCTs patients (pts) relapsing after conventional-dose salvage chemotherapy (CDCT) are candidates to receive HDCT with hematopoietic stem cell (SC) support. We have previously reported (Ann Oncol 2014; 25:1775-82) that non-refractory pts can benefit from HDCT. We here analyzed the efficacy of the induction regimen EPI-TAX. Methods: All male GCTs pts treated by EPI-TAX between 1998 and 2015 were identified from clinical records at Tenon Hospital. Primary aim was response rate after EPI-TAX. Secondary aims were efficacy of SC harvest, Beyer score, toxicities and overall survival (OS) after HDCT. Kaplan-Meier methods were used for analysis. Results: Of the 170 pts treated (EPI 100 mg/m2, TAX 250 mg/m2, days 1-15), 142 (83.5%) had received &gt; 2 previous lines of CDCT. 79 (46.5%) had disease progression at the time of treatment and 44 were absolutely refractory to cisplatin. The other pts were in remission (65) or had stable disease (SD, 26). Most of pts (75.3%) had Beyer score &gt; 1. Following EPI-TAX, favorable responses were achieved in 140 pts (82.4%,CI95% 79.8-85.0; 21 complete responses, 68 partial responses and 51 SD). EPI-TAX was able to control disease in 56 (70.9%, CI95% 61.0-80.8) out of 79 pts who were in progression. Beyer score after EPI-TAX resulted 0 in 70.6% of pts. Successful harvested of SC was achieved in 146 (85.8%, CI95% 80.5-91.1) pts. EPI-TAX was well tolerated with peripheral neuropathy as the main non-hematopoietic toxicity. Treatment discontinuation was needed in 3 (1.8%) pts and 2 (1.2%) related deaths were observed. Following EPI-TAX, 155 (91.2%) pts received HDCT. HDCT was given in consolidation, once progressive disease was controlled by EPI-TAX or for progressive pts. With a median follow-up of 31 months (0.5-223) the 2- and 10-years OS for the subgroup consolidation were 78.2% (95%CI 69.1-87.4) and 66.9% (95%CI 55.4-78.6). Disease control by EPI-TAX resulted in 55.8% (95%CI 42.4-69.2) and 38.2% (95%CI 24.9-51.4) 2- and 10-y OS compared to 14.6% (95%CI 0-33.2, logrank p = 0.006) 2-y OS for progressive pts. Conclusions: EPI-TAX is effective to collect SC and to control disease of pts who were in progression after CDCT allowing them to receive HDCT.