Project description:Bone marrow (BM) niche contributes to hematopoietic regeneration under stress like irradiation and leukemia. However, the mechanisms remain poorly defined. We here report that Lama4 deletion in mice results in reduction of mesenchymal progenitors (MPCs) and endothelial cells in BM. Following irradiation, Lama4-/- mice displayed impaired hematopoiesis recovery accompanied with dysregulation of BM niche factors like angiopoietin-1 and Tgfb1 in the MPCs. Post-transplantation of MLL-AF9 acute myeloid leukemia (AML) cells, we observed accelerated AML onset in Lama4-/- mice. Moreover, these Lama4-/- AML mice displayed faster relapse after therapeutic BM transplantation. Mechanistically, Lama4-/- niche promoted AML cell proliferation and chemoresistance to chemotherapy cytarabine by conferring AML greater antioxidant activity. Together, our study demonstrates that Lama4 is required to maintain hematopoietic niche integrity and to suppress AML progression and chemoresistance by restricting metabolic defense support to AML. Therefore, activating Lama4 signaling pathways may offer potential new therapeutic options for AML.
Project description:Bone marrow inflammation has been linked to acute myeloid leukemia (AML) progression. Studies have demonstrated that leukemic blasts propagate acute inflammation in the AML niche, but the involvment of normal hematopoietic stem and progenitor cells (HSPCs) in the inflammatory crosstalk is not well understood. To better model compartmental inflammation in AML, we first established a highly penetrant, immunocompetent, fully congenic system. Using the monoblastic AML cell line C1498 (CD45.2+), we grafted non-condition C57BL/6J (CD45.1) mice, avoiding changes in BM niche function. We then fluoresence-activated cell sorting (FACS)-sorted residual normal HSPCs for single-cell RNA-sequencing analysis. We show that residual normal HSPCs from C1498-grafted mice expresses key inflammatory signature and are enriched in inflammatory signaling related pathways. Overall, we show that normal HSPCs engages in inflammatory signaling in AML niche.
Project description:Although 80% of AML patients can initially achieve a complete remission, the long-term disease-free survival is only 40% at 6 years with a 10% 5-year survival rate from first relapse. Most patients do not achieve a second remission. Therefore, relapse after initial response to chemotherapy remains a serious clinical challenge requiring new therapeutic strategies. Annual relapse rates have been calculated 40%, 17%, and 2% in years 1-3, respectively. One of the issues hindering the successful treatment of AML patients, and contributing to disease relapse, is leukaemic cell adhesion and retention in the protective niche of the BMME. Here, the leukaemic cells are surrounded by other cell types that promote their survival, by enabling them to evade destruction by both the immune system and intra-vascular therapies, ultimately leading to the emergence of drug resistance. Given the dependence of AML cells on the BMME, a better understanding of the biological interactions between the leukaemic cells and the haematopoietic niche is needed. In addition, the identification and development of therapies to target these adhesive interactions will enable AML cells to be forced out of their BMME protective niche, into the peripheral circulation, where they will be more susceptible to conventional drug regimens. We have developed and optimised a robust, reproducible, in vitro co-culture model of the AML-BMME. Using the optimised model, several adhesion blocking agents were tested to reduce the number of adhered AML cells. Anti-CD44 treatment was established as the most effective in preventing AML adhesion of OCI-AML3, KG1a and primary AML cells. However, even with maximum dose of the most promising blocking agent, some AML cells still adhered. Following this observation, KG1a and OCI-AML3 cells were treated in co-culture and monoculture. Subsequently paired adhered, non-adhered and monoculture cells were isolated and sent for RNA sequencing in order to perform comparative transcriptomic analysis. The results from these experiments helped us identify novel targets from the persistently adhered AML cells in order to more effectively block their adhesion on our model.
Project description:Inflammation in the bone marrow (BM) microenvironment is a constitutive component of acute myeloid leukemia (AML) pathogenesis. Studies have demonstrated that leukemic blasts propagate acute inflammation in the AML niche. Our recent studies in a congenic AML model suggest residual healthy hematopoietic stem and progenitor cells (HSPCs) participate in the inflammatory crosstalk. However, the underlying mechanism that drives the inflammatory conversion of HSPCs remains unclear. Here, we ask whether AML-derived extracellular vesicles (EV-AML) can convert HSPCs into an inflammatory active state in vivo. Using EV-AML purified from inducible (i)MLL-AF9 AML blasts (AF9-EV-AML), we challenged healthy C57BL/6J mice with serial injections of AF9-EVAML and analyzed HSPCs transcriptome. We show that HSPC transcriptome corroborates the enrichment of inflammatory and innate immune responses in EVAML-challenged BM HSPCs compared to controls. Our findings suggest that AML converts HSPCs into an inflammatory hub via EVAML in the AML niche.
Project description:In acute myeloid leukemia (AML), malignant cells surviving chemotherapy rely on high mRNA translation and their microenvironmental metabolic support to drive relapse. However, the role of translational reprogramming in the niche is unclear. Here we found that relapsing AML cells increase translation in their bone marrow (BM) niches, where BM mesenchymal stromal cells (BMSCs) become a source of eIF4A-cap-dependent translation machinery that is transferred to AML cells via extracellular vesicles (EVs), to meet their translational demands. In two independent models of highly chemo-resistant AML driven by MLL-AF9 or FLT3-ITD;NPMc mutations, protein synthesis levels increase in refractory AML dependently on nestin+ BMSCs. Inhibiting cap-dependent translation in BMSCs abolishes their chemoprotective ability, while EVs from BMSCs carrying eIF4A boost AML cell translation and survival. Consequently, eIF4A inhibition synergizes with conventional chemotherapy. Together, these results suggest that AML cells rely on BMSCs to maintain an oncogenic translational program required for relapse
Project description:In acute myeloid leukemia (AML), malignant cells surviving chemotherapy rely on high mRNA translation and their microenvironmental metabolic support to drive relapse. However, the role of translational reprogramming in the niche is unclear. Here we found that relapsing AML cells increase translation in their bone marrow (BM) niches, where BM mesenchymal stromal cells (BMSCs) become a source of eIF4A-cap-dependent translation machinery that is transferred to AML cells via extracellular vesicles (EVs), to meet their translational demands. In two independent models of highly chemo-resistant AML driven by MLL-AF9 or FLT3-ITD;NPMc mutations, protein synthesis levels increase in refractory AML dependently on nestin+ BMSCs. Inhibiting cap-dependent translation in BMSCs abolishes their chemoprotective ability, while EVs from BMSCs carrying eIF4A boost AML cell translation and survival. Consequently, eIF4A inhibition synergizes with conventional chemotherapy. Together, these results suggest that AML cells rely on BMSCs to maintain an oncogenic translational program required for relapse.
Project description:The Cxcr4-Cxcl12 axis has been postulated as a critical pathway dictating leukemia stem cell (LSCs) chemoresistance in AML due to its role in controlling cellular egress from the marrow. Nevertheless, the cellular source of Cxcl12 in the AML microenvironment and the mechanism by which Cxcl12 exert its protective role in AML in vivo remain unresolved. We have evaluated the functional role of Cxcl12 secreted by early mesenchymal stromal cells (MSCs) and osteolineage committed cells in acute myeloid leukemia (AML) maintenance in vivo. Our results demonstrate that early MSCs, in contrast to committed osteoblasts, are integral part of the MLL::AF9 derived AML niche and control LSCs maintenance through Cxcl12 secretion. Cxcl12 from MSCs regulates the oxidative state of LSCs and promotes energy metabolism. Furthermore, the protective role of the niche through the activation of the CXCL12-CXCR4 axis, may also represent a biological hallmark in human pediatric and adult AML, hence, reinforcing the notion that targeting the MSCs-derived CXCL12 may help eradicate leukemia.
Project description:MSC and AML dual targeting to treat pediatric AML Bone marrow (BM) microenvironment supports the regulation of normal hematopoiesis through a finely tuned balance of self-renewal and differentiation processes, cell-cell interaction and secretion of cytokines that during leukemogenesis are severely compromised and favor tumor cell growth. In pediatric acute myeloid leukemia (AML), chemotherapy is the standard of care, but still >30% of patients relapse. The need to accelerate the evaluation of innovative medicines prompted us to investigate the mesenchymal stromal cell (MSCs) role in the leukemic niche to define its contribution to the mechanisms of leukemia escape. We generated humanized three-dimensional (3D) niche with AML cells and MSCs derived from patients (AML-MSCs) or healthy donors. We observed that AML cells establish physical connections with MSCs, mediating a reprogrammed transcriptome inducing aberrant cell proliferation and differentiation, and severely compromising their immunomodulatory capability. We confirmed AML cells endow h-MSCs with a pro-oncogenic transcriptional profile and functions similar to the AML-MSCs when co-cultured in vitro. Conversely, MSCs derived from BM of patients at time of disease remission showed recovered healthy features, at transcriptional and functional levels, including the secretome. We sustained AML blasts altering MSC cell activities in the BM niche in order to favor disease development and progression, becoming a pharmacological target. We discovered that a novel AML-MSCs selective CaV1.2 channel blocker drug, Lercanidipine, is able to impair leukemia progression in 3D both, in vitro and when implanted in vivo, if used in combination with chemotherapy, supporting the hypothesis that synergistic effects can be obtained by dual targeting approaches.