Transcriptomic profiling of the myeloma bone-lining niche reveals BMP signalling inhibition to improve bone disease

Stromal alterations in patients with monoclonal gammopathy of undetermined significance, smoldering myeloma, and multiple myeloma

ABSTRACT

The hallmark of multiple myeloma (MM) is a clonal plasma cell infiltration in the bone marrow accompanied by myelosuppression and osteolysis. Premalignant stages such as monoclonal gammopathy of undetermined significance (MGUS) and asymptomatic stages such as smoldering myeloma (SMM) can progress to MM. Mesenchymal stromal cells (MSCs) are an integral component of the bone marrow microenvironment and play an important role in osteoblast differentiation and hematopoietic support. Although stromal alterations have been reported in MM contributing to hematopoietic insufficiency and osteolysis, it is not clear whether alterations in MSC already occur in MGUS or SMM. In this study, we analyzed MSCs from MGUS, SMM, and MM regarding their properties and functionality and performed messenger RNA sequencing to find underlying molecular signatures in different disease stages. A high number of senescent cells and a reduced osteogenic differentiation capacity and hematopoietic support were already present in MGUS MSC. As shown by RNA sequencing, there was a broad spectrum of differentially expressed genes including genes of the BMP/TGF-signaling pathway, detected already in MGUS and that clearly increases in patients with SMM and MM. Our data may help to block these signaling pathways in the future to hinder progression to MM.

Single-cell analysis of the CD8+ T-cell compartment in multiple myeloma reveals disease specific changes are chiefly restricted to a CD69- subset suggesting potent cytotoxic effectors exist within the tumor bed

Multiple myeloma (MM) is an incurable disease of the bone marrow (BM) characterized by the uncontrolled proliferation of neoplastic plasma cells. While CD8+ T cells have an established role in disease control, few studies have focused on these cells within the MM tumor microenvironment (TME). We analyzed CD8+ T cells in the BM and peripheral blood (PB) of untreated patients with MM and non-myeloma controls using flow cytometry, mass cytometry and single-cell RNA sequencing, using several novel bioinformatics workflows. Inter-tissue differences were most evident in the differential expression of Granzymes B and K, which were strongly associated with two distinct subsets of CD8+ T cells delineated by the expression of CD69, accounting for roughly 50% of BM-CD8+ T cells of all assessed cohorts. While few differences were observable between health and disease in the BM-restricted CD8CD69+ T-cell subset, the CD8+CD69- T-cell subset in the BM of untreated MM patients demonstrated increased representation of highly differentiated effector cells and evident compositional parallels between the PB, absent in age-matched controls, where a marked reduction of effector cells was observed. We demonstrate the transcriptional signature of BM-CD8+ T cells from patients with MM more closely resembles TCR-activated CD8+ T cells from age-matched controls than their resting counterparts.

Mesenchymal stromal cells, metabolism, and mitochondrial transfer in bone marrow normal and malignant hematopoiesis

Hematopoietic stem cell (HSC) transplantation-based treatments are in different phases of clinical development, ranging from current therapies to a promise in the repair and regeneration of diseased tissues and organs. Mesenchymal stromal/stem cells (MSCs), which are fibroblast-like heterogeneous progenitors with multilineage differentiation (osteogenic, chondrogenic, and adipogenic) and self-renewal potential, and exist in the bone marrow (BM), adipose, and synovium, among other tissues, represent one of the most widely used sources of stem cells in regenerative medicine. MSCs derived from bone marrow (BM-MSCs) exhibit a variety of traits, including the potential to drive HSC fate and anti-inflammatory and immunosuppressive capabilities via paracrine activities and interactions with the innate and adaptive immune systems. The role of BM-MSC-derived adipocytes is more controversial and may act as positive or negative regulators of benign or malignant hematopoiesis based on their anatomical location and functional crosstalk with surrounding cells in the BM microenvironment. This review highlights the most recent clinical and pre-clinical findings on how BM-MSCs interact with the surrounding HSCs, progenitors, and immune cells, and address some recent insights on the mechanisms that mediate MSCs and adipocyte metabolic control through a metabolic crosstalk between BM microenvironment cells and intercellular mitochondrial transfer in normal and malignant hematopoiesis.

Advances in the pathogenesis of multiple myeloma bone disease

Multiple myeloma (MM) is a clonal proliferative malignant tumor of plasma cells in bone marrow. With the aging of population in China, the incidence of MM is on the rise. Multiple myeloma bone disease (MBD) is one of the common clinical manifestations of MM, and 80%-90% of MM patients are accompanied by osteolytic lesions at the time of their first visit to the clinic. MBD not only increases the disability rate of patients, but also severely reduces the physical function of patients due to skeletal lesions and bone-related events. Currently available drugs for treating of MBD are ineffective and associated with side effects. Therefore, it is important to find new therapeutic approaches for the treatment of MBD. It is generally believed that the increased osteoclast activity and suppressed osteoblast function are the main pathologic mechanisms for MBD. However, more and more studies have suggested that soluble molecules in the bone marrow microenvironment, including cytokines, extracellular bodies, and metabolites, play an important role in the development of MBD. Therefore, exploring the occurrence and potential molecular mechanisms for MBD from multiple perspectives, and identifying the predictive biomarkers and potential therapeutic targets are of significance for the clinical treatment of MBD.

Oncofetal reprogramming in tumor development and progression: novel insights into cancer therapy

Emerging evidence indicates that cancer cells can mimic characteristics of embryonic development, promoting their development and progression. Cancer cells share features with embryonic development, characterized by robust proliferation and differentiation regulated by signaling pathways such as Wnt, Notch, hedgehog, and Hippo signaling. In certain phase, these cells also mimic embryonic diapause and fertilized egg implantation to evade treatments or immune elimination and promote metastasis. Additionally, the upregulation of ATP-binding cassette (ABC) transporters, including multidrug resistance protein 1 (MDR1), multidrug resistance-associated protein 1 (MRP1), and breast cancer-resistant protein (BCRP), in drug-resistant cancer cells, analogous to their role in placental development, may facilitate chemotherapy efflux, further resulting in treatment resistance. In this review, we concentrate on the underlying mechanisms that contribute to tumor development and progression from the perspective of embryonic development, encompassing the dysregulation of developmental signaling pathways, the emergence of dormant cancer cells, immune microenvironment remodeling, and the hyperactivation of ABC transporters. Furthermore, we synthesize and emphasize the connections between cancer hallmarks and embryonic development, offering novel insights for the development of innovative cancer treatment strategies.

Advances in chimeric antigen receptor T cells therapy in the treatment of breast cancer

Breast cancer (BC) is the most frequently occurring cancer type seriously threatening the lives of women worldwide. Clinically, the high frequency of diverse resistance to current therapeutic strategies advocates a demand to develop novel and effective approaches for the efficient treatment of BC. The chimeric antigen receptor T (CAR-T) cells therapy, one of the immunotherapies, has displayed powerful capacity to specifically kill and eliminate tumors. Due to the success of CAR-T therapy achieved in treating hematological malignancy, the effect of CAR-T cells therapy has been tested in various human diseases including breast cancer. This review summarized and discussed the landscape of the CAR-T therapy for breast cancer, including the advances, challenge and countermeasure of CAR-T therapy in research and clinical application. The roles of potential antigen targets, tumor microenvironment, immune escape in regulating CAR-T therapy, the combination of CAR-T therapy with other therapeutic strategies to further enhance therapeutic efficacy of CAR-T treatment were also highlighted. Therefore, our review provided a comprehensive understanding of CAR-T cell therapy in breast cancer which will awake huge interests for future in-depth investigation of CAR-T based therapy in cancer treatment.

Excessive serine from the bone marrow microenvironment impairs megakaryopoiesis and thrombopoiesis in Multiple Myeloma

Thrombocytopenia is a major complication in a subset of patients with multiple myeloma (MM). However, little is known about its development and significance during MM. Here, we show thrombocytopenia is linked to poor prognosis in MM. In addition, we identify serine, which is released from MM cells into the bone marrow microenvironment, as a key metabolic factor that suppresses megakaryopoiesis and thrombopoiesis. The impact of excessive serine on thrombocytopenia is mainly mediated through the suppression of megakaryocyte (MK) differentiation. Extrinsic serine is transported into MKs through SLC38A1 and downregulates SVIL via SAM-mediated tri-methylation of H3K9, ultimately leading to the impairment of megakaryopoiesis. Inhibition of serine utilization or treatment with TPO enhances megakaryopoiesis and thrombopoiesis and suppresses MM progression. Together, we identify serine as a key metabolic regulator of thrombocytopenia, unveil molecular mechanisms governing MM progression, and provide potential therapeutic strategies for treating MM patients by targeting thrombocytopenia.

Bone morphogenetic protein pathway responses and alterations of osteogenesis in metastatic prostate cancers

BACKGROUND

Prostate cancer is a common cancer in men that annually results in more than 33 000 US deaths. Mortality from prostate cancer is largely from metastatic disease, reflecting on the great strides in the last century of treatments in care for the localized disease. Metastatic castrate resistant prostate cancer (mCRPC) will commonly travel to the bone, creating unique bone pathology that requires nuanced treatments in those sites with surgical, radio and chemotherapeutic interventions. The bone morphogenetic protein (BMP) pathway has been historically studied in the capacity to regulate the osteogenic nature of new bone. New mineralized bone generation is a frequent and common observation in mCRPC and referred to as blastic bone lesions. Less common are bone destructive lesions that are termed lytic.

METHODS

We queried the cancer genome atlas (TCGA) prostate cancer databases for the expression of the BMP pathway and found that distinct gene expression of the ligands, soluble antagonists, receptors, and intracellular mediators were altered in localized versus metastatic disease. Human prostate cancer cell lines have an innate ability to promote blastic- or lytic-like bone lesions and we hypothesized that inhibiting BMP signaling in these cell lines would result in a distinct change in osteogenesis gene expression with BMP inhibition.

RESULTS

We found unique and common changes by comparing these cell lines response and unique BMP pathway alterations. We treated human PCa cell lines with distinct bone pathologic phenotypes with the BMP inhibitor DMH1 and found distinct osteogenesis responses. We analyzed distinct sites of metastatic PCa in the TCGA and found that BMP signaling was selectively altered in commons sites such as lymph node, bone and liver compared to primary tumors.

CONCLUSIONS

Overall we conclude that BMPs in metastatic prostate cancer are important signals and functional mediators of diverse processes that have potential for individualized precision oncology in mCRPC.

Muscle and Bone Defects in Metastatic Disease

PURPOSE OF REVIEW

The present review addresses most recently identified mechanisms implicated in metastasis-induced bone resorption and muscle-wasting syndrome, known as cachexia.

RECENT FINDINGS

Metastatic disease in bone and soft tissues is often associated with skeletal muscle defects. Recent studies have identified a number of secreted molecules and extracellular vesicles that contribute to cancer cell growth and metastasis leading to bone destruction and muscle atrophy. In addition, alterations in muscle microenvironment including dysfunctions in hepatic and mitochondrial metabolism have been implicated in cancer-induced regeneration defect and muscle loss. Moreover, we review novel in vitro and animal models including promising new drug candidates for bone metastases and cancer cachexia. Preservation of bone health could be highly beneficial for maintaining muscle mass and function. Therefore, a better understanding of molecular pathways implicated in bone and muscle crosstalk in metastatic disease may provide new insights and identify new strategies to improve current anticancer therapeutics.

Functional role of cyanidin-3-O-glucoside in osteogenesis: A pilot study based on RNA-seq analysis

Cyanidin-3-O-glucoside (C3G) is the most widely distributed anthocyanin and it can reportedly reduce the risk of osteoporosis, but the molecular mechanism by which C3G promotes bone formation is poorly understood. In the current study, RNA sequencing (RNA-seq) was used to investigate the mechanism of action of C3G in osteogenesis. MC3T3-E1 mouse osteoblasts were divided into a C3G (100 μmol/L)-treated group and a vehicle-treated control group, and differentially expressed genes (DEGs) in groups were evaluated via RNA-seq analysis. The functions of the DEGs were evaluated by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, and the genes were validated by quantitative real-time PCR. The RNA-seq analysis identified 34 genes that were upregulated in C3G-treated cells compared to vehicle-treated cells, and 17 that were downregulated GO and KEGG pathway analyses indicated that these genes were highly enriched in functions related to lysosomes and glycolipid biosynthesis, among others. The differential expression of ATPase H+-transporting V0 subunit C (Atp6v0c), chemokine (C-X3-C motif) ligand 1 (Cx3cl1), and lymphocyte antigen 6 complex, locus A (Ly6a) genes was validated by quantitative real-time-PCR. Because these genes have been previously implicated in osteoporosis, they are potential target genes of C3G action in MC3T3-E1 cells. These results provide molecular level evidence for the therapeutic potential of C3G in the treatment of osteoporosis and other disorders of bone metabolism.

CST6 suppresses osteolytic bone disease in multiple myeloma by blocking osteoclast differentiation

Osteolytic bone disease is a hallmark of multiple myeloma (MM). A significant fraction (~20%) of MM patients do not develop osteolytic lesions (OL). The molecular basis for the absence of bone disease in MM is not understood. We combined PET-CT and gene expression profiling (GEP) of purified bone marrow (BM) CD138+ MM cells from 512 newly diagnosed MM patients to reveal that elevated expression of cystatin M/E (CST6) was significantly associated with the absence of OL in MM. An enzyme-linked immunosorbent assay revealed a strong correlation between CST6 levels in BM serum/plasma and CST6 mRNA expression. Both recombinant CST6 protein and BM serum from patients with high CST6 significantly inhibited the activity of the osteoclast-specific protease cathepsin K, and blocked osteoclast differentiation and function. Recombinant CST6 inhibited bone destruction in ex vivo and in vivo myeloma models. Single cell RNA-sequencing identified that CST6 attenuates polarization of monocytes to osteoclast precursors. Furthermore, CST6 protein blocks osteoclast differentiation by suppressing cathepsin-mediated cleavage of NF-κB/p100 and TRAF3 following RANKL stimulation. Secretion by MM cells of CST6, an inhibitor of osteoclast differentiation and function, suppresses osteolytic bone disease in MM and probably other diseases associated with osteoclast-mediated bone loss.

BMPR1α promotes osteolytic lesion of oral squamous cell carcinoma by SHH‐dependent osteoclastogenesis

Oral squamous cell carcinoma (OSCC) is an aggressive tumor that usually invades the maxilla or mandible. The extent and pattern of mandibular bone invasion caused by OSCC are the most important factors determining the treatment plan and patients' prognosis. Yet, the process of mandibular invasion is not fully understood. The following study explores the molecular mechanism that regulates the mandibular invasion of OSCC by focusing on bone morphogenetic protein receptor 1α (BMPR1α) and Sonic hedgehog (SHH) signals. We found that BMPR1α was positively correlated to bone defect of OSCC patients. Mechanistically, BMPR1α signaling regulated the differentiation and resorption activity of osteoclasts through the interaction of OSCC cells and osteoclast progenitors, and this process was mediated by SHH secreted by tumor cells. The inhibition of SHH protected bone from tumor‐induced osteolytic activity. These results provide a potential new treatment strategy for controlling OSCC from invading the jawbones.

Natural Killer Cells in the Malignant Niche of Multiple Myeloma

Natural killer (NK) cells represent a subset of CD3- CD7+ CD56+/dim lymphocytes with cytotoxic and suppressor activity against virus-infected cells and cancer cells. The overall potential of NK cells has brought them to the spotlight of targeted immunotherapy in solid and hematological malignancies, including multiple myeloma (MM). Nonetheless, NK cells are subjected to a variety of cancer defense mechanisms, leading to impaired maturation, chemotaxis, target recognition, and killing. This review aims to summarize the available and most current knowledge about cancer-related impairment of NK cell function occurring in MM.

Using MMRFBiolinks R-Package for Discovering Prognostic Markers in Multiple Myeloma

Multiple myeloma (MM) is the second most frequent hematological malignancy in the world although the related pathogenesis remains unclear. Gene profiling studies, commonly carried out through next-generation sequencing (NGS) and Microarrays technologies, represent powerful tools for discovering prognostic markers in MM. NGS technologies have made great leaps forward both economically and technically gaining in popularity. As NGS techniques becomes simpler and cheaper, researchers choose NGS over microarrays for more of their genomic applications. However, Microarrays still provide significant benefits with respect to NGS. For instance, RNA-Seq requires more complex bioinformatic analysis with respect to Microarray as well as it lacks of standardized protocols for analysis. Therefore, a synergy between the two technologies may be well expected in the future. In order to take up this challenge, a valid tool for integrative analysis of MM data retrieved through NGS techniques is MMRFBiolinks, a new R package for integrating and analyzing datasets from the Multiple Myeloma Research Foundation (MMRF) CoMMpass (Clinical Outcomes in MM to Personal Assessment of Genetic Profile) study, available at MMRF Researcher Gateway (MMRF-RG), and at the National Cancer Institute Genomic Data Commons (NCI-GDC) Data Portal. Instead of developing a completely new package from scratch, we decided to leverage TC-GABiolinks, an R/Bioconductor package, because it provides some useful methods to access and analyze MMRF-CoMMpass data. An integrative analysis workflow based on the usage of MMRFBiolinks is illustrated.In particular, it leads towards a comparative analysis of RNA-Seq data stored at GDC Data Portal that allows to carry out a Kaplan Meier (KM ) Survival Analysis and an enrichment analysis for a Differential Gene Expression (DGE) gene set.Furthermore, it deals with MMRF-RG data for analyzing the correlation between canonical variants and treatment outcome as well as treatment class. In order to show the potential of the workflow, we present two case studies. The former deals with data of MM Bone Marrow sample types available at GDC Data Portal. The latter deals with MMRF-RG data for analyzing the correlation between canonical variants in a gene set obtained from the case study 1 and the treatment outcome as well as the treatment class.

Spatiotemporally controlled calcitonin delivery: Long-term and targeted therapy of skeletal diseases

Bone is a connective tissue that support the entire body and protect the internal organs. However, there are great challenges on curing intractable skeletal diseases such as hypercalcemia, osteoporosis and osteoarthritis. To address these issues, calcitonin (CT) therapy is an effective treatment alternative to regulate calcium metabolism and suppress inflammation response, which are closely related to skeletal diseases. Traditional calcitonin formulation requires frequent administration due to the low bioavailability resulting from the short half-life and abundant calcitonin receptors distributed through the whole body. Therefore, long-term and targeted calcitonin delivery systems (LCDS and TCDS) have been widely explored as the popular strategies to overcome the intrinsic limitations of calcitonin and improve the functions of calcium management and inflammation inhibition in recent years. In this review, we first explain the physiological effects of calcitonin on bone remodeling: (i) inhibitory effects on osteoclasts and (ii) facilitated effects on osteoblasts. Then we summarized four strategies for spatiotemporally controlled delivery of calcitonin: micro-/nanomedicine (e.g. inorganic micro-/nanomedicine, polymeric micro-/nanomedicine and supramolecular assemblies), hydrogels (especially thermosensitive hydrogels), prodrug (PEGylation and targeting design) and hybrid biomaterials. Subsequently, we discussed the application of LCDS and TCDS in treating hypercalcemia, osteoporosis, and arthritis. Understanding and analyzing these advanced calcitonin delivery applications are essential for future development of calcitonin therapies toward skeletal diseases with superior efficacy in clinic.

A functional three-dimensional microphysiological human model of myeloma bone disease

Human myeloma bone disease (MBD) occurs when malignant plasma cells migrate to the bone marrow and commence inimical interactions with stromal cells, disrupting the skeletal remodeling process. The myeloma cells simultaneously suppress osteoblastic bone formation while promoting excessive osteoclastic resorption. This bone metabolism imbalance produces osteolytic lesions that cause chronic bone pain and reduce trabecular and cortical bone structural integrity, and often culminate in pathological fractures. Few bone models exist that enable scientists to study MBD and the effect therapies have on restoring the bone metabolism imbalance. The purpose of this research was to develop a well characterized three-dimensional (3D) bone organoid that could be used to study MBD and current or potential treatment options. First, bone marrow stromal cell-derived osteoblasts (OBs) mineralized an endosteal-like extracellular matrix (ECM) over 21 days. Multiple analyses confirmed the generation of hydroxyapatite (HA)-rich bone-like tissue fragments that were abundant in alkaline phosphatase, calcium, and markers of osteoblastic gene expression. On day 22, bone marrow macrophage (BMM)-derived osteoclasts (OCs) were introduced to enhance the resorptive capability of the model and recapitulate the balanced homeostatic nature of skeletal remodeling. Tartrate-resistant acid phosphatase 5b (TRAcP-5b), type I collagen C-telopeptide (CTX-1), and gene expression analysis confirmed OC activity in the normal 3D organoid (3D in vitro model of normal bonelike fragments [3D-NBF]). On day 30, a human multiple myeloma (MM)-derived plasmacytoma cell line was introduced to the 3D-NBF to generate the 3D-myeloma bone disease organoid (3D-MBD). After 12 days, the 3D-MBD had significantly reduced total HA, increased TRAcP-5b levels, increases levels of CTX-1, and decreased expression of osteoblastic genes. Therapeutic intervention with pharmaceutical agents including an immunomodulatory drug, a bisphosphonate, and monoclonal restored HA content and reduced free CTX-1 in a dose-dependent manner. This osteogenically functional model of MBD provides a novel tool to study biological mechanisms guiding the disease and to screen potential therapeutics. © 2021 American Society for Bone and Mineral Research (ASBMR).

Rebuilding the hematopoietic stem cell niche: Recent developments and future prospects

Hematopoietic stem cells (HSCs) have proven their clinical relevance in stem cell transplantation to cure patients with hematological disorders. Key to their regenerative potential is their natural microenvironment - their niche - in the bone marrow (BM). Developments in the field of biomaterials enable the recreation of such environments with increasing preciseness in the laboratory. Such artificial niches help to gain a fundamental understanding of the biophysical and biochemical processes underlying the interaction of HSCs with the materials in their environment and the disturbance of this interplay during diseases affecting the BM. Artificial niches also have the potential to multiply HSCs in vitro, to enable the targeted differentiation of HSCs into mature blood cells or to serve as drug-testing platforms. In this review, we will introduce the importance of artificial niches followed by the biology and biophysics of the natural archetype. We will outline how 2D biomaterials can be used to dissect the complexity of the natural niche into individual parameters for fundamental research and how 3D systems evolved from them. We will present commonly used biomaterials for HSC research and their applications. Finally, we will highlight two areas in the field of HSC research, which just started to unlock the possibilities provided by novel biomaterials, in vitro blood production and studying the pathophysiology of the niche in vitro. With these contents, the review aims to give a broad overview of the different biomaterials applied for HSC research and to discuss their potentials, challenges and future directions in the field. STATEMENT OF SIGNIFICANCE: Hematopoietic stem cells (HSCs) are multipotent cells responsible for maintaining the turnover of all blood cells. They are routinely applied to treat patients with hematological diseases. This high clinical relevance explains the necessity of multiplication or differentiation of HSCs in the laboratory, which is hampered by the missing natural microenvironment - the so called niche. Biomaterials offer the possibility to mimic the niche and thus overcome this hurdle. The review introduces the HSC niche in the bone marrow and discusses the utility of biomaterials in creating artificial niches. It outlines how 2D systems evolved into sophisticated 3D platforms, which opened the gateway to applications such as, expansion of clinically relevant HSCs, in vitro blood production, studying niche pathologies and drug testing.

Myeloma Bone Disease: The Osteoblast in the Spotlight

Lytic bone disease remains a life-altering complication of multiple myeloma, with up to 90% of sufferers experiencing skeletal events at some point in their cancer journey. This tumour-induced bone disease is driven by an upregulation of bone resorption (via increased osteoclast (OC) activity) and a downregulation of bone formation (via reduced osteoblast (OB) activity), leading to phenotypic osteolysis. Treatments are limited, and currently exclusively target OCs. Despite existing bone targeting therapies, patients successfully achieving remission from their cancer can still be left with chronic pain, poor mobility, and reduced quality of life as a result of bone disease. As such, the field is desperately in need of new and improved bone-modulating therapeutic agents. One such option is the use of bone anabolics, drugs that are gaining traction in the osteoporosis field following successful clinical trials. The prospect of using these therapies in relation to myeloma is an attractive option, as they aim to stimulate OBs, as opposed to existing therapeutics that do little to orchestrate new bone formation. The preclinical application of bone anabolics in myeloma mouse models has demonstrated positive outcomes for bone repair and fracture resistance. Here, we review the role of the OB in the pathophysiology of myeloma-induced bone disease and explore whether novel OB targeted therapies could improve outcomes for patients.

Rationally integrating peptide-induced targeting and multimodal therapies in a dual-shell theranostic platform for orthotopic metastatic spinal tumors

Metastatic tumors present great challenges in diagnosis and treatment. Herein, a proof-of-concept theranostic nanoplatform composed of an Au nanoparticle core and a double-shell of metal-organic framework (MOF) and mesoporous silica (MS) is developed for combating spinal metastasis of lung cancer in an orthotopic model. Two drugs, Alpelisib (BYL719) as an inhibitor and cisplatin as a chemotherapeutic drug, are separately loaded into the double-shell with high loading content. A targeting peptide called dYNH and indocyanine green (ICG) are conjugated onto the outmost MS layer for specifically targeting metastatic tumor cells and enhancing photothermal effect. The resultant Au@MOF@MS-ICG -dYNH-PAA (AMMD) shows enhanced cellular uptake on tumor cells and accumulation at metastatic spinal tumors, as evidenced by fluorescent and photoacoustic imaging. Benefiting from this ultra-high affinity to tumor cells and the photothermal effect of ICG, the dual-drug-loaded AMMD (BCAMMD) modified with ICG exhibits superior therapeutic efficacy on spinal tumors. More importantly, bone destruction, which frequently occurs in bone-related tumors, is effectively suppressed by BYL719 in BCAMMD. Hence, by rationally integrating multiple functions, including excellent targeting ability, dual-drug loading, photothermal therapy, and photoacoustic imaging, the developed all-in-one theranostic nanoplatform provides a useful paradigm of employing nanomedicine to treat metastatic spinal tumors efficiently.

Bone Marrow Mesenchymal Stromal Cells in Multiple Myeloma: Their Role as Active Contributors to Myeloma Progression

Multiple myeloma (MM) is a hematological malignancy of plasma cells that proliferate and accumulate within the bone marrow (BM). Work from many groups has made evident that the complex microenvironment of the BM plays a crucial role in myeloma progression and response to therapeutic agents. Within the cellular components of the BM, we will specifically focus on mesenchymal stromal cells (MSCs), which are known to interact with myeloma cells and the other components of the BM through cell to cell, soluble factors and, as more recently evidenced, through extracellular vesicles. Multiple structural and functional abnormalities have been found when characterizing MSCs derived from myeloma patients (MM-MSCs) and comparing them to those from healthy donors (HD-MSCs). Other studies have identified differences in genomic, mRNA, microRNA, histone modification, and DNA methylation profiles. We discuss these distinctive features shaping MM-MSCs and propose a model for the transition from HD-MSCs to MM-MSCs as a consequence of the interaction with myeloma cells. Finally, we review the contribution of MM-MSCs to several aspects of myeloma pathology, specifically to myeloma growth and survival, drug resistance, dissemination and homing, myeloma bone disease, and the induction of a pro-inflammatory and immunosuppressive microenvironment.

The Evaluation of the Multiple Myeloma Pathological Osseous Tissue of Microarchitecture

BACKGROUND

The typical imaging finding of MM is bone destruction in the form of diffuse patchy osteolytic lesions or punctate destruction. However, it is difficult to accurately determine the fine structure of bone affected by MM with these techniques due to low specificity and sensitivity.

INTRODUCTION

This study aimed to investigate the microscopic anatomical morphology and analyze the microstructure changes of trabeculae affected by multiple myeloma (MM) based on micro-CT.

METHODS

MM-affected and normal trabecular bone samples were imaged by micro-CT to obtain bone structure parameters to assess statistical differences between them and evaluate the degree of microstructural damage of MM-affected trabeculae.

RESULTS

Micro CT images clearly showed the microstructure of MM-affected trabeculae. The degree of trabecular osteoporosis varied with the severity of MM. There were significant differences in the structural parameters between MM-affected and normal trabeculae (P < 0.05).

CONCLUSION

Micro-CT clearly reveals the microstructure of MM-affected trabeculae. The obtained bone structure data will help to determine the degree of bone damage caused by MM and assess the efficacy.

The hepcidin regulator erythroferrone is a new member of the erythropoiesis-iron-bone circuitry

Background

Erythroblast erythroferrone (ERFE) secretion inhibits hepcidin expression by sequestering several bone morphogenetic protein (BMP) family members to increase iron availability for erythropoiesis.

Methods

To address whether ERFE functions also in bone and whether the mechanism of ERFE action in bone involves BMPs, we utilize the Erfe-/- mouse model as well as β-thalassemic (Hbbth3/+) mice with systemic loss of ERFE expression. In additional, we employ comprehensive skeletal phenotyping analyses as well as functional assays in vitro to address mechanistically the function of ERFE in bone.

Results

We report that ERFE expression in osteoblasts is higher compared with erythroblasts, is independent of erythropoietin, and functional in suppressing hepatocyte hepcidin expression. Erfe-/- mice display low-bone-mass arising from increased bone resorption despite a concomitant increase in bone formation. Consistently, Erfe-/- osteoblasts exhibit enhanced mineralization, Sost and Rankl expression, and BMP-mediated signaling ex vivo. The ERFE effect on osteoclasts is mediated through increased osteoblastic RANKL and sclerostin expression, increasing osteoclastogenesis in Erfe-/- mice. Importantly, Erfe loss in Hbbth3/+mice, a disease model with increased ERFE expression, triggers profound osteoclastic bone resorption and bone loss.

Conclusions

Together, ERFE exerts an osteoprotective effect by modulating BMP signaling in osteoblasts, decreasing RANKL production to limit osteoclastogenesis, and prevents excessive bone loss during expanded erythropoiesis in β-thalassemia.

Funding

YZG acknowledges the support of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) (R01 DK107670 to YZG and DK095112 to RF, SR, and YZG). MZ acknowledges the support of the National Institute on Aging (U19 AG60917) and NIDDK (R01 DK113627). TY acknowledges the support of the National Institute on Aging (R01 AG71870). SR acknowledges the support of NIDDK (R01 DK090554) and Commonwealth Universal Research Enhancement (CURE) Program Pennsylvania.

tRNA-derived fragments as novel potential biomarkers for relapsed/refractory multiple myeloma

Background

tRNA-derived fragments have been reported to be key regulatory factors in human tumors. However, their roles in the progression of multiple myeloma remain unknown.

Results

This study employed RNA-sequencing to explore the expression profiles of tRFs/tiRNAs in new diagnosed MM and relapsed/refractory MM samples. The expression of selected tRFs/tiRNAs were further validated in clinical specimens and myeloma cell lines by qPCR. Bioinformatic analysis was performed to predict their roles in multiple myeloma progression.We identified 10 upregulated tRFs/tiRNAs and 16 downregulated tRFs/tiRNAs. GO enrichment and KEGG pathway analysis were performed to analyse the functions of 1 significantly up-regulated and 1 significantly down-regulated tRNA-derived fragments. tRFs/tiRNAs may be involved in MM progression and drug-resistance.

Conclusion

tRFs/tiRNAs were dysregulated and could be potential biomarkers for relapsed/refractory MM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-021-04167-8.

Systems level profiling of chemotherapy-induced stress resolution in cancer cells reveals druggable trade-offs

Cancer cells can survive chemotherapy-induced stress, but how they recover from it is not known. Using a temporal multiomics approach, we delineate the global mechanisms of proteotoxic stress resolution in multiple myeloma cells recovering from proteasome inhibition. Our observations define layered and protracted programs for stress resolution that encompass extensive changes across the transcriptome, proteome, and metabolome. Cellular recovery from proteasome inhibition involved protracted and dynamic changes of glucose and lipid metabolism and suppression of mitochondrial function. We demonstrate that recovering cells are more vulnerable to specific insults than acutely stressed cells and identify the general control nonderepressable 2 (GCN2)-driven cellular response to amino acid scarcity as a key recovery-associated vulnerability. Using a transcriptome analysis pipeline, we further show that GCN2 is also a stress-independent bona fide target in transcriptional signature-defined subsets of solid cancers that share molecular characteristics. Thus, identifying cellular trade-offs tied to the resolution of chemotherapy-induced stress in tumor cells may reveal new therapeutic targets and routes for cancer therapy optimization.

Expression Profiles of tRNA-Derived Fragments and Their Potential Roles in Multiple Myeloma

Background

Multiple myeloma is an incurable hematologic malignancy. The discovery of mechanisms may help to find new therapeutic targets and prolong survival. tRNA-related fragments (tRF) and tRNA halves (tiRNA) are small RNA derived from tRNAs and implicated in a wide variety of pathological processes, including cancer initiation and progression. However, there are almost no research reporting the role of these tRNA derived fragments in myeloma as far as we know.

Methods

In this study, we proposed the expression profiles of tRFs/tiRNAs in myeloma through RNA-sequencing in new diagnosed myeloma and healthy donors. The expression of selected tRFs/tiRNAs was further validated in clinical specimens by qPCR. Bioinformatic analysis was performed to predict their potential roles in multiple myeloma.

Results

A total of 33 upregulated tRFs/tiRNAs and 22 downregulated tRFs/tiRNAs were identified. GO enrichment and KEGG pathway analysis were performed to analyze the functions of one significantly up-regulated and one significantly down-regulated tRNA-derived fragments. tRFs/tiRNAs may be involved in MM initiation and progression.

Conclusion

We concluded that tRFs/tiRNAs were dysregulated and could be potential biomarkers for multiple myeloma.

RIP1 Perturbation Induces Chondrocyte Necroptosis and Promotes Osteoarthritis Pathogenesis via Targeting BMP7

Osteoarthritis (OA) is a highly prevalent and debilitating joint disorder that characterized by progressive destruction of articular cartilage. There is no effective disease-modifying therapy for the condition due to limited understanding of the molecular mechanisms on cartilage maintenance and destruction. Receptor-interacting protein kinase 1 (RIP1)-mediated necroptosis plays a vital role in various diseases, but the involvement of RIP1 in OA pathogenesis remains largely unknown. Here we show that typical necrotic cell morphology is observed within human OA cartilage samples in situ, and that RIP1 is significantly upregulated in cartilage from both OA patients and experimental OA rat models. Intra-articular RIP1 overexpression is sufficient to induce structural and functional defects of cartilage in rats, highlighting the crucial role of RIP1 during OA onset and progression by mediating chondrocyte necroptosis and disrupting extracellular matrix (ECM) metabolism homeostasis. Inhibition of RIP1 activity by its inhibitor necrostatin-1 protects the rats from trauma-induced cartilage degradation as well as limb pain. More importantly, we identify bone morphogenetic protein 7 (BMP7) as a novel downstream target that mediates RIP1-induced chondrocyte necroptosis and OA manifestations, thereby representing a non-canonical regulation mode of necroptosis. Our study supports a model whereby the activation of RIP1-BMP7 functional axis promotes chondrocyte necroptosis and subsequent OA pathogenesis, thus providing a new therapeutic target for OA.

MMRFBiolinks: an R-package for integrating and analyzing MMRF-CoMMpass data

In order to understand the mechanisms underlying the onset and the drug responses in multiple myeloma (MM), the second most frequent hematological cancer, the use of appropriate bioinformatic tools for integrative analysis of publicly available genomic data is required. We present MMRFBiolinks, a new R package for integrating and analyzing datasets from the Multiple Myeloma Research Foundation (MMRF) CoMMpass (Clinical Outcomes in MM to Personal Assessment of Genetic Profile) study, available at MMRF Researcher Gateway (MMRF-RG), and from the National Cancer Institute Genomic Data Commons (NCI-GDC) Data Portal. The package provides several methods for integrative analysis (array-array intensity correlation, Kaplan-Meier survival analysis) and visualization (response to treatments plot) of MMRF data, for performing an easily comprehensible analysis workflow. MMRFBiolinks extends the TCGABiolinks package by providing 13 new functions to analyze MMRF-CoMMpass data: six dealing with MMRF-RG data and seven with NCI-GDC data. As validation of the tool, we present two cases studies for searching, downloading and analyzing MMRF data. The former presents a workflow for identifying genes involved in survival depending on treatment. The latter presents an analysis workflow for analyzing the Best Overall (BO) response through correlation plots between the BO Response with respect to treatments, time, duration of treatment and annotated variants, as well as through Kaplan-Meier survival curves. The case studies demonstrate how MMRFBiolinks is able of overcoming the limitations of the analysis tools available at NCI-GDC and MMRF-RG, facilitating and making more comprehensive the retrieval, downloading and analysis of MMRF data.

The Landscape of Signaling Pathways and Proteasome Inhibitors Combinations in Multiple Myeloma

Multiple myeloma is a malignancy of terminally differentiated plasma cells, characterized by an extreme genetic heterogeneity that poses great challenges for its successful treatment. Due to antibody overproduction, MM cells depend on the precise regulation of the protein degradation systems. Despite the success of PIs in MM treatment, resistance and adverse toxic effects such as peripheral neuropathy and cardiotoxicity could arise. To this end, the use of rational combinatorial treatments might allow lowering the dose of inhibitors and therefore, minimize their side-effects. Even though the suppression of different cellular pathways in combination with proteasome inhibitors have shown remarkable anti-myeloma activities in preclinical models, many of these promising combinations often failed in clinical trials. Substantial progress has been made by the simultaneous targeting of proteasome and different aspects of MM-associated immune dysfunctions. Moreover, targeting deranged metabolic hubs could represent a new avenue to identify effective therapeutic combinations with PIs. Finally, epigenetic drugs targeting either DNA methylation, histone modifiers/readers, or chromatin remodelers are showing pleiotropic anti-myeloma effects alone and in combination with PIs. We envisage that the positive outcome of patients will probably depend on the availability of more effective drug combinations and treatment of early MM stages. Therefore, the identification of sensitive targets and aberrant signaling pathways is instrumental for the development of new personalized therapies for MM patients.

Multiple Myeloma Bone Disease: Implication of MicroRNAs in Its Molecular Background

Multiple myeloma (MM) is a common hematological malignancy arising from terminally differentiated plasma cells. In the majority of cases, symptomatic disease is characterized by the presence of bone disease. Multiple myeloma bone disease (MMBD) is a result of an imbalance in the bone-remodeling process that leads to increased osteoclast activity and decreased osteoblast activity. The molecular background of MMBD appears intriguingly complex, as several signaling pathways and cell-to-cell interactions are implicated in the pathophysiology of MMBD. MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate the expression of their target mRNAs. Numerous miRNAs have been witnessed to be involved in cancer and hematological malignancies and their role has been characterized either as oncogenic or oncosuppressive. Recently, scientific research turned towards miRNAs as regulators of MMBD. Scientific data support that miRNAs finely regulate the majority of the signaling pathways implicated in MMBD. In this review, we provide concise information regarding the molecular pathways with a significant role in MMBD and the miRNAs implicated in their regulation. Moreover, we discuss their utility as molecular biomarkers and highlight the putative usage of miRNAs as novel molecular targets for targeted therapy in MMBD.

Morphogens and growth factor signalling in the myeloma bone-lining niche

Multiple myeloma is a malignancy caused by the clonal expansion of abnormal plasma cells. Myeloma cells have proven to be incredibly successful at manipulating their microenvironment to promote growth and to evade modern therapies. They have evolved to utilise the integral signalling pathways of the bone and bone marrow to drive disease progression. The bone marrow is often described in the context of a single structure that fills the bone cavity and supports normal haematopoiesis. However, within that structure exists two anatomically different niches, the perivascular niche and the endosteal niche. These contain different cell types functioning to support normal immune and blood cell production as well as healthy bone. These cells secrete numerous signalling molecules that can influence myeloma cell biology and behaviour. The endosteal niche is home to specific bone cell lineages and plays a pivotal role in myeloma cell establishment and survival. This review will concentrate on some of the signalling pathways that are hijacked by myeloma cells to shape a favourable environment, and the different influences myeloma cells are exposed to depending on their spatial location within the bone marrow.

Targeting the BMP Pathway in Prostate Cancer Induced Bone Disease

From the 33,000 men in the U.S. who die from prostate cancer each year, the majority of these patients exhibit metastatic disease with bone being the most common site of metastasis. Prostate cancer bone metastases are commonly blastic, exhibiting new growth of unhealthy sclerotic bone, which can cause painful skeletal related events. Patient's current care entails androgen deprivation therapy, anti-resorptive agents, radiation, and chemotherapy to help control the spread of the cancer but little intervention is available to treat blastic bone disease. The transforming growth factor beta (TGFβ) and bone morphogenetic protein (BMP) pathways are known to regulate bone growth and resorption of destructive lytic bone lesions, yet the role of TGFβ/BMP signaling in prostate cancer blastic vs lytic bone lesions are not fully understood. We hypothesized that to target the BMP/TGFβ pathway, a useful biomarker of bone lytic or blastic pathology would have superior response. We show distinct BMP vs. TGFβ signaling in clinical samples of human prostate cancer bone metastases with either lytic or blastic pathologies. BMPs exhibit distinct effects on bone homeostasis, so to examine the effect of BMP inhibition on healthy bone, we treated mice with the BMP receptor small molecule antagonist DMH1 and saw a modest temporary improvement in bone health, with increased trabecular bone. We next sought to use the BMP inhibitor DMH1 to treat bone metastasis engraftment seeded by a caudal artery injection of the lytic human prostate cell line PC3 in immunodeficient mice. The colonization by PC3 cells to the bone were restricted with DMH1 treatment and bone health was importantly preserved. We next proceeded to test BMP inhibition in an injury model of established bone metastasis via intratibial injection of the MYC-CaP mouse prostate cell line into FVBN syngeneic mice. DMH1 treated mice had a modest decrease in trabecular bone and reduced lymphocytes in circulation without affecting tumor growth. Taken together we show unique responses to BMP inhibition in metastatic prostate cancer in the bone. These studies suggest that profiling bone lesions in metastatic prostate cancer can help identify therapeutic targets that not only treat the metastatic tumor but also address the need to better treat the distinct tumor induced bone disease.

Current Understanding of Myelomatous Mesenchymal Stromal Cells Extended through Advances in Experimental Methods

Simple Summary

As the amount of information available has grown, now it is known that many types of non-hematopoietic cells, including mesenchymal stem/progenitor cells, mature mesenchymal cells, and endothelial cells, as well as mature hematopoietic cells such as monocytes, macrophages, T-cells, and B-cells, have roles in the pathogenesis of multiple myeloma. This review focuses on the role of mesenchymal cells in the microenvironment of multiple myeloma. We summarize the experimental strategies and current understanding of the biological roles in the pathogenesis of myeloma. Furthermore, we discuss the possible clinical applications targeting mesenchymal cells.

Abstract

Multiple myeloma is an incurable cancer formed by malignant plasma cells. For the proliferation and survival of myeloma cells, as well as the occurrence of the complications, numerous intra- and extra-cellular mechanisms are involved. The interaction of myeloma cells with the microenvironment is known to be one of the most critical mechanisms. A specific microenvironment could affect the progression and growth of tumor cells, as well as drug resistance. Among various microenvironment components, such as hematological and non-hematological cells, and soluble factors (cytokines, chemokines, and extracellular matrix (ECM) proteins), in this review, we focus on the role of mesenchymal cells. We aimed to summarize the experimental strategies used for conducting studies and current understanding of the biological roles in the pathogenesis of myeloma. Furthermore, we discuss the possible clinical applications targeting mesenchymal cells.

Receptor binding competition: A paradigm for regulating TGF-β family action

The transforming growth factor (TGF)-β family is a group of structurally related, multifunctional growth factors, or ligands that are crucially involved in the development, regulation, and maintenance of animal tissues. In humans, the family counts over 33 members. These secreted ligands typically form multimeric complexes with two type I and two type II receptors to activate one of two distinct signal transduction branches. A striking feature of the family is its promiscuity, i.e., many ligands bind the same receptors and compete with each other for binding to these receptors. Although several explanations for this feature have been considered, its functional significance has remained puzzling. However, several recent reports have promoted the idea that ligand-receptor binding promiscuity and competition are critical features of the TGF-β family that provide an essential regulating function. Namely, they allow a cell to read and process multi-ligand inputs. This capability may be necessary for producing subtle, distinctive, or adaptive responses and, possibly, for facilitating developmental plasticity. Here, we review the molecular basis for ligand competition, with emphasis on molecular structures and binding affinities. We give an overview of methods that were used to establish experimentally ligand competition. Finally, we discuss how the concept of ligand competition may be fundamentally tied to human physiology, disease, and therapy.

The microenvironment in myeloma

PURPOSE OF REVIEW

The aim of the review is to describe recent advances in our understanding of how multiple myeloma interacts with its cellular and molecular neighbours in the bone marrow microenvironment, and how this may provide targets for prognostication and prevention.

RECENT FINDINGS

The bone marrow microenvironment in myeloma is beginning to yield targets that are amenable to therapy. A number of trials demonstrate some clinical efficacy in heavily pretreated disease. The challenge remains for how and when these therapeutic interventions are of particular benefit early in disease progression.

SUMMARY

Multiple myeloma is rarely curable and its interactions with the bone marrow microenvironment are evident. However, separating cause from effect remains a challenge. We propose that targeting specific niches within the bone marrow will yield therapies that have the potential for significant benefit in myeloma and may facilitate earlier intervention to disrupt an environment that is permissive for myeloma progression.

The dormant cancer cell life cycle

The success of targeted therapies and immunotherapies has created optimism that cancers may be curable. However, not all patients respond, drug resistance is common and many patients relapse owing to dormant cancer cells. These rare and elusive cells can disseminate early and hide in specialized niches in distant organs before being reactivated to cause disease relapse after successful treatment of the primary tumour. Despite their importance, we are yet to leverage knowledge generated from experimental models and translate the potential of targeting dormant cancer cells to prevent disease relapse in the clinic. This is due, at least in part, to the lack of adherence to consensus definitions by researchers, limited models that faithfully recapitulate this stage of metastatic spread and an absence of interdisciplinary approaches. However, the application of new high-resolution, single-cell technologies is starting to revolutionize the field and transcend classical reductionist models of studying individual cell types or genes in isolation to provide a global view of the complex underlying cellular ecosystem and transcriptional landscape that controls dormancy. In this Perspective, we synthesize some of these recent advances to describe the hallmarks of cancer cell dormancy and how the dormant cancer cell life cycle offers opportunities to target not only the cancer but also its environment to achieve a durable cure for seemingly incurable cancers.

MMRF-CoMMpass Data Integration and Analysis for Identifying Prognostic Markers

Multiple Myeloma (MM) is the second most frequent haematological malignancy in the world although the related pathogenesis remains unclear. The study of how gene expression profiling (GEP) is correlated with patients’ survival could be important for understanding the initiation and progression of MM.

In order to aid researchers in identifying new prognostic RNA biomarkers as targets for functional cell-based studies, the use of appropriate bioinformatic tools for integrative analysis is required.

The main contribution of this paper is the development of a set of functionalities, extending TCGAbiolinks package, for downloading and analysing Multiple Myeloma Research Foundation (MMRF) CoMMpass study data available at the NCI’s Genomic Data Commons (GDC) Data Portal. In this context, we present further a workflow based on the use of this new functionalities that allows to i) download data; ii) perform and plot the Array Array Intensity correlation matrix; ii) correlate gene expression and Survival Analysis to obtain a Kaplan–Meier survival plot.

Loss of Myeloid BMPR1a Alters Differentiation and Reduces Mouse Prostate Cancer Growth

The Bone Morphogenetic Protein (BMP) pathway is a member of the TGFβ signaling family and has complex roles in cancer. BMP signaling is rarely mutated and can be frequently overexpressed in many human cancers. The dichotomous role of BMPs as both tumor promoters and suppressors appears to be largely context based in both the cancer cell and the surrounding microenvironment. Myeloid cells including macrophages and neutrophils have been shown to be tumor promoting when stimulated from BMPs. We found that conditional deletion of BMPR1a in myeloid cells (LysMCre) restricts tumor progression in a syngeneic mouse prostate cancer model. Specific changes occurred in myeloid cells both in tumor bearing mice and tumor naïve mice throughout multiple tissues. We profiled myeloid subsets in the bone marrow, spleen and primary tumor and found myeloid BMPR1a loss altered the differentiation and lineage capability of distinct populations by histologic, flow cytometry and high dimensional mass cytometry analysis. We further confirmed the requirement for BMP signaling with pharmacologic inhibition of THP-1 and Raw264.7 activated into M2 macrophages with the BMP inhibitor DMH1. M2 polarized primary bone marrow derived cells from LysMCre BMPR1a knockout mice indicated a distinct requirement for BMP signaling in myeloid cells during M2 activation. These results indicate a unique necessity for BMP signaling in myeloid cells during tumor progression.

Integrating the immune microenvironment of prostate cancer induced bone disease

Prostate cancer (PCa) is the most frequently diagnosed cancer for men in the U.S. but does not impede patient survival until the disease is metastatic. Metastatic lesions most frequently occur in the bone, which exhibits a distinct microenvironment of immune and bone cell populations. Advances in the diagnosis and treatment of primary PCa allow for the use of tailored therapeutic approaches based on biomarkers, protein expression, and histopathology. Understanding the molecular and cellular characteristics of primary tumors has advanced therapeutic development and survival for patients with PCa. Personalized medicine has only recently emerged for the treatment of metastatic bone lesions. Tumor induced bone disease (TIBD) in patients with PCa can be classified into lytic, blastic, or mixed pathologies, with most patients exhibiting the blastic phenotype. Progress has been made in treating TIBD, but metastatic PCa has yet to be cured. Immune checkpoint inhibitors have exhibited limited responses in immunosuppressive PCa tumors, but have yet to be assessed in metastatic sites which may be susceptible to an increased inflammatory response. Recent discoveries have uncovered distinct tumor microenvironments (TMEs) of blastic and lytic bone metastases from patients with PCa, identifying actionable targets for therapeutic applications, including immune checkpoint inhibitors and targeted therapeutics. Enrichment for macrophages and T cells in patient samples suggests metastatic sites may be reappraised as immunologically targetable, despite their immunologically "cold" primary tumors. The practice of performing bone biopsies will help identify unique cellular and protein targets in the bone TME that can guide therapy decisions.

Targeting BMP signaling in the bone marrow microenvironment of myeloid leukemia

The bone morphogenetic protein (BMP) pathway regulates the fate and proliferation of normal hematopoietic stem cells (HSC) as well as interactions with their niche. While BMP2 and BMP4 promote HSC differentiation, only BMP4 maintains HSC pool and favors interactions with their niche. In myeloid leukemia, we have identified intrinsic and extrinsic dysregulations of the BMP pathway in Chronic Myeloid Leukemia (CML) and Acute Myeloid leukemia (AML) responsible for leukemic stem cells (LSC) survival. In AML, BMP pathway alterations sustain and promote resistant immature-like leukemic cells by activating a new signaling cascade. Binding of BMP4 to BMPR1A leads to ΔNp73 expression, which in turn induces NANOG, altogether associated with a poor patient's prognosis. Despite efficient targeted therapies, like Tyrosine Kinase Inhibitors (TKI) in CML, many patients retain LSCs. Our laboratory demonstrated that the BMP pathway sustains a permanent pool of LSCs expressing high levels of BMPR1B receptor, that evolve upon treatment to progressively implement a BMP4 autocrine loop, leading to TKI-resistant cells. Single cell RNA-Seq analysis of TKI-persisting LSCs showed a co-enrichment of BMP with Jak2-signaling, quiescence and stem cell (SC) signatures. Using a new model of persisting LSCs, we recently demonstrated that BMPR1B+ cells display co-activated Smad1/5/8 and Stat3 pathways and could be targeted by blocking BMPR1B/Jak2 signal. Lastly, a specific BMPR1B inhibitor impaired BMP4-mediated LSC protection against TKIs. Altogether, data based on various studies including ours, indicate that BMP targeting could eliminate leukemic cells within a protective bone marrow microenvironment to efficiently impact residual resistance or persistence of LSCs in myeloid leukemia.