Exosomes in multiple myeloma: from bench to bedside

Recent advancements in nanomedicine as a revolutionary approach to treating multiple myeloma

Multiple myeloma, the second most common hematological malignancy, remains incurable with a 5-year survival rate of approximately 50 % and recurrence rates near 100 %, despite significant attempts to develop effective medicines. Therefore, there is a pressing demand in the medical field for innovative and more efficient treatments for MM. Currently, the standard approach for treating MM involves administering high-dose chemotherapy, which frequently correlates with improved results; however, one major limiting factor is the significant side effects of these medications. Furthermore, the strategies used to deliver medications to tumors limit their efficacy, whether by rapid clearance from circulation or an insufficient concentration in cancer cells. Cancer treatment has shifted from cytotoxic, nonspecific chemotherapy regimens to molecularly targeted, rationally developed drugs with improved efficacy and fewer side effects. Nanomedicines may provide an effective alternative way to avoid these limits by delivering drugs into the complicated bone marrow microenvironment and efficiently reaching myeloma cells. Putting drugs into nanoparticles can make their pharmacokinetic and pharmacodynamic profiles much better. This can increase the drug's effectiveness in tumors, extend its time in circulation in the blood, and lower its off-target toxicity. In this review, we introduce several criteria for the rational design of nanomedicine to achieve the best anti-tumoral therapeutic results. Next, we discuss recent advances in nanomedicine for MM therapy.

LILRB4 on multiple myeloma cells promotes bone lesion by p-SHP2/NF-κB/RELT signal pathway

BACKGROUND

Leukocyte Ig-like receptor B family 4 (LILRB4) as an immune checkpoint on myeloid cells is a potential target for tumor therapy. Extensive osteolytic bone lesion is the most characteristic feature of multiple myeloma. It is unclear whether ectopic LILRB4 on multiple myeloma regulates bone lesion.

METHODS

The conditioned medium (CM) from LILRB4-WT and -KO cells was used to analyze the effects of LILRB4 on osteoclasts and osteoblasts. Xenograft, syngeneic and patient derived xenograft models were constructed, and micro-CT, H&E staining were used to observe the bone lesion. RNA-seq, cytokine array, qPCR, the activity of luciferase, Co-IP and western blotting were used to clarify the mechanism by which LILRB4 mediated bone damage in multiple myeloma.

RESULTS

We comprehensively analyzed the expression of LILRB4 in various tumor tissue arrays, and found that LILRB4 was highly expressed in multiple myeloma samples. The patient's imaging data showed that the higher the expression level of LILRB4, the more serious the bone lesion in patients with multiple myeloma. The conditioned medium from LILRB4-WT not -KO cells could significantly promote the differentiation and maturation of osteoclasts. Xenograft, syngeneic and patient derived xenograft models furtherly confirmed that LILRB4 could mediate bone lesion of multiple myeloma. Next, cytokine array was performed to identify the differentially expressed cytokines, and RELT was identified and regulated by LILRB4. The overexpression or exogenous RELT could regenerate the bone damage in LILRB4-KO cells in vitro and in vivo. The deletion of LILRB4, anti-LILRB4 alone or in combination with bortezomib could significantly delay the progression of bone lesion of multiple myeloma.

CONCLUSIONS

Our findings indicated that LILRB4 promoted the bone lesion by promoting the differentiation and mature of osteoclasts through secreting RELT, and blocking LILRB4 singling pathway could inhibit the bone lesion.

Pathways to therapy resistance: The sheltering effect of the bone marrow microenvironment to multiple myeloma cells

Multiple Myeloma (MM) is a malignant expansion of plasma cells in the bone marrow (BM), resulting in a disease characterized by symptoms of end organ damage from light chain secretion, crowding of the BM, and bone lesions. Although the past two decades have been characterized by numerous novel therapies emerging, the disease remains incurable due to intrinsic or acquired drug resistance. A major player in MM's drug resistance arises from its intimate relationship with the BM microenvironment (BMME). Through stress-inducing conditions, soluble messengers, and physical adhesion to BM elements, the BMME activates numerous pathways in the myeloma cell. This not only propagates myeloma progression through survival and growth signals, but also specific mechanisms to circumvent therapeutic actions. In this review, we provide an overview of the BMME, the role of individual components in MM survival, and various therapy-specific resistance mechanisms reported in the literature.

Exosomal noncoding RNAs in gynecological cancers: implications for therapy resistance and biomarkers

Gynecologic cancers, including ovarian cancer (OC), cervical cancer (CC), and endometrial cancer (EC), pose a serious threat to women's health and quality of life due to their high incidence and lethality. Therapeutic resistance in tumors refers to reduced sensitivity of tumor cells to therapeutic drugs or radiation, which compromises the efficacy of treatment or renders it ineffective. Therapeutic resistance significantly contributes to treatment failure in gynecologic tumors, although the specific molecular mechanisms remain unclear. Exosomes are nanoscale vesicles released and received by distinct kinds of cells. Exosomes contain proteins, lipids, and RNAs closely linked to their origins and functions. Recent studies have demonstrated that exosomal ncRNAs may be involved in intercellular communication and can modulate the progression of tumorigenesis, aggravation and metastasis, tumor microenvironment (TME), and drug resistance. Besides, exosomal ncRNAs also have the potential to become significant diagnostic and prognostic biomarkers in various of diseases. In this paper, we reviewed the biological roles and mechanisms of exosomal ncRNAs in the drug resistance of gynecologic tumors, as well as explored the potential of exosomal ncRNAs acting as the liquid biopsy molecular markers in gynecologic cancers.

Clearing soluble MIC reverses the impaired function of natural killer cells from patients with multiple myeloma

BACKGROUND

Major histocompatibility complex (MHC) class I chain-related protein (MIC) is a stress-induced ligand released from multiple myeloma (MM) cells during progression, and soluble MIC impairs natural killer group 2D (NKG2D) activating receptor-mediated recognition and function of natural killer (NK) cells. However, whether clearing soluble MIC with a monoclonal antibody (mAb) can restore NK cell activity of MM patients remains undetermined.

METHODS

We analyzed The Cancer Genome Atlas (TCGA) Multiple Myeloma Research Foundation (MMRF) CoMMpass data set to examine the prognostic significance of MIC expression in MM. We examined the level of soluble MIC in paired peripheral blood (PB) and bone marrow (BM) plasma of patients with MM at diagnosis by ELISA. We evaluated the correlation between the level of soluble MIC and immunophenotype of NK cells from MM patients by multicolor flow cytometry. We also generated MIC-overexpressing MM cell line and characterized the cytotoxic function of patient NK cells in the presence of soluble MIC, and examined the impact of clearing soluble MIC with a humanized mAb (huB10G5).

RESULTS

We characterize the importance of MICA in MM by revealing the significantly better overall survival of patients with high MICA expression from TCGA MMRF CoMMpass data set. The level of soluble MICA is more highly elevated in MM than in precursor stages, and the concentration of soluble MICA is higher in BM plasma than in PB. The concentration of soluble MICA in BM was correlated with myeloma burden, while it was negatively correlated with the frequency of NKG2D+ NK cells in diagnostic BM aspirates of MM patients. Soluble MICA downregulated NKG2D expression and decreased cytotoxicity of MM patient NK cells ex vivo, which were reversed by a humanized soluble MIC-clearing mAb (huB10G5) with enhanced degranulation of NK cells.

CONCLUSIONS

Our findings indicate targeting soluble MIC with huB10G5 might be a viable therapeutic approach to promote NKG2D-dependent cellular immunotherapy outcome in MM.

Hypoxic Bone Marrow Stromal Cells Secrete miR-140-5p and miR-28-3p That Target SPRED1 to Confer Drug Resistance in Multiple Myeloma

Bone marrow stromal cell (BMSC)-derived small extracellular vesicles (sEV) promote drug resistance to bortezomib in multiple myeloma cells. Elucidating the components of BMSC sEV that induce drug resistance in multiple myeloma cells could help identify strategies to overcome resistance. Considering the hypoxic nature of the myeloma microenvironment, we explored the role of hypoxia in regulating BMSC sEV cargo and investigated whether hypoxia-driven sEV miRNAs contribute to the drug resistance in multiple myeloma cells. Hypoxia increased the release of sEVs from BMSCs, and these sEVs more strongly attenuated bortezomib sensitivity in multiple myeloma cells than sEVs from BMSCs under normoxic conditions. RNA sequencing revealed that significantly elevated levels of miR-140-5p and miR-28-3p were enclosed in hypoxic BMSC-derived sEVs. Both miR-140-5p and miR-28-3p conferred bortezomib resistance in multiple myeloma cells by synergistically targeting SPRED1, a member of the Sprouty protein family that regulates MAPK activation. SPRED1 inhibition reduced sensitivity to bortezomib in multiple myeloma cells through activating MAPK-related pathways and significantly promoted multiple myeloma bortezomib resistance and tumor growth in a mouse model. These findings shed light on the role of hypoxia-induced miRNAs shuttled in BMSC-derived sEVs to multiple myeloma cells in inducing drug resistance and identify the miR-140-5p/miR-28-3p/SPRED1/MAPK pathway as a potential targetable axis for treating multiple myeloma.

SIGNIFICANCE

Hypoxia induces stromal cells to secrete extracellular vesicles with increased miR-140-5p and miR-28-3p that are transferred to multiple myeloma cells and drive drug resistance by increasing the MAPK signaling.

Exosomal miR-182 derived from bone marrow mesenchymal stem cells drives carfilzomib resistance of multiple myeloma cells by targeting SOX6

BACKGROUND

Multiple myeloma (MM) is a common hematological malignancy. Drug resistance remains to be a major clinical challenge in MM therapy. In this study, we aim to investigate the functional roles of bone marrow mesenchymal stem cells (BMSC)-derived exosomal miR-182 on the carfilzomib resistance of MM and its underlying mechanism.

METHODS

qRT-PCR and Western blot methods were utilized to confirm the gene or protein expressions. CCK-8 and transwell assays were performed to measure the capabilities of proliferation, migration, and invasion. The molecular interactions were validated through ChIP and Dual luciferase assay.

RESULTS

Our findings indicated that miR-182 expression was upregulated in serum, BMSCs and BMSC-derived exosomes from MM patients. Hypoxia-inducible factor-1α (HIF-1α), a key transcriptional factor in tumor microenvironment, could boost miR-182 expression by directly binding to its promoter, thus favoring exosomal secretion. Moreover, exosomal miR-182 from BMSCs could be transferred to MM cells and was able to promote malignant proliferation, metastasis, and invasion, as well as decrease the sensitivity of MM cells against carfilzomib. Additionally, SOX6 was identified as a downstream target of miR-182 in MM cells, and its expression was negatively regulated by miR-182. Rescue experiments proved that loss of SOX6 in MM cells dramatically reversed the promoting roles of BMSC-secreted exosomal miR-182 on proliferation, metastasis, and carfilzomib resistance in MM cells.

CONCLUSION

Collectively, our findings indicated that exosomal miR-182 derived from BMSCs contributed to the metastasis and carfilzomib resistance of MM cells by targeting SOX6. This study sheds light on the pathogenesis of the BMSC-derived exosome containing miR-182 in the malignant behaviors of MM cells and carfzomib resistance.

Unraveling the Emerging Niche Role of Hepatic Stellate Cell-derived Exosomes in Liver Diseases

Hepatic stellate cells (HSCs) play an essential role in various liver diseases, and exosomes are critical mediators of intercellular communication in local and distant microenvironments. Cellular crosstalk between HSCs and surrounding multiple tissue-resident cells promotes or inhibits the activation of HSCs. Substantial evidence has revealed that HSC-derived exosomes are involved in the occurrence and development of liver diseases through the regulation of retinoid metabolism, lipid metabolism, glucose metabolism, protein metabolism, and mitochondrial metabolism. HSC-derived exosomes are underpinned by vehicle molecules, such as mRNAs and microRNAs, that function in, and significantly affect, the processes of various liver diseases, such as acute liver injury, alcoholic liver disease, nonalcoholic fatty liver disease, viral hepatitis, fibrosis, and cancer. As such, numerous exosomes derived from HSCs or HSC-associated exosomes have attracted attention because of their biological roles and translational applications as potential targets for therapeutic targets. Herein, we review the pathophysiological and metabolic processes associated with HSC-derived exosomes, their roles in various liver diseases and their potential clinical application.

Exosomes, MDSCs and Tregs: A new frontier for GVHD prevention and treatment

The development of graft versus host disease (GVHD) represents a long-standing complication of allogeneic hematopoietic cell transplantation (allo-HCT). Different approaches have been used to control the development of GVHD with most relying on variations of chemotherapy drugs to eliminate allo-reactive T cells. While these approaches have proven effective, it is generally accepted that safer, and less toxic GVHD prophylaxis drugs are required to reduce the health burden placed on allo-HCT recipients. In this review, we will summarize the emerging concepts revolving around three biologic-based therapies for GVHD using T regulatory cells (Tregs), myeloid-derived-suppressor-cells (MDSCs) and mesenchymal stromal cell (MSC) exosomes. This review will highlight how each specific modality is unique in its mechanism of action, but also share a common theme in their ability to preferentially activate and expand Treg populations in vivo. As these three GVHD prevention/treatment modalities continue their path toward clinical application, it is imperative the field understand both the biological advantages and disadvantages of each approach.

In-Depth Proteomic Analysis of Blood Circulating Small Extracellular Vesicles

Circulating small extracellular vesicles (sEVs), also called exosomes, are key players in the investigation of cell-cell communication mechanisms and in the identification of new potential biomarkers. These particles can carry proteins, DNA, mRNA, miRNA, lipids and metabolites that are transported all over the human body, potentially reaching all the cells. In particular, proteins, which are well-known biological actors in cell signalling, will be discussed in this context. In this article, we present a mass spectrometry approach for the in-depth characterization of the sEVs proteome. The protocols include strategies for the isolation and purification of sEVs, for the extraction of proteins and the purification of sEVs proteins by the immunodepletion of the most abundant plasmatic proteins. Finally, bioinformatic analysis for the extraction of the most important biological features associated with the proteomic content of sEVs is reported.

Bone marrow microenvironment- induced regulation of Bcl-2 family members in multiple myeloma (MM): Therapeutic implications

In Multiple Myeloma (MM) the finely tuned homeostasis of the bone marrow (BM) microenvironment is disrupted. Evasion of programmed cell death (apoptosis) represents a hallmark of cancer. Besides genetic aberrations, the supportive and protective MM BM milieu, which is constituted by cytokines and growth factors, intercellular and cell: extracellular matrix (ECM) interactions and exosomes, in particular, plays a key role in the abundance of pro-survival members of the Bcl-2 family (i.e., Mcl-1, Bcl-2, and Bcl-xL) in tumor cells. Moreover, microenvironmental cues have also an impact on stability- regulating post-translational modifications of anti-apoptotic proteins including de/phosphorylation, polyubiquitination; on their intracellular binding affinities, and localization. Advances of our molecular knowledge on the escape of cancer cells from apoptosis have informed the development of a new class of small molecules that mimic the action of BH3-only proteins. Indeed, approaches to directly target anti-apoptotic Bcl-2 family members are among today's most promising therapeutic strategies and BH3-mimetics (i.e., venetoclax) are currently revolutionizing not only the treatment of CLL and AML, but also hold great therapeutic promise in MM. Furthermore, approaches that activate apoptotic pathways indirectly via modification of the tumor microenvironment have already entered clinical practice. The present review article will summarize our up-to-date knowledge on molecular mechanisms by which the MM BM microenvironment, cytokines, and growth factors in particular, mediates tumor cell evasion from apoptosis. Moreover, it will discuss some of the most promising science- derived therapeutic strategies to overcome Bcl-2- mediated tumor cell survival in order to further improve MM patient outcome.

Extracellular Vesicles and Their Roles in the Tumor Immune Microenvironment

Tumor cells actively incorporate molecules (e.g., proteins, lipids, RNA) into particles named extracellular vesicles (EVs). Several groups have demonstrated that EVs can be transferred to target (recipient) cells, making EVs an important means of intercellular communication. Indeed, EVs are able to modulate the functions of target cells by reprogramming signaling pathways. In a cancer context, EVs promote the formation of a supportive tumor microenvironment (TME) and (pre)metastatic niches. Recent studies have revealed that immune cells, tumor cells and their secretome, including EVs, promote changes in the TME and immunosuppressive functions of immune cells (e.g., natural killer, dendritic cells, T and B cells, monocytes, macrophages) that allow tumor cells to establish and propagate. Despite the growing knowledge on EVs and on their roles in cancer and as modulators of the immune response/escape, the translation into clinical practice remains in its early stages, hence requiring improved translational research in the EVs field. Here, we comprehensively review the current knowledge and most recent research on the roles of EVs in tumor immune evasion and immunosuppression in both solid tumors and hematological malignancies. We also highlight the clinical utility of EV-mediated immunosuppression targeting and EV-engineering. Importantly, we discuss the controversial role of EVs in cancer biology, current limitations and future perspectives to further the EV knowledge into clinical practice.