Targeting the bone marrow microenvironment in multiple myeloma

Hepatitis B and C virus infection and risk of multiple myeloma: a systematic review and meta-analysis

BACKGROUND

Multiple myeloma (MM) is a clonal proliferative disorder of plasma cells with limited curative options. Hepatitis B (HBV) and hepatitis C (HCV) viruses have been implicated in the development of various hematological malignancies, but their association with MM remains unclear. This systematic review and meta-analysis aimed to investigate the risk of MM in individuals with HBV and HCV infections.

METHODS

A comprehensive literature search was conducted across PubMed, Scopus, Web of Science, Embase, and additional sources for cohort and case-control studies published between January 1990 and January 2025. The relative risk (RR) of developing MM in individuals with HBV and HCV infections was pooled using a random-effects model. Subgroup analyses were performed based on age, geographic region, and diagnostic method. The Newcastle-Ottawa Scale (NOS) was used to assess study quality. Statistical heterogeneity was evaluated using the I² statistic, and publication bias was assessed using Egger's test.

RESULTS

Seventeen studies, comprising 1 cohort and 16 case-control studies, were included. Nine studies examined the association between HBV and MM, yielding a pooled RR of 1.25 (95% CI: 0.99-1.58) with moderate heterogeneity (I² = 56.52%). Fifteen studies evaluated the association between HCV and MM, with a pooled RR of 1.84 (95% CI: 1.27-2.67), indicating a higher risk in HCV-infected individuals. Subgroup analysis revealed a stronger association in European populations for both HBV (RR: 1.67, 95% CI: 1.05-2.66) and HCV (RR: 2.27, 95% CI: 1.21-4.25). No significant publication bias was detected for either HBV or HCV analyses.

CONCLUSION

HBV and HCV infections are associated with an increased risk of developing multiple myeloma, with HCV demonstrating a stronger association. These findings highlight the importance of screening and monitoring patients with chronic hepatitis for potential hematological malignancies, especially in high-risk regions.

Targeting capacity, safety and efficacy of engineered extracellular vesicles delivered by transdermal microneedles to treat plasmacytoma in mice

BACKGROUND

Engineered extracellular vesicles (EVs) are emerging as a highly potential platform for targeted drug delivery in cancer therapy. Although intravenous injection is commonly used in EV treatment, there is growing interest in using microneedles (MNs) for transdermal EV delivery; however, comprehensive studies comparing the tissue distribution, safety and antitumour efficacy of these two approaches for delivering engineered EVs remain scarce.

METHODS

We used EVs derived from umbilical cord mesenchymal stem cells, modified with phospholipid‒polyethylene glycol‒N-hydroxysuccinimide and conjugated with CD38 peptides (CD38-EVs), to target myeloma cells that highly express CD38 antigen, and tested their safety and antitumour efficacy in mice with subcutaneous plasmacytoma, administrated via dissolvable transdermal MNs or intravenous injection. Flow cytometry, immunofluorescence and fluorescence molecular projection imaging analysis were employed to evaluate the distribution of CD38-EVs at the cellular level and within living systems. Additionally, histopathological analysis and biochemical analyses were conducted to assess the antitumour effects and safety of CD38-EVs loaded with doxorubicin (CD38-EVs-Dox).

RESULTS

Compared to standard EVs, CD38-EVs exhibited enhanced uptake by CD38high tumour cells and reduced uptake by CD38-negative non-tumour cells in vitro. In plasmacytoma NOD/SCID mouse models, CD38-EVs encapsulated within MNs (CD38-EVsMNs) effectively targeted the tumour cells much more than the standard EVs encapsulated within MNs (EVsMNs) and CD38-EVs intravenously administrated (CD38-EVsi.v), with reduced distribution to the lungs and spleen. Additionally, CD38-EVs-Dox induced significantly greater cytotoxicity against the tumour cells than EVs-Dox in vitro, and CD38-EVs-DoxMNs significantly reduced tumour burden compared to both EVs-DoxMNs and CD38-EVs-Doxi.v, while maintaining favourable safety profiles.

CONCLUSIONS

CD38-EVs-DoxMNs have superior efficacy and safety in treating plasmacytoma mice, compared to CD38-EVs-Doxi.v, providing novel insights into the potential of MNs as a platform for delivering targeted engineered EVs in tumour therapy.

HIGHLIGHTS

Enhanced tumor targeting: CD38-modified EVs (CD38-EVs) showed increased uptake by CD38high tumor cells while reducing uptake by CD38-negative non-tumor cells. Optimized delivery: MN-loaded CD38-EVs targeted tumors more effectively than MN-loaded EVs and intravenously injected CD38-EVs, with lower lung and spleen accumulation. Superior antitumor efficacy: MN-delivered CD38-EVs-Dox significantly suppressed tumor growth, outperforming intravenous CD38-EVs-Dox and MN-delivered EVs-Dox.

A thematic analysis of prognostic, diagnostic, and therapeutic of circulating miRNA biomarkers in bortezomib-resistant multiple myeloma

Objective

The increasing demand for precision medicine has spurred molecular diagnostic investigations to emphasize the utility of miRNA as significant biomarkers. Recent studies have underscored miRNA's role as prognostic, diagnostic, and therapeutic biomarkers in managing and monitoring multiple myeloma patients. This review aims to present the latest insights on the potential of circulating miRNA as prognostic, diagnostic, and therapeutic biomarkers in bortezomib-resistant multiple myeloma.

Methods

For this purpose, a comprehensive thematic literature review from January 2014 and August 2024 was conducted utilizing the databases CINAHL, Pubmed, and Google Scholar. Twenty pertinent studies were meticulously analyzed and categorized into the following sections: Bortezomib (BTZ) resistance in multiple myeloma, the predictive role of miRNAs in BTZ resistance, the impact of circulating miRNAs in multiple myeloma, and the potential of circulating miRNA as prognostic, diagnostic, and therapeutic biomarkers.

Results

Of note, eight studies identified circulating miRNAs as diagnostic miRNA biomarkers (i.e., miR-744, miR-130a, let-7d, let-7e, miR-34a, etc.). In comparison, nine studies identified several circulating miRNAs that can be used as prognostic biomarkers (i.e., miR-20a, miR-483-5p, mir-1246, let-7a, let-7e, etc.). Moreover, five studies identified circulating miRNAs as promising therapeutic biomarkers (i.e., mir-15a, mir-92a, mir-19a, etc.). This discovery can significantly enhance early detection, accurate diagnosis, prognosis, overall survival rates, and quality of life for patients with multiple myeloma.

Conclusion

Based on this evidence, exploring circulating miRNAs as a potential noninvasive biomarker for multiple myeloma represents a noteworthy advancement. This is attributed to the abundance of miRNAs in plasma or serum, which exhibits remarkable stability against enzymatic degradation.

Generation of allogeneic CAR-NKT cells from hematopoietic stem and progenitor cells using a clinically guided culture method

Cancer immunotherapy with autologous chimeric antigen receptor (CAR) T cells faces challenges in manufacturing and patient selection that could be avoided by using 'off-the-shelf' products, such as allogeneic CAR natural killer T (AlloCAR-NKT) cells. Previously, we reported a system for differentiating human hematopoietic stem and progenitor cells into AlloCAR-NKT cells, but the use of three-dimensional culture and xenogeneic feeders precluded its clinical application. Here we describe a clinically guided method to differentiate and expand IL-15-enhanced AlloCAR-NKT cells with high yield and purity. We generated AlloCAR-NKT cells targeting seven cancers and, in a multiple myeloma model, demonstrated their antitumor efficacy, expansion and persistence. The cells also selectively depleted immunosuppressive cells in the tumor microenviroment and antagonized tumor immune evasion via triple targeting of CAR, TCR and NK receptors. They exhibited a stable hypoimmunogenic phenotype associated with epigenetic and signaling regulation and did not induce detectable graft versus host disease or cytokine release syndrome. These properties of AlloCAR-NKT cells support their potential for clinical translation.

Effects of mesenchymal stem cells from different sources on the biological functions of multiple myeloma cells

BACKGROUND

The therapeutic benefits of mesenchymal stromal cells (MSCs) are largely dependent on paracrine factors, but the supernatants of the different MSCs may have different effects on multiple myeloma (MM) cells. Therefore, this study compared supernatants of bone marrow-derived mesenchymal stromal cells (BM-MSCs) with umbilical cord wharton's jelly's mesenchymal stem cells (UC-WJ MSCs) in different states (non-senescent and replicative senescence) on the MM cells.

METHODS

We extracted human BM-MSCs and UC-WJ MSCs in vitro and used H2O2 to induce replicative senescence. Concentrated supernatants from MSCs and senescent MSCs (SMSCs) were added to MM cells. Cell proliferation, the cell cycle, apoptosis, cell migration, tumor stemness factor expression, and cytokine expression levels were analyzed. Transcription regulation of signaling pathways was discussed.

RESULTS

We successfully isolated and identified BM-MSCs, UC-WJ MSCs, and SMSCs. When concentrated supernatants from BM-MSCs, UC-WJ MSCs, senescent BM-MSCs (SBM-MSCs), senescent UCWJ MSCs (SUC-WJ MSCs) were used to treat MM cells, BMMSCs and SBM-MSCs supernatants promoted the proliferation of MM cells, with a more pronounced effect by SBM-MSCs. UC-WJ MSCs and SUC-WJ MSCs supernatants inhibited the viability and proliferation of MM cells. BM-MSCs and SBM-MSCs supernatants increased the proportion of MM cells in the S-phase, with the effect of SBM-MSCs being more evident. UC-WJ MSCs and SUC-WJ MSCs supernatants arrested MM cells in the G0/G1 phase. BM-MSCs and SBM-MSCs supernatants enhanced the migration and tumor stemness of MM cells, with SBMMSCs having a more dramatic effect. UC-WJ MSCs and SUC-WJ MSCs supernatants inhibited the migration and tumor stemness of MM cells, with UC-WJ MSCs having a more inhibitory effect. IL-6 and VEGFA expression correlated negatively with the survival of patients with MM according to online database analysis, in addition, we found that the expression of IL-6 and VEGFA was higher in MM patients through GEO database analysis. BM-MSCs and SBM-MSCs supernatants treatment increased the expression of IL-6 and VEGFA on MM cells, while UC-WJ MSCs and SUC-WJ MSCs supernatants inhibited their expression. Signal pathway validation showed that the biological function of MSCs in MM is closely related to the PI3K/AKT/NF-κB pathway.

CONCLUSION

The supernatants of BM-MSCs promote the proliferation of MM cells, On the contrary, the supernatants of UC-WJ MSCs inhibit MM cell proliferation. We observed that MSCs from different sources and different states have contrasting biological functions in MM cells. Furthermore, this research was provided to the optimal cancer gene therapy vector for MM was UC-WJ MSCs, even UC-WJ MSCs was in the state of senescence.

In Vitro 3D Models of Haematological Malignancies: Current Trends and the Road Ahead?

Haematological malignancies comprise a diverse group of life-threatening systemic diseases, including leukaemia, lymphoma, and multiple myeloma. Currently available therapies, including chemotherapy, immunotherapy, and CAR-T cells, are often associated with important side effects and with the development of drug resistance and, consequently, disease relapse. In the last decades, it was largely demonstrated that the tumor microenvironment significantly affects cancer cell proliferation and tumor response to treatment. The development of biomimetic, in vitro models may promote the investigation of the interactions between cancer cells and the tumor microenvironment and may help to better understand the mechanisms leading to drug resistance. Although advanced in vitro models have been largely explored in the field of solid tumors, due to the complex nature of the blood cancer tumor microenvironment, the mimicking of haematological malignancies mostly relies on simpler systems, often limited to two-dimensional cell culture, which intrinsically excludes the microenvironmental niche, or to ethically debated animal models. This review aims at reporting an updated overview of state-of-the-art hematological malignancies 3D in vitro models, emphasizing the key features and limitations of existing systems to inspire further research in this underexplored field.

New horizons in our understanding of precursor multiple myeloma and early interception

Multiple myeloma is an incurable plasma cell malignancy that evolves over decades through the selection and malignant transformation of monoclonal plasma cells. The evolution from precursor states to symptomatic disease is characterized by an increasing complexity of genomic alterations within the plasma cells and a remodelling of the microenvironment towards an immunosuppressive state. Notably, in patients with advanced disease, similar mechanisms of tumour escape and immune dysfunction mediate resistance to modern T cell-based therapies, such as T cell-engaging bispecific antibodies and chimeric antigen receptor (CAR)-T cells. Thus, an increasing number of clinical trials are assessing the efficiency and safety of these therapies in individuals with newly diagnosed multiple myeloma and high-risk smoldering multiple myeloma. In this Review, we summarize the current knowledge about tumour intrinsic and extrinsic processes underlying progression from precursor states to symptomatic myeloma and discuss the rationale for early interception including the use of T cell-redirecting therapies.

IL-10R inhibition reprograms tumor-associated macrophages and reverses drug resistance in multiple myeloma

Multiple myeloma (MM) is the cancer of plasma cells within the bone marrow and remains incurable. Tumor-associated macrophages (TAMs) within the tumor microenvironment often display a pro-tumor phenotype and correlate with tumor proliferation, survival, and therapy resistance. IL-10 is a key immunosuppressive cytokine that leads to recruitment and development of TAMs. In this study, we investigated the role of IL-10 in MM TAM development as well as the therapeutic application of IL-10/IL-10R/STAT3 signaling inhibition. We demonstrated that IL-10 is overexpressed in MM BM and mediates M2-like polarization of TAMs in patient BM, 3D co-cultures in vitro, and mouse models. In turn, TAMs promote MM proliferation and drug resistance, both in vitro and in vivo. Moreover, inhibition of IL-10/IL-10R/STAT3 axis using a blocking IL-10R monoclonal antibody and STAT3 protein degrader/PROTAC prevented M2 polarization of TAMs and the consequent TAM-induced proliferation of MM, and re-sensitized MM to therapy, in vitro and in vivo. Therefore, our findings suggest that inhibition of IL-10/IL-10R/STAT3 axis is a novel therapeutic strategy with monotherapy efficacy and can be further combined with current anti-MM therapy, such as immunomodulatory drugs, to overcome drug resistance. Future investigation is warranted to evaluate the potential of such therapy in MM patients.

Reconstitution of the Multiple Myeloma Microenvironment Following Lymphodepletion with BCMA CAR-T Therapy

PURPOSE

The purpose of this study was to investigate the remodeling of the multiple myeloma microenvironment after B-cell maturation antigen (BCMA)-targeted chimeric antigen receptor T (CAR-T) cell therapy.

EXPERIMENTAL DESIGN

We performed single-cell RNA sequencing on paired bone marrow specimens (n = 14) from seven patients with multiple myeloma before (i.e., baseline, "day -4") and after (i.e., "day 28") lymphodepleted BCMA CAR-T cell therapy.

RESULTS

Our analysis revealed heterogeneity in gene expression profiles among multiple myeloma cells, even those harboring the same cytogenetic abnormalities. The best overall responses of patients over the 15-month follow-up are positively correlated with the abundance and targeted cytotoxic activity of CD8+ effector CAR-T cells on day 28 after CAR-T cell infusion. Additionally, favorable responses are associated with attenuated immunosuppression mediated by regulatory T cells, enhanced CD8+ effector T-cell cytotoxic activity, and elevated type 1 conventional dendritic cell (DC) antigen presentation ability. DC re-clustering inferred intramedullary-originated type 3 conventional DCs with extramedullary migration. Cell-cell communication network analysis indicated that BCMA CAR-T therapy mitigates BAFF/GALECTIN/MK pathway-mediated immunosuppression and activates MIF pathway-mediated anti-multiple myeloma immunity.

CONCLUSIONS

Our study sheds light on multiple myeloma microenvironment dynamics after BCMA CAR-T therapy, offering clues for predicting treatment responsivity.

Association of ADAM family members with proliferation signaling and disease progression in multiple myeloma

Multiple myeloma (MM) is a hematological malignancy whose curability is greatly challenged by recurrent patient relapses and therapy resistance. We have previously proposed the high expression of ADAM8, ADAM9 and ADAM15 (A Disintegrin And Metalloproteinase 8/9/15) as adverse prognostic markers in MM. This study focused on the so far scarcely researched role of ADAM8/9/15 in MM using two patient cohorts and seven human MM cell lines (HMCL). High ADAM8/9/15 expression was associated with high-risk cytogenetic abnormalities and extramedullary disease. Furthermore, ADAM8/15 expression increased with MM progression and in relapsed/refractory MM compared to untreated patient samples. RNA sequencing and gene set enrichment analysis comparing ADAM8/9/15high/low patient samples revealed an upregulation of proliferation markers and proliferation-associated gene sets in ADAM8/9/15high patient samples. High ADAM8/9/15 expression correlated with high Ki67 and high ADAM8/15 expression with high MYC protein expression in immunohistochemical stainings of patient tissue. Conversely, siRNA-mediated knockdown of ADAM8/9/15 in HMCL downregulated proliferation-related gene sets. Western blotting revealed that ADAM8 knockdown regulated IGF1R/AKT signaling and ADAM9 knockdown decreased mTOR activation. Lastly, high ADAM8/9/15 expression levels were verified as prognostic markers independent of Ki67/MYC expression and/or high-risk abnormalities. Overall, these findings suggest that ADAM8/9/15 play a role in MM progression and proliferation signaling.

Just scratching the surface: novel treatment approaches for multiple myeloma targeting cell membrane proteins

A better understanding of the roles of the adaptive and innate immune systems in the oncogenesis of cancers including multiple myeloma (MM) has led to the development of novel immune-based therapies. B cell maturation antigen (BCMA), G protein-coupled receptor family C group 5 member D (GPRC5D) and Fc receptor-like protein 5 (FcRL5, also known as FcRH5) are cell-surface transmembrane proteins expressed by plasma cells, and have been identified as prominent immunotherapeutic targets in MM, with promising activity demonstrated in patients with heavily pretreated relapsed and/or refractory disease. Indeed, since 2020, antibody-drug conjugates, bispecific T cell engagers and autologous chimeric antigen receptor T cells targeting BCMA or GPRC5D have been approved for the treatment of relapsed and/or refractory MM. However, responses to these therapies are not universal, and acquired resistance invariably occurs. In this Review, we discuss the various immunotherapeutic approaches targeting BCMA, GPRC5D and FcRL5 that are currently either available or in clinical development for patients with MM. We also review the mechanisms underlying resistance to such therapies, and discuss potential strategies to overcome these mechanisms and improve patient outcomes.

A comprehensive review of the PTEN/PI3K/Akt axis in multiple myeloma: From molecular interactions to potential therapeutic targets

Phosphatase and tensin homolog (PTEN), phosphatidylinositol 3-kinase (PI3K), and protein kinase B (Akt) signaling pathways contribute to the development of several cancers, including multiple myeloma (MM). PTEN is a tumor suppressor that influences the PI3K/Akt/mTOR pathway, which in turn impacts vital cellular processes like growth, survival, and treatment resistance. The current study aims to present the role of PTEN and PI3K/Akt/mTOR signaling in the development of MM and its response to treatment. In addition, the molecular interactions in MM that underpin the PI3K/Akt/mTOR pathway and address potential implications for the development of successful treatment plans are also discussed in detail. We investigate their relationship to both upstream and downstream regulators, highlighting new developments in combined therapies that target the PTEN/PI3K/Akt axis to overcome drug resistance, including the use of PI3K and mitogen-activated protein kinase (MAPK) inhibitors. We also emphasize that PTEN/PI3K/Akt pathway elements may be used in MM diagnosis, prognosis, and therapeutic targets.

Bone marrow fibrosis in newly diagnosed multiple myeloma and its correlation with clinicopathological factors

BACKGROUND

Bone marrow fibrosis (BMF) severely impacts both the quality of life and the efficacy of diagnostic procedures. However, the correlation between BMF and clinicopathological features, cytogenetic changes, and prognosis of newly diagnosed multiple myeloma (NDMM) remains unclear. This study determined the incidence, patient characteristics, and clinical outcomes of patients with NDMM with BMF.

METHODS

The clinical data, histological features, and clinical outcomes of patients with NDMM were collected. Reticular fiber staining was performed on the enrolled cases, and the degree of reticular fiber overgrowth was graded. Patients with MF-2 and MF-3 were classified as the BMF+ group, and those with MF-0 and MF-1 were classified as the BMF- group, and BMF incidence was calculated. The differences in clinical data, histological features, and clinical outcomes between the BMF+ group and the BMF- group were compared.

RESULTS

A consecutive series of 146 patients with NDMM were included. The incidence of MF-0, MF-1, MF-2, and MF-3 was 7.53% (11/146), 34.93% (51/146), 51.37% (75/146), and 6.16% (9/146), respectively. The incidence of BMF-MF-2 and MF-3-was 57.53% (84/146). A significant correlation was identified between the pattern of infiltration and BMF (P < 0.001). In the BMF- group, the distribution of cases with interstitial, nodular, and diffuse infiltration of plasma cells was 16 (25.8%), 21 (33.9%), and 25 (40.3%), respectively. Conversely, in the BMF+ group, these values for interstitial, nodular, and diffuse tumor cells were 9 (10.7%), 15 (17.9%), and 60 (71.4%). Furthermore, BMF was associated with a diffuse infiltration pattern. The overall survival (OS) of the BMF+ group (39.1 months; 95% confidence interval [CI]: 34.0-44.3) was lower than that of the BMF- group (45.4 months; 95% CI: 39.5-51.3), but there was no significant difference between the two groups (P = 0.221). Univariate and multivariate analyses showed that the BMF+ status was not associated with OS in patients with NDMM (P = 0.381 and P = 0.748, respectively).

CONCLUSIONS

Our findings suggest that BMF is linked to a diffuse infiltration pattern, and its occurrence is not related to the prognosis of patients with NDMM, providing a basis for further exploring the BMF value in NDMM diagnosis and treatment.

Advancements in microenvironment-based therapies: transforming the landscape of multiple myeloma treatment

Multiple myeloma (MM) is the most prevalent malignant monoclonal disease of plasma cells. There is mounting evidence that interactions with the bone marrow (BM) niche are essential for the differentiation, proliferation, survival, migration, and treatment resistance of myeloma cells. For this reason, gaining a deeper comprehension of how BM microenvironment compartments interact with myeloma cells may inspire new therapeutic ideas that enhance patient outcomes. This review will concentrate on the most recent findings regarding the mechanisms of interaction between microenvironment and MM and highlight research on treatment targeting the BM niche.

[Expression and clinical significance of CCL17, CCL22, and CCR4 in newly diagnosed multiple myeloma]

Objective: To study the expressions of C-C class chemokine 17 (CCL17), C-C class chemokine 22 (CCL22), and C-C chemokine receptor 4 (CCR4) in newly diagnosed multiple myeloma (NDMM) for analyzing their correlations with clinical features and to preliminarily explore their roles in the development of NDMM. Methods: The study included 40 patients with NDMM and 20 healthy volunteers from the Department of Hematology of the Affiliated Hospital of Zunyi Medical University from July 2020 to December 2022. Peripheral blood, bone marrow, and bone marrow biopsy tissue samples were collected from the two groups. The expression levels of CCL17, CCL22, and CCR4 in patients with NDMM were analyzed using real-time quantitative reverse transcriptase polymerase chain reaction (RQ-PCR), enzyme-linked immunosorbent assay (ELISA), and immunohistochemistry. The mRNA expression levels of CCL17, CCL22, and CCR4 in the bone marrow mononuclear cell (BMMNC) of patients with NDMM were analyzed to assess their correlations with clinical indicators. Results: The mRNA expression levels of CCL17, CCL22, and CCR4 in BMMNC were higher in patients with NDMM than in controls (all P<0.05). The protein expression levels of CCL17 and CCL22 in peripheral blood supernatants and bone marrow supernatants were higher in patients with NDMM than in controls (all P<0.05). The expression levels of CCL17, CCL22, and CCR4 in bone marrow biopsy tissues were higher in patients with NDMM than in controls (all P<0.05). The mRNA expression level of CCL17 was increased in NDMM patients with combined anemia, bone damage, renal damage, and M protein level ≥30 g/L (all P<0.05). The mRNA expression level of CCL22 was increased in NDMM patients with combined anemia, bone damage, and renal damage (all P<0.05). The mRNA expression level of CCR4 was increased in NDMM patients with combined anemia and renal damage (all P<0.05) . Conclusion: CCL17, CCL22, and CCR4 were highly expressed in clinical samples from patients with NDMM compared to those from controls, and they may be involved in the occurrence and development of NDMM.

Multiple myeloma

Multiple myeloma (MM) is a haematological lymphoid malignancy involving tumoural plasma cells and is usually characterized by the presence of a monoclonal immunoglobulin protein. MM is the second most common haematological malignancy, with an increasing global incidence. It remains incurable because most patients relapse or become refractory to treatments. MM is a genetically complex disease with high heterogeneity that develops as a multistep process, involving acquisition of genetic alterations in the tumour cells and changes in the bone marrow microenvironment. Symptomatic MM is diagnosed using the International Myeloma Working Group criteria as a bone marrow infiltration of ≥10% clonal plasma cells, and the presence of at least one myeloma-defining event, either standard CRAB features (hypercalcaemia, renal failure, anaemia and/or lytic bone lesions) or biomarkers of imminent organ damage. Younger and fit patients are considered eligible for transplant. They receive an induction, followed by consolidation with high-dose melphalan and autologous haematopoietic cell transplantation, and maintenance therapy. In older adults (ineligible for transplant), the combination of daratumumab, lenalidomide and dexamethasone is the preferred option. If relapse occurs and requires further therapy, the choice of therapy will be based on previous treatment and response and now includes immunotherapies, such as bi-specific monoclonal antibodies and chimeric antigen receptor T cell therapy.

Current status of bispecific antibodies and CAR-T therapies in multiple myeloma

Multiple myeloma (MM), a malignancy of plasma cells, is an incurable disease that is characterized by the neoplastic proliferation of plasma cells leading to extensive skeletal destruction. This includes osteolytic lesions, osteopenia, and pathologic fractures. MM is clinically manifested through bone pain, renal insufficiency, hypercalcemia, anemia, and recurrent infections. Its prevalence and the need for effective treatment underscore the importance of this research. Recent advancements in MM therapy have been significant, particularly with the integration of daratumumab into first-line treatments. The use of daratumumab in regimens such as DRD (Daratumumab, Revlimid, Dexamethasone) and D-RVd (Daratumumab, Lenalidomide, Bortezomib, Dexamethasone) represents a paradigm shift in the treatment landscape. GRIFFIN and CASSIOPEIA trials have highlighted the efficacy of these regimens, particularly in prolonging progression-free survival and deepening patient responses. The shift from older regimens like MPV (Melphalan, Prednisone, Velcade) to more effective ones like DRD and RVD has been pivotal in treatment strategies. This review also focuses on the potential of Chimeric Antigen Receptor T-cell therapy and bispecific antibodies in MM. CAR-T therapy, which has shown success in other hematological malignancies, is being explored for its ability to specifically target MM cells. The latest clinical trials and research findings are analyzed to evaluate the efficacy and challenges of CAR-T therapy in MM. Additionally, the role of bispecific antibodies, which are designed to bind both cancer cells and T cells, is explored. These antibodies offer a unique mechanism that could complement the effects of CAR-T therapy.

Engineering allorejection-resistant CAR-NKT cells from hematopoietic stem cells for off-the-shelf cancer immunotherapy

The clinical potential of current FDA-approved chimeric antigen receptor (CAR)-engineered T (CAR-T) cell therapy is encumbered by its autologous nature, which presents notable challenges related to manufacturing complexities, heightened costs, and limitations in patient selection. Therefore, there is a growing demand for off-the-shelf universal cell therapies. In this study, we have generated universal CAR-engineered NKT (UCAR-NKT) cells by integrating iNKT TCR engineering and HLA gene editing on hematopoietic stem cells (HSCs), along with an ex vivo, feeder-free HSC differentiation culture. The UCAR-NKT cells are produced with high yield, purity, and robustness, and they display a stable HLA-ablated phenotype that enables resistance to host cell-mediated allorejection. These UCAR-NKT cells exhibit potent antitumor efficacy to blood cancers and solid tumors, both in vitro and in vivo, employing a multifaceted array of tumor-targeting mechanisms. These cells are further capable of altering the tumor microenvironment by selectively depleting immunosuppressive tumor-associated macrophages and myeloid-derived suppressor cells. In addition, UCAR-NKT cells demonstrate a favorable safety profile with low risks of graft-versus-host disease and cytokine release syndrome. Collectively, these preclinical studies underscore the feasibility and significant therapeutic potential of UCAR-NKT cell products and lay a foundation for their translational and clinical development.

Identification of biomarkers in multiple myeloma: A comprehensive study combining microarray analysis and Mendelian randomization

Despite remarkable advancements in the treatment of multiple myeloma (MM), relapse remains a challenge. However, the mechanisms underlying this disease remain unclear. This study aimed to identify potential biomarkers that could open new avenues for MM treatment. Microarray data and clinical characteristics of patients with MM were obtained from the Gene Expression Omnibus database. Differential expression analysis and protein-protein interaction (PPI) network construction were used to identify hub genes associated with MM. Predictive performance was further assessed using receiver operating characteristic curves and nomogram construction. Functional enrichment analysis was conducted to investigate possible mechanisms. Mendelian randomization (MR) was used to evaluate the causal relationship between the crucial gene and MM risk. Topological analysis of the PPI network revealed five hub genes associated with MM, with myeloperoxidase (MPO) being the key gene owing to its highest degree and area under the curve values. MPO showed significant differences between patients with MM and controls across all datasets. Functional enrichment analysis revealed a strong association between MPO and immune-related pathways in MM. MR analysis confirmed a causal relationship between MPO and the risk of MM. By integrating microarray analysis and MR, we successfully identified and validated MPO as a promising biomarker for MM that is potentially implicated in MM pathogenesis and progression through immune-related pathways.

A single-cell atlas characterizes dysregulation of the bone marrow immune microenvironment associated with outcomes in multiple myeloma

Multiple Myeloma (MM) remains incurable despite advances in treatment options. Although tumor subtypes and specific DNA abnormalities are linked to worse prognosis, the impact of immune dysfunction on disease emergence and/or treatment sensitivity remains unclear. We established a harmonized consortium to generate an Immune Atlas of MM aimed at informing disease etiology, risk stratification, and potential therapeutic strategies. We generated a transcriptome profile of 1,149,344 single cells from the bone marrow of 263 newly diagnosed patients enrolled in the CoMMpass study and characterized immune and hematopoietic cell populations. Associating cell abundances and gene expression with disease progression revealed the presence of a proinflammatory immune senescence-associated secretory phenotype in rapidly progressing patients. Furthermore, signaling analyses suggested active intercellular communication involving APRIL-BCMA, potentially promoting tumor growth and survival. Finally, we demonstrate that integrating immune cell levels with genetic information can significantly improve patient stratification.

An IL-1β-driven neutrophil-stromal cell axis fosters a BAFF-rich protumor microenvironment in individuals with multiple myeloma

Human bone marrow permanently harbors high numbers of neutrophils, and a tumor-supportive bias of these cells could significantly impact bone marrow-confined malignancies. In individuals with multiple myeloma, the bone marrow is characterized by inflammatory stromal cells with the potential to influence neutrophils. We investigated myeloma-associated alterations in human marrow neutrophils and the impact of stromal inflammation on neutrophil function. Mature neutrophils in myeloma marrow are activated and tumor supportive and transcribe increased levels of IL1B and myeloma cell survival factor TNFSF13B (BAFF). Interactions with inflammatory stromal cells induce neutrophil activation, including BAFF secretion, in a STAT3-dependent manner, and once activated, neutrophils gain the ability to reciprocally induce stromal activation. After first-line myeloid-depleting antimyeloma treatment, human bone marrow retains residual stromal inflammation, and newly formed neutrophils are reactivated. Combined, we identify a neutrophil-stromal cell feed-forward loop driving tumor-supportive inflammation that persists after treatment and warrants novel strategies to target both stromal and immune microenvironments in multiple myeloma.

HIF-1α is an important regulator of IL-8 expression in human bone marrow stromal cells under hypoxic microenvironment

The secretion of IL-8 has been found increasing for different reasons in human bone marrow stromal cells (BMSCs), resulting in poor prognosis in patients with hematologic neoplasms. Hypoxia, a typical feature of numerous hematologic neoplasms microenvironment, often produces hypoxia inducible factor-1α (HIF-1α) which stabilizes and promotes tumor progression. Besides, hypoxic conditions also induce IL-8 production in BMSCs. However, very little is known about the mechanism of increased IL-8 expression in BMSCs caused by hypoxia. In the present study, HIF-1α and IL-8 were found highly expressed in BMSC lines under hypoxic conditions. In addition, the expression and secretion of IL-8 were significantly inhibited by the knockdown of HIF-1α under hypoxic conditions. Furthermore, HIF-1α was found to transcriptionally regulate IL-8 by binding to the region of IL-8 promoter at - 147 to - 140. Collectively, these results demonstrate that IL-8's increase is partly due to the hypoxic microenvironment in hematologic neoplasms, and activation of HIF-1α in BMSCs contributes to the induction and transcriptional regulation of IL-8 expression.

Quinazoline-chalcone hybrids as HDAC/EGFR dual inhibitors: Design, synthesis, mechanistic, and in-silico studies of potential anticancer activity against multiple myeloma

Two new series of quinazoline-chalcone hybrids were designed, synthesized as histone deacetylase (HDAC)/epidermal growth factor receptor (EGFR) dual inhibitors, and screened in vitro against the NCI 60 human cancer cell line panel. The most potent derivative, compound 5e bearing a 3,4,5-trimethoxyphenyl chalcone moiety, showed the most effective growth inhibition value against the panel of NCI 60 human cancer cell lines. Thus, it was selected for further investigation for NCI 5 log doses. Interestingly, this trimethoxy-substituted analog inhibited the proliferation of Roswell Park Memorial Institute (RPMI)-8226 cells by 96%, at 10 µM with IC50 = 9.09 ± 0.34 µM and selectivity index = 7.19 against normal blood cells. To confirm the selectivity of this compound, it was evaluated against a panel of tyrosine kinase enzymes. Mechanistically, it successfully and selectively inhibited HDAC6, HDAC8, and EGFR with IC50 = 0.41 ± 0.015, 0.61 ± 0.027, and 0.09 ± 0.004 µM, respectively. Furthermore, the selected derivative induced apoptosis via the mitochondrial apoptotic pathway by raising the Bax/Bcl-2 ratio and activating caspases 3, 7, and 9. Also, the flow cytometry analysis of RPMI-8226 cells showed that the trimethoxy-substituted analog produced cell cycle arrest in the G1 and S phases at 55.82%. Finally, an in silico study was performed to explore the binding interaction of the most active compound within the zinc-containing binding site of HDAC6 and HDAC8.

Role of Immune Cells and Immunotherapy in Multiple Myeloma

The clinical signs of multiple myeloma, a plasma cell (PC) dyscrasia, include bone loss, renal damage, and paraproteinemia. It can be defined as the uncontrolled growth of malignant PCs within the bone marrow. The distinctive bone marrow milieu that regulates the progression of myeloma disease involves interactions between plasma and stromal cells, and myeloid and lymphoid cells. These cells affect the immune system independently or because of a complicated web of interconnections, which promotes disease development and immune evasion. Due to the importance of these factors in the onset of disease, various therapeutic strategies have been created that either target or improve the immunological processes that influence disease progression. The immune system has a role in the mechanism of action of multiple myeloma treatments. The main contributions of immune cells to the bone marrow microenvironment, as well as how they interact and how immune regulation might lead to therapeutic effects, are covered in this study.

Immune profiles to predict bortezomib-based treatment response for multiple myeloma patients

BACKGROUND

To evaluate the distribution of bone marrow immune cell subsets and their correlation with treatment efficacy in patients with multiple myeloma (MM).

METHODS

We analyzed the bone marrow lymphocyte subsets of 186 newly diagnosed MM patients at diagnosis and their correlation with clinical characteristics. In our study, eight-color flow cytometry, a method commonly used to detect plasma cell phenotypes, was used to analyze seven bone marrow immune cell groups by change gate-strategy.

RESULTS

First, for all the 7 immune cell groups, the percentage of immature B cells was significantly lower in stage III patients than in stage I patients, while the trend was reversed in memory B cells in both the International Staging System(p = 0.004) and Revised International Staging System(p = 0.018). Second, the percentage of naïve B cells were significantly lower in patients with severe anemia, while the percentage of memory B cells had reversed trend. The percentage of immature B cells were lower in patients with Cr ≥ 2 mg/dL than in patients with Cr < 2 mg/dL. Then we followed the treatment efficacy of 152 patients who received four cycles of induction therapy (bortezomib + dexamethasone or bortezomib + lenalidomide + dexamethasone) and analyzed the relationship between bone marrow lymphocyte subsets at the initial stage and treatment response datasets. We found that both the percentage of B cells(p＜0.001) and immature B(p = 0.002) were increased in patients who achieved very good partial remission(VGPR) after four cycles of induction therapy. The ROC results indicated the combination of the multiple immune subgroups had predictive values (AUC = 0.802, p<0.001) in the treatment effect after four cycles of induction therapy.

CONCLUSIONS

Overall, these results suggest that the analysis of lymphocyte subsets along with plasma cell immunophenotyping could be a potential index for determining the prognosis of MM patients.

The bone ecosystem facilitates multiple myeloma relapse and the evolution of heterogeneous drug resistant disease

Multiple myeloma (MM) is an osteolytic malignancy that is incurable due to the emergence of treatment resistant disease. Defining how, when and where myeloma cell intrinsic and extrinsic bone microenvironmental mechanisms cause relapse is challenging with current biological approaches. Here, we report a biology-driven spatiotemporal hybrid agent-based model of the MM-bone microenvironment. Results indicate MM intrinsic mechanisms drive the evolution of treatment resistant disease but that the protective effects of bone microenvironment mediated drug resistance (EMDR) significantly enhances the probability and heterogeneity of resistant clones arising under treatment. Further, the model predicts that targeting of EMDR deepens therapy response by eliminating sensitive clones proximal to stroma and bone, a finding supported by in vivo studies. Altogether, our model allows for the study of MM clonal evolution over time in the bone microenvironment and will be beneficial for optimizing treatment efficacy so as to significantly delay disease relapse.

Prognostic marker CD27 and its micro-environmental in multiple myeloma

BACKGROUND

The Cluster of Differentiation 27 (CD27) is aberrantly expressed in multiple myeloma (MM) -derived. This expression facilitates the interaction between tumor and immune cells within TME via the CD27-CD70 pathway, resulting in immune evasion and subsequent tumor progression. The objective of this study is to investigate the correlation between CD27 expression and the prognosis of MM, and to elucidate its potential relationship with the immune microenvironment.

METHODS

In this research, CD27 expression in T cells within the 82 newly diagnosed MM microenvironment was assessed via flow cytometry. We then examined the association between CD27 expression levels and patient survival. Subsequent a series of bioinformatics and in vitro experiments were conducted to reveal the role of CD27 in MM.

RESULTS

Clinical evidence suggests that elevated CD27 expression in T cells within the bone marrow serves as a negative prognostic marker for MM survival. Data analysis from the GEO database has demonstrated a strong association between MM-derived CD27 and the immune response, as well as the hematopoietic system. Importantly, patients with elevated levels of CD27 expression were also found to have an increased presence of MDSCs and macrophages in the bone marrow microenvironment. Furthermore, the PERK-ATF4 signaling pathway has been implicated in mediating the effects of CD27 in MM.

CONCLUSIONS

We revealed that CD27 expression levels serve as an indicative marker for the prognosis of MM patients. The CD27- PERK-ATF4 is a promising target for the treatment of MM.

FHND004 inhibits malignant proliferation of multiple myeloma by targeting PDZ-binding kinase in MAPK pathway

Inhibitors of Epidermal growth factor receptor tyrosine kinase (EGFR-TKIs) are producing impressive benefits to responsive types of cancers but challenged with drug resistances. FHND drugs are newly modified small molecule inhibitors based on the third-generation EGFR-TKI AZD9291 (Osimertinib) that are mainly for targeting the mutant-selective EGFR, particularly for the non-small cell lung cancer (NSCLC). Successful applications of EGFR-TKIs to other cancers are less certain, thus the present pre-clinical study aims to explore the anticancer effect and downstream targets of FHND in multiple myeloma (MM), which is an incurable hematological malignancy and reported to be insensitive to first/second generation EGFR-TKIs (Gefitinib/Afatinib). Cell-based assays revealed that FHND004 and FHND008 significantly inhibited MM cell proliferation and promoted apoptosis. The RNA-seq identified the involvement of the MAPK signaling pathway. The protein chip screened PDZ-binding kinase (PBK) as a potential drug target. The interaction between PBK and FHND004 was verified by molecular docking and microscale thermophoresis (MST) assay with site mutation (N124/D125). Moreover, the public clinical datasets showed high expression of PBK was associated with poor clinical outcomes. PBK overexpression evidently promoted the proliferation of two MM cell lines, whereas the FHND004 treatment significantly inhibited survival of 5TMM3VT cell-derived model mice and growth of patient-derived xenograft (PDX) tumors. The mechanistic study showed that FHND004 downregulated PBK expression, thus mediating ERK1/2 phosphorylation in the MAPK pathway. Our study not only demonstrates PBK as a promising novel target of FHND004 to inhibit MM cell proliferation, but also expands the EGFR kinase-independent direction for developing anti-myeloma therapy.

Tumor integrin targeted theranostic iron oxide nanoparticles for delivery of caffeic acid phenethyl ester: preparation, characterization, and anti-myeloma activities

Multiple myeloma (MM) is characterized by the accumulation of malignant plasma cells preferentially in the bone marrow. Currently, emerging chemotherapy drugs with improved biosafety profiles, such as immunomodulatory agents and protease inhibitors, have been used in clinics to treat MM in both initial therapy or maintenance therapy post autologous hematopoietic stem cell transplantation (ASCT). We previously discovered that caffeic acid phenethyl ester (CAPE), a water-insoluble natural compound, inhibited the growth of MM cells by inducing oxidative stress. As part of our continuous effort to pursue a less toxic yet more effective therapeutic approach for MM, the objective of this study is to investigate the potential of CAPE for in vivo applications by using magnetic resonance imaging (MRI)-capable superparamagnetic iron oxide nanoparticles (IONP) as carriers. Cyclo (Arg-Gly-Asp-D-Phe-Cys) (RGD) is conjugated to IONP (RGD-IONP/CAPE) to target the overexpressed αvβ3 integrin on MM cells for receptor-mediated internalization and intracellular delivery of CAPE. A stable loading of CAPE on IONP can be achieved with a loading efficiency of 48.7% ± 3.3% (wt%). The drug-release studies indicate RGD-IONP/CAPE is stable at physiological (pH 7.4) and basic pH (pH 9.5) and subject to release of CAPE at acidic pH (pH 5.5) mimicking the tumor and lysosomal condition. RGD-IONP/CAPE causes cytotoxicity specific to human MM RPMI8226, U266, and NCI-H929 cells, but not to normal peripheral blood mononuclear cells (PBMCs), with IC50s of 7.97 ± 1.39, 16.75 ± 1.62, and 24.38 ± 1.71 μM after 72-h treatment, respectively. Apoptosis assays indicate RGD-IONP/CAPE induces apoptosis of RPMI8226 cells through a caspase-9 mediated intrinsic pathway, the same as applying CAPE alone. The apoptogenic effect of RGD-IONP/CAPE was also confirmed on the RPMI8226 cells co-cultured with human bone marrow stromal cells HS-5 in a Transwell model to mimic the MM microenvironment in the bone marrow. In conclusion, we demonstrate that water-insoluble CAPE can be loaded to RGD-IONP to greatly improve the biocompatibility and significantly inhibit the growth of MM cells in vitro through the induction of apoptosis. This study paves the way for investigating the MRI-trackable delivery of CAPE for MM treatment in animal models in the future.

Zinc Oxide Nanoparticles Trigger Autophagy in the Human Multiple Myeloma Cell Line RPMI8226: an In Vitro Study

Multiple myeloma (MM) is a malignant clonal proliferative plasma cell tumor. Zinc oxide nanoparticles (ZnO NPs) are used for antibacterial and antitumor applications in the biomedical field. This study investigated the autophagy-induced effects of ZnO NPs on the MM cell line RPMI8226 and the underlying mechanism. After RPMI8226 cells were exposed to various concentrations of ZnO NPs, the cell survival rate, morphological changes, lactate dehydrogenase (LDH) levels, cell cycle arrest, and autophagic vacuoles were monitored. Moreover, we investigated the expression of Beclin 1 (Becn1), autophagy-related gene 5 (Atg5), and Atg12 at the mRNA and protein levels, as well as the level of light chain 3 (LC3). The results showed that ZnO NPs could effectively inhibit the proliferation and promote the death of RPMI8226 cells in vitro in a dose- and time-dependent manner. ZnO NPs increased LDH levels, enhanced monodansylcadaverine (MDC) fluorescence intensity, and induced cell cycle arrest at the G2/M phases in RPMI8226 cells. Moreover, ZnO NPs significantly increased the expression of Becn1, Atg5, and Atg12 at the mRNA and protein levels and stimulated the production of LC3. We further validated the results using the autophagy inhibitor 3-methyladenine (3‑MA). Overall, we observed that ZnO NPs can trigger autophagy signaling in RPMI8226 cells, which may be a potential therapeutic approach for MM.

Different evasion strategies in multiple myeloma

Multiple myeloma is the second most common malignant hematologic malignancy which evolved different strategies for immune escape from the host immune surveillance and drug resistance, including uncontrolled proliferation of malignant plasma cells in the bone marrow, genetic mutations, or deletion of tumor antigens to escape from special targets and so. Therefore, it is a big challenge to efficiently treat multiple myeloma patients. Despite recent applications of immunomodulatory drugs (IMiDS), protease inhibitors (PI), targeted monoclonal antibodies (mAb), and even hematopoietic stem cell transplantation (HSCT), it remains hardly curable. Summarizing the possible evasion strategies can help design specific drugs for multiple myeloma treatment. This review aims to provide an integrative overview of the intrinsic and extrinsic evasion mechanisms as well as recently discovered microbiota utilized by multiple myeloma for immune evasion and drug resistance, hopefully providing a theoretical basis for the rational design of specific immunotherapies or drug combinations to prevent the uncontrolled proliferation of MM, overcome drug resistance and improve patient survival.

Identification of an angiogenesis-related risk score model for survival prediction and immunosubtype screening in multiple myeloma

BACKGROUND

Multiple myeloma (MM) is an incurable B-cell malignancy, but with the emergence of immunotherapy, a potential cure is hopeful. The individualized interaction between the tumor and bone marrow (BM) microenvironment determines the response to immunotherapy. Angiogenesis is a constant hallmark of the BM microenvironment in MM. However, little is known about the potency ability of angiogenesis-associated genes (AAGs) to regulate the immune microenvironment of MM patients.

METHODS

We comprehensively dissected the associations between angiogenesis and genomic landscapes, prognosis, and the immune microenvironment by integrating 36 AAGs. Immunohistochemistry was performed to verify the correlation between angiogenic factor expression and patient prognosis. Single-sample gene set enrichment analysis was applied to quantify the relative abundance of 28 infiltrating cells. The AAG score was constructed using the least absolute shrinkage and selection operator Cox regression model.

RESULTS

Angiogenesis was closely correlated with MM patient prognosis, and the mutation intensity of the AAGs was low. Immunohistochemistry confirmed that high microvessel density predicted poor prognosis. Three AAG clusters and two gene clusters with distinct clinical outcomes and immune characteristics were identified. The established AAG_score model performed well in predicting patient prognosis and active immunotherapy response. The high-AAG_score subgroup was characterized by reduced immune cell infiltration, poor prognosis, and inactive immunotherapy response. Multivariate analyses indicated that the AAG_score was strongly robust and independent among the prognostic variables.

CONCLUSION

This study revealed that angiogenesis is significantly related to MM patient prognosis and immune phenotype. Evaluating the AAG signature was conducive to predicting patient response to immunotherapy and guiding more efficacious immunotherapy strategies.

Targeting the DNA damage response in hematological malignancies

Deregulation of the DNA damage response (DDR) plays a critical role in the pathogenesis and progression of many cancers. The dependency of certain cancers on DDR pathways has enabled exploitation of such through synthetically lethal relationships e.g., Poly ADP-Ribose Polymerase (PARP) inhibitors for BRCA deficient ovarian cancers. Though lagging behind that of solid cancers, DDR inhibitors (DDRi) are being clinically developed for haematological cancers. Furthermore, a high proliferative index characterize many such cancers, suggesting a rationale for combinatorial strategies targeting DDR and replicative stress. In this review, we summarize pre-clinical and clinical data on DDR inhibition in haematological malignancies and highlight distinct haematological cancer subtypes with activity of DDR agents as single agents or in combination with chemotherapeutics and targeted agents. We aim to provide a framework to guide the design of future clinical trials involving haematological cancers for this important class of drugs.

PSGL-1 decorated with sialyl Lewisa/x promotes high affinity binding of myeloma cells to P-selectin but is dispensable for E-selectin engagement

Dissemination of multiple myeloma into the bone marrow proceeds through sequential steps mediated by a variety of adhesion molecules and chemokines that eventually results in the extravasation of malignant plasma cells into this protective niche. Selectins are a class of C-type lectins that recognize carbohydrate structures exposed on blood borne cells and participate in the first step of the extravasation cascade, serving as brakes to slow down circulating cells enabling them to establish firm adhesion onto the endothelium. Myeloma cells enriched for the expression of selectin ligands present an aggressive disease in vivo that is refractory to bortezomib treatment and can be reverted by small molecules targeting E-selectin. In this study, we have defined the molecular determinants of the selectin ligands expressed on myeloma cells. We show that PSGL-1 is the main protein carrier of sialyl Lewisa/x-related structures in myeloma. PSGL-1 decorated with sialyl Lewisa/x is essential for P-selectin binding but dispensable for E-selectin binding. Moreover, sialylation is required for E-selectin engagement whereas high affinity binding to P-selectin occurs even in the absence of sialic acid. This study provides further knowledge on the biology of selectin ligands in myeloma, opening the way to their clinical application as diagnostic tools and therapeutic targets.

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.

CTPS1 is a novel therapeutic target in multiple myeloma which synergizes with inhibition of CHEK1, ATR or WEE1

Targeting nucleotide biosynthesis is a proven strategy for the treatment of cancer but is limited by toxicity, reflecting the fundamental nucleotide requirement of dividing cells. The rate limiting step in de novo pyrimidine synthesis is of interest, being catalyzed by two homologous enzymes, CTP synthase 1 (CTPS1) and CTPS2, that could be differentially targeted. Herein, analyses of publicly available datasets identified an essential role for CTPS1 in multiple myeloma (MM), linking high expression of CTPS1 (but not CTPS2) with advanced disease and poor outcomes. In cellular experiments, CTPS1 knockout induced apoptosis of MM cell lines. Exposure of MM cells to STP-B, a novel and highly selective pharmacological inhibitor of CTPS1, inhibited proliferation, induced S phase arrest and led to cell death by apoptosis. Mechanistically, CTPS1 inhibition by STP-B activated DNA damage response (DDR) pathways and induced double-strand DNA breaks which accumulated in early S phase. Combination of STP-B with pharmacological inhibitors of key components of the DDR pathway (ATR, CHEK1 or WEE1) resulted in synergistic growth inhibition and early apoptosis. Taken together, these findings identify CTPS1 as a promising new target in MM, either alone or in combination with DDR pathway inhibition.

RING box protein-1(RBX1), a key component of SCF E3 ligase, induced multiple myeloma cell drug-resistance though suppressing p27

Multiple myeloma (MM) is a clonal disease of plasma cells that remains, for the most part, incurable despite the advent of several novel therapeutics. The elevated expression of p27 and its association with cell-cycle arrest is speculated to be one of the major mechanisms by which MM cells escape the cytotoxic effects of therapeutic agents. In this study, we demonstrated that RBX1 silencing could inhibit MM cell growth and promote cell drug resistance. RBX1 directly interacted with and triggered the ubiquitination and degradation of p27, ultimately causing p27 reduction. Additionally, cell growth and apoptosis analysis indicated that the role of RBX1 in regulating myeloma cell proliferation and drug resistance resulted from p27 accumulation, which occurred in a Thr187 phosphorylation-dependent manner. Furthermore, the cell-cycle analysis demonstrated that RBX1 overexpression induced cells to enter the cell cycle (S-phase) and partially inhibited chemotherapeutic drugs-mediated cell cycle arrest. Notably, the forced expression of RBX1 also inhibited the cell adhesion-mediated elevation of p27 and induced the accumulation of adherent cells in apoptosis, especially the proteolytic cleavage of caspase-3. Additionally, RBX1 knockdown significantly inhibited myeloma development in SCID-Hu mice and in a human MM xenotransplant model. Overall, these in vitro and in vivo experiments indicated that the RBX1-p27 axis could be a central molecular mechanism by which RBX1 functions as a tumor promoter and stimulates cell growth in chemotherapeutic drugs treated MM cells.

Immunomodulation of NK, NKT and B/T cell subtypes in relapsed/refractory multiple myeloma patients treated with pomalidomide along with velcade and dexamethasone and its association with improved progression-free survival

Background

Multiple Myeloma (MM) patients exhibit dysregulated immune system, which is further weakened by chemotherapeutic agents. While cereblon-modulating agents, such as pomalidomide and lenalidomide, have been found to improve the immune profile, the efficacy of their impact in combination with other treatments is yet unknown.

Methods

We conducted an immune-profiling of a longitudinal cohort of 366 peripheral blood samples from the CC4047-MM-007 (OPTIMISMM, NCT01734928) study. This study followed relapsed/refractory Multiple Myeloma (RRMM) patients who were treated with Velcade + dexamethasone (Vd), or Vd with pomalidomide (PVd). 366 blood samples from 186 patients were evaluated using multi-color flow cytometry at 3 timepoints: screening, day 8 of cycle 1, and cycle 3.

Results

Among NK and NKT cell populations, adding pomalidomide showed no inhibition in the frequency of NK cells. When expression of double positivity for activation markers like, p46/NKG2D, on NK cells was higher than the median, PVd treated patients showed significantly better (p=0.05) progression-free survival (PFS) (additional 15 months) than patients with lower than the median expression of p46/NKG2D on NK cells. PVd treated patients who expressed CD158a/b below the median at cycle 1 demonstrated a significantly better PFS (more than 18months). Among B cell subtypes, PVd treatment significantly increased the abundance of B1b cells (p<0.05) and decreased Bregs (p<0.05) at day 8 of both cycle 1 and cycle 3 when compared to screening samples. Of all the B cell-markers evaluated among paired samples, a higher expression of MZB cells at day 8 of cycle 1 has resulted in enhanced PFS in PVd treated patients. Within T cells, pomalidomide treatment did not decrease the frequency of CD8 T cells when compared with screening samples. The higher the surface expression of OX-40 on CD8 T cells and the lower the expression of PD-1 and CD25 on CD4 T cells by PVd treatment resulted in improved PFS.

Conclusion

The prognostic significance for the number of immune markers is only seen in the PVd arm and none of these immune markers exhibit prognostic values in the Vd arm. This study demonstrates the importance of the immunomodulatory effects and the therapeutic benefit of adding pomalidomide to Vd treatment.

Changes in immune cell populations following KappaMab, lenalidomide and low-dose dexamethasone treatment in multiple myeloma

Objectives

Lenalidomide (LEN) is used to treat multiple myeloma (MM) and shows in vitro synergy with KappaMab (KM), a chimeric antibody specific for Kappa Myeloma antigen, an antigen exclusively expressed on the surface of kappa-restricted MM cells. Lenalidomide, dexamethasone (DEX) and KM control MM via multiple immunomodulatory mechanisms; however, there are several additional effects of the drug combination on immune cells. Lenalidomide can increase T cell and NKT cell cytotoxicity and dendritic cell (DC) activation in vitro. We investigated the immune cell populations in bone marrow of patients treated with KM, LEN and low-dose DEX in kappa-restricted relapsed/refractory MM ex vivo and assessed association of those changes with patient outcome.

Methods

A cohort (n = 40) of patients with kappa-restricted relapsed/refractory MM, treated with KM, LEN and low-dose DEX, was analysed using a mass cytometry panel that allowed identification of immune cell subsets. Clustering analyses were used to determine significant changes in immune cell populations at time periods after treatment.

Results

We found changes in five DC and 17 T-cell populations throughout treatment. We showed an increase in activated conventional DC populations, a decrease in immature/precursor DC populations, a decrease in activated CD4 T cells and an increase in effector-memory CD4 T cells and effector CD8 T cells, indicating an activated immune response.

Conclusion

These data characterise the effects of LEN, DEX, and KM treatment on non-target immune cells in MM. Treatment may support destruction of MM cells by both direct action and indirect mechanisms via immune cells.

Engagement of Mesenchymal Stromal Cells in the Remodeling of the Bone Marrow Microenvironment in Hematological Cancers

Mesenchymal stromal cells (MSCs) are a subset of heterogeneous, non-hematopoietic fibroblast-like cells which play important roles in tissue repair, inflammation, and immune modulation. MSCs residing in the bone marrow microenvironment (BMME) functionally interact with hematopoietic stem progenitor cells regulating hematopoiesis. However, MSCs have also emerged in recent years as key regulators of the tumor microenvironment. Indeed, they are now considered active players in the pathophysiology of hematologic malignancies rather than passive bystanders in the hematopoietic microenvironment. Once a malignant event occurs, the BMME acquires cellular, molecular, and epigenetic abnormalities affecting tumor growth and progression. In this context, MSC behavior is affected by signals coming from cancer cells. Furthermore, it has been shown that stromal cells themselves play a major role in several hematological malignancies' pathogenesis. This bidirectional crosstalk creates a functional tumor niche unit wherein tumor cells acquire a selective advantage over their normal counterparts and are protected from drug treatment. It is therefore of critical importance to unveil the underlying mechanisms which activate a protumor phenotype of MSCs for defining the unmasked vulnerabilities of hematological cancer cells which could be pharmacologically exploited to disrupt tumor/MSC coupling. The present review focuses on the current knowledge about MSC dysfunction mechanisms in the BMME of hematological cancers, sustaining tumor growth, immune escape, and cancer progression.

Breaking barriers: NEK2 inhibition shines in multiple myeloma treatment

In their article, Cheng et al.1 reveal that NEK2 loss reshapes the tumor microenvironment, reducing tumor-associated macrophages and decreasing T cell exhaustion. They show that this ultimately favors the immune system's anti-cancer response in multiple myeloma.

Definers and drivers of functional high-risk multiple myeloma: insights from genomic, transcriptomic, and immune profiling

Traditional prognostic models for newly diagnosed patients with multiple myeloma (MM), including International Staging System criteria and number of high-risk chromosomal abnormalities, are based on disease characteristics at diagnosis. However, the identification of patients at risk of more rapidly progressive MM is inherently a dynamic assessment. In a subset of patients with MM, adverse disease biology only becomes evident after the failure of first-line therapy. We define this entity as functional high-risk MM (FHRMM), encompassing relapse within 18 months of treatment initiation and/or within 12 months of frontline autologous stem cell transplantation. FHRMM is not adequately captured by traditional prognostic models, and there is a need for better understanding of mechanisms or risk factors for early relapse or progression. In this review, we explore potential definitions of FHRMM before delving into its underlying drivers based on genetic, transcriptomic, and immune cell profiling studies. Emerging data suggest that specific features of both myeloma cells and immune cells can enable the FHRMM phenotype. We conclude our review by discussing ongoing and future studies that seek to identify and intervene upon patients with FHRMM preemptively.

Essential procedures of single-cell RNA sequencing in multiple myeloma and its translational value

Multiple myeloma (MM) is a malignant neoplasm characterized by clonal proliferation of abnormal plasma cells. In many countries, it ranks as the second most prevalent malignant neoplasm of the hematopoietic system. Although treatment methods for MM have been continuously improved and the survival of patients has been dramatically prolonged, MM remains an incurable disease with a high probability of recurrence. As such, there are still many challenges to be addressed. One promising approach is single-cell RNA sequencing (scRNA-seq), which can elucidate the transcriptome heterogeneity of individual cells and reveal previously unknown cell types or states in complex tissues. In this review, we outlined the experimental workflow of scRNA-seq in MM, listed some commonly used scRNA-seq platforms and analytical tools. In addition, with the advent of scRNA-seq, many studies have made new progress in the key molecular mechanisms during MM clonal evolution, cell interactions and molecular regulation in the microenvironment, and drug resistance mechanisms in target therapy. We summarized the main findings and sequencing platforms for applying scRNA-seq to MM research and proposed broad directions for targeted therapies based on these findings.

RXR Agonists Enhance Lenalidomide Anti-Myeloma Activity and T Cell Functions while Retaining Glucose-Lowering Effect

Retinoid X receptor (RXR) heterodimerizes with the PPAR nuclear hormone receptor and regulates its downstream events. We investigated the effects of RXR agonists (LG100754, bexarotene, AGN194204, and LG101506) on lenalidomide's anti-myeloma activity, T cell functions, and the level of glucose and lipids in vivo. Genetic overexpression and CRISPR/Cas9 knockout experiments were conducted in multiple myeloma (MM) cell lines and Jurkat T cell lines to determine the roles of CRBN in RXR-agonist mediated effects. A xenograft mouse model of MM was established to determine the combination effect of LG100754 and lenalidomide. The combination of RXR agonists and lenalidomide demonstrated synergistic activity in increasing CRBN expression and killing myeloma cells. Mechanistically, the RXR agonists reduced the binding of PPARs to the CRBN promoter, thereby relieving the repressor effect of PPARs on CRBN transcription. RXR agonists downregulated the exhaustion markers and increased the activation markers of Jurkat T cells and primary human T cells. Co-administration of LG100754 and lenalidomide showed enhanced anti-tumor activity in vivo. LG100754 retained its glucose- and lipid-lowering effects. RXR agonists demonstrate potential utility in enhancing drug sensitivity and T-cell function in the treatment of myeloma.

Mitochondrial dysfunction and drug targets in multiple myeloma

Multiple myeloma (MM) is the second most common hematological cancer that has no cure. Although currently there are several novel drugs, most MM patients experience drug resistance and disease relapse. The results of previous studies suggest that aberrant mitochondrial function may contribute to tumor progression and drug resistance. Mitochondrial DNA mutations and metabolic reprogramming have been reported in MM patients. Several preclinical and clinical studies have shown encouraging results of mitochondria-targeting therapy in MM patients. In this review, we have summarized our current understanding of mitochondrial biology in MM. More importantly, we have reviewed mitochondrial targeting strategies in MM treatment.

Delivery of Therapeutic RNA to the Bone Marrow in Multiple Myeloma Using CD38-Targeted Lipid Nanoparticles

Multiple myeloma (MM) is a cancer of differentiated plasma cells that occurs in the bone marrow (BM). Despite the recent advancements in drug development, most patients with MM eventually relapse and the disease remains incurable. RNA therapy delivered via lipid nanoparticles (LNPs) has the potential to be a promising cancer treatment, however, its clinical implementation is limited due to inefficient delivery to non-hepatic tissues. Here, targeted (t)LNPs designed for delivery of RNA payload to MM cells are presented. The tLNPs consist of a novel ionizable lipid and are coated with an anti-CD38 antibody (αCD38-tLNPs). To explore their therapeutic potential, it is demonstrated that LNPs encapsulating small interference RNA (siRNA) against cytoskeleton-associated protein 5 (CKAP5) lead to a ≈90% decrease in cell viability of MM cells in vitro. Next, a new xenograft MM mouse model is employed, which clinically resembles the human disease and demonstrates efficient homing of MM cells to the BM. Specific delivery of αCD38-tLNPs to BM-residing and disseminated MM cells and the improvement in therapeutic outcome of MM-bearing mice treated with αCD38-tLNPs-siRNA-CKAP5 are shown. These results underscore the potential of RNA therapeutics for treatment of MM and the importance of developing effective targeted delivery systems and reliable preclinical models.

Exosome miRNAs profiling in serum and prognostic evaluation in patients with multiple myeloma

MicroRNAs (MiRNAs) carried by exosomes play pivotal roles in the crosstalk between cell components in the tumor microenvironment. Our study aimed at identifying the expression profile of exosomal miRNAs (exo-miRNAs) in the serum of multiple myeloma (MM) patients and investigating the regulation networks and their potential functions by integrated bioinformatics analysis. Exosomes in serum from 19 newly diagnosed MM patients and 9 healthy donors were isolated and the miRNA profile was investigated by small RNA sequencing. Differential expression of exo-miRNAs was calculated and target genes of miRNAs were predicted. CytoHubba was applied to identify the hub miRNAs and core target genes. The LASSO Cox regression model was used to develop the prognostic model, and the ESTIMATE immune score was calculated to investigate the correlation between the model and immune status in MM patients. The top six hub differentially expressed serum exo-miRNAs were identified. 513 target genes of the six hub exo-miRNAs were confirmed to be differentially expressed in MM cells in the Zhan Myeloma microarray dataset. Functional enrichment analysis indicated that these target genes were mainly involved in mRNA splicing, cellular response to stress, and deubiquitination. 13 core exo-miRNA target genes were applied to create a novel prognostic signature to provide risk stratification for MM patients, which is associated with the immune microenvironment of MM patients. Our study comprehensively investigated the exo-miRNA profiles in MM patients. A novel prognostic signature was constructed to facilitate the risk stratification of MM patients with distinct outcomes.

Cancer-associated fibroblast-derived exosome microRNA-21 promotes angiogenesis in multiple myeloma

Multiple myeloma (MM) is the second most common hematological malignancy, and angiogenesis determines its progression. In the tumor microenvironment, normal fibroblasts (NFs) are transformed into cancer-associated fibroblasts (CAFs), which can promote angiogenesis. Microribonucleic acid-21 (miR-21) is highly expressed in various tumors. However, research on the relationship between tumor angiogenesis and miR-21 is rare. We analyzed the relationship between miR-21, CAFs, and angiogenesis in MM. NFs and CAFs were isolated from the bone marrow fluids of patients with dystrophic anemia and newly-diagnosed MM. Co-culturing of CAF exosomes with multiple myeloma endothelial cells (MMECs) showed that CAF exosomes were able to enter MMECs in a time-dependent manner and initiate angiogenesis by promoting proliferation, migration, and tubulogenesis. We found that miR-21 was abundant in CAF exosomes, entering MMECs and regulating angiogenesis in MM. By transfecting NFs with mimic NC, miR-21 mimic, inhibitor NC, and miR-21 inhibitor, we found that miR-21 significantly increased the expression of alpha-smooth muscle actin and fibroblast activation protein in NFs. Our results showed that miR-21 can transform NFs into CAFs, and that CAF exosomes promote angiogenesis by carrying miR-21 into MMECs. Therefore, CAF-derived exosomal miR-21 may serve as a novel diagnostic biomarker and therapeutic target for MM.

Single-cell technologies in multiple myeloma: new insights into disease pathogenesis and translational implications

Multiple myeloma (MM) is a hematological malignancy characterized by clonal proliferation of plasma cells. Although therapeutic advances have been made to improve clinical outcomes and to prolong patients' survival in the past two decades, MM remains largely incurable. Single-cell sequencing (SCS) is a powerful method to dissect the cellular and molecular landscape at single-cell resolution, instead of providing averaged results. The application of single-cell technologies promises to address outstanding questions in myeloma biology and has revolutionized our understanding of the inter- and intra-tumor heterogeneity, tumor microenvironment, and mechanisms of therapeutic resistance in MM. In this review, we summarize the recently developed SCS methodologies and latest MM research progress achieved by single-cell profiling, including information regarding the cancer and immune cell landscapes, tumor heterogeneities, underlying mechanisms and biomarkers associated with therapeutic response and resistance. We also discuss future directions of applying transformative SCS approaches with contribution to clinical translation.

Simultaneously Targeting Two Coupled Signalling Molecules in the Mesenchymal Stem Cell Support Efficiently Sensitises the Multiple Myeloma Cell Line H929 to Bortezomib

Several studies have shown that diverse components of the bone marrow (BM) microenvironment play a central role in the progression, pathophysiology, and drug resistance in multiple myeloma (MM). In particular, the dynamic interaction between BM mesenchymal stem cells (BM-MSC) and MM cells has shown great relevance. Here we showed that inhibiting both PKC and NF-κB signalling pathways in BM-MSC reduced cell survival in the MM cell line H929 and increased its susceptibility to the proteasome inhibitor bortezomib. PKC-mediated cell survival inhibition and bortezomib susceptibility induction were better performed by the chimeric peptide HKPS than by the classical enzastaurin inhibitor, probably due to its greatest ability to inhibit cell adhesion and its increased capability to counteract the NF-κB-related signalling molecules increased by the co-cultivation of BM-MSC with H929 cells. Thus, inhibiting two coupled signalling molecules in BM-MSC was more effective in blocking the supportive cues emerging from the mesenchymal stroma. Considering that H929 cells were also directly susceptible to PKC and NF-κB inhibition, we showed that treatment of co-cultures with the HKPS peptide and BAY11-7082, followed by bortezomib, increased H929 cell death. Therefore, targeting simultaneously connected signalling elements of BM-MSC responsible for MM cells support with compounds that also have anti-MM activity can be an improved treatment strategy.