Myeloma Bone Disease Research Articles

Wound healing after surgical therapy for multiple myeloma: a case-control study.

The aim of this study was to observe the surgical wound healing process in patients with multiple myeloma who had undergone surgery. We collected clinical data on patients with multiple myeloma and observed wound healing following surgical therapy. Additionally, we compared the expression of angiogenesis markers in patients with and without multiple myeloma (undergoing surgical excision of other tumour tissues). In patients who had multiple myeloma bone disease, we examined several clinical features: haemoglobin levels; albumin levels; blood glucose levels; and surgery programme. We then compared expression levels of the angiogenesis markers CD31, CD34 and vascular endothelial growth factor (VEGF) in samples scraped from the skin margin of the surgical incision in 12 patients without multiple myeloma (control) and nine patients with multiple myeloma. All 61 patients with multiple myeloma observed showed no disunion, no delayed union and no infection in their wound healing. CD31 and VEGF expression was higher in the nine patients with multiple myeloma compared with the 12 control patients without. We observed no difference in CD34 expression between control and experimental groups. The results of this study suggest that patients with multiple myeloma who have undergone surgery recover well and produce higher quantities of new vessels compared with patients without multiple myeloma. This occurs through increased expression of CD31 and VEGF, angiogenic factors which promote wound healing. We did not observe higher expression of these factors contributing to increased incisional implantation metastasis.

Research Advances of Exosomes in Pathogenesis of Multiple Myeloma --Review

Research on the participation of exosomes in pathogenesis and prognosis of multiple myeloma (MM) has made encouraging progress. However, the specific mechanism has not yet been clarified. Recently, domestic and foreign researchers have pressed forward on deeper study on exosomes. This article mainly summarizes the role of exosomes in the pathophysiological processes, such as bone marrow microenvironment changes, immunosuppression, myeloma bone disease generation and myeloma drug resistance, so as to provide new reference for further clinical research of exosomes as potential biomarkers for MM.

Bone mechanical properties were altered in a mouse model of multiple myeloma bone disease

Multiple myeloma bone disease (MMBD) is characterized by the growth of malignant plasma cells in bone marrow, leading to an imbalance in bone (re)modeling favoring excessive resorption. Loss of bone mass and altered microstructure characterize MMBD in humans and preclinical animal models, although, no study to date has examined bone composition or material properties. We hypothesized that MMBD alters bone composition, mineral crystal properties and mechanical properties in the MOPC315.BM.Luc model after intra-tibial injection of myeloma cells and three weeks of daily in vivo tibial loading. Decreased cortical bone elastic modulus and hardness measured by nanoindentation of tibiae were observed in MM-injected mice compared to PBS-injected mice, whereas cortical bone composition, mineral crystal properties measured by Fourier-transform infrared imaging or small angle X-ray scattering, respectively remained unchanged. However, MM-injected mice had thinner cancellous bone mineral particles compared to PBS-injected mice. Mechanical loading did not lead to altered cortical bone composition, mineral structure, or mechanical properties in the context of MM. Unexpectedly, we observed the intra-tibial injection itself altered the material composition of bone, manifested by increased matrix mineralization and crystal size of the hydroxyapatite crystals in the bone matrix. In conclusion, our data suggest that mechanical stimuli can be used as an adjuvant bone anabolic therapy in patients with MMBD to rebuild bone with unaltered composition and mineral structure to reduce subsequent fracture risk.

3D osteocyte lacunar morphometry of human bone biopsies with high resolution microCT: From monoclonal gammopathy to newly diagnosed multiple myeloma

Osteocytes are mechanosensitive, bone-embedded cells which are connected via dendrites in a lacuno-canalicular network and regulate bone resorption and formation balance. Alterations in osteocyte lacunar volume, shape and density have been identified in conditions of aging, osteoporosis and osteolytic bone metastasis, indicating patterns of impaired bone remodeling, osteolysis and disease progression. Osteolytic bone disease is a hallmark of the hematologic malignancy multiple myeloma (MM), in which monoclonal plasma cells in the bone marrow disrupt the bone homeostasis and induce excessive resorption at local and distant sites. Qualitative and quantitative changes in the 3D osteocyte lacunar morphometry have not yet been evaluated in MM, nor in the precursor conditions monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM). In this study, we characterized the osteocyte lacunar morphology in trabecular bone of the iliac crest at the ultrastructural level using high resolution microCT in human bone biopsy samples of three MGUS, two SMM and six newly diagnosed MM. In MGUS, SMM and MM we found a trend for lower lacunar density and a shift towards larger lacunae with disease progression (higher 50 % cutoff of the lacunar volume cumulative distribution) in the small osteocyte lacunae 20–900 μm3 range compared to control samples. In the larger lacunae 900–3000 μm3 range, we detected significantly higher lacunar density and microporosity in the MM group compared to the MGUS/SMM group. Regarding the shape distribution, the MGUS/SMM group showed a trend for flatter, more elongated and anisotropic osteocyte lacunae compared to the control group. Altogether, our findings suggest that osteocytes in human MM bone disease undergo changes in their lacunae density, volume and shape, which could be an indicator for osteolysis and disease progression. Future studies are needed to understand whether alterations of the lacunae architecture affect the mechanoresponsiveness of osteocytes, and ultimately bone adaptation and fracture resistance in MM and its precursors conditions.

First-Line Combination with Proteasome Inhibitor-Based Treatment and Zoledronic Acid Is Effective in Reducing Later Fractures in Multiple Myeloma Irrespective of Multiple Myeloma Bone Disease at Diagnosis.

The present study provides real-world evidence on the treatment of multiple myeloma (MM) bone disease with various bisphosphonates combined for different myeloma-specific treatments as no validated data regarding the best combination treatment for bone disease associated with MM are available. We examined retrospectively 345 MM patients treated with autologous stem cell transplantation in Finland during 1996-2020. The median age of the patients was 60 years with a median follow-up time of 50 months (1-339). At diagnosis, 72.1% of the patients had myeloma-associated bone disease and 45.8% had fractures. Most patients (58.8%) received proteasome inhibitor (PI)-containing treatment at first line. MM bone disease was treated in 91.6% of the patients; 49.9% received zoledronic acid (ZA) and 29.9% pamidronate. Inferior overall survival was associated with MM bone disease at diagnosis (p = 0.005) or a fracture at diagnosis (p = 0.003). A later fracture was identified in 29% of the patients, and in those patients without MM bone disease at diagnosis later fractures were less common after ZA treatment (p = 0.049). PI-based treatment plus ZA (p = 0.019) seemed to be the best combination to prevent later fractures, even though the same patient subgroup was more likely to experience relapse (p = 0.018), and also when excluding patients with previous induction therapy without novel agents (p = 0.008). To conclude, this study suggests that the best therapy to prevent later fractures in MM might be PI-based treatment combined with ZA.

Evidence for peri-lacunar remodeling and altered osteocyte lacuno-canalicular network in mouse models of myeloma-induced bone disease.

Myeloma bone disease (MBD) affects ~90% of multiple myeloma patients, but current treatment options are suboptimal. Therefore, to successfully develop new therapies or optimize current ones, we must improve our fundamental knowledge of how myeloma affects bone microstructure and function. Here, we have investigated the osteocyte lacuno-canalicular network (LCN) in MBD, as bone porosity affects bone quality and resilience. We used the syngeneic 5TGM1-C57BL-Kalwrij and the xenograft U266-NSG models at end stage and compared them to healthy controls (naïve). Micro-computed tomography (μCT) and histomorphometry indicated the 5TGM1 and U266 models developed mild and extensive MBD, respectively, with the U266 model producing large osteolytic lesions. High-resolution synchrotron micro-CT (SR-μCT) revealed significant osteocyte lacunae changes in U266 bones but not 5TGM1, with a reduction in lacunae number and sphericity, and an increase in lacunae volume compared with naïve. Canalicular length, visualized using histological Ploton silver staining, appeared significantly shorter in 5TGM1 and U266 bones compared with naïve. Canalicular area as a proportion of the bone was also decreased by 24.2% in the U266 model. We observed significant upregulation of genes implicated in peri-lacunar remodeling (PLR), but immunohistochemistry confirmed that the osteocyte-specific protein sclerostin, a known driver of PLR, was unchanged between MBD and naïve bones. In summary, we have demonstrated evidence of PLR and altered organization of the osteocyte LCN in MBD mouse models. The next step would be to further understand the drivers and implications of PLR in MBD, and whether treatments to manipulate PLR and the LCN may improve patient outcomes.

Bone Metabolism of Multiple Myeloma Bone Disease Patients with Different Blood Separation Results

To investigate the clinical significance of bone metabolic indexes for disease assessment and curative effect monitoring in multiple myeloma (MM) bone disease (MBD) patients with different blood separation results. A total of 134 newly diagnosed MM patients treated in Cangzhou Hospital of Integrated TCM-WM-Hebei were enrolled and divided into control group [119 cases, serum, colloid and red blood cell (RBC) from top to bottom of sample] and abnormal group (15 cases, serum, mixed layer of RBC and serum, colloid and RBC from top to bottom of sample) according to the results of blood separation. According to the imaging findings, MBD was classified into grade 0-4, grade 0-2 was mild, and grade 3-4 was severe. The MBD grade of patients in the two groups was analyzed. The curative effect of MBD patients after chemotherapy and the changes of blood separation results and bone metabolic indexes before and after treatment were evaluated. The correlation between β2-microglobulin (MG) and bone metabolic indexes was analyzed by Pearson correlation analysis. In the control group, there were 69 cases of grade 0-2 and 50 cases of grade 3-4, while in the abnormal group, there were 5 cases of grade 0-2 and 10 cases of grade 3-4, the difference was statistically significant (P < 0.05). The serum β2-MG, β-CTX levels in abnormal group were both significantly higher than those in control group, while the levels of P1NP and osteocalcin (OC) were significantly lower (all P < 0.001). In the control group, there were 95 patients with ≥ partial response (PR) and the blood separation results were not changed, while 24 patients with <PR and 5 of them had abnormal blood separation results. In the abnormal group, 9 patients with efficacy ≥PR showed normal blood separation results, while 6 patients with efficacy < PR and 5 of them still remained abnormal blood separation results. Compared with before treatment, β-CTX and β2-MG of patients with efficacy ≥PR were significantly decreased but P1NP and OC increased in the control group (all P < 0.001), which was the same as abnoraml group (both P < 0.001, P < 0.01). There were no significant changes in the levels of all indexes in the two groups of patients with efficacy < PR (P >0.05). Compared with before treatment, the levels of β-CTX and β2-MG in the control group with unchanged blood separation results were significantly decreased (both P < 0.001), while the levels of P1NP and OC were significantly increased (P < 0.01, P < 0.001), and the level of each index in the patients transformed to abnormal blood separation result after treatment did not significantly change (P >0.05); the levels of β-CTX and β2-MG in the abnormal group transformed to normal blood separation result were significantly decreased (both P < 0.01), while the levels of P1NP and OC were significantly increased (P < 0.001, P < 0.01), and the level of each index in patients with unchanged blood separation results did not significantly change (P>0.05). Pearson correlation analysis showed that serum β2-MG was positively correlated with β-CTX (r =0.709, P < 0.001), and negatively correlated with P1NP and OC (r =-0.410,r =-0.412, both P < 0.001). MBD patients with abnormal blood separation results have higher bone disease grade and poor prognosis, which is closely related to the significant increase of bone resorption index β-CTX level and decrease of bone formation index P1NP and OC levels, leading to more serious bone metabolic homeostasis disorder. The results of blood separation combined with the changes of bone metabolic indexes can be used as one of the comprehensive predictors of disease condition, efficacy monitoring and prognosis evaluation of MBD patients.

Exercise in newly diagnosed patients with multiple myeloma: A randomized controlled trial of effects on physical function, physical activity, lean body mass, bone mineral density, pain, and quality of life.

Reduced physical function caused by bone destruction, pain, anemia, infections, and weight loss is common in multiple myeloma (MM). Myeloma bone disease challenges physical exercise. Knowledge on the effects and safety of physical exercise in newly diagnosed patients with MM is limited. In a randomized, controlled trial, we studied the effect of a 10-week individualized physical exercise program on physical function, physical activity, lean body mass (LBM), bone mineral density (BMD), quality of life (QoL), and pain in patients newly diagnosed with MM. Lytic bone disease was assessed, and exercise was adjusted accordingly. Primary outcome: knee extension strength. Secondary outcomes: Six-Minute-Walk-Test, 30-s Sit-to-Stand-Test (SST), grip strength, level of physical activity, LBM, BMD, QoL, and pain. Measurements were conducted pre- and post-intervention, and after 6 and 12 months. We included 100 patients, 86 were evaluable; 44 in the intervention group (IG) and 42 in the control group (CG). No statistically significant differences between groups were observed. Knee extension strength declined in the IG (p = .02). SST, aerobic capacity, and global QoL improved in both groups. Pain decreased consistently in the IG regardless of pain outcome. No significant safety concerns of physical exercise in newly diagnosed patients with MM were observed.

Diagnostic reliability of DKK-1, sclerostin, sRANKL, osteopontin and periostin as markers for assessing the myeloma bone disease

Diagnostic reliability of DKK-1, sclerostin, sRANKL, osteopontin and periostin as markers for assessing the myeloma bone disease

Analysis of the efficacy and safety of bone disease treatment in patients with newly diagnosed multiple myeloma treated with denosumab or zoledronic acid

Objective: This study investigated the efficacy and safety of denosumab (DENOS) versus zoledronic acid (ZOL) in the bone disease treatment of newly diagnosed multiple myeloma. Methods: The clinical data of 80 patients with myeloma bone disease (MBD) at the Fifth Medical Center of PLA General Hospital between March 1, 2021 and June 30, 2023 were retrospectively reviewed. Eighteen patients with severe renal impairment (SRI, endogenous creatinine clearance rate<30 ml/min) were treated with DENOS, and 62 non-SRI patients were divided into DENOS (30 patients) and ZOL group (32 patients) . Results: Hypocalcemia was observed in 26 (33%) patients, and 22 patients developed hypocalcemia during the first treatment course. The incidence of hypocalcemia in the non-SRI patients of DENOS group was higher than that in the ZOL group [20% (6/30) vs 13% (4/32), P=0.028]. The incidence of hypocalcemia in SRI was 89% (16/18). Multivariate logistic regression analysis revealed that endogenous creatinine clearance rate<30 ml/min was significantly associated with hypocalcemia after DENOS administration (P<0.001). After 1 month of antiresorptive (AR) drug application, the decrease in the serum β-C-terminal cross-linked carboxy-telopeptide of collagen type I concentrations of SRI and non-SRI patients in the DENOS group were significantly higher than that in the ZOL group (68% vs 59% vs 27%, P<0.001). The increase in serum procollagen type Ⅰ N-terminal propeptide concentrations of patients with or without SRI in the DENOS group were significantly higher than that in the ZOL group (34% vs 20% vs 11%, P<0.05). The level of intact parathyroid hormone in each group increased after AR drug treatment. None of the patients developed osteonecrosis of the jaw and renal adverse events, and no statistically significant differences in the overall response rate, complete remission and stringent complete remission rates were found among the groups (P>0.05), and the median PFS and OS time were not reached (P>0.05) . Conclusions: In the treatment of MBD, DENOS minimizes nephrotoxicity and has strong AR effect. Hypocalcemia is a common adverse event but is usually mild or moderate and manageable.

Guideline for the diagnosis and management of multiple myeloma-related renal impairment (2024 version)

Renal impairment is a common complication of multiple myeloma (MM). All patients with MM should be assessed for the presence and severity of renal impairment. The clinicopathological manifestations of MM-related renal impairment are diverse and complex; accordingly, except for light-chain nephropathy, which can often be diagnosed without biopsy based solely on clinical criteria, a renal biopsy is needed for an accurate diagnosis. Supportive care, such as adequate hydration, is required for all patients with MM-related renal impairment. The guideline provide the principles for dose adjustment of the drugs used for MM with renal impairment, including proteasome inhibitors, immunomodulators, monoclonal antibodies, small molecule inhibitors, and alkylating agents, as well as those used for myeloma bone disease. Autologous stem cell transplantation (ASCT) and chimeric antigen receptor T-cell immunotherapy (CAR-T) are effective in patients with moderate renal impairment and are tolerated by the patients. The Chinese Hematology Association; the Chinese Geriatrics Association, Society of Hematology; and the Chinese Research Hospital Association, Society of Nephrology asked experts to collate information on current progress in clinical research relating to MM with renal impairment. This guideline was developed based on the gathered data combined with the latest international consensus and clinical practice guidelines.

Significance of PET/CT Imaging in Myeloma Assessment: Exploring Novel Applications beyond Osteolytic Lesion Detection and Treatment Response

In multiple myeloma (MM), specific cytokines produced by plasma cells disrupt the equilibrium between osteoblasts and osteoclasts. As a result, MM patients experience an increase in osteoclast activity and a decrease in osteoblast activity. This disparity is fundamental to the development of myeloma bone disease. Lytic lesions, which are a feature of MM, can result in pathologic fractures and excruciating pain. For many years, whole-body X-ray radiography has been the standard imaging method for identifying lytic lesions. However, its sensitivity is limited because it can only detect lesions once the bone mass has been reduced by 30% to 50%. Hence, utilizing advanced and sensitive imaging modalities, such as positron emission tomography (PET) fused with computed tomography (CT), is crucial for the early detection of osteolytic lesions. Among radiotracers used in PET imaging, 1⁸F-fluorodeoxyglucose ([18F]FDG) is the most commonly employed in the field of oncology. Currently, most guidelines include [18F]FDG PET/CT in the assessment of myeloma patients, particularly for detecting osteolytic lesions, evaluating treatment response, and assessing extramedullary and residual disease. Nonetheless, in recent years, new applications of PET/CT for evaluating myeloma have been investigated. These include assessing aspects such as bone turnover, dual-time-point imaging (early and delayed scans), the impact of chemotherapy on the brain (commonly known as ‘chemo brain’), innovative PET radiotracers, and the use of artificial intelligence technology. This article aims to provide a comprehensive review of both conventional and innovative uses of PET/CT in evaluating multiple myeloma.

BCMA- and CST6-specific CAR T cells lyse multiple myeloma cells and suppress murine osteolytic lesions.

We have previously demonstrated that cystatin E/M (CST6), which is elevated in a subset of patients with multiple myeloma (MM) lacking osteolytic lesions (OLs), suppresses MM bone disease by blocking osteoclast differentiation and function. CST6 is a secreted type 2 cystatin, a cysteine protease inhibitor that regulates lysosomal cysteine proteases and the asparaginyl endopeptidase legumain. Here, we developed B cell maturation antigen (BCMA) CST6 chimeric antigen receptor T cells (CAR-T cells), which lysed MM cells and released CST6 proteins. Our in vitro studies show that these CAR-T cells suppressed the differentiation and formation of tartrate-resistant acid phosphatase-positive (TRAP+) osteoclasts. Using xenografted MM mice, bioluminescence images showed that both BCMA-CAR-T and BCMA-CST6-CAR-T cells inhibited MM growth to a similar extent. Reconstructed micro-computed tomography images revealed that BCMA-CST6-CAR-T cells, but not BCMA-CAR-T cells, prevented MM-induced bone damage and decreased osteoclast numbers. Our results provide a CAR-T strategy that targets tumor cells directly and delivers an inhibitor of bone resorption.

Increased Bone Turnover and Decreased BCMA Levels in Patients with Response to Anti-BCMA CAR T Cell Therapy in Relapsed/Refractory Multiple Myeloma

Introduction For most patients (pts), multiple myeloma (MM) remains an incurable disease. Osteolytic lesions (OL) are present in 80% of pts at diagnosis and skeletal-related events are the most common cause for symptomatic relapse. Hence, myeloma bone disease (MBD) is a major cause of morbidity and mortality especially among pts with relapsed/refractory MM (RRMM). B cell maturation antigen (BCMA) targeted chimeric antigen receptor (CAR) T cells have revolutionized treatment of patients with RRMM. While remission rates are high and pts experience long-standing treatment free intervals after CAR T cell treatment, little is known about its effects on MBD and bone turnover. The latter can be determined in plasma by measuring markers of bone formation and resorption. We aimed to analyze the longitudinal development of bone turnover during and after anti-BCMA CAR T cell treatment in RRMM pts. Methods We analyzed 28 consecutive pts with RRMM who underwent treatment with either Idecabtagene-Vicleucel (n=27) or Ciltacabtagen-Autoleucel (n=1) at our center between December 2021 and February 2023. Median age at infusion was 63 (range 39-75) years. 57% of pts were male. All pts were triple-class exposed, 21% had penta-class refractory disease. Status prior to CAR T cell infusion was complete remission (CR, 11%), partial remission (PR, 21%), very good PR (14%), stable disease (4%), or progressive disease (PD, 50%). The impact of CAR T cell treatment on bone turnover was assessed by collecting plasma samples on the day of T cell apheresis, as well as days (d) 30 and 100 after CAR T cell infusion. Samples were analyzed by ELISA to evaluate plasma levels of bone formation marker Osteocalcin (OCN), bone resorption markers Tartrate-resistant acid phosphatase 5b (TRAcP5b) and fibroblast growth factor 23 (FGF23) as well as BCMA as a marker for the targeted myeloma cells. Median levels were compared between subgroups by Wilcoxon tests. Remission status after CAR T cell therapy was first evaluated at d 30 according to International Myeloma Working Group consensus criteria. Median follow-up was 6 months. Results Of the 28 pts treated with anti-BCMA CAR T cells, 64% achieved at least a PR (responders), while 36% had PD shortly (30 d) after. Within 14 d after infusion, 82% developed a cytokine release syndrome (CRS, °I or II), in 30% of which Tocilizumab was applied. Only 1 pt developed immune effector cell-associated neurotoxicity syndrome. In responders, BCMA levels in plasma decreased significantly between apheresis and d 30 ( P&amp;lt;.01) and between apheresis and d 100 ( P&amp;lt;.01), while pts with PD showed no significant change in BCMA levels at the same timepoints ( P=.6 and P=.8). Furthermore, BCMA levels were significantly higher in pts with PD at d 30 ( P&amp;lt;.01) and d 100 ( P=.02), compared to responders (Figure 1). Regarding bone resorption markers, TRAcP5b levels were significantly increased in responders ( P=.01) but not pts with PD ( P=.56) on d 30 after apheresis. Furthermore, we determined a significant increase of intact FGF23 between apheresis and d 30 ( P&amp;lt;.01) and a subsequent significant decrease of intact FGF23 ( P=.02) between d 30 and d 100 in responders. Since FGF23 and interleukin-6 (IL-6) are physiologically dependent, the observed FGF23 dynamics are likely to be an effect of increasing IL-6 in the context of CRS. Aptly, pts who received Tocilizumab because of full-blown CRS had higher intact FGF23 levels at d 30 ( P=.02) compared to pts without Tocilizumab treatment. The bone formation marker OCN showed a significant increase in responders between apheresis and d 100 ( P=.01), as well as between d30 and d100 ( P=.02), while there were no significant changes in OCN levels over the time in pts with PD (Figure 2). Conclusion Pts responding to treatment with anti-BCMA CAR T cells, showed an increased bone turnover shortly after infusion. The increase of bone resorption marker levels appeared to be a short-term trend and could possibly be related to inflammation and high interleukin levels during the first days after infusion. However, we also saw a steady increase of bone formation marker OCN, which remained significant till d 100 in responders. Our data implies, that response to anti-BCMA CAR T cells is accompanied by increasing bone formation. Further analyses are needed to evaluate, whether this treatment can have positive long-term effects on MBD.

Checkpoint Inhibitor PD-1H/VISTA Affects Myeloma Bone Disease By Osteoclast Cytoskeleton Remodeling

Introduction We have recently described the critical role of checkpoint inhibitor PD-1H/VISTA in osteoclast activation and multiple myeloma bone disease. Highly expressed in osteoclast precursors and mature osteoclasts, PD-1H functions as the receptor for osteoclastogenic factor MMP-13 and mediates MMP-13 induced osteoclast activation and myeloma bone disease ( Nat Commun14, 4271 (2023)). Despite the extensive functional study of PD-1H in immune disease models, the PD-1H interacting cellular complex is yet to be defined. Here we report how PD-1H interacts with cytoskeleton proteins contributing to osteoclast remodeling in multiple myeloma bone disease. Methods and Results To identify interacting proteins of PD-1H, PD-1H-His 6 recombinant protein was overexpressed in mouse mononuclear BMCs, and PD-1H-His 6 binding protein complex was pulled down by Ni-NTA agarose beads followed by mass spectrum analysis (Figure A). LIM and SH3 domain protein 1 (LASP1) was one of the most abundant cytoskeleton proteins identified in the PD-1H complex. We therefore first confirmed its binding to PD-1H by two-way co-IP assays (Figure B and C). Co-localization of LASP1 and PD-1H were further confirmed by immunofluorescence assay when co-expressed in HEK293 cells (Figure D). LASP1 is an F-actin-binding protein that stabilizes F-actin bundles and is involved in podosome regulation in macrophages (PLoS ONE 7(4): e35340). It has four domains: LIM, two nebulin-like repeats (N1 and N2) and SH3 domains. While nebulin-like repeats mediate binding to F-actin, SH3 domain is the major protein-protein binding site (PLoS ONE 7(4): e35340). In co-IP assay using PD-1H and domain deleted LASP1, deletion of LIM (△LIM) or either one or both nebulin-like repeats (△N1, △N2 and △N1/2) did not affect the binding to PD-1H. Instead, deletion of SH3 (△SH3) in LASP1 lead to loss of PD-1H binding, demonstrating that PD-1H binds to LASP1 at the SH3 domain (Figure E). Next, the association of LASP1 and PD-1H in the osteoclast cytoskeleton was demonstrated by confocal immunofluorescence microscopy. LASP1 co-localized with F-actin (Figure F) and PD-1H (Figure G) at the sealing ring in mature osteoclasts. Interestingly, although MMP-13 stimulation increased the size of osteoclasts and the sealing ring, MMP-13 did not change the co-localization pattern of LASP1 with PD-1H or F-actin. Conclusions Taken together, this study reveals the novel mechanism of PD-1H regulation of osteoclasts cytoskeleton reorganization, which is critical for osteoclast bone resorption activity. PD-1H directly associates with LASP1 at its C-terminal SH3 domain. Although LASP1 was reported to regulates podosomes function in macrophages, its role in osteoclast cytoskeletons remain largely obscure. The future study will be focused on delineating the role of LASP1 in osteoclast function, and its role in MMP-13/PD-1H signaling regulated myeloma bone disease.

Imaging Practices in Patients with Plasma Cell Dyscrasias across the Asian Myeloma Network - Survey Results and Recommendations

Objective: Though consensus imaging guidelines from International Myeloma Working Group (IMWG) for the detection of bone and marrow lesions in plasma cell disorders are available, significant challenges remain in adoption of such guidelines in Asia. The objectives of this study were: (1) To survey, document and evaluate the imaging practices in plasma cell disorders across Asian Myeloma Network (AMN) member countries and (2) To identify factors influencing decision making in choosing the imaging modalities with a view to explore barriers and solutions. Methods: AMN Members from China, Japan, Republic of Korea, Malaysia, Taiwan, Thailand and Singapore participated in the bone imaging work group organized during the 6 th AMN summit in Sep 2022 at Singapore. Members discussed the prevailing bone imaging practices and how they relate to IMWG recommendations. A bone imaging survey questionnaire was then designed from these inputs and circulated to the wider AMN members. The results were collated and analyzed. Results &amp; Discussion: Forty-Eight responses were received from 37 public tertiary or academic hospitals, 9 from peripheral hospitals and 2 from private hospitals. With regards to precursor plasma cell disorders (MGUS / SMM Vs MM), the preferred imaging modalities for screening bone disease in patients suspected to have myeloma were skeletal survey (SS) (n=13, 27%), whole body low dose CT (WBLDCT) (n=13, 27%) and PET CT (n=14, 29%). The preferred mode for 1 st line imaging in patients with confirmed newly diagnosed myeloma was PET CT (n=25, 52%) however half of the participants opted for SS (n=7, 15%), WBLDCT (n=10, 21%) and whole-body MRI (WBMRI) (n=6, 13%). Using SS prior to myeloma treatment or to differentiate SMM from MM can lead to significant under-recognition of bone disease and its consequences on disease classification and impact on treatment. Centers which are performing SS but have compatible CT scanners could consider adopting a WBLDCT protocol which is relatively easy and cost-effective. Preferred first-line imaging options for Plasmacytoma and EMD were largely appropriate with 70-80% opting for PET CT or WBMRI. However, for response assessment in MM, the majority chose PET CT or MRI, some members or institutions are still using SS or WBLDCT. While CT scan might be able to show some sclerotic healing or a worsening lytic component, SS is unlikely to provide any useful information in this situation and should be avoided to reduce unnecessary radiation exposure. At least 5 participants indicated that they do not perform routine imaging in newly diagnosed multiple myeloma for disease response assessment. Barriers identified in establishing cross-sectional imaging service include lack of financial reimbursement or subsidies, equipment, or personnel availability like the presence of nuclear medicine or specialized radiologists. While 81% of participants reported financial reimbursements for SS, only about 50% reported subsidies for WBMRI (56%) or PET CT (54%). One shortfall of this study is that our survey was conducted within the framework of an academic myeloma community and while it may not be representative of the practices in the whole region, the use of sub-optimal imaging like SS underlines the need for standardisation and adoption of cross-sectional imaging. Conclusion: There is considerable variation in imaging practices for precursor plasma cell disorders and myeloma in centres across Asia. Resource limitation, specifically lack of financial subsidies for imaging, infrastructure or lack of experienced personnel all remain as major challenges in the implementation of standardized imaging practice for myeloma in Asia. However increased adoption of cross-sectional imaging in large tertiary centres are to be welcomed and suggest that in these centres, practices do closely mirror those in the IMWG recommendations. Increasing awareness of the potentially catastrophic nature of myeloma bone disease and the preventive role that cross sectional imaging could provide, representations and dialogues with healthcare funders to this aspect of myeloma care, incorporation of low dose CT protocols to help move away from skeletal survey in centres which already have CT scanners as well as myeloma patient and Physician education could all be useful tools to enhance bone imaging standards in Asia.

Transgenic Mouse Model for Translational Immunotherapy Studies on Multiple Myeloma

Background Genetically engineered mouse models that recapitulate key immunological features of human multiple myeloma may lend themselves to preclinical design and testing of novel immune therapies that target members of the tumor necrosis factor (TNF) receptor superfamily in addition to BCMA. One model of this sort are double-transgenic IL6Myc mice that spontaneously develop myeloma-like plasma cell tumors (PCTs) with full genetic penetrance (100% tumor incidence) and relatively short latency (4-5 months) in presence of an intact innate and adaptive immune system (Rutsch et. al. Blood 2010). IL6Myc mice exhibit serum M-spikes, respond to proteasome inhibition, and develop osteolytic lesions mimicking myeloma bone disease (Duncan K et. al. Blood Cancer J 2013, Sun F et. al. Haematologica 2020). Here, we examined changes in the immune tumor microenvironment during PCT progression in IL6Myc mice. We found that neoplastic plasma cell development was accompanied by accumulation of inhibitory T cells, T cell exhaustion, and elevated serum levels of MIP-3α and MCP-5. A subset of aberrant plasma cells expressed the TNF receptors, TACI and BAFF-R, which, together with their ligands, APRIL and BAFF, may serve as immunotherapeutic targets in myeloma not responding to BCMA-targeted treatment (Wong DP et. al. Nat Commun 2022, Braunstein M et. al. Expert Rev Hematol 2021). Materials and methods Double-transgenic IL6Myc mice were bred by intercrossing homozygous transgenic C.iMyc ΔEμ (Duncan K et. al. Blood Cancer J 2013) and heterozygous transgenic C.IL6 mice (Kovalchuk AL. et. al. Proc Natl Acad Sci USA 2002). Age-matched IL6Myc mice were investigated at an early (5-7 weeks), intermediate (10-12 weeks) and late (14-17 weeks) stage of PCT development using flow cytometry (Cytek Aurora) and serum cytokine levels (Bio-Plex) as main research tools. Results Bone marrow (BM) plasma cells, defined as CD45-gated B220 -CD138 + cells, increased during PCT development, as one might have expected: 10.5 ± 5.8% and 26.8 ± 6.4% ( p&amp;lt; 0.05) in early- and late-stage mice, respectively. The proportion of B220 +CD19 + B cells fell accordingly: 29.6 ± 4.1% vs 5.5 ± 4.9% ( p&amp;lt; 0.0001). Consistent with the notion that the BM microenvironment of PCT-bearing mice is immunosuppressive, there was a 2-fold elevation of TGF-β expressing T cells and a 4-fold elevation of IL-10 expressing T cells in the BM when late-stage mice were compared to early-stage mice. A sizeable fraction of aberrant plasma cells expressed TACI and BAFF-R in addition to BCMA ( Figure 1, left). Spleens of IL6Myc mice undergoing tumor development contained increasing numbers of FoxP3 + regulatory T cells (8.6 ± 2.1% at early stage vs 14.0 ± 4.6% at late stage, p&amp;lt; 0.05) and CD11b +Ly-6G/C + myeloid-derived suppressor cells (21.2 ± 9.2% vs 51.6 ± 10.1%, p&amp;lt; 0.01). Exhausted T cells, detected via expression of PD-1, TIM-3, LAG-3 and TIGIT, increased in sync with PCT progression ( Figure 1, right). Elevated serum levels of inflammatory cytokines, including MIP-3α (95.3 ± 41.9 pg/ml in early-stage mice vs 514 ± 279 pg/ml in late-stage mice, p&amp;lt; 0.01) and MCP-5 (121 ± 43.9 pg/ml vs 284 ± 70.5 pg/ml, p&amp;lt; 0.05), agreed with flow-based tissue data. Conclusion Neoplastic plasma cell development in IL6Myc mice takes place in an immune suppressed tumor microenvironment similar to that promoting human myeloma. IL6Myc-driven PCTs may provide a good experimental model system for novel immunotherapeutic approaches that target TACI and BAFF-R or their ligands, APRIL and BAFF. Previous work to that end holds great promise but has been challenging thus far (Goodman DB et. al. Sci Transl Med 2022, Lee L et. al. J Immunother Cancer 2023).

Novel_circ_003686 regulates the osteogenic differentiation of MSCs in patients with myeloma bone disease through miR-142-5p/IGF1 axis

ObjectivesCirc_003686 is a novel_circRNA with abnormally low expression found in the samples of multiple myeloma bone disease (MBD) patients. The current research intended to investigate the effects of novel_circ_003686 in osteogenesis-induced differentiation of bone marrow mesenchymal stem cells (BMSCs) in MBD. MethodsBMSCs were extracted from MBD patients and normal participants, the pcDNA3.1 encoding the circ_003686 (ov-circ_003686), miR-142-5p-mimic/inhibitor and siRNA oligonucleotides targeting insulin like growth factor 1 (IGF1, si-IGF1) were applied to intervene circ_003686, miR-142-5p and IGF1 levels, respectively. Results: Results showed that ov-circ_003686 could mediate the osteogenesis-induced differentiation of MBD-BMSC, and luciferase assay and RIP experiments confirmed that circ_003686 could bind to miR-142-5p. MiR-142-5p-inhibitor helped osteogenesis-induced differentiation, while miR-142-5p-mimic inhibited osteogenesis-induced differentiation and reversed the promoting effect of ov-circ_003686, suggesting that circ_003686/miR-142-5p axis participated in osteogenesis-induced differentiation of MBD-BMSC. In addition, miR-142-5p binds to the target gene IGF1 and negatively adjust its expression. Si-IGF1 significantly inhibited the osteogenesis-induced differentiation and reversed the promotion effects of miR-142-5p-inhibitor and ov-circ_003686. Moreover, circ_003686/miR-142-5p/IGF1 axis meaningfully regulates protein expressions in the PI3K/AKT pathway. ConclusionIn conclusion, this research confirmed that circ_003686 regulated the osteogenesis-induced differentiation of MBD-BMSC by sponging miR-142-5p and mediating IGF1, and the PI3K/AKT pathway may also be involved.

The BCMA-Targeted Fourth-Generation CAR-T Cells Secreting CST6 Against Multiple Myeloma and Suppresses Osteolytic Lesions

651 Multiple Myeloma and Plasma Cell Dyscrasias: Basic and Translational Introduction: Multiple myeloma (MM) is characterized by osteolytic lesions, and our previous research has shown that cystatin E/M (CST6) effectively mitigates MM bone disease by inhibiting osteoclast differentiation. However, the therapeutic application of recombinant CST6 protein faces challenges due to its short serum half-life in mouse models, necessitating maintenance of constantly elevated CST6 concentrations for optimal efficacy. In this study, we explore the potential of utilizing fourth-generation B cell maturation antigen (BCMA)-specific chimeric antigen receptor (CAR)-T cell therapies to address this limitation. By leveraging the secretion capabilities of CST6, we engineered BCMA-CST6-CAR-T cells to precisely target nascent focal lesions. Our results demonstrate that these engineered CAR-T cells effectively target MM cells and concurrently suppress osteolytic lesions, presenting a promising approach for combating MM and its associated bone pathology. Methods: The BCMA-CST6-CAR vector comprises BCMA-scFv, a 4-1BB co-activation domain, and CD3ζ. To facilitate separate expression, a P2A self-cleaving peptide was introduced between CAR and CST6. CAR-T cells were co-cultured with MM1.S cells at a 5:1 ratio for 24 hours. To assess in vivo anti-tumor activity and anti-bone resorption of BCMA-CST6-CAR-T cells, we engrafted luciferase-expressing MM1.S cells into NSG mice. On day 7, mice with established MM received CAR-T cell infusions. At day 35, the mice were euthanized, and we analyzed serum CST6 concentrations using ELISA. Additionally, we collected mouse tibiae to perform μCT scans and TRAP staining to evaluate bone resorption. Results: The co-culturing of BCMA-CST6-CAR-T cells with MM1.S cells resulted in a remarkable 77.2% lysis of MM1.S cells after 24 hours, with no significant difference in killing observed between the BCMA-CAR-T and BCMA-CST6-CAR-T groups. However, T cell activation marker CD69 exhibited a significant increase in the BCMA-CST6-CAR-T group (70.9%) compared to the MOCK-CAR-T group (9.2%). In the MM-bearing mouse model, bioluminescence imaging revealed that BCMA-CST6-CAR-T cells exhibited excellent antitumor activity, leading to near-complete tumor clearance by day 21. Notably, both BCMA-CST6-CAR-T and BCMA-CAR-T cells showed similar effects in inhibiting tumor growth. The in vivo serum concentration of CST6 was significantly higher in the BCMA-CST6-CAR-T group (938.4 ng/ml) compared to the MOCK group (60.9 ng/ml) and BCMA-CAR-T group (64.2 ng/ml) (P &amp;lt; 0.001), highlighting the robust secretion of CST6 protein by BCMA-CST6-CAR-T cells. Moreover, μCT images of mouse tibiae demonstrated that BCMA-CST6-CAR-T cells effectively suppressed osteolytic lesions in MM-bearing mice. This finding was further corroborated by TRAP staining of mouse tibia sections, which showed a significant reduction in osteoclast numbers and the proportion of bone surface occupied by osteoclasts in the presence of BCMA-CST6-CAR-T cells. Conclusion: These results underscore the potent antitumor and anti-bone resorption effects of BCMA-CST6-CAR-T cells and their potential as a promising therapeutic approach for multiple myeloma.

Matrix metalloproteinases and tissue inhibitors in multiple myeloma: promote or inhibit?

Matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) play a vital role in the pathogenesis of multiple myeloma (MM), especially for tumor invasion and osteolytic osteopathy. By breaking down extracellular matrix (ECM) components and releasing the proteins composing the ECM and growth factors, as well as their receptors, MMPs affect tissue integrity and promote cancer cell invasion and metastasis. A vital pathophysiological characteristic of MM is the progress of osteolytic lesions, which are brought on by interactions between myeloma cells and the bone marrow microenvironment. MMPs, certainly, are one of the fundamental causes of myeloma bone disease due to their ability to degrade various types of collagens. TIMPs, as important regulators of MMP hydrolysis or activation, also participate in the occurrence and evolution of MM and the formation of bone disease. This review focuses on the role of MMP-1, MMP-2, MMP-7, MMP-9, MMP-13, MMP-14, and MMP-15 and the four types of TIMPs in the invasion of myeloma cells, angiogenesis, osteolytic osteopathy, to offer some novel perspectives on the clinical diagnostics and therapeutics of MM.