Effects of proteasome inhibitors on bone cancer

Inhibition of Neddylation Suppresses Osteoclast Differentiation and Function In Vitro and Alleviates Osteoporosis In Vivo

Neddylation, or the covalent addition of NEDD8 to specific lysine residue of proteins, is a reversible posttranslational modification, which regulates numerous biological functions; however, its involvement and therapeutic significance in osteoporosis remains unknown. Our results revealed that during the soluble receptor activator of nuclear factor-κB ligand (sRANKL)-stimulated osteoclast differentiation, the neddylation and expression of UBA3, the NEDD8-activating enzyme (NAE) catalytic subunit, were dose- and time-dependently upregulated in RAW 264.7 macrophages. UBA3 knockdown for diminishing NAE activity or administering low doses of the NAE inhibitor MLN4924 significantly suppressed sRANKL-stimulated osteoclast differentiation and bone-resorbing activity in the macrophages by inhibiting sRANKL-stimulated neddylation and tumor necrosis factor receptor-associated factor 6 (TRAF6)-activated transforming growth factor-β-activated kinase 1 (TAK1) downstream signaling for diminishing nuclear factor-activated T cells c1 (NFATc1) expression. sRANKL enhanced the interaction of TRAF6 with the neddylated proteins and the polyubiquitination of TRAF6's lysine 63, which activated TAK1 downstream signaling; however, this process was inhibited by MLN4924. MLN4924 significantly reduced osteoporosis in an ovariectomy- and sRANKL-induced osteoporosis mouse model in vivo. Our novel finding was that NAE-mediated neddylation participates in RANKL-activated TRAF6-TAK1-NFATc1 signaling during osteoclast differentiation and osteoporosis, suggesting that neddylation may be a new target for treating osteoporosis.

Translational Strategies to Target Metastatic Bone Disease

Metastatic bone disease is a common and devastating complication to cancer, confounding treatments and recovery efforts and presenting a significant barrier to de-escalating the adverse outcomes associated with disease progression. Despite significant advances in the field, bone metastases remain presently incurable and contribute heavily to cancer-associated morbidity and mortality. Mechanisms associated with metastatic bone disease perpetuation and paralleled disruption of bone remodeling are highlighted to convey how they provide the foundation for therapeutic targets to stem disease escalation. The focus of this review aims to describe the preclinical modeling and diagnostic evaluation of metastatic bone disease as well as discuss the range of therapeutic modalities used clinically and how they may impact skeletal tissue.

Adjuvant drug-assisted bone healing: Part III - Further strategies for local and systemic modulation

In this third in a series of reviews on adjuvant drug-assisted bone healing, further approaches aiming at influencing the healing process are discussed. Local and systemic modulation of bone metabolism is pursued with use of a number of drugs with completely different indications, which are characterized by a pleiotropic spectrum of action. These include drugs used to treat lipid disorders (HMG-CoA reductase inhibitors), hypertension (ACE inhibitors), osteoporosis (bisphosphonates), cancer (proteasome inhibitors) and others. Potential applications to enhance bone healing are discussed.

Effects of proteasome inhibitors on cytokines, metalloproteinases and their inhibitors and collagen type-I expression in periprosthetic tissues and fibroblasts from loose arthroplasty endoprostheses

Objective: Aseptic loosening is a major problem in total joint replacement. Implant wear debris provokes a foreign body host response and activates cells to produce a variety of mediators and ROS, leading to periprosthetic osteolysis. Elevated ROS levels can harm proteasome function. Proteasome inhibitors have been reported to alter the secretory profile of cells involved in inflammation and also to induce ROS production. In this work, we aimed to document the effects of proteasome inhibitors MG-132 and Epoxomicin, on the production of factors involved in aseptic loosening, in periprosthetic tissues and fibroblasts, and investigate the role of proteasome impairment in periprosthetic osteolysis. Materials and methods: IL-6 levels in tissue cultures were determined by sandwich ELISA. MMP-1, -3, -13, -14 and TIMP-1 levels in tissue or cell cultures were determined by indirect ELISA. Results for MMP-1 and TIMP-1 in tissue cultures were confirmed by Western blotting. MMP-2 and MMP-9 levels were determined by gelatin zymography. Gene expression of IL-6, MMP-1,-3,-14, TIMP-1 and collagen type-I was determined by RT-PCR. Results: Results show that proteasome inhibition induces the expression of ΜΜΡ-1, -2, -3, -9 and suppresses that of IL-6, MMP-14, -13, TIMP-1 and collagen type I, enhancing the collagenolytic and gelatinolytic activity already present in periprosthetic tissues, as documented in various studies. Conclusions: These findings suggest that proteasome impairment could be a contributing factor to aseptic loosening. Protection and enhancement of proteasome efficacy could thus be considered as an alternative strategy toward disease treatment.

Bortezomib prevents ovariectomy-induced osteoporosis in mice by inhibiting osteoclast differentiation

Bone homeostasis is achieved through coordinated activities of bone-forming osteoblasts and bone-resorbing osteoclasts. When the balance is skewed in favor of osteoclasts due to hormonal or inflammatory issues, pathologic bone loss occurs leading to conditions such as osteoporosis, rheumatoid arthritis, and periodontitis. Bortezomib is the first in-class of proteasome inhibitors used as an anti-myeloma agent. In the present study, we show that bortezomib directly inhibited the receptor activator of nuclear factor κB ligand (RANKL)-dependent osteoclast differentiation of mouse bone marrow macrophages. Bortezomib significantly reduced the induction of osteoclast marker genes and proteins including nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1). The intraperitoneal injection of bortezomib reduced ovariectomy-induced osteoclastogenesis and protected the mice from bone loss. These data propose novel use of bortezomib as a potential anti-resorptive agent.

Translation, adaptation and validation of two versions of the Chronic Liver Disease Questionnaire in Malaysian patients for speakers of both English and Malay languages: a cross-sectional study

OBJECTIVE

We aimed to adapt, translate and validate the Chronic Liver Disease Questionnaire (CLDQ) in Malaysian patients with chronic liver diseases of various aetiologies.

SETTING

Tertiary level teaching institution in Malaysia.

PARTICIPANTS

The validation process involved 211 adult patients (English language n=101, Malay language n=110) with chronic liver disease. Characteristics of the study subjects were as follows: mean (SD) age was 56 (12.8) years, 58.3% were male and 41.7% female. The inclusion criteria were patients 18 years or older with chronic hepatitis and/or liver cirrhosis of any aetiology. The exclusion criteria were as follows: presence of hepatic encephalopathy, ongoing treatment with interferon and presence of other chronic conditions that have an impact on health-related quality of life (HRQOL).

METHODS

A cross-sectional study was conducted. Cultural adaptation of the English version of the CLDQ was performed, and a Malay version was developed following standard forward-backward translation by independent native speakers. Psychometric properties of both versions were determined by assessing their internal consistency, test-retest reliability and discriminant and convergent validity.

RESULTS

Cronbach's alpha for internal consistency across the various domains of the CLDQ was 0.95 for the English version and 0.92 for the Malay version. Test-retest analysis showed excellent reliability with an intraclass correlation coefficient of 0.89 for the English version and 0.93 for the Malay version. The average scores of both the English and Malay versions of the CLDQ demonstrated adequate discriminant validity by differentiating between non-cirrhosis (English 6.3, Malay 6.1), compensated cirrhosis (English 5.6, Malay 6.0) and decompensated cirrhosis (English 5.1, Malay 4.9) (p<0.001). Convergent validity showed that correlation was fair between the English (ρ=0.59) and Malay (p=0.47) CLDQ versions with the EQ-5D, a generic HRQOL instrument.

CONCLUSION

The English and Malay versions of the CLDQ are reliable and valid disease-specific instruments for assessing HRQOL in Malaysian patients with chronic liver disease.

The role of osteoblasts in bone metastasis

The primary role of osteoblasts is to lay down new bone during skeletal development and remodelling. Throughout this process osteoblasts directly interact with other cell types within bone, including osteocytes and haematopoietic stem cells. Osteoblastic cells also signal indirectly to bone-resorbing osteoclasts via the secretion of RANKL. Through these mechanisms, cells of the osteoblast lineage help retain the homeostatic balance between bone formation and bone resorption. When tumour cells disseminate in the bone microenvironment, they hijack these mechanisms, homing to osteoblasts and disrupting bone homeostasis. This review describes the role of osteoblasts in normal bone physiology, as well as interactions between tumour cells and osteoblasts during the processes of tumour cell homing to bone, colonisation of this metastatic site and development of overt bone metastases.

The effects of proteasome inhibitors on bone remodeling in multiple myeloma

Bone disease is a characteristic feature of multiple myeloma, a malignant plasma cell dyscrasia. In patients with multiple myeloma, the normal process of bone remodeling is dysregulated by aberrant bone marrow plasma cells, resulting in increased bone resorption, prevention of new bone formation, and consequent bone destruction. The ubiquitin-proteasome system, which is hyperactive in patients with multiple myeloma, controls the catabolism of several proteins that regulate bone remodeling. Clinical studies have reported that treatment with the first-in-class proteasome inhibitor bortezomib reduces bone resorption and increases bone formation and bone mineral density in patients with multiple myeloma. Since the introduction of bortezomib in 2003, several next-generation proteasome inhibitors have also been used clinically, including carfilzomib, oprozomib, ixazomib, and delanzomib. This review summarizes the available preclinical and clinical evidence regarding the effect of proteasome inhibitors on bone remodeling in multiple myeloma.

miRNA-202 in bone marrow stromal cells affects the growth and adhesion of multiple myeloma cells by regulating B cell-activating factor

Bone marrow stromal cells (BMSCs) up-regulate B cell-activating factor (BAFF) in multiple myeloma. Increasing experimental evidence has shown that microRNAs play a causal role in hematology tumorigenesis. In this study, we characterized the role of miR-202 in regulating the expression of BAFF in BMSCs. It was found that expressions of BAFF mRNA and protein were increased in BMSCs treated with miR-202 inhibitor. The growth rate of miR-202 mimics transfection cells was significantly lower than that of non-transfected cells. The expression of Bcl-2 protein was down-regulated, and Bax protein was up-regulated after miR-202 mimics transfection. Over-expression of miR-202 in BMSCs rendered MM cells more sensitive to bortezomib. More significantly, the regulatory effect of miR-202 could inhibit the activation of NF-κB pathway in BMSCs. These results suggest that miR-202 functions as a modulator that can negatively regulate BAFF by inhibiting MM cell survival, growth, and adhesion in the bone marrow microenvironment.