Bone antiresorptive agents in the treatment of bone metastases associated with solid tumours or multiple myeloma

EZH2 serves as a viable therapeutic target for myeloma-induced osteolytic bone destruction

Myelomatous bone disease is a complication characterized by lytic bone lesions, reduced bone formation, bone pain, and increased fracture risk. Understanding these underlying mechanisms is crucial for developing effective therapeutic approaches. Here we show the role of enhancer of zeste homolog 2 (EZH2) in bone lesions induced by myeloma cells. Our research reveals that cytokines produced by myeloma-associated adipocytes activate the expression of EZH2 in myeloma cells. Furthermore, we find that EZH2 forms a transcriptional repression complex with transcription factor AP2α. This complex promotes trimethylation at lysine 27 of histone H3 (H3K27me3) in the promoter region of the tumor suppressor gene EMP1, resulting in transcriptional silencing. EMP1 silencing leads to increased myeloma cell proliferation and the concomitant secretion of osteolytic cytokines that contribute to bone destruction. Importantly, EZH2 inhibitors effectively treat myeloma-induced osteolytic lesions. Thus, targeting EZH2 represents a potential therapeutic strategy for preventing and managing myeloma bone disease.

Deciphering Cathepsin K inhibitors: a combined QSAR, docking and MD simulation based machine learning approaches for drug design

Cathepsin K (CatK), a lysosomal cysteine protease, contributes to skeletal abnormalities, heart diseases, lung inflammation, and central nervous system and immune disorders. Currently, CatK inhibitors are associated with severe adverse effects, therefore limiting their clinical utility. This study focuses on exploring quantitative structure-activity relationships (QSAR) on a dataset of CatK inhibitors (1804) compiled from the ChEMBL database to predict the inhibitory activities. After data cleaning and pre-processing, a total of 1568 structures were selected for exploratory data analysis which revealed physicochemical properties, distributions and statistical significance between the two groups of inhibitors. PubChem fingerprinting with 11 different machine-learning classification models was computed. The comparative analysis showed the ET model performed well with accuracy values for the training set (0.999), cross-validation (0.970) and test set (0.977) in line with OECD guidelines. Moreover, to gain structural insights on the origin of CatK inhibition, 15 diverse molecules were selected for molecular docking. The CatK inhibitors (1 and 2) exhibited strong binding energies of -8.3 and -7.2 kcal/mol, respectively. MD simulation (300 ns) showed strong structural stability, flexibility and interactions in selected complexes. This synergy between QSAR, docking, MD simulation and machine learning models strengthen our evidence for developing novel and resilient CatK inhibitors.

Pharmacologic Hedgehog inhibition modulates the cytokine profile of osteolytic breast cancer cells

The establishment and progression of bone metastatic breast cancer is supported by immunosuppressive myeloid populations that enable tumor growth by dampening the innate and adaptive immune response. Much work remains to understand how to target these tumor-myeloid interactions to improve treatment outcomes. Noncanonical Hedgehog signaling is an essential component of bone metastatic tumor progression, and prior literature suggests a potential role for Hedgehog signaling and its downstream effector Gli2 in modulating immune responses. In this work, we sought to identify if inhibition of noncanonical Hedgehog signaling alters the cytokine profile of osteolytic breast cancer cells and the subsequent communication between the tumor cells and myeloid cells. Examination of large patient databases revealed significant relationships between Gli2 expression and expression of markers of myeloid maturation and activation as well as cytokine expression. We found that treatment with HPI-1 reduced tumor cell expression of numerous cytokine genes, including CSF1, CSF2, and CSF3, as well as CCL2 and IL6. Secreted CSF-1 (M-CSF) was also reduced by treatment. Changes in tumor-secreted factors resulted in polarization of THP-1 monocytes toward a proinflammatory phenotype, characterized by increased CD14 and CD40 surface marker expression. We therefore propose M-CSF as a novel target of Hedgehog inhibition with potential future applications in altering the immune microenvironment in addition to its known roles in reducing tumor-induced bone disease.

Molecular landscape of prostate cancer bone metastasis

Prostate cancer (PC) has a high propensity to develop bone metastases, causing severe pain and pathological fractures that profoundly impact a patients' normal functions. Current clinical intervention is mainly palliative focused on pain management, and tumor progression is refractory to standard therapeutic regimens. This limited treatment efficacy is at least partially due to a lack of comprehensive understanding of the molecular landscape of the disease pathology, along with the intensive overlapping of physiological and pathological molecular signaling. The niche is overwhelmed with diverse cell types with inter- and intra-heterogeneity, along with growth factor-enriched cells that are supportive of invading cell proliferation, providing an additional layer of complexity. This review seeks to provide molecular insights into mechanisms underlying PC bone metastasis development and progression.

Clinicopathological correlation of Cathepsin K expression in salivary gland carcinomas; relation to patients` outcome

BACKGROUND

Salivary gland carcinomas (SGCs) represent various groups of tumors that demonstrate marked diversity in their prognosis owing to different histology and clinical characteristics. One of the poor prognostic indicators is distant metastasis which is considered the major reason for death in SGC patients. Discovering new biomarkers is urgently required to aid in the detection of cancer onset and progression. Cathepsin K (CTSK), the lysosomal cysteine protease has a principal role in cancer invasion and progression through interaction with the tumor microenvironment, degradation of extracellular membrane proteins and destruction of the elastic lamina of blood vessels. In the English literature, little information was present about the role of CTSK in SGCs. The current study aimed to assess the immunohistochemical expression of CTSK in SGCs and correlate its expression to different clinicopathologic parameters.

METHODS

The retrospective study applied to 45 cases of SGCs categorized as high-grade (33 cases) and low-grade SGCs (12 cases) following the criteria of WHO classification (2017) of head and neck tumors. All patients` clinicopathological and follow-up records were retrieved. The following statistical tests were used to study the variance of CTSK expression in SGCs concerning different clinicopathological parameters; Pearson`s Chi-square test, unpaired two-tailed student t-test, One-way ANOVA, and Post Hoc tests. Disease-free survival (DFS) and Overall survival (OS) were calculated and displayed with the Kaplan-Meier strategy and analyzed with the log-rank test. Univariate and multivariate survival analyses were performed with Cox regression. A P-value lesser than 0.05 was considered statistically significant.

RESULTS

Strong CTSK expression was significantly related to high-grade SGCs (P = 0.000), large infiltrating carcinomas (P = 0.000), presence of nodal (P = 0.041) and distant metastasis (P = 0.009), advanced TNM clinical stage (P = 0.000), the incidence of recurrence (P = 0.009), and reduced DFS (P = 0.006). Distant metastasis was the independent predictor for DFS using Cox regression model.

CONCLUSIONS

CTSK has a great role in cancer progression by triggering many signaling pathways. Its level in cancerous tissue is considered an effective index for predicting the severity and prognosis of cancer. Therefore, we indicate its utility as a prognostic tool and therapeutic target for cancer treatment.

TRIAL REGISTRATION

Retrospectively registered.

Cathepsin K: A Versatile Potential Biomarker and Therapeutic Target for Various Cancers

Cancer, a common malignant disease, is one of the predominant causes of diseases that lead to death. Additionally, cancer is often detected in advanced stages and cannot be radically cured. Consequently, there is an urgent need for reliable and easily detectable markers to identify and monitor cancer onset and progression as early as possible. Our aim was to systematically review the relevant roles of cathepsin K (CTSK) in various possible cancers in existing studies. CTSK, a well-known key enzyme in the bone resorption process and most studied for its roles in the effective degradation of the bone extracellular matrix, is expressed in various organs. Nowadays, CTSK has been involved in various cancers such as prostate cancer, breast cancer, bone cancer, renal carcinoma, lung cancer and other cancers. In addition, CTSK can promote tumor cells proliferation, invasion and migration, and its mechanism may be related to RANK/RANKL, TGF-β, mTOR and the Wnt/β-catenin signaling pathway. Clinically, some progress has been made with the use of cathepsin K inhibitors in the treatment of certain cancers. This paper reviewed our current understanding of the possible roles of CTSK in various cancers and discussed its potential as a biomarker and/or novel molecular target for various cancers.

The Potential Roles of Exosomal miR-214 in Bone Metastasis of Lung Adenocarcinoma

Bone metastasis is closely related to the alterations of bone microenvironment. In this article, we hypothesize that exosomes may be involved in the "vicious circle" by transferring miR-214. miR-214 is highly expressed in lung adenocarcinoma, and is closely related to the degree of lung cancer progression. As a key regulator of bone homeostasis, miR-214 promotes osteoclast differentiation and mediates intercellular communication between osteoclasts and osteoblasts via the way of exosomal miRNA. Therefore, it is highly probable that exosomal miR-214 derived from lung adenocarcinoma may disrupt bone homeostasis by enhancing bone resorption. Exosomal miR-214 can be released by lung adenocarcinoma cells, enters peripheral circulation, and is taken up by osteoclasts, consequently stimulating osteoclast differentiation. The enhanced bone resorption alters the bone microenvironment by releasing multiple cytokines and growth factors favoring cancer cells. The circulating cancer cells migrate to bone, proliferate, and colonize, resulting in the formation of metastasis. Furthermore, osteoclasts derived exosomal miR-214 may in turn contribute to cancer progression. In this way, the exosomal miR-214 from osteoclasts and lung adenocarcinoma cells mediates the positive interaction between bone resorption and bone metastasis. The levels of exosomal miR-214 in the peripheral circulation may help predict the risk of bone metastasis. The exosomal miR-214 may be a potential therapeutic target for both prevention and treatment of bone metastasis in patients with lung adenocarcinoma.

Prognosis of medication-related osteonecrosis of the jaws in metastatic prostate cancer patients

OBJECTIVES

The aim of this study was to find out the prognosis of medication-related osteonecrosis of the jaws (MRONJ) in prostate cancer patients who received two different types of antiresorptive agents for bone metastasis.

MATERIALS AND METHODS

We retrospectively surveyed a cohort of 95 metastatic prostate cancer patients with 122 MRONJ lesions treated in a single medical center. Treatment outcomes and prognostic factors were investigated. The cumulative complete response rate was calculated with the Kaplan-Meier method, and significance was examined with the log-rank and Breslow tests. Cox regression was used for the univariate and multivariate analyses of prognostic factors.

RESULTS

The cumulative complete response rate of all patients at 12 months was 37.8%, and that of patients treated with zoledronic acid and denosumab was 22.9% and 70.5%, respectively. Denosumab, pretreatment C-terminal telopeptide of collagen I (CTX) level > 150 pg/ml, and anemia were identified as independent prognostic factors in a multivariate analysis with adjusted hazard ratios of 3.18 (95% confidence interval [CI], 1.24-8.11), 3.24 (95% CI, 1.39-7.53), and 0.42 (95% CI, 0.19-0.93), respectively.

CONCLUSION

A higher pretreatment level of CTX, using denosumab as the antiresorptive agent and without anemia, indicates a better treatment outcome of MRONJ in prostate cancer patients.

Targeting the tumour stroma to improve cancer therapy

Cancers are not composed merely of cancer cells alone; instead, they are complex 'ecosystems' comprising many different cell types and noncellular factors. The tumour stroma is a critical component of the tumour microenvironment, where it has crucial roles in tumour initiation, progression, and metastasis. Most anticancer therapies target cancer cells specifically, but the tumour stroma can promote the resistance of cancer cells to such therapies, eventually resulting in fatal disease. Therefore, novel treatment strategies should combine anticancer and antistromal agents. Herein, we provide an overview of the advances in understanding the complex cancer cell-tumour stroma interactions and discuss how this knowledge can result in more effective therapeutic strategies, which might ultimately improve patient outcomes.

Understanding the Progression of Bone Metastases to Identify Novel Therapeutic Targets

Bone is one of the most preferential target site for cancer metastases, particularly for prostate, breast, kidney, lung and thyroid primary tumours. Indeed, numerous chemical signals and growth factors produced by the bone microenvironment constitute factors promoting cancer cell invasion and aggression. After reviewing the different theories proposed to provide mechanism for metastatic progression, we report on the gene expression profile of bone-seeking cancer cells. We also discuss the cross-talk between the bone microenvironment and invading cells, which impacts on the tumour actions on surrounding bone tissue. Lastly, we detail therapies for bone metastases. Due to poor prognosis for patients, the strategies mainly aim at reducing the impact of skeletal-related events on patients' quality of life. However, recent advances have led to a better understanding of molecular mechanisms underlying bone metastases progression, and therefore of novel therapeutic targets.

Methods to Investigate the Role of Rho GTPases in Osteoclast Function

The actin cytoskeleton is essential for the biology of osteoclasts, in particular during bone resorption. As key regulators of actin dynamics, the small GTPases of the Rho family are very important in the control of osteoclast activity. The study of Rho GTPase signaling pathways is essential to uncover the mechanisms of bone resorption and can have interesting applications for the treatment of osteolytic diseases. In this chapter, we describe various techniques to obtain primary osteoclasts from murine bone marrow cells, to measure Rho GTPase activation levels, to monitor bone resorption activity of osteoclasts and to introduce the expression of proteins of interest using a retroviral approach. We illustrate the different methods with experimental examples of the effect of Rac1 activation by the exchange factor Dock5 on bone resorption by osteoclasts.

The prevention of fragility fractures in patients with non-metastatic prostate cancer: a position statement by the international osteoporosis foundation

Androgen deprivation therapy is commonly employed for the treatment of non-metastatic prostate cancer as primary or adjuvant treatment. The skeleton is greatly compromised in men with prostate cancer during androgen deprivation therapy because of the lack of androgens and estrogens, which are trophic factors for bone. Men receiving androgen deprivation therapy sustain variable degrees of bone loss with an increased risk of fragility fractures. Several bone antiresorptive agents have been tested in randomized controlled trials in these patients. Oral bisphosphonates, such as alendronate and risedronate, and intravenous bisphosphonates, such as pamidronate and zoledronic acid, have been shown to increase bone density and decrease the risk of fractures in men receiving androgen deprivation therapy. Denosumab, a fully monoclonal antibody that inhibits osteoclastic-mediated bone resorption, is also effective in increasing bone mineral density and reducing fracture rates in these patients. The assessment of fracture risk, T-score and/or the evaluation of prevalent fragility fractures are mandatory for the selection of patients who will benefit from antiresorptive therapy. In the future, new agents modulating bone turnover and skeletal muscle metabolism will be available for testing in these subjects.

Adipose, Bone, and Myeloma: Contributions from the Microenvironment

Researchers globally are working towards finding a cure for multiple myeloma (MM), a destructive blood cancer diagnosed yearly in ~750,000 people worldwide (Podar et al. in Expert Opin Emerg Drugs 14:99-127, 2009). Although MM targets multiple organ systems, it is the devastating skeletal destruction experienced by over 90 % of patients that often most severely impacts patient morbidity, pain, and quality of life. Preventing bone disease is therefore a priority in MM treatment, and understanding how and why myeloma cells target the bone marrow (BM) is fundamental to this process. This review focuses on a key area of MM research: the contributions of the bone microenvironment to disease origins, progression, and drug resistance. We describe some of the key cell types in the BM niche: osteoclasts, osteoblasts, osteocytes, adipocytes, and mesenchymal stem cells. We then focus on how these key cellular players are, or could be, regulating a range of disease-related processes spanning MM growth, drug resistance, and bone disease (including osteolysis, fracture, and hypercalcemia). We summarize the literature regarding MM-bone cell and MM-adipocyte relationships and subsequent phenotypic changes or adaptations in MM cells, with the aim of providing a deeper understanding of how myeloma cells grow in the skeleton to cause bone destruction. We identify avenues and therapies that intervene in these networks to stop tumor growth and/or induce bone regeneration. Overall, we aim to illustrate how novel therapeutic target molecules, proteins, and cellular mediators may offer new avenues to attack this disease while reviewing currently utilized therapies.

Emerging treatment approaches for myeloma-related bone disease

INTRODUCTION

Multiple myeloma is characterized by the presence of osteolytic lesions that leads to devastating skeletal-related events in the majority of patients. Myeloma bone disease is attributed to increased osteoclastic and suppressed osteoblastic activity. Areas covered: Bisphosphonates remain the main treatment option, however they have limitations on their own. Understanding the pathogenesis of myeloma bone disease may provide a roadmap for new therapeutic approaches. The pathway of RANKRANKLOPG pathway has revealed denosumab, a monoclonal antibody targeting RANKL as a novel emerging therapy for myeloma-related bone disease. Furthermore, the Wnt signaling inhibitors dicckopf-1 and sclerostin that are implicated in the pathogenesis of bone destruction of myeloma are now targeted by novel monoclonal antibodies. Activin-A is a TGF-beta superfamily member which increases osteoclast activity and inhibits osteoblast function in myeloma; sotatercept and other molecules targeting activin-A have entered into clinical development. Several other molecules and pathways that play an important role in the pathogenesis of bone destruction in myeloma, such as periostin, adiponectin, Notch and BTK signaling are also targeted in an attempt to develop novel therapies for myeloma-related bone disease. Expert commentary: We summarize the current advances in the biology of myeloma bone disease and the potential therapeutic targets.

Thymidine phosphorylase exerts complex effects on bone resorption and formation in myeloma

Myelomatous bone disease is characterized by the development of lytic bone lesions and a concomitant reduction in bone formation, leading to chronic bone pain and fractures. To understand the underlying mechanism, we investigated the contribution of myeloma-expressed thymidine phosphorylase (TP) to bone lesions. In osteoblast progenitors, TP up-regulated the methylation of RUNX2 and osterix, leading to decreased bone formation. In osteoclast progenitors, TP up-regulated the methylation of IRF8 and thereby enhanced expression of NFATc1 (nuclear factor of activated T cells, cytoplasmic 1 protein), leading to increased bone resorption. TP reversibly catalyzes thymidine into thymine and 2-deoxy-d-ribose (2DDR). Myeloma-secreted 2DDR bound to integrin αVβ3/α5β1 in the progenitors, activated PI3K (phosphoinositide 3-kinase)/Akt signaling, and increased DNMT3A (DNA methyltransferase 3A) expression, resulting in hypermethylation of RUNX2, osterix, and IRF8 This study elucidates an important mechanism for myeloma-induced bone lesions, suggesting that targeting TP may be a viable approach to healing resorbed bone in patients. Because TP overexpression is common in bone-metastatic tumors, our findings could have additional mechanistic implications.