Osteoclast inhibitors to prevent bone metastases in men with high-risk, non-metastatic prostate cancer: A systematic review and meta-analysis

Macrophage heterogeneity in bone metastasis

Previous studies illustrated that macrophage, a type of innate immune cell, plays critical roles in tumour progression and metastasis. Bone is the most frequent site of metastasis for several cancer types including breast, prostate, and lung. In bone metastasis, osteoclast, a macrophage subset specialized in bone resorption, was heavily investigated in the past. Recent studies illustrated that other macrophage subsets, e.g. monocyte-derived macrophages, and bone resident macrophages, promoted bone metastasis independent of osteoclast function. These novel mechanisms further improved our understanding of macrophage heterogeneity in the context of bone metastasis and illustrated new opportunities for future studies.

Conditional knockout of PDK1 in osteoclasts suppressed osteoclastogenesis and ameliorated prostate cancer-induced osteolysis in murine model

BACKGROUND

The development and maintenance of normal bone tissue is maintained by balanced communication between osteoblasts and osteoclasts. The invasion of cancer cells disrupts this balance, leading to osteolysis. As the only bone resorbing cells in vivo, osteoclasts play important roles in cancer-induced osteolysis. However, the role of 3-phosphoinositide-dependent protein kinase-1 (PDK1) in osteoclast resorption remains unclear.

METHODS

In our study, we used a receptor activator of nuclear factor-kappa B (RANK) promoter-driven Cre-LoxP system to conditionally delete the PDK1 gene in osteoclasts in mice. We observed the effect of osteoclast-specific knockout of PDK1 on prostate cancer-induced osteolysis. Bone marrow-derived macrophage cells (BMMs) were extracted and induced to differentiate osteoclasts in vitro to explore the role of PDK1 in osteoclasts.

RESULTS

In this study, we found that PDK1 conditional knockout (cKO) mice exhibited smaller body sizes when compared to the wild-type (WT) mice. Moreover, deletion of PDK1 in osteoclasts ameliorated osteolysis and rPDK1educed bone resorption markers in the murine model of prostate cancer-induced osteolysis. In vivo, we discovered that osteoclast-specific knockout of suppressed RANKL-induced osteoclastogenesis, bone resorption function, and osteoclast-specific gene expression (Ctsk, TRAP, MMP-9, NFATc1). Western blot analyses of RANKL-induced signaling pathways showed that conditional knockout of PDK1 in osteoclasts inhibited the early nuclear factor κB (NF-κB) activation, which consequently suppressed the downstream induction of NFATc1.

CONCLUSION

These findings demonstrated that PDK1 performs an important role in osteoclastogenesis and prostate cancer-induced osteolysis by modulating the PDK1/AKT/NF-κB signaling pathway.

Unveiling novel insights in prostate cancer through single-cell RNA sequencing

Single-cell RNA sequencing (scRNA-seq) is a cutting-edge technology that provides insights at the individual cell level. In contrast to traditional bulk RNA-seq, which captures gene expression at an average level and may overlook important details, scRNA-seq examines each individual cell as a fundamental unit and is particularly well-suited for identifying rare cell populations. Analogous to a microscope that distinguishes various cell types within a tissue sample, scRNA-seq unravels the heterogeneity and diversity within a single cell species, offering great potential as a leading sequencing method in the future. In the context of prostate cancer (PCa), a disease characterized by significant heterogeneity and multiple stages of progression, scRNA-seq emerges as a powerful tool for uncovering its intricate secrets.

Prostate cancer and bone: clinical presentation and molecular mechanisms

Prostate cancer (PCa) is an increasingly prevalent health problem in the developed world. Effective treatment options exist for localized PCa, but metastatic PCa has fewer treatment options and shorter patient survival. PCa and bone health are strongly entwined, as PCa commonly metastasizes to the skeleton. Since androgen receptor signaling drives PCa growth, androgen-deprivation therapy whose sequelae reduce bone strength constitutes the foundation of advanced PCa treatment. The homeostatic process of bone remodeling - produced by concerted actions of bone-building osteoblasts, bone-resorbing osteoclasts, and regulatory osteocytes - may also be subverted by PCa to promote metastatic growth. Mechanisms driving skeletal development and homeostasis, such as regional hypoxia or matrix-embedded growth factors, may be subjugated by bone metastatic PCa. In this way, the biology that sustains bone is integrated into adaptive mechanisms for the growth and survival of PCa in bone. Skeletally metastatic PCa is difficult to investigate due to the entwined nature of bone biology and cancer biology. Herein, we survey PCa from origin, presentation, and clinical treatment to bone composition and structure and molecular mediators of PCa metastasis to bone. Our intent is to quickly yet effectively reduce barriers to team science across multiple disciplines that focuses on PCa and metastatic bone disease. We also introduce concepts of tissue engineering as a novel perspective to model, capture, and study complex cancer-microenvironment interactions.

Biological and Clinical Aspects of Metastatic Spinal Tumors

Simple Summary

Spine metastases are a common life-threatening complication of advanced-stage malignancies and often result in poor prognosis. Symptomatic spine metastases develop in the course of about 10% of malignant neoplasms. Therefore, it is essential for contemporary medicine to understand metastatic processes in order to find appropriate, targeted therapeutic options. Our literature review aimed to describe the up-to-date knowledge about the molecular pathways and biomarkers engaged in the spine’s metastatic processes. Moreover, we described current data regarding bone-targeted treatment, the emerging targeted therapies, radiotherapy, and immunotherapy used for the treatment of spine metastases. We hope that knowledge comprehensively presented in our review will contribute to the development of novel drugs targeting specific biomarkers and pathways. The more we learn about the molecular aspects of cancer metastasis, the easier it will be to look for treatment methods that will allow us to precisely kill tumor cells.

Abstract

Spine metastases are a common life-threatening complication of advanced-stage malignancies and often result in poor prognosis. Symptomatic spine metastases develop in the course of about 10% of malignant neoplasms. Therefore, it is essential for contemporary medicine to understand metastatic processes in order to find appropriate, targeted therapeutic options. Thanks to continuous research, there appears more and more detailed knowledge about cancer and metastasis, but these transformations are extremely complicated, e.g., due to the complexity of reactions, the variety of places where they occur, or the participation of both tumor cells and host cells in these transitions. The right target points in tumor metastasis mechanisms are still being researched; that will help us in the proper diagnosis as well as in finding the right treatment. In this literature review, we described the current knowledge about the molecular pathways and biomarkers engaged in metastatic processes involving the spine. We also presented a current bone-targeted treatment for spine metastases and the emerging therapies targeting the discussed molecular mechanisms.

Application and prospect of single-cell sequencing in cancer metastasis

Cancer metastasis is a complicated process driven by internal genetic variations and developed through interactions with the external environment. This process usually causes therapeutic resistance and results in a low survival rate. In recent years, single-cell sequencing has become a popular method for revealing the tumor evolutionary genetic lineage, intra-tumoral heterogeneity and tumor microenvironment of the metastasis process. So as to find more therapeutic targets for clinical application, the spatial transcriptomics method has become a new rising field of cancer studies, which promotes the combination between clinical medicine and molecular biology. In future prospects, more accurate and personalized treatment models will come into reality.

Osteonecrosis of the Jaw and Antiresorptive Agents in Benign and Malignant Diseases: A Critical Review Organized by the ECTS

CONTEXT

Antiresorptive therapy significantly reduces fracture risk in patients with benign bone disease and skeletal-related events (SREs) in patients with bone metastases (BM). Osteonecrosis of the jaw (ONJ) is a rare but severe condition manifested as necrotic bone lesion or lesions of the jaws. ONJ has been linked to the use of potent antiresorptive agents, termed medication-related ONJ (MRONJ).

OBJECTIVE

We aimed to identify the differences various aspects of MRONJ among distinct patient categories and provide recommendations on how to mitigate the risk and optimally manage MRONJ in each of them.

METHODS

A working group of the European Calcified Tissue Society (ECTS) and 2 experts performed an updated detailed review of existing literature on MRONJ incidence, characteristics, and treatment applied in bone diseases with variable severity of skeletal insult, ranging from osteoporosis to prevention of cancer treatment-induced bone loss and SREs in cancer patients with BM.

RESULTS

The risk for MRONJ is much higher in patients with advanced malignancies compared to those with benign bone diseases because of the higher doses and more frequent administration of antiresorptive agents in individuals with compromised general health, along with coadministration of other medications that predispose to MRONJ. The overall risk for MRONJ is considerably lower than the benefits in all categories of patients.

CONCLUSION

The risk for MRONJ largely depends on the underlying bone disease and the relevant antiresorptive regimen applied. Physicians and dentists should keep in mind that the benefits of antiresorptive therapy far outweigh the risk for MRONJ development.

IL4/IL4R signaling promotes the osteolysis in metastatic bone of CRC through regulating the proliferation of osteoclast precursors

BACKGROUND

Bone metastasis of colorectal cancer (CRC) often indicates a poor prognosis. Osteolysis can be observed in metastatic sites, implying an aberrant activation of osteoclasts. However, how osteoclastogenesis is regulated in metastatic microenvironment caused by colorectal cancer is still unclear.

METHODS

In this study, mice bone metastatic model of CRC was established through injection of MC-38 or CT-26 cells. BrdU assays showed primary CD115 ( +) osteoclast precursors (OCPs) proliferated at the first 2 weeks. Transcriptomic profiling was performed to identify differentially expressing genes and pathways in OCPs indirectly co-cultured with CRC cells RESULTS: The expression of IL4Rα was found to be significantly upregulated in OCPs stimulated by tumor conditioned medium (CM). Further investigation indicated that IL-4 signaling regulated proliferation of OPCs through interacting with type I IL4 receptor, and neutrophils were the main source of IL-4 in bone marrow. The proliferation of OCPs can be inhibited in IL4 deficiency mice. In addition, ERK pathway was activated by IL4/IL4R signaling. Ravoxertinib, an ERK antagonists, could significantly prevent bone destruction through inhibiting the proliferation of OCPs.

CONCLUSION

Our study indicates the essential role of IL4/IL4R signaling for the proliferation of OCPs in early metastasis of CRC predominantly through activating ERK pathway, which remarkedly impacts the number of osteoclasts in later stage and leads to osteolytic lesions. Moreover, Ravoxertinib could be a new therapeutical target for bone metastasis of CRC.

Jaw osteonecrosis in patients treated with denosumab 120 mg with regular dental monitoring: 4-year retrospective study

Background: Medication-related osteonecrosis of the jaw (MRONJ) is an expected, but rare adverse effect of denosumab. There are few data denosumab 120 mg related MRONJ occurrence when regular dental monitoring is planned. International and French recommendations do not detail the schedule of the follow-up visits, allowing local interpretations. Methods: The aim of this retrospective study was to describe our local experience of regular dental monitoring in patients receiving denosumab 120 mg. We included all ≥18-year-old patients exposed to denosumab 120 mg, bisphosphonate- and denosumab-naive, and with regular dental monitoring (pre-treatment and every 4 months after denosumab initiation) at the University Hospital Center, France, from 2015 to 2019. The crude incidence of denosumab-related osteonecrosis of the jaw was estimated per 100 person-years (95% confidence interval). Results: During the study period, 251 patients were included, of whom 77 did not attend the 1st follow-up visit at 4 months. Almost all patients had osteonecrosis of the jaw risk factors. Ten MRONJ cases were reported (four stage 0 and six stage 1). The crude incidence rate was 5.1 per 100 person-years (95% CI: 1.9–8.2). Denosumab was stopped in all patients who developed MRONJ, with favorable outcome for 3 cases and stabilization in 4 cases after osteonecrosis of the jaw management. Conclusion: This study suggested that a regular dental follow-up every 4 months may be a suitable option for prevention and early detection/treatment of MRONJ. A randomized study should be performed to determine the best dental monitoring schedule.

Cancer Treatment–Induced Bone Loss and Role of Denosumab in Nonmetastatic Prostate Cancer: A Narrative Review

Bone loss is an important complication of prostate cancer and its associated treatments, especially androgen-deprivation therapy (ADT). There is a 5 to 10 times increased loss of bone mineral density (BMD) in men receiving ADT with yearly 4 to 13% BMD loss. The risk of fracture increases yearly by 5 to 8% with ADT. ADT associated bone loss of 10 to 15% of BMD doubles the risk of fractures. Hence, BMD evaluation through dual-energy X-ray absorptiometry and evaluation of individual fracture risk assessed before initiating ADT. The use of vitamin D, calcium, bisphosphonates, and denosumab has shown improved bone health in men with prostate cancer receiving ADT. Denosumab 60 mg is approved to increase bone mass in men at high risk for fractures receiving ADT for nonmetastatic prostate cancer. Denosumab has shown improvement of 5.6% BMD at 2 years in nonmetastatic prostate cancer patients, with significant improvements seen at the total hip, femoral neck, and distal third of the radius. Denosumab has shown a 62% decreased incidence of new vertebral fractures at 36 months. Furthermore, denosumab delays the onset of bone metastases in high-risk nonmetastatic prostate cancer patients. Denosumab can be preferred over other bone modifying agents owing to several advantages, such as subcutaneous administration and no requirement of hospitalization, no dose modifications in renal impairment and less incidence of acute phase anaphylactic reactions. We review the available evidence of denosumab for managing bone loss in nonmetastatic prostate cancer patients. The relevant articles used in this narrative review were obtained through general search on google and PubMed using the key terms “non-metastatic prostate cancer,” “denosumab,” “bone loss,” “bone mineral density,” “fracture,” “CTIBL,” and “chemotherapy induced bone loss.”

Hypocalcemia in a Patient With Metastatic Prostate Cancer From Denosumab Treatment

Denosumab is a humanized monoclonal antibody that binds RANKL to inhibit osteoclast activity. It is indicated for the prevention of skeletal-related events (SRE) in patients with solid tumors who have bone metastasis and in patients with multiple myeloma. Hypocalcemia is one of the known side effects of denosumab, which can be prevented with calcium supplementation.

We present a case of a 72-year-old male with diagnosed metastatic prostate cancer who had received one dose of denosumab 10 days prior to presentation with fatigue, insomnia, and somnolence. His labs showed severe (Grade 4) hypocalcemia, which improved with intravenous calcium supplementation. This case highlights a known but life-threatening side effect of denosumab and the potential need for prolonged calcium monitoring in patients placed on the drug.

Bisphosphonate-Based Conjugates and Derivatives as Potential Therapeutic Agents in Osteoporosis, Bone Cancer and Metastatic Bone Cancer

Metastatic bone cancer occurs in every type of cancer but is prevalent in lung, breast, and prostate cancers. These metastases can cause extensive morbidity, including a range of skeletal-related events, often painful and linked with substantial hospital resource usage. The treatment used is a combination of chemotherapy and surgery. However, anticancer drugs are still limited due to severe side effects, drug resistance, poor blood supply, and non-specific drug uptake, necessitating high toxic doses. Bisphosphonates are the main class of drugs utilized to inhibit metastatic bone cancer. It is also used for the treatment of osteoporosis and other bone diseases. However, bisphosphonate also suffers from serious side effects. Thus, there is a serious need to develop bisphosphonate conjugates with promising therapeutic outcomes for treating metastatic bone cancer and osteoporosis. This review article focuses on the biological outcomes of designed bisphosphonate-based conjugates for the treatment of metastatic bone cancer and osteoporosis.

Single-cell analysis reveals transcriptomic remodellings in distinct cell types that contribute to human prostate cancer progression

Prostate cancer shows remarkable clinical heterogeneity, which manifests in spatial and clonal genomic diversity. By contrast, the transcriptomic heterogeneity of prostate tumours is poorly understood. Here we have profiled the transcriptomes of 36,424 single cells from 13 prostate tumours and identified the epithelial cells underlying disease aggressiveness. The tumour microenvironment (TME) showed activation of multiple progression-associated transcriptomic programs. Notably, we observed promiscuous KLK3 expression and validated the ability of cancer cells in altering T-cell transcriptomes. Profiling of a primary tumour and two matched lymph nodes provided evidence that KLK3 ectopic expression is associated with micrometastases. Close cell-cell communication exists among cells. We identified an endothelial subset harbouring active communication (activated endothelial cells, aECs) with tumour cells. Together with sequencing of an additional 11 samples, we showed that aECs are enriched in castration-resistant prostate cancer and promote cancer cell invasion. Finally, we created a user-friendly web interface for users to explore the sequenced data.

A Novel Salicylanilide Derivative Induces Autophagy Cell Death in Castration-Resistant Prostate Cancer via ER Stress-Activated PERK Signaling Pathway

Metastatic castration-resistant prostate cancer (CRPC) is currently incurable. Cancer growth and progression is intimately affected by its interaction with host microenvironment. Cotargeting of the stroma and prostate cancer is therefore an emerging therapeutic strategy for metastatic CRPC. Cancer-induced osteoclastogenesis is known to contribute to CRPC bone metastasis. This study is to extend pharmacologic value of our synthesized LCC03, a derivative of 5-(2',4'-difluorophenyl)-salicylanilide that has previously testified for its osteoclastogenesis activity, by exploring its additional cytotoxic properties and underlying mechanism in CRPC cells. LCC03 was chemically synthesized and examined for cell growth inhibition in a serial of CRPC cell lines. We demonstrated that LCC03 dose-dependently suppressed proliferation and retarded cell-cycle progression in CRPC cells. The classical autophagy features, including autophagosome formation and LC3-II conversion, were dramatically shown in LCC03-treated CRPC cells, and it was associated with the suppressed AKT/mTOR signaling pathways, a major negative regulator of autophagy. Moreover, an expanded morphology of the endoplasmic reticulum (ER), increased expression of the ER stress markers GRP78 and PERK, and eIF2α phosphorylation were observed. Blockage of autophagy and PERK pathways using small molecule inhibitors or shRNA knockdown reversed LCC03-induced autophagy and cell death, thus indicating that the PERK-eIF2α pathway contributed to the LCC03-induced autophagy. Furthermore, treatment of tumor-bearing mice with intraperitoneal administered LCC03 suppressed the growth of CRPC xenografts in mouse bone without systemic toxicity. The dual action of 5-(2',4'-difluorophenyl)-salicylanilide on targeting both the osteoclasts and the tumor cells strongly indicates that LCC03 is a promising anticancer candidate for preventing and treating metastatic CRPC.

Denosumab for bone health in prostate and breast cancer patients receiving endocrine therapy? A systematic review and a meta-analysis of randomized trials

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Hormonal receptors positive breast tumor and prostate cancer are managed with endocrine therapies.

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Endocrine therapies designed for breast and prostate cancer are often associated to serious adverse skeletal related events, such fractures.

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Denosumab is a monoclonal anti-body binding RANKL which acts as inhibitor of osteoclasts activity, thus increasing bone mass.

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Denosumab was showed to strongly prevent hormonal therapies-related skeletal issues.

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Denosumab administration results safe in bone mass increase and reduction of fractures risk.

Hormonal therapies for receptor positive-breast and prostate cancer patients have shown clinical efficacy but also several side effects including osteoporosis, loss of bone mass and increased fracture risk. Denosumab represents an anti RANKL (receptor activator of nuclear factor-kB ligand) monoclonal anti-body acting as inhibitor of osteoclasts formation, function, and survival, then increasing bone mass. Herein, we performed a systematic review and meta-analysis of randomized controlled trials (RCTs) to evaluate the role of Denosumab in saving bone health in prostate and breast cancer patients receiving respectively androgen deprivation therapy and adjuvant endocrine therapy. Moreover, selected patients have to be treated with Denosumab at the dose of 60 mg every six month or placebo. Outcomes studied included the bone mass density (BMD) increase at 24 and 36 months, BMD loss, reduction of fractures risk (in particular vertebral) at 24 and 36 months and safety (overall, serious adverse events – SAEs and discontinuation rate). Our results showed a reduction of the BMD loss up to 36 months both at the lumbar and femoral level and a BMD increase both at 24 and 36 months. It was also found a reduction in the number of new vertebral and femoral fractures at 24 and 36 months. Finally, our pooled analysis showed that Denosumab did not affect both the SAEs and therapy discontinuation risk. In conclusion, Denosumab administration can be considered effective and safe in the prevention and management of the above mentioned adverse events related to hormonal therapies designed for breast and prostate tumors.

The Bone Microenvironment in Prostate Cancer Metastasis

The propensity of prostate cancer cells to seed the skeleton and then progress into clinically relevant metastatic tumors is widely recognized and a major cause of morbidity and mortality for patients. The natural history of prostate adenocarcinoma most frequently begins with a tumor diagnosed at a localized stage, which is successfully treated by surgical and/or radiation therapy modalities. A relevant percentage of patients are clinically cured but approximately 20-30% will develop biochemical signs of recurrence, which respond to the inhibition of androgen receptor (AR) signaling by hormone-deprivation and receptor antagonists, before the inevitable transition into castration-resistant prostate cancer (CRPC). This stage simultaneously presents with or is rapidly followed by secondary tumors, which involve the skeleton in more than 90% of cases (mCRPC). While generalization in clinical practice is always unwise, it is indisputable that bone-metastatic prostate cancer is virtually incurable. Decades of research have revealed that the tissue microenvironment provided by the bone marrow is as important as the cell-autonomous features of tumor cells in fostering the right conditions that lead to establishment and progression of metastatic tumors in the skeleton.

The Current Role of Osteoclast Inhibitors in Patients with Prostate Cancer

Purpose

Prostate cancer (PCa) is one of the most frequently diagnosed malignancies worldwide. Hormonal deprivation therapy is a well-established treatment for locally advanced or metastatic diseases but exposes patients to the risk of osteoporosis and fragility fractures. Furthermore, the tropism of the PCa cells to osseous metastases increases the incidence of skeletal-related events (SREs).

Methods

A nonsystematic review of the international literature was performed in respect to the use of osteoclast inhibitors zoledronic acid (ZA) and denosumab (DEN) in PCa patients.

Results

DEN and ZA have proved their efficacy in preventing osteoporosis and bone mass loss in patients treated with hormonal therapy with no proven superiority of one agent over the other. However, the effectiveness in reducing fragility fractures has been proved only for DEN so far. In metastatic-free castrate-sensitive high-risk PCa patients, ZA has not shown any efficacy in preventing osseous metastasis, and evidence is lacking in favor or against the use of DEN. The use of osteoclasts inhibitors had no evident positive effect in overall and disease-specific survival in this group of patients. In advanced castrate-refractory malignancy, DEN has shown clinical superiority over ZA in preventing new SRE but not in overall survival.

Conclusion

Superiority of DEN over ZA has been proved only in advanced castrate refractory disease in terms of preventing new SRE. In the rest of the cases, the selection of either agent should be based on the clinical condition of each patient and the cost of the treatment.

The homogeneous and heterogeneous risk factors for the morbidity and prognosis of bone metastasis in patients with prostate cancer

Purpose

Using the Surveillance, Epidemiology, and End Results database (SEER) to assess the incidence and risk factors of morbidity and prognosis for bone metastases in initial metastatic prostate cancer.

Patients and methods

The records of 249,331 prostate cancer patients in the SEER database, diagnosed between 2010 and 2014, were obtained were obtained to investigate the risk factors for developing bone metastasis, and the records of 9925 of them who registered before 2013 were retrieved (with at least 1 year follow up) to explore the prognostic factors for bone metastasis. Multivariate logistic and Cox regression were used to identify risk factors and prognostic factors for bone metastases, respectively.

Results

In total, 12,794 patients (5.1%) were diagnosed with bone metastases at the initial diagnosis. Older age, unmarried status, lymph node metastasis, poor tumor differentiation grade (Gleason grade), metastases at lung, brain, and liver were all positively associated with risk for the morbidity and prognosis of bone metastasis in prostate cancer. Black race and higher T stage were positively associated with bone metastasis development; however, they were not associated with a prognosis of bone metastasis.

Conclusion

The incidence of bone metastasis in prostate cancer was approximately 5% with poor survival. The prostate cancer has homogeneous and heterogeneous risk factors for incidence and prognosis of bone metastasis, which may provide potential guidelines for the screening and preventive treatment for the bone metastasis of prostate cancer.