Skeletal metastases and impact of anticancer and bone-targeted agents in patients with castration-resistant prostate cancer

Crosstalk between bone metastatic cancer cells and sensory nerves in bone metastatic progression

Although the role of peripheral nerves in cancer progression has been appreciated, little is known regarding cancer/sensory nerve crosstalk and its contribution to bone metastasis and associated pain. In this study, we revealed that the cancer/sensory nerve crosstalk plays a crucial role in bone metastatic progression. We found that (i) periosteal sensory nerves expressing calcitonin gene-related peptide (CGRP) are enriched in mice with bone metastasis; (ii) cancer patients with bone metastasis have elevated CGRP serum levels; (iii) bone metastatic patient tumor samples express elevated calcitonin receptor-like receptor (CRLR, a CGRP receptor component); (iv) higher CRLR levels in cancer patients are negatively correlated with recurrence-free survival; (v) CGRP induces cancer cell proliferation through the CRLR/p38/HSP27 pathway; and (vi) blocking sensory neuron-derived CGRP reduces cancer cell proliferation in vitro and bone metastatic progression in vivo. This suggests that CGRP-expressing sensory nerves are involved in bone metastatic progression and that the CGRP/CRLR axis may serve as a potential therapeutic target for bone metastasis.

Role of osteoclast inhibitors in prostate cancer bone metastasis; a narrative review

OBJECTIVE

To study the role of Osteoclast inhibitors in advanced prostate cancer metastasis treatment and their efficacy in reducing skeletal related events.

METHODS: DATA SOURCE

A comprehensive search was done using search terms as "osteoclast inhibitors" "Bisphosphonates" "Zoledronic acid" " pamidronate" " Alendronate" "Denosumab" " Prostate cancer metastasis" in pubmed and Google scholar. Relevant articles were screened and collected . The collected articles were used to frame the review and data showing use of Osteoclast inhibitors In prostate cancer bone metastasis was collected.

DATA SUMMARY

Prostate cancer metastasizes most commonly to the skeleton thus leading to significant morbidity ranging from pain, pathological fractures to spinal cord compression and are the primary cause of patient disability and reduced quality of life.Initially, radiation therapy and radiopharmaceuticals were the mainstay of treatment however the role of Bisphosphonates and denosumab has become an integral part of therapy to manage metastatic prostate cancer. These agents significantly decrease skeletal related events and enhance patients quality of life. Emerging therapies like Radium-223 have also shown promise in reducing skeletal related events and also improving survival rates in patients with bone metastasis. Other treatment options which are being used are systemic agents like Docetaxel, cabazitaxel, hormonal therapies like abiraterone and enzalutamide. Immunotherapy with sipuleucel-T has demonstrated a reduction in mortality among prostate cancer patients with metastasis, highlighting the need for further research in this area. Ongoing studies are investigating novel agents that target both tumor cells and the bone microenvironment.

CONCLUSION

Osteoclast inhibitors are effective in reducing skeletal related events in advanced bone metastasis and improve the quality of life of patients.

Identification of Molecular Markers Associated with Prostate Cancer Subtypes: An Integrative Bioinformatics Approach

Prostate cancer (PCa) is characterised by androgen dependency. Unfortunately, under anti-androgen treatment pressure, castration-resistant prostate cancer (CRPC) emerges, characterised by heterogeneous cell populations that, over time, lead to the development of different androgen-dependent or -independent phenotypes. Despite important advances in therapeutic strategies, CRPC remains incurable. Context-specific essential genes represent valuable candidates for targeted anti-cancer therapies. Through the investigation of gene and protein annotations and the integration of published transcriptomic data, we identified two consensus lists to stratify PCa patients' risk and discriminate CRPC phenotypes based on androgen receptor activity. ROC and Kaplan-Meier survival analyses were used for gene set validation in independent datasets. We further evaluated these genes for their association with cancer dependency. The deregulated expression of the PCa-related genes was associated with overall and disease-specific survival, metastasis and/or high recurrence risk, while the CRPC-related genes clearly discriminated between adeno and neuroendocrine phenotypes. Some of the genes showed context-specific essentiality. We further identified candidate drugs through a computational repositioning approach for targeting these genes and treating lethal variants of PCa. This work provides a proof-of-concept for the use of an integrative approach to identify candidate biomarkers involved in PCa progression and CRPC pathogenesis within the goal of precision medicine.

Improving Bone Health in Patients with Metastatic Prostate Cancer with the Use of Algorithm-Based Clinical Practice Tool

Background: The bone health of patients with locally advanced and metastatic prostate cancer is at risk from treatment-related bone density loss and skeletal-related events from metastatic disease in bones. Evidence-based guidelines recommend using denosumab or zoledronic acid at bone metastasis-indicated dosages in the setting of castration-resistant prostate cancer with bone metastases and at the osteoporosis-indicated dosages in the hormone-sensitive setting in patients with a significant risk of fragility fracture. For the concerns of jaw osteonecrosis, a dental evaluation is recommended before starting bone-modifying agents. The literature review suggests a limited evidence-based practice for bone health with prostate cancer in the real world. Both under-treatment and inappropriate dosing of bone remodeling therapies place additional risks to bone health. An incomplete dental work up before starting bone-modifying agents increases the risk of jaw osteonecrosis. Methods: We created an algorithm-based clinical practice tool to minimize the deviation from evidence-based guidelines at our center and provide appropriate bone health care to our patients by ensuring indication-appropriate dosing and dental screening rates. This order set was incorporated into the electronic medical record system for ordering a bone remodeling agent for prostate cancer. The tool prompts the clinicians to follow the appropriate algorithm in a stepwise manner to ensure a pretreatment dental evaluation and use of the correct dosage of drugs. Results: We analyzed the data from Sept 2019 to April 2022 following the incorporation of this tool. 0/35 (0%) patients were placed on inappropriate bone modifying agent dosing, and dental health was addressed in every patient before initiating treatment. We compared the change in the practice of prescribing and noted a significant difference in the clinician’s practice while prescribing denosumab/zoledronic acid before and after implementation of this tool [incorrect dosing: 24/41 vs. 0/35 (p < 0.00001)]; and an improvement in pretreatment dental checkup before and after implementation of the tool was noted to be [missed dental evaluation:12/41 vs. 0/35 (p < 0.00001)]. Conclusion: We found that incorporating an evidence-based algorithm in the order set while prescribing bone remodeling agents significantly improved our institutional clinical practice of indication-appropriate dosing and dental screening rates, and facilitated high-quality, evidence-based care to our patients with prostate cancer.

Outcomes Following Abiraterone versus Enzalutamide for Prostate Cancer: A Scoping Review

Abiraterone acetate (AA) and enzalutamide (ENZ) are commonly used for metastatic prostate cancer. It is unclear how their outcomes and toxicities vary with patient-specific factors because clinical trials typically exclude patients with significant comorbidities. This study aims to fill this knowledge gap and facilitate informed treatment decision making. A registered protocol utilizing PRISMA scoping review methodology was utilized to identify real-world studies. Of 433 non-duplicated publications, 23 were selected by three independent reviewers. ENZ offered a faster and more frequent biochemical response (30-50% vs. 70-75%), slowed progression (HR 0.66; 95% CI 0.50-0.88), and improved overall survival versus AA. ENZ was associated with more fatigue and neurological adverse effects. Conversely, AA increased risk of cardiovascular- (HR 1.82; 95% CI 1.09-3.05) and heart failure-related (HR 2.88; 95% CI 1.09-7.63) hospitalizations. Ultimately, AA was associated with increased length of hospital stay, emergency department visits, and hospitalizations (HR 1.26; 95% CI 1.04-1.53). Accordingly, total costs were higher for AA, although pharmacy costs alone were higher for ENZ. Existing data suggest that AA and ENZ have important differences in outcomes including toxicities, response, disease progression, and survival. Additionally, adherence, healthcare utilization, and costs differ. Further investigation is warranted to inform treatment decisions which optimize patient outcomes.

Comprehensive Analysis of m5C Methylation Regulatory Genes and Tumor Microenvironment in Prostate Cancer

Background

5-Methylcytidine (m5C) methylation is an emerging epigenetic modification in recent years, which is associated with the development and progression of various cancers. However, the prognostic value of m5C regulatory genes and the correlation between m5C methylation and the tumor microenvironment (TME) in prostate cancer remain unknown.

Methods

In the current study, the genetic and transcriptional alterations and prognostic value of m5C regulatory genes were investigated in The Cancer Genome Atlas and Gene Expression Omnibus datasets. Then, an m5C prognostic model was established by LASSO Cox regression analysis. Gene set variation analyses (GSVA), gene set enrichment analysis (GSEA), clinical relevance, and TME analyses were conducted to explain the biological functions and quantify the TME scores between high-risk and low-risk subgroups. m5C regulatory gene clusters and m5C immune subtypes were identified using consensus unsupervised clustering analysis. The Cell-type Identification By Estimating Relative Subsets of RNA Transcripts algorithm was used to calculate the contents of immune cells.

Results

TET3 was upregulated at transcriptional levels in PCa compared with normal tissues, and a high TET3 expression was associated with poor prognosis. An m5C prognostic model consisting of 3 genes (NSUN2, TET3, and YBX1) was developed and a nomogram was constructed for improving the clinical applicability of the model. Functional analysis revealed the enrichment of pathways and the biological processes associated with RNA regulation and immune function. Significant differences were also found in the expression levels of m5C regulatory genes, TME scores, and immune cell infiltration levels between different risk subgroups. We identified two distinct m5C gene clusters and found their correlation with patient prognosis and immune cell infiltration characteristics. Naive B cells, CD8+ T cells, M1 macrophages and M2 macrophages were obtained and 2 m5C immune subtypes were identified. CTLA4, NSUN6, TET1, and TET3 were differentially expressed between immune subtypes. The expression of CTLA4 was found to be correlated with the degree of immune cell infiltration.

Conclusions

Our comprehensive analysis of m5C regulatory genes in PCa demonstrated their potential roles in the prognosis, clinical features, and TME. These findings may improve our understanding of m5C regulatory genes in the tumor biology of PCa.

Role of radium-223 discontinuation due to adverse events in castration-resistant prostate cancer patients. A retrospective monocentric analysis

Background:

Radium 223 (Ra-223) was approved for the treatment of metastatic castration resistant prostate cancer (mCRPC) patients with bone-only disease, following demonstration of significant improvement in overall survival (OS). To date, there are no validated prognostic factors useful in predicting outcome of mCRPC patients treated with Ra-223. Our retrospective study aims to evaluate the prognostic role of treatment discontinuation due to adverse events in mCRPC patients treated with Ra-223, and to identify which factors correlate with the toxicity onset.

Methods:

We performed a retrospective analysis of all consecutive mCRPC patients treated with Ra-223 from September 2013 to December 2019 at our institute. Patients were divided in 2 groups according to the reason of Ra-223 therapy discontinuation: toxicity versus other causes. Outcome measures were progression-free survival (PFS) and OS.

Results:

In the overall population (75 patients) median PFS and OS were 5.46 months and 11.15 months respectively. Patients who discontinued treatment due to toxicity had a lower median PFS (3.49 vs 5.89 months, HR: 1.88, 95% CI: 1.14-3.12, p = 0.014) and OS (8.59 vs 14.7 months HR: 3.33, 95% CI: 1.85-6.01, p < 0.001) than patients who discontinued therapy due to other causes. The risk of Ra-223 discontinuation due to toxicity correlates with the number of previous treatments ( p = 0.002), previous chemotherapy treatment ( p = 0.039), baseline LDH ( p = 0.012), Hb ( p = 0.021) and platelet-to-lymphocyte ratio ( p = 0.024).

Conclusions:

Discontinuation due to toxicity is associated with worse outcomes in mCRPC patients treated with Ra-223. To reduce the risk of developing toxicities that may compromise treatment efficacy, Ra-223 should be used early in mCRPC patients.

Symptomatic Skeletal Events and the Use of Bone Health Agents in a Real-World Treated Metastatic Castration Resistant Prostate Cancer Population: Results From the CAPRI-Study in the Netherlands

BACKGROUND

Patients with metastatic castration resistant prostate cancer (mCRPC) are at risk of symptomatic skeletal events (SSE). Bone health agents (BHA, ie bisphosphonates and denosumab) and new life-prolonging drugs (LPDs) can delay SSEs. The aim of this study is to investigate the use of BHAs in relation to SSEs in treated real-world mCRPC population.

PATIENTS AND METHODS

We included patients from the CAPRI registry who were treated with at least one LPD and diagnosed with bone metastases prior to the start of first LPD (LPD1). Outcomes were SSEs (external beam radiation therapy (EBRT) to the bone, orthopedic surgery, pathologic fracture or spinal cord compression) and SSE-free survival (SSE-FS) since LPD1.

RESULTS

One-thousand nine hundred and twenty-three patients were included with a median follow-up from LPD1 of 16.7 months. Fifty-two percent (n = 996) started BHA prior or within 4 weeks after the start of LPD1 (early BHA). In total, 41% experienced at least one SSE. SSE incidence rate was 0.29 per patient year for patients without BHA and 0.27 for patients with early BHA. Median SSE-FS from LPD1 was 12.9 months. SSE-FS was longer in patients who started BHA early versus patients without BHA (13.2 vs. 11.0 months, P = .001).

CONCLUSION

In a real-world population we observed an undertreatment with BHAs, although patients with early BHA use had lower incidence rates of SSEs and longer SSE-FS. This finding was irrespective of type of SSE and presence of risk factors. In addition to LPD treatment, timely initiation of BHAs is recommended in bone metastatic CRPC-patients with both pain and/or opioid use and prior SSE.

Overview of the Most Promising Radionuclides for Targeted Alpha Therapy: The "Hopeful Eight"

Among all existing radionuclides, only a few are of interest for therapeutic applications and more specifically for targeted alpha therapy (TAT). From this selection, actinium-225, astatine-211, bismuth-212, bismuth-213, lead-212, radium-223, terbium-149 and thorium-227 are considered as the most suitable. Despite common general features, they all have their own physical characteristics that make them singular and so promising for TAT. These radionuclides were largely studied over the last two decades, leading to a better knowledge of their production process and chemical behavior, allowing for an increasing number of biological evaluations. The aim of this review is to summarize the main properties of these eight chosen radionuclides. An overview from their availability to the resulting clinical studies, by way of chemical design and preclinical studies is discussed.

Implication of Prophetic Variables and their Impulsive Interplay in CA Prostate Patients Experiencing Osteo-Metastasis

AIMS

To identify variables having a critical role in prostate cancer patients experiencing osteometastasis.

BACKGROUND

Prostatic carcinoma is a multifactorial complex disorder that exhibits an increased propensity to develop bone metastasis. An interplay of inflammatory and bone remodeling parameters promotes the formation of pre-metastatic niches in bones of patients, which could render them more vulnerable to skeletal disabilities.

OBJECTIVE

To evaluate the multi-dynamic inter-relationship of circulating variables in prostate cancer patients experiencing osteo-metastasis.

MATERIALS AND METHODS

Fifty-seven (n=57) men with clinically confirmed prostate cancer, fifty-nine (n=59) with skeletal metastases, and one hundred (n=100) healthy subjects i.e., men aging from 53-84 years with no clinical evidence of prostate were recruited from the Jinnah Hospital Lahore, Pakistan. Informed consent was obtained, and a venous blood sample was drawn and stored at -70oC until assayed. Levels of variables were evaluated using appropriate methods. Levels of Matrix Metalloproteinases (MMPs), Osteopontin (OPN), TGH- β, and sRANKL were estimated by the ELISA method. Each sample was suspended and the given protocol was employed. ELISA readings were obtained for the estimation of all variables.

RESULTS

Highly significant (P˂0.05) differential expression of oxidative stress, inflammatory cytokines, and bone remodeling variables were observed in localized and osteo-metastatic CA prostate patients. A strong positive correlation was revealed among OPN, sRANKL, MMP-7, MMP-9, PSA, and TGF-β (OPN vs. MMP-7, r=0.698* and OPN vs. MMP-9, r=0.765**, OPN vs. RANKL, =0.856*, sRANKL vs. MMP-9, r=0.825**, TGF- β vs. RANKL, r=0.868* and PSA vs. TGF- β, r=0.752*); lower levels of OPG were estimated in metastasized patients, showing that both osteolytic and osteoblastic phases of bone remodeling occur simultaneously.

CONCLUSION

The altered oxidative and inflammatory responses endorse Matrix Metalloproteinases (MMPs) increased activity, RANKL/OPG imbalance, and enhanced bone matrix proteins turnover, which can foster the process of osteo-metastasis. The perturbed RANKL/OPG drift and enhanced PSA levels are associated with increased TGF-β activity to aggravate Epithelial Mesenchymal transition (EM) and osteo-tropism of prostate cancer. Thus, designing novel targets of these major variables can minimize the incidence of prostate cancer patients.

Progress in Targeted Alpha-Particle-Emitting Radiopharmaceuticals as Treatments for Prostate Cancer Patients with Bone Metastases

Bone metastasis remains a major cause of death in cancer patients, and current therapies for bone metastatic disease are mainly palliative. Bone metastases arise after cancer cells have colonized the bone and co-opted the normal bone remodeling process. In addition to bone-targeted therapies (e.g., bisphosphonate and denosumab), hormone therapy, chemotherapy, external beam radiation therapy, and surgical intervention, attempts have been made to use systemic radiotherapy as a means of delivering cytocidal radiation to every bone metastatic lesion. Initially, several bone-seeking beta-minus-particle-emitting radiopharmaceuticals were incorporated into the treatment for bone metastases, but they failed to extend the overall survival in patients. However, recent clinical trials indicate that radium-223 dichloride (223RaCl2), an alpha-particle-emitting radiopharmaceutical, improves the overall survival of prostate cancer patients with bone metastases. This success has renewed interest in targeted alpha-particle therapy development for visceral and bone metastasis. This review will discuss (i) the biology of bone metastasis, especially focusing on the vicious cycle of bone metastasis, (ii) how bone remodeling has been exploited to administer systemic radiotherapies, and (iii) targeted radiotherapy development and progress in the development of targeted alpha-particle therapy for the treatment of prostate cancer bone metastasis.

Osteoblasts derived from mouse mandible enhance tumor growth of prostate cancer more than osteoblasts derived from long bone

Prostate cancer (PCa) metastasizes to bone, where the bone marrow microenvironment controls disease progression. However, the cellular interactions that result in active bone marrow metastases are poorly understood. A better understanding of these interactions is critical to success in the pursuit of effective treatments for this life ending disease. Anecdotally, we observe that after intracardiac injection of PCa cells, one of the greatest tools to investigate the mechanisms of bone-metastatic disease, animals frequently present with mandible metastasis before hind limb metastasis. Therefore, in this study, we investigated whether the bone cells derived from the mouse mandible influence PCa progression differently than those from the hind limb. Interestingly, we found that osteoblasts harvested from mouse mandibles grew faster, expressed more vascular endothelial growth factor (VEGF), increased vascularity and formed more bone, and stimulated faster growth of PCa cells when cultured together than osteoblasts harvested from mouse hind limbs. Additionally, these findings were confirmed in vivo when mouse mandible osteoblasts were co-implanted into mice with PCa cells. Importantly, the enhancement of PCa growth mediated by mandible osteoblasts was not shown to be due to their differentiation or proliferation activities, but may be partly due to increased vascularization and expression of VEGF.

Role of the CXCR4/ALK5/Smad3 Signaling Pathway in Cancer-Induced Bone Pain

Purpose

The chemokine receptor, CXCR4, and the transforming growth factor-beta receptor, ALK5, both contribute to various processes associated with the sensation of pain. However, the relationship between CXCR4 and ALK5 and the possible mechanisms promoted by ALK5 in the development of pain have not been evaluated.

Materials and Methods

Tumor cell implantation (TCI) technology was used to generate a model of cancer-induced bone pain (CIBP) in rats; intrathecal (i.t.) injections of small interfering (si) RNAs targeting CXCR4 and the ALK5-specific inhibitor, RepSox, were performed. Behavioral outcomes, Western blotting, and immunofluorescence techniques were used to evaluate the expression of the aforementioned specific target proteins in the CIBP model.

Results

The results revealed that i.t. administration of siRNAs targeting CXCR4 resulted in significant reductions in both mechanical and thermal hyperalgesia in rats with CIBP and likewise significantly reduced the expression of ALK5 in the spinal cord. Similarly, i.t. administration of RepSox also resulted in significant reductions in mechanical and thermal hyperalgesia in rats with CIBP together with diminished levels of spinal p-Smad3.

Conclusion

Taken together, our results suggest that CXCR4 expression in the spinal cord may be a critical mediator of CIBP via its capacity to activate ALK5 and downstream signaling pathways.

Spine and Non-spine Bone Metastases - Current Controversies and Future Direction

Bone is a common site of metastases in advanced cancers. The main symptom is pain, which increases morbidity and reduces quality of life. The treatment of bone metastases needs a multidisciplinary approach, with the main aim of relieving pain and improving quality of life. Apart from systemic anticancer therapy (hormonal therapy, chemotherapy or immunotherapy), there are several therapeutic options available to achieve palliation, including analgesics, surgery, local radiotherapy, bone-seeking radioisotopes and bone-modifying agents. Long-term use of non-steroidal analgesics and opiates is associated with significant side-effects, and tachyphylaxis. Radiotherapy is effective mainly in localised disease sites. Bone-targeting radionuclides are useful in patients with multiple metastatic lesions. Bone-modifying agents are beneficial in reducing skeletal-related events. This overview focuses on the role of surgery, including minimally invasive treatments, conventional radiotherapy in spinal and non-spinal bone metastases, bone-targeting radionuclides and bone-modifying agents in achieving palliation. We present the clinical data and their associated toxicity. Recent advances are also discussed.

Pathophysiology of Bone Loss in Patients with Prostate Cancer Receiving Androgen-Deprivation Therapy and Lifestyle Modifications for the Management of Bone Health: A Comprehensive Review

Androgen-deprivation therapy (ADT) is a systemic therapy administered for the management of advanced prostate cancer (PCa). Although ADT may improve survival, long-term use reduces bone mass density (BMD), posing an increased risk of fracture. Considering the long natural history of PCa, it is essential to preserve bone health and quality-of-life in patients on long-term ADT. As an alternative to pharmacological interventions targeted at preserving BMD, current evidence recommends lifestyle modifications, including individualized exercise and nutritional interventions. Exercise interventions include resistance training, aerobic exercise, and weight-bearing impact exercise, and have shown efficacy in preserving BMD. At the same time, it is important to take into account that PCa is a progressive and debilitating disease in which a substantial proportion of patients on long-term ADT are older individuals who harbor axial bone metastases. Smoking cessation and limited alcohol consumption are commonly recommended lifestyle measures in patients receiving ADT. Contemporary guidelines regarding lifestyle modifications vary by country, organization, and expert opinion. This comprehensive review will provide an evidence-based, updated summary of lifestyle interventions that could be implemented to preserve bone health and maintain quality-of-life throughout the disease course of PCa.

Switching Homes: How Cancer Moves to Bone

Bone metastases (BM) are a very common complication of the most prevalent human cancers. BM are extremely painful and may be life-threatening when associated with hypercalcaemia. BM can lead to kidney failure and cardiac arrhythmias and arrest, but why and how do cancer cells decide to "switch homes" and move to bone? In this review, we will present what answers science has provided so far, with focus on the molecular mechanisms and cellular aspects of well-established findings, such as the concept of "vicious cycle" and "osteolytic" vs. "osteosclerotic" bone metastases; as well as on novel concepts, such as cellular dormancy and extracellular vesicles. At the molecular level, we will focus on hypoxia-associated factors and angiogenesis, the Wnt pathway, parathyroid hormone-related peptide (PTHrP) and chemokines. At the supramolecular/cellular level, we will discuss tumour dormancy, id est the mechanisms through which a small contingent of tumour cells coming from the primary site may be kept dormant in the endosteal niche for many years. Finally, we will present a potential role for the multimolecular mediators known as extracellular vesicles in determining bone-tropism and establishing a premetastatic niche by influencing the bone microenvironment.

Cabozantinib Reverses Renal Cell Carcinoma-mediated Osteoblast Inhibition in Three-dimensional Coculture In Vitro and Reduces Bone Osteolysis In Vivo

Renal cell carcinoma bone metastases (RCCBM) are typically osteolytic. We previously showed that BIGH3 (beta Ig-h3/TGFBI), secreted by 786-O renal cell carcinoma, plays a role in osteolytic bone lesion in RCCBM through inhibition of osteoblast (OSB) differentiation. To study this interaction, we employed three-dimensional (3D) hydrogels to coculture bone-derived 786-O (Bo-786) renal cell carcinoma cells with MC3T3-E1 pre-OSBs. Culturing pre-OSBs in the 3D hydrogels preserved their ability to differentiate into mature OSB; however, this process was decreased when pre-OSBs were cocultured with Bo-786 cells. Knockdown of BIGH3 in Bo-786 cells recovered OSB differentiation. Furthermore, treatment with bone morphogenetic protein 4, which stimulates OSB differentiation, or cabozantinib (CBZ), which inhibits VEGFR1 and MET tyrosine kinase activities, also increased OSB differentiation in the coculture. CBZ also inhibited pre-osteoclast RAW264.7 cell differentiation. Using RCCBM mouse models, we showed that CBZ inhibited Bo-786 tumor growth in bone. CBZ treatment also increased bone volume and OSB number, and decreased osteoclast number and blood vessel density. When tested in SN12PM6 renal cell carcinoma cells that have been transduced to overexpress BIGH3, CBZ also inhibited SN12PM6 tumor growth in bone. These observations suggest that enhancing OSB differentiation could be one of the therapeutic strategies for treating RCCBM that exhibit OSB inhibition characteristics, and that this 3D coculture system is an effective tool for screening osteoanabolic agents for further in vivo studies.

Bone Health in Men with Prostate Cancer: Review Article

PURPOSE OF REVIEW

The improvement in prostate cancer survival over time, even in those with advanced disease, has led to an increasing recognition of the impact of prostate cancer and its treatment on bone health. Cancer treatment-induced bone loss (CTIBL) is a well-recognized entity but greater awareness of the risks associated with CTIBL and its treatment is required.

RECENT FINDINGS

The principal culprit in causing CTIBL is hormonal ablation induced by prostate cancer treatment, including several new agents which have been developed in recent years which significantly improve survival, but may cause CTIBL. This review discusses the impact of prostate cancer and its treatment on bone health, including published evidence on the underlying pathophysiology, assessment of bone health, and strategies for prevention and treatment. It is important to recognize the potential cumulative impact of systemic prostate cancer treatments on bone health.

Prognostic significance of the presence of intraductal carcinoma of the prostate and bone metastasis in needle biopsy for prostate carcinoma patients with Grade Group 5

Intraductal carcinoma of the prostate (IDC-P) and bone metastasis have been both identified to associate with unfavorable clinical outcome of the prostate carcinoma (PCa). Our objective is to examine whether IDC-P or bone metastasis at diagnostic biopsies was associated with each other and whether they were linked with overall survival (OS) and cancer specific survival (CSS) of Grade Group 5 patients. We retrospectively selected the prostate biopsy specimens of 120 PCa patients with Grade Group 5 from Qilu Hospital of Shandong University between 2012 and 2016. There were 12 patients with IDC-P only, 52 patients with bone metastasis only and 10 patients with both IDC-P and bone metastasis. Overall, there was a significant correlation between the presences of the IDC-P and bone metastasis (P = 0.003). Kaplan-Meier survival analysis demonstrated that the presence of IDC-P and bone metastasis in diagnostic needle biopsy both conferred unfavorable CSS of Grade Group 5 patients. In addition, the presence of bone metastasis was a poor predictor of OS. Univariate and multivariate analysis revealed that bone metastasis was an independent prognostic factor for OS of Grade Group 5 patients, but IDC-P failed to be significant for either OS or CSS. Collectively, our study suggested that bone metastasis is an important prognostic factor and superior than the presence of the IDC-P for PCa patients with Grade Group 5.

Targeted Alpha Therapy, an Emerging Class of Cancer Agents: A Review

Importance

Targeted alpha therapy attempts to deliver systemic radiation selectively to cancer cells while minimizing systemic toxic effects and may lead to additional treatment options for many cancer types.

Observations

Theoretically, the high-energy emission of short-range alpha particles causes complex double-stranded DNA breaks, eliciting cell death. No known resistance mechanism to alpha particles has been reported or scientifically established. The short-range emission of alpha particle radiation confines its cytotoxic effect to cancerous lesions and the surrounding tumor microenvironment while limiting toxic effects to noncancerous tissues. The high level of radiobiological effectiveness of alpha particles, in comparison with beta emissions, requires fewer particle tracks to induce cell death. Clinically effective alpha particle-emitting isotopes for cancer therapy should have a short half-life, which will limit long-term radiation exposure and allow for the production, preparation, and administration of these isotopes for clinical use and application. Radium 223 dichloride is the first-in-class, commercially available targeted alpha therapy approved for the treatment of patients with metastatic castration-resistant prostate cancer with bone metastases. Given the established overall survival benefit conferred by radium 223 for patients with metastatic castration-resistant prostate cancer, several other targeted alpha therapies are being investigated in clinical trials across many tumor types.

Conclusions and Relevance

Targeted alpha therapy represents an emerging treatment approach and provides for the possibility to bypass mechanisms of acquired resistance in selected tumors. In addition, developing novel radionuclide conjugation strategies may overcome targeting limitations. So far, the clinical success of radium 223 has demonstrated the proof of concept for targeted alpha therapy, and future studies may lead to additional treatment options for many cancer types.

Predictors of skeletal-related events and mortality in men with metastatic, castration-resistant prostate cancer: Results from the Shared Equal Access Regional Cancer Hospital (SEARCH) database

BACKGROUND

Although skeletal-related events (SREs) are linked with a reduced quality of life and worse outcomes, to the authors' knowledge the factors that predict SREs are minimally understood. The objective of the current study was to identify predictors of SREs and all-cause mortality among men with metastatic castration-resistant prostate cancer (mCRPC).

METHODS

Data were collected on 837 men with bone mCRPC at 8 Veterans Affairs medical centers within the Shared Equal Access Regional Cancer Hospital (SEARCH) database from 2000 through 2017. Patients were followed to assess development of SREs (pathological fracture, radiotherapy to bone, spinal cord compression, or surgery to bone). Cox proportional hazards models were used to evaluate predictors of SREs and mortality.

RESULTS

Of the 837 men with bone mCRPC, 287 developed a SRE and 740 men died (median follow-up, 26 months). Bone pain was found to be the strongest predictor of SREs (hazard ratio [HR], 2.96; 95% CI, 2.25-3.89). A shorter time from CRPC to the development of metastasis (HR, 0.92; 95% CI, 0.85-0.99), shorter progression to CRPC (HR, 0.94; 95% CI, 0.91-0.98), and visceral metastasis at the time of diagnosis of bone metastasis (HR, 1.91; 95% CI, 1.18-3.09) were associated with an increased risk of SREs. Ten or more bone metastases (HR, 2.17; 95% CI, 1.72-2.74), undergoing radical prostatectomy (HR, 0.73; 95% CI, 0.61-0.89), shorter progression to CRPC (HR, 0.97; 95% CI, 0.94-0.99), older age (HR, 1.03; 95% CI, 1.02-1.04), higher prostate-specific antigen level at the time of diagnosis of metastasis (HR, 1.21; 95% CI, 1.14-1.28), bone pain (HR, 1.44; 95% CI, 1.23-1.70), and visceral metastasis (HR, 1.72; 95% CI, 1.23-2.39) were associated with an increased mortality risk.

CONCLUSIONS

Among men with bone mCRPC, bone pain was found to be the strongest predictor of SREs and the number of bone metastases was a strong predictor of mortality. If validated, these factors potentially may be used for risk stratification and for SRE prevention strategies.

Metastatic prostate cancer remains incurable, why?

Metastatic prostate cancer patients present in two ways-with already disseminated disease at the time of presentation or with disease recurrence after definitive local therapy. Androgen deprivation therapy is given as the most effective initial treatment to patients. However, after the initial response, almost all patients will eventually progress despite the low levels of testosterone. Disease at this stage is termed castration resistant prostate cancer (CRPC). Before 2010, the taxane docetaxel was the first and only life prolonging agent for metastatic CRPC (mCRPC). The last decade has witnessed robust progress in CRPC therapeutics development. Abiraterone, enzalutamide, apalutamide and sipuleucel-T have been evaluated as first- and second-line agents in mCRPC patients, while cabazitaxel was approved as a second-line treatment. Radium-223 dichloride was approved in symptomatic patients with bone metastases and no known visceral metastases pre- and post-docetaxel. However, despite significant advances, mCRPC remains a lethal disease. Both primary and acquired resistance have been observed in CRPC patients treated by these new agents. It could be solely cell intrinsic or it is possible that the clonal heterogeneity in treated tumors may result from the adaptive responses to the selective pressures within the tumor microenvironment. The aim of this review is to list current treatment agents of CRPC and summarize recent findings in therapeutic resistance mechanisms.

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.

Alloreactive cytotoxic T lymphocyte immunotherapy treatment of a patient with metastatic prostate cancer: A case report

RATIONALE

Cytotoxic T lymphocyte (CTL) immunotherapy is an autologous cellular immune therapy that has been approved for treating patients with malignant tumors. However, there is still limited information regarding the impact of CTL on metastatic prostate cancer (PC) patients with bone metastatic lesions.

PATIENT CONCERNS

An 82-year-old male patient complained of interrupted urination, urination pain, and significant dysuria on November 24, 2014. Transurethral resection of the prostate (TURP) and postoperative pathological examination showed prostatic adenocarcinoma, and a SPECT/CT scan demonstrated multiple bone metastases. In addition, prostate specific antigen (PSA) and free PSA (FPSA) levels were 54.54 μg/mL and 2.63 μg/mL, respectively, at the beginning of treatment.

DIAGNOSES

The man was diagnosed with prostatic adenocarcinoma and multiple bone metastases.

INTERVENTIONS

The patient received 30 cycles of alloreactive CTL (ACTL) immunotherapy regularly.

OUTCOMES

Over the course of the 2-year treatment, the PC patient exhibited diminished bone metastasis accompanied by a marked reduction of serum PSA and FPSA from 54.54 and 2.63 μg/ml to 0.003 and <0.006 μg/ml, respectively.

LESSONS

Our clinical observations demonstrate that CTL immunotherapy is a viable treatment option for PC patients, particularly those with bone metastatic lesions and high serum levels of PSA and FPSA.

Targeted alpha therapy using Radium-223: From physics to biological effects

With the advance of the use of ionizing radiation in therapy, targeted alpha therapy (TAT) has assumed an important role around the world. This kind of therapy can potentially reduce side effects caused by radiation in normal tissues and increased destructive radiobiological effects in tumor cells. However, in many countries, the use of this therapy is still in a pioneering phase. Radium-223 (²²³Ra), an alpha-emitting radionuclide, has been the first of its kind to be approved for the treatment of bone metastasis in metastatic castration-resistant prostate cancer. Nevertheless, the interaction mechanism and the direct effects of this radiopharmaceutical in tumor cells are not fully understood neither characterized at a molecular level. In fact, the ways how TAT is linked to radiobiological effects in cancer is not yet revised. Therefore, this review introduces some physical properties of TAT that leads to biological effects and links this information to the hallmarks of cancer. The authors also collected the studies developed with ²²³Ra to correlate with the three categories reviewed - properties of TAT, 5 R's of radiobiology and hallmarks of cancer- and with the promising future to this radiopharmaceutical.

Inhibition of Histone Deacetylases Attenuates Morphine Tolerance and Restores MOR Expression in the DRG of BCP Rats

The easily developed morphine tolerance in bone cancer pain (BCP) significantly hindered its clinical use. Increasing evidence suggests that histone deacetylases (HDACs) regulate analgesic tolerance subsequent to continuous opioid exposure. However, whether HDACs contribute to morphine tolerance in the pathogenesis of BCP is still unknown. In the current study, we explored the possible engagement of HDACs in morphine tolerance during the pathogenesis of BCP. After intra-tibia tumor cell inoculation (TCI), we found that the increased expression of HDACs was negatively correlated with the decreased expression of MOR in the DRG following TCI. The paw withdrawal threshold (PWT) and percentage maximum possible effects (MPEs) decreased rapidly in TCI rats when morphine was used alone. In contrast, the concomitant use of SAHA and morphine significantly elevated the PWT and MPEs of TCI rats compared to morphine alone. Additionally, we found that SAHA administration significantly elevated MOR expression in the DRG of TCI rats with or without morphine treatment. Moreover, the TCI-induced increase in the co-expression of MOR and HDAC1 in neurons was significantly decreased after SAHA administration. These results suggest that HDACs are correlated with the downregulation of MOR in the DRG during the pathogenesis of BCP. Inhibition of HDACs using SAHA can be used to attenuate morphine tolerance in BCP.

Role of the Bone Microenvironment in the Development of Painful Complications of Skeletal Metastases

Cancer-induced bone pain (CIBP) is the most common and painful complication in patients with bone metastases. It causes a significant reduction in patient quality of life. Available analgesic treatments for CIBP, such as opioids that target the central nervous system, come with severe side effects as well as the risk of abuse and addiction. Therefore, alternative treatments for CIBP are desperately needed. Although the exact mechanisms of CIBP have not been fully elucidated, recent studies using preclinical models have demonstrated the role of the bone marrow microenvironment (e.g., osteoclasts, osteoblasts, macrophages, mast cells, mesenchymal stem cells, and fibroblasts) in CIBP development. Several clinical trials have been performed based on these findings. CIBP is a complex and challenging condition that currently has no standard effective treatments other than opioids. Further studies are clearly warranted to better understand this painful condition and develop more effective and safer targeted therapies.

The role of bisphosphonates or denosumab in light of the availability of new therapies for prostate cancer

Most men with advanced prostate cancer will develop bone metastases, which have a substantial impact on quality of life. Bone metastases can lead to skeletal-related events (SREs), which place a burden on patients and healthcare systems. For men with castration-resistant prostate cancer (CRPC) and bone metastases, the treatment landscape has evolved rapidly over the past few years. The relatively recent approvals of the hormonal agents abiraterone acetate and enzalutamide, second-line chemotherapy cabazitaxel, and the radiopharmaceutical radium-223 dichloride (radium-223), have provided clinicians with a greater choice of treatments. These compounds have benefits in terms of overall survival based on the results of pivotal phase 3 studies. The bisphosphonate zoledronic acid and the RANK ligand inhibitor denosumab are indicated for the prevention of SREs in men with metastatic CRPC but studies of these compounds have not demonstrated a survival benefit. The important question of the role of bisphosphonates or denosumab in combination with these new agents has thus materialised. Current and emerging evidence from clinical studies of abiraterone acetate, enzalutamide and radium-223, suggest that addition of bisphosphonates or denosumab to these new therapies may provide further clinical benefits for patients with prostate cancer and bone metastases. This evidence may help to shape clinical practice but are based largely on post hoc analyses of clinical trial data. It is therefore apparent that further data are required from both clinical studies and real-world settings to enable physicians to understand the efficacy and safety of combination therapy with the new agents plus bisphosphonates or denosumab.

Radium-223 for primary bone metastases in patients with hormone-sensitive prostate cancer after radical prostatectomy

Radium-223 dichloride (Ra-223) is the first bone-targeting agent showing improvement in overall survival in patients with castration-resistant prostate cancer (CRPC) and bone metastases. We aimed to assess feasibility of Ra-223 treatment in patients with metastatic hormone-sensitive prostate cancer (mHSPC). Ten patients with primary bone metastases received Ra-223 following radical prostatectomy (RP). Changes in alkaline phosphatase (ALP) and prostate-specific antigen (PSA) were recorded, while pain intensity was evaluated using the self-reporting Brief Pain Inventory (BPI) questionnaire. Bone scintigraphy (BS) was performed to assess treatment response. Seven patients completed six cycles of Ra-223. Discontinuation was due to leuko- and lymphopenia, progressive lymph node metastasis or newly diagnosed liver metastasis. Treatment-related adverse events occurred in three patients and included leuko- and lymphopenia, fatigue, abdominal discomfort and nausea. Overall, a median decrease of 28% in ALP and a median decrease of 83% in PSA were noted at follow-up. However, PSA progressed in five patients at follow-up. Improvement of pain was observed in all patients (median decrease of 36% after 3 cycles and of 40% at the end of therapy). On BS, three patients showed remission, four had stable disease, and one showed progressive disease at follow-up. Our results suggest that Ra-223 for primary bone metastases in patients with mHSPC after RP is feasible and alleviates pain. ALP, rather than PSA, may be a good marker for assessing treatment response. Ra-223 could therefore be taken into consideration as part of a multimodal approach for carefully selected patients with advanced prostate cancer.

Bisphosphonates for advanced prostate cancer

BACKGROUND

The prevalence and incidence of pain and skeletal complications of metastatic bone disease such as pathologic fractures, spinal cord compression and hypercalcemia is high and an important contributor to morbidity, poor performance status and decreased quality of life. Moreover, pathologic fractures are associated with increased risk of death in people with disseminated malignancies. Therefore, prevention of pain and fractures are important goals in men with prostate cancer at risk for skeletal complications.

OBJECTIVES

To assess the effects of bisphosphonates in men with bone metastases from prostate cancer.

SEARCH METHODS

We identified studies by electronic search of bibliographic databases including the Cochrane Controlled Trials Register and MEDLINE on 13 July 2017 and trial registries. We handsearched the Proceedings of American Society of Clinical Oncology (to July 2017) and reference lists of all eligible trials identified. This is an update of a review last published in 2006.

SELECTION CRITERIA

We included randomized controlled studies comparing the effectiveness of bisphosphonates in men with bone metastases from prostate cancer.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the quality of trials. We defined the proportion of participants with pain response as the primary end point; secondary outcomes were skeletal-related events, mortality, quality of life, adverse events, analgesic consumption and disease progression. We assessed the quality of the evidence for the main outcomes using the GRADE approach.

MAIN RESULTS

We included 18 trials reporting on 4843 participants comparing the effect of bisphosphonate administration to control regimens.

PRIMARY OUTCOME

there was no clear difference in the proportion of participants with pain response (RR 1.15, 95% CI 0.93 to 1.43; P = 0.20; I² = 0%; 3 trials; 876 participants; low quality evidence). In absolute terms, bisphosphonates resulted in a pain response in 40 more participants per 1000 (19 fewer to 114 more).

SECONDARY OUTCOMES

bisphosphonates probably reduced the incidence of skeletal-related events in participants with prostate cancer metastatic to bone (RR 0.87, 95% CI 0.81 to 0.94; P = 0.27; I² = 19%; 9 trials; 3153 participants; moderate quality evidence). In absolute terms, bisphosphonates resulted in 58 fewer SREs per 1000 (85 fewer to 27 fewer).We found no clinically relevant differences in mortality (RR 0.97, 95% CI 0.91 to 1.04; P = 0.43; I² = 1%; 9 trials; 2450 participants; moderate quality evidence). In absolute terms, bisphosphonates resulted in 16 fewer deaths per 1000 (47 fewer to 21 more).Outcome definition of quality of life and the measurement tools varied greatly across trials and we were unable to extract any quantitative data for meta-analysis.Bisphosphonates probably increased the number of participants affected by nausea (RR 1.19, 95% CI 1.00 to 1.41; P = 0.05; I² = 0%; 9 trials; 3008 participants; moderate quality evidence). In absolute terms, bisphosphonates resulted in seven more cases of nausea per 1000 (0 fewer to 14 more). Bisphosphonates probably increased the number of renal adverse events (RR 1.65, 95% CI 1.11 to 2.46; P = 0.01; I² = 0%; 7 trials; 1794 participants; moderate quality evidence). In absolute terms, bisphosphonates resulted in 22 more renal adverse events per 1000 (4 more to 50 more). We found no clear difference in the number of participants with osteonecrosis of the jaw between groups (RR 1.92, 95% CI 0.75 to 4.90; P = 0.17; I² = 0%; 5 trials; 1626 participants; very low quality evidence). In absolute terms, bisphosphonates resulted in seven more cases with osteonecrosis of the jaw per 1000 (2 fewer to 29 more). We observed no clinically relevant difference in the proportion of participants with decreased analgesic consumption (RR 1.19, 95% CI 0.87 to 1.63; P = 0.28; I² = 37%; 4 trials; 416 participants). Statistical analysis revealed that bisphosphonates probably reduced the number of participants with disease progression (RR 0.94, 95% CI 0.90 to 0.98; P = 0.006; I² = 0%; 7 trials; 2115 participants; moderate quality evidence). In absolute terms, bisphosphonates resulted in 36 fewer cases of disease progression per 1000 (71 fewer to 7 fewer).Findings of our predefined subgroup and sensitivity analyses were no different from those of the primary analyses.

AUTHORS' CONCLUSIONS

Based on low quality evidence, there may be no clinically relevant difference in the proportion of men with pain response between bisphosphonates and control regimens in men with bone metastases from prostate cancer. Bisphosphonates probably decrease the number of skeletal-related events and disease progression. These benefits need to be weighed against the increased risk of renal impairment and nausea in men receiving bisphosphonates. Future studies should explicitly evaluate patient important outcomes such as quality of life and pain by using standardized and comparable assessment tools.

The Contemporary Use of Radium-223 in Metastatic Castration-resistant Prostate Cancer

Radium-223 dichloride (radium-223) was approved for the treatment of patients with castration-resistant prostate cancer (CRPC) and symptomatic bone metastases in the United States and Europe in 2013. This followed a reported overall survival benefit for patients treated with radium-223 and best standard of care (BSoC) when compared with placebo and BSoC in the ALpharadin in SYMptomatic Prostate CAncer (ALSYMPCA) trial. At that time, docetaxel was the standard first-line choice for patients with metastatic CRPC (mCRPC). Since then, the treatment landscape has changed dramatically with new hormonal agents (abiraterone and enzalutamide) considered to be the first-line choice for many patients. The optimal patient profile for radium-223 in the modern setting, and its best use either in sequence or in combination with other approved agents are unclear, with few definitive guidelines available. This article reports on the views of a group of urologists and medical oncologists experienced in treating patients with mCRPC with radium-223 in routine clinical practice. The aim is to provide an overview of the current use of radium-223 in the treatment of patients with mCRPC, and to discuss best practices for patient selection and on-treatment monitoring. Where agreement was reached, guidance on the optimal use of radium-223 is provided.

Biochemical Changes in the Niche Following Tumor Cell Invasion

Metastatic cancer is the leading cause of all cancer related deaths. Prostate cancer (PCa) metastasizes preferentially to the bone marrow, specifically within the endosteal niche. Endosteal cells secrete homing molecules that may recruit PCa cells to the bone marrow. Once there, the biochemical signature of this niche regulates PCa fate including cellular dormancy or cell cycle arrest, reactivation and resistance to chemotherapeutics. Growth factors, interleukins, adhesion molecules, as well as extra-cellular matrix proteins can collectively change the phenotype of PCa cells. Understanding the biochemical signature of endosteal niche parasitism by PCa is imperative for the establishment of new and innovative therapeutic strategies. This review seeks to summarize these important niche signatures and the potential therapeutic approaches to target metastatic PCa within the bone marrow hematopoietic stem cell (HSC) niche. J. Cell. Biochem. 118: 1956-1964, 2017. © 2016 Wiley Periodicals, Inc.

Modern treatment of metastatic prostate cancer

The treatment of prostate cancer with remote metastases has advanced greatly in recent years. Treatment options are dependent on the extent of the metastases, the patient’s general condition and wishes, and the treatment response. We present an overview of the latest options for systemic treatment of patients with metastatic prostate cancer, based on availability in Norway.

Cellular determinants and microenvironmental regulation of prostate cancer metastasis

Metastasis causes more than 90% of cancer-related deaths and most prostate cancer (PCa) patients also die from metastasis. The 'metastatic cascade' is a complex biological process that encompasses tumor cell dissociation (from the primary tumor), local invasion, intravasation, transport in circulation, extravasation, colonization, and overt growth in end organs. It has become clear that successful metastasis not only involves many tumor cell-intrinsic properties but also depends on productive interactions between cancer cells and the tumor microenvironment. In this Review, we begin with a general summary on cancer metastasis and a specific discussion on PCa metastasis. We then discuss recent advances in our knowledge of the cellular determinants of PCa metastasis and the importance of tumor microenvironment, especially an immunosuppressive tumor microenvironment, in shaping metastatic propensities. We conclude with a presentation of current and future therapeutic options for patients with PCa metastasis, emphasizing the development of novel, mechanism-based combinatorial strategies for treating metastatic and castration-resistant PCa.

Overcoming immunosuppression in bone metastases

Bone metastases are present in up to 70% of advanced prostate and breast cancers and occur at significant rates in a variety of other cancers. Bone metastases can be associated with significant morbidity. The establishment of bone metastasis activates several immunosuppressive mechanisms. Hence, understanding the tumor-bone microenvironment is crucial to inform the development of novel therapies. This review describes the current standard of care for patients with bone metastatic disease and novel treatment options targeting the microenvironment. Treatments reviewed include immunotherapies, cryoablation, and targeted therapies. Combinatorial treatment strategies including targeted therapies and immunotherapies show promise in pre-clinical and clinical studies to overcome the suppressive environment and improve treatment of bone metastases.

Patients' Preferences for the Treatment of Metastatic Castrate-resistant Prostate Cancer: A Discrete Choice Experiment

PURPOSE

Patient treatment preferences are increasingly being used to inform health care decision making. This discrete choice experiment assessed how men perceive the risks and benefits of hypothetical treatment options for metastatic castrate-resistant prostate cancer (mCRPC).

METHODS

Treatment attributes for inclusion were identified through a review of the literature and product labels. Expert interviews confirmed clinical appropriateness and patient relevance of the attributes, which included effectiveness (delay in months before chemotherapy), steroid use, possible drug interactions (additional hospital visits for monitoring), fogginess (effects on cognition and memory), fatigue (extreme tiredness), food restrictions, and bone pain. Following a pilot, the final discrete choice experiment included 18 choice sets presenting treatments for mCRPC and was completed by men with mCRPC in France, Germany, and the United Kingdom. Data were analyzed using a conditional logit model, with odds ratios (ORs) used to indicate preference for attributes, and tradeoff measures (TOM) were estimated using the ratio of coefficients.

FINDINGS

Within each attribute category and with all other factors being equal, participants (N = 285) indicated a strong preference for treatments that fully control bone pain (OR = 12.069 [95% CI, 10.555-13.800]) and for treatments that delay chemotherapy (OR, 1.727 [95% CI, 1.548-1.927]). They also preferred treatments that were associated with the lowest risk of fogginess (OR, 2.115 [95% CI, 1.849-2.420]), a lower risk of fatigue (OR, 1.365 [95% CI 1.219-1.528]), and fewer additional hospital visits (OR, 1.245 [95% CI 1.111-1.397]) than the respective reference categories. Participants preferred to use steroids under advice from a physician (OR, 1.275 [95% CI 1.132-1.437]). Food restrictions related to taking medication were not a significant concern for participants. TOM results indicated that large tradeoffs in effectiveness, fogginess, and fatigue are required for patients to prefer a treatment with uncontrolled bone pain that is very difficult to live with.

IMPLICATIONS

Men with mCRPC consider a wide range of factors when making decisions regarding their treatment. They showed a strong preference for treatment associated with better control of bone pain. They also placed value on treatments that could delay the need for chemotherapy, and they preferred to avoid side effects such as cognition and memory loss, and extreme tiredness. TOMs highlighted the importance of symptom control, even compared with potential side effects. An understanding of the degree to which patients value the attributes associated with various treatment options will assist clinicians and health care professionals when making decisions regarding the management of men with mCRPC.

Radium-223 Inhibits Osseous Prostate Cancer Growth by Dual Targeting of Cancer Cells and Bone Microenvironment in Mouse Models

Purpose: Radium-223 dichloride (radium-223, Xofigo), a targeted alpha therapy, is currently used for the treatment of patients with castration-resistant prostate cancer (CRPC) with bone metastases. This study examines the mode-of-action and antitumor efficacy of radium-223 in two prostate cancer xenograft models.Experimental Design: Mice bearing intratibial LNCaP or LuCaP 58 tumors were randomized into groups (n = 12-17) based on lesion grade and/or serum PSA level and administered radium-223 (300 kBq/kg) or vehicle, twice at 4-week intervals. X-rays and serum samples were obtained biweekly. Soft tissue tumors were observed macroscopically at sacrifice. Tibiae were analyzed by gamma counter, micro-CT, autoradiography and histology.Results: Radium-223 inhibited tumor-induced osteoblastic bone growth and protected normal bone architecture, leading to reduced bone volume in LNCaP and abiraterone-resistant LuCaP 58 models. Furthermore, radium-223 resulted in lower PSA values and reduced total tissue and tumor areas, indicating that treatment constrains prostate cancer growth in bone. In addition, radium-223 suppressed abnormal bone metabolic activity as evidenced by decreased number of osteoblasts and osteoclasts and reduced level of the bone formation marker PINP. Mode-of-action studies revealed that radium-223 was deposited in the intratumoral bone matrix. DNA double-strand breaks were induced in cancer cells within 24 hours after radium-223 treatment, and PSA levels were significantly lower 72 hours after treatment, providing further evidence of the antitumor effects.Conclusions: Taken together, radium-223 therapy exhibits a dual targeting mode-of-action that induces tumor cell death and suppresses tumor-induced pathologic bone formation in tumor microenvironment of osseous CRPC growth in mice. Clin Cancer Res; 23(15); 4335-46. ©2017 AACR.

Therapeutic management of bone metastasis in prostate cancer: an update

INTRODUCTION

Bone metastases affect the majority of patients with castration-resistant prostate cancer (CRPC), resulting in significant morbidity and mortality. This review describes the current therapies available for the management of CRPC patients with bone metastases. Areas covered: Studies on the use of currently available therapeutic approaches for palliating pain, delaying skeletal-related events (SREs) and prolonging survival in CRPC patients with bone metastases have been examined. PubMed database was searched in May 2016 starting with the following keywords: ('castration-resistant prostate cancer' OR 'CRPC') AND 'bone metastases', and approximately 270 results were retrieved. More specific searches were then performed on the epidemiology and molecular pathogenesis (in particular, 'vicious cycle' was used as a keyword), the management of pain, SREs and survival. The following keywords were also used individually: abiraterone, cabazitaxel, denosumab, docetaxel, enzalutamide, radium-223, sipuleucel-T, samarium-153, strontium-89, zoledronate. Randomized-controlled trials, observational studies, reviews, systematic reviews and meta-analyses were selected and articles were excluded if not in English. Expert commentary: Currently, clear recommendations on the optimal use of the agents available to treat mCRPC are lacking. Therefore, to ensure patients the best treatment, both their clinical characteristics and the features of each product have to be considered.

Specific bone region localization of osteolytic versus osteoblastic lesions in a patient-derived xenograft model of bone metastatic prostate cancer

Objective

Bone metastasis occurs in up to 90% of men with advanced prostate cancer and leads to fractures, severe pain and therapy-resistance. Bone metastases induce a spectrum of types of bone lesions which can respond differently to therapy even within individual prostate cancer patients. Thus, the special environment of the bone makes the disease more complicated and incurable. A model in which bone lesions are reproducibly induced that mirrors the complexity seen in patients would be invaluable for pre-clinical testing of novel treatments. The microstructural changes in the femurs of mice implanted with PCSD1, a new patient-derived xenograft from a surgical prostate cancer bone metastasis specimen, were determined.

Methods

Quantitative micro-computed tomography (micro-CT) and histological analyses were performed to evaluate the effects of direct injection of PCSD1 cells or media alone (Control) into the right femurs of Rag2^−/−γc^−/− male mice.

Results

Bone lesions formed only in femurs of mice injected with PCSD1 cells. Bone volume (BV) was significantly decreased at the proximal and distal ends of the femurs (p < 0.01) whereas BV (p < 0.05) and bone shaft diameter (p < 0.01) were significantly increased along the femur shaft.

Conclusion

PCSD1 cells reproducibly induced bone loss leading to osteolytic lesions at the ends of the femur, and, in contrast, induced aberrant bone formation leading to osteoblastic lesions along the femur shaft. Therefore, the interaction of PCSD1 cells with different bone region-specific microenvironments specified the type of bone lesion. Our approach can be used to determine if different bone regions support more therapy resistant tumor growth, thus, requiring novel treatments.

Molecular Mechanisms of Bone Metastasis: Which Targets Came from the Bench to the Bedside?

Bone metastases ultimately result from a complex interaction between cancer cells and bone microenvironment. However, prior to the colonization of the bone, cancer cells must succeed through a series of steps that will allow them to detach from the primary tumor, enter into circulation, recognize and adhere to specific endothelium, and overcome dormancy. We now know that as important as the metastatic cascade, tumor cells prime the secondary organ microenvironment prior to their arrival, reflecting the existence of specific metastasis-initiating cells in the primary tumor and circulating osteotropic factors. The deep comprehension of the molecular mechanisms of bone metastases may allow the future development of specific anti-tumoral therapies, but so far the approved and effective therapies for bone metastatic disease are mostly based in bone-targeted agents, like bisphosphonates, denosumab and, for prostate cancer, radium-223. Bisphosphonates and denosumab have proven to be effective in blocking bone resorption and decreasing morbidity; furthermore, in the adjuvant setting, these agents can decrease bone relapse after breast cancer surgery in postmenopausal women. In this review, we will present and discuss some examples of applied knowledge from the bench to the bed side in the field of bone metastasis.

Targeting multidrug-resistant ovarian cancer through estrogen receptor α dependent ATP depletion caused by hyperactivation of the unfolded protein response

Ovarian cancers often recur and tumors acquire resistance to chemotherapy due to overexpression of the ATP-dependent efflux pump, multidrug resistance protein 1 (MDR1/P-glycoprotein/ABCB1). Nontoxic small molecule inhibitors targeting MDR1 have remained largely elusive. Instead, in a novel application of our recently described estrogen receptor α (ERα) biomodulator, BHPI, we targeted MDR1’s substrate, ATP. BHPI depletes intracellular ATP and nearly blocks MDR1-mediated drug efflux in ovarian cancer cells by inducing toxic hyperactivation of the endoplasmic reticulum stress sensor, the unfolded protein response (UPR). BHPI increased sensitivity of MDR1 overexpressing multidrug resistant OVCAR-3 ovarian cancer cells to killing by paclitaxel by >1,000 fold. BHPI also restored doxorubicin sensitivity in OVCAR-3 cells and in MDR1 overexpressing breast cancer cells. In an orthotopic OVCAR-3 xenograft model, paclitaxel was ineffective and the paclitaxel-treated group was uniquely prone to form large secondary tumors in adjacent tissue. BHPI alone strongly reduced tumor growth. Notably, tumors were undetectable in mice treated with BHPI plus paclitaxel. Compared to control ovarian tumors, after the combination therapy, levels of the plasma ovarian cancer biomarker CA125 were at least several hundred folds lower; moreover, CA125 levels progressively declined to undetectable. Targeting MDR1 through UPR-dependent ATP depletion represents a promising therapeutic strategy.

Synthesis of Psoralidin derivatives and their anticancer activity: First synthesis of Lespeflorin I1

Synthetic scheme for the preparation of a number of different derivatives of anticancer natural product Psoralidin is described. A convergent synthetic approach is followed using simple starting materials like substituted phenyl acetic esters and benzoic acids. The developed synthetic route leads us to complete the first synthesis of an analogous natural product Lespeflorin I₁, a mild melanin synthesis inhibitor. Preliminary bioactivity studies of the synthesized compounds are carried out against two commonly used prostate cancer cell lines. Results show that the bioactivity of the compounds can be manipulated by the simple modification of the functional groups.