Mechanisms of Osteoblastic Bone Metastasis in Prostate Cancer: Role of Prostatic Acid Phosphatase

Immunogenicity of radiotherapy on bone metastases from prostate adenocarcinoma: What is the future for the combination with radiotherapy/immunotherapy?

Bone metastatic prostate cancers (PCa) are resistant to usual immunotherapies such as checkpoint inhibitors. The main hypothesis related to this immunoresistance is the lack of antigens to stimulate anti-tumor immunity. External radiation is a potential inducer antigens presentation and thus to immunotherapy proprieties. The aim of this review is to describe the tumor microenvironment specificities, especially in bone metastasis and the immune modifications after radiation therapy on a metastatic castration-resistant PCa population. PCa microenvironment is immunosuppressive because of many tumor factors. The complex interplay between PCa cells and bone microenvironment leads to a 'vicious circle' promoting bone metastasis. Furthermore, the immune and bone systems, are connected through an osteoclastogenic cytokine: the Receptor Activator Nuclear Factor Kappa B ligand. Adapted doses of ionizing radiation play a dual role on the tumor. Indeed, radiotherapy leads to immunogenicity by inducing damage associated with molecular patterns. However, it also induces an immunosuppressive effect by increasing the number of immunosuppressive cells. Interestingly, the abscopal effect could be used to optimize immunotherapy potential, especially on bone metastasis. Radiotherapy and immunotherapy combination is a promising strategy, however further studies are necessary to determine the more efficient types of radiation and to control the abscopal effect.

Immunotherapy Innovations in the Fight against Osteosarcoma: Emerging Strategies and Promising Progress

Immunosuppressive elements within the tumor microenvironment are the primary drivers of tumorigenesis and malignant advancement. The presence, as well as the crosstalk between myeloid-derived suppressor cells (MDSCs), osteosarcoma-associated macrophages (OS-Ms), regulatory T cells (Tregs), and endothelial cells (ECs) with osteosarcoma cells cause the poor prognosis of OS. In addition, the consequent immunosuppressive factors favor the loss of treatment potential. Nanoparticles offer a means to dynamically and locally manipulate immuno-nanoparticles, which present a promising strategy for transforming OS-TME. Additionally, chimeric antigen receptor (CAR) technology is effective in combating OS. This review summarizes the essential mechanisms of immunosuppressive cells in the OS-TME and the current immune-associated strategies. The last part highlights the limitations of existing therapies and offers insights into future research directions.

Superscan on 68Ga PSMA PET/CT in patients with metastatic prostate carcinoma: A case series

Prostate cancer is the second most common malignancy in men worldwide, with a good prognosis when is detected and treated in early stages, but, when it presents progression to castration-resistant metastatic prostate cancer, most of the cases will have bone metastasis, decreasing the quality of life and life expectancy. For the evaluation of the disease in the routinary clinical practice, 68Ga-PSMA PET/CT, among others is a valuable tool for the evaluation of the disease extension. 68Ga-PSMA PET/CT detects the presence of PSMA receptor in the tumoral tissue, but also has physiologic uptake in certain organs, such as liver, spleen, intestine, kidneys, lacrimal and salivary glands. Total or partial absence of uptake in those organs is rare and may be due to a high metastatic tumor burden, a phenomenon originally described in bone scintigraphy as super scan. We describe a case series of seven patients with prostate cancer from the National Institute of Cancerology in Colombia, in which a super scan pattern was found in the evaluation with 68Ga-PSMA PET/CT, proposing the suppression of uptake in the intestine, liver, spleen, lacrimal and salivary glands as the main criteria for its definition, and showing that renal uptake persists in most cases, considering that, unlike the super scan in conventional bone scintigraphy, this is not a criterion necessary for its definition in the study with 68Ga-PSMA.

Prognostic analysis of percutaneous vertebroplasty (PVP) combined with 125I implantation on lumbosacral vertebral osteoblastic metastases

OBJECTIVE

Lumbosacral vertebral osteoblastic metastasis is treated with percutaneous vertebroplasty (PVP) combined with 125I seed implantation and PVP alone. Compared to PVP alone, we evaluated the effects of combination therapy with PVP and 125I seed implantation on pain, physical condition, and survival and evaluated the clinical value of PVP combined with 125I particle implantation.

METHODS

We retrospectively analyzed 62 patients with lumbosacral vertebral osseous metastases treated at our hospital between 2016 and 2019. All the patients met the inclusion criteria for 125I implantation, and they were randomly divided into a combined treatment group and a pure PVP surgery group. The visual analog pain scale (VAS), Karnofsky Performance Status (KPS), and survival time were recorded at different time points, including preoperative, postoperative 1 day, 1 month, 3 months, 6 months, 12 months, and 36 months in each group. The variation in clinical indicators and differences between the groups were analyzed using SPSS version 20.0. Correlations between different variables were analyzed using the nonparametric Spearman's rank test. The Kaplan-Meier method was used to estimate the relationship between survival time and KPS score, VAS score, or primary tumor progression, and survival differences were analyzed using the log-rank test. Multivariate analyses were performed using a stepwise Cox proportional hazards model to identify independent prognostic factors.

RESULTS

Compared to the PVP treatment group, the pain level in the combined treatment group was significantly reduced (P = 0.000), and the patient's physical condition in the combination treatment group significantly improved. Kaplan-Meier analysis showed that the survival rate of the PVP group was significantly lower than that of the combination group (P = 0.038). We also found that the median survival of patients in both groups significantly increased with an increase in the KPS score (14 months vs. 33 months) (P = 0.020). Patients with more than three transfer sections had significantly lower survival rates than those with one or two segments of the section (P = 0.001). Further, Cox regression analysis showed that age (P = 0.002), the spinal segment for spinal metastasis (P = 0.000), and primary tumor growth rate (P = 0.005) were independent factors that affected the long-term survival of patients with lumbosacral vertebral osseous metastases.

CONCLUSIONS

PVP combined 125I seeds implantation surgery demonstrated superior effectiveness compared to PVP surgery alone in treating lumbosacral vertebral osseous metastases, which had feasibility in the clinical operation. Preoperative KPS score, spine transfer section, and primary tumor growth rate were closely related to the survival of patients with lumbosacral vertebral osteoblastic metastasis. Age, spinal segment for spinal metastasis, and primary tumor growth can serve as prognostic indicators and guide clinical treatment.

Regucalcin Is a Potential Regulator in Human Cancer: Aiming to Expand into Cancer Therapy

Regucalcin, a calcium-binding protein lacking the EF-hand motif, was initially discovered in 1978. Its name is indicative of its function in calcium signaling regulation. The rgn gene encodes for regucalcin and is situated on the X chromosome in both humans and vertebrates. Regucalcin regulates pivotal enzymes involved in signal transduction and has an inhibitory function, which includes protein kinases, protein phosphatases, cysteinyl protease, nitric oxide dynthetase, aminoacyl-transfer ribonucleic acid (tRNA) synthetase, and protein synthesis. This cytoplasmic protein is transported to the nucleus where it regulates deoxyribonucleic acid and RNA synthesis as well as gene expression. Overexpression of regucalcin inhibits proliferation in both normal and cancer cells in vitro, independent of apoptosis. During liver regeneration in vivo, endogenous regucalcin suppresses cell growth when overexpressed. Regucalcin mRNA and protein expressions are significantly downregulated in tumor tissues of patients with various types of cancers. Patients exhibiting upregulated regucalcin in tumor tissue have shown prolonged survival. The decrease of regucalcin expression is linked to the advancement of cancer. Overexpression of regucalcin carries the potential for preventing and treating carcinogenesis. Additionally, extracellular regucalcin has displayed control over various types of human cancer cells. Regucalcin may hold a prominent role as a regulatory factor in cancer development. Supplying the regucalcin gene could prove to be a valuable asset in cancer treatment. The therapeutic value of regucalcin suggests its potential significance in treating cancer patients. This review delves into the most recent research on the regulatory role of regucalcin in human cancer development, providing a novel approach for treatment.

Expression of microRNA-379 reduces metastatic spread of prostate cancer

Introduction

Prostate cancer (PCa) is the most common type of cancer in males, and the metastatic form is a leading cause of death worldwide. There are currently no curative treatments for this subset of patients. To decrease the mortality of this disease, greater focus must be placed on developing therapeutics to reduce metastatic spread. We focus on dissemination to the bone since this is both the most common site of metastatic spread and associated with extreme pain and discomfort for patients. Our strategy is to exploit microRNAs (miRNAs) to disrupt the spread of primary PCa to the bone.

Methods

PCa cell lines were transduced to overexpress microRNA-379 (miR-379). These transduced PCa cells were assessed using cell growth, migration, colony formation and adhesion assays. We also performed in vivo intracardiac injections to look at metastatic spread in NSG mice. A cytokine array was also performed to identify targets of miR-379 that may drive metastatic spread.

Results

PCa cells with increased levels of miR-379 showed a significant decrease in proliferation, migration, colony formation, and adhesion to bone cells in vitro. In vivo miR-379 overexpression in PC3 cells significantly decreased metastatic spread to bone and reduced levels of miR-379 were seen in patients with metastases. We identified GDF-15 to be secreted from osteoblasts when grown in conditioned media from PCa cells with reduced miR-379 levels.

Discussion

Taken together, our in vitro and in vivo functional assays support a role for miR-379 as a tumour suppressor. A potential mechanism is unravelled whereby miR-379 deregulation in PCa cells affects the secretion of GDF-15 from osteoblasts which in turn facilitates the metastatic establishment in bone. Our findings support the potential role of miR-379 as a therapeutic solution for prostate cancer.

The Bone Microenvironment Soil in Prostate Cancer Metastasis: An miRNA Approach

Bone metastatic prostate cancer (PCa) is associated with a high risk of mortality. Changes in the expression pattern of miRNAs seem to be related to early aspects of prostate cancer, as well as its establishment and proliferation, including the necessary steps for metastasis. Here we compiled, for the first time, the important roles of miRNAs in the development, diagnosis, and treatment of bone metastasis, focusing on recent in vivo and in vitro studies. PCa exosomes are proven to promote metastasis-related events, such as osteoblast and osteoclast differentiation and proliferation. Aberrant miRNA expression in PCa may induce abnormal bone remodeling and support tumor development. Furthermore, miRNAs are capable of binding to multiple mRNA targets, a dynamic property that can be harnessed for the development of treatment tools, such as antagomiRs and miRNA mimics, which have emerged as promising candidates in PCa treatment. Finally, miRNAs may serve as noninvasive biomarkers, as they can be detected in tissue and bodily fluids, are highly stable, and show differential expression between nonmetastatic PCa and bone metastatic samples. Taken together, the findings underscore the importance of miRNA expression profiles and miRNA-based tools as rational technologies to increase the quality of life and longevity of patients.

Spatially patterned 3D model mimics key features of cancer metastasis to bone

Bone is the most common target of metastasis in breast cancer and prostate cancer, leading to significant mortality due to lack of effective treatments. The discovery of novel therapies has been hampered by a lack of physiologically relevant in vitro models that can mimic key clinical features of bone metastases. To fill this critical gap, here we report spatially patterned, tissue engineered 3D models of breast cancer and prostate cancer bone metastasis which mimic bone-specific invasion, cancer aggressiveness, cancer-induced dysregulation of bone remodeling, and in vivo drug response. We demonstrate the potential of integrating such 3D models with single-cell RNA sequencing to identify key signaling drivers of cancer metastasis to bone. Together, these results validate that spatially patterned 3D bone metastasis models mimic key clinical features of bone metastasis and can serve as a novel research tool to elucidate bone metastasis biology and expedite drug discovery.

Chimeric antigen receptor-modified T cells therapy in prostate cancer: A comprehensive review on the current state and prospects

Recent immunotherapy research has focused on chimeric antigen receptor-modified T cells (CAR-Ts). CAR-T therapies have been clinically applied to manage hematologic malignancies with satisfactory effectiveness. However, the application of CAR-T immunotherapy in solid tumors remains challenging. Even so, current CAR-T immunotherapies for prostate cancer (PCa) have shown some promise, giving hope to patients with advanced metastatic PCa. This review aimed to elucidate different types of prostate tumor-associated antigen targets, such as prostate-specific membrane antigen and prostate stem cell antigen, and their effects. The current status of the corresponding targets in clinical research through their applications was also discussed. To improve the efficacy of CAR-T immunotherapy, we addressed the possible applications of multimodal immunotherapy, chemotherapy, and CAR-T combined therapies. The obstacles of solid tumors were concisely elaborated. Further studies should aim to discover novel potential targets and establish new models by overcoming the inherent barriers of solid tumors, such as tumor heterogeneity and the immunosuppressive nature of the tumor microenvironment.

Clinical and Histopathological Aspects of MRONJ in Cancer Patients

Medication-related osteonecrosis of the jaw (MRONJ) is a major complication of bisphosphonate treatment in cancer patients, and its etiology is not completely clarified. The study's goal is to find connections between the clinical and histopathological characteristics of osteonecrosis and bisphosphonates in a cohort of cancer patients who had osteonecrosis treated surgically. The retrospective study includes 51 patients of both sexes, aged 46 to 85 years, who underwent surgical treatment for MRONJ in two oral and maxillofacial surgery clinics (Craiova and Constanța). Demographic, clinical, and imaging data from the records of patients with osteonecrosis were analyzed. The surgical treatment removed the necrotic bone, and the harvested fragments were analyzed from a histopathological perspective. The histopathological examination data were evaluated and statistically processed to look for viable bone, granulation tissue, bacterial colonies, and inflammatory infiltrate. In the study groups, MRONJ was found particularly in the posterior regions of the mandible. Tooth extraction, but also periapical or periodontal infections, represented the trigger factors in most of the cases. The surgical therapy consisted of sequestrectomy or bone resection, and the histopathological examination of the fragments revealed osteonecrosis-specific features, such as the lack of bone cells, the development of an inflammatory infiltrate, and the existence of bacterial colonies. MRONJ in cancer patients receiving zoledronic acid is a severe complication that significantly lowers quality of life. Since these patients are not usually monitored by the dentist, they are identified in advanced stages of MRONJ. For these patients, thorough dental monitoring could reduce the incidence of osteonecrosis and its related complications.

Prostate cancer bone metastases biology and clinical management (Review)

Prostate cancer (PCa) is one of the most prominent causes of cancer-related mortality in the male population. A highly impactful prognostic factor for patients diagnosed with PCa is the presence or absence of bone metastases. The formation of secondary tumours at the bone is the most commonly observed site for the establishment of PCa metastases and is associated with reduced survival of patients in addition to a cohort of life-debilitating symptoms, including mobility issues and chronic pain. Despite the prevalence of this disease presentation and the high medical relevance of bone metastases, the mechanisms underlying the formation of metastases to the bone and the understanding of what drives the osteotropism exhibited by prostate tumours remain to be fully elucidated. This lack of in-depth understanding manifests in limited effective treatment options for patients with advanced metastatic PCa and culminates in the low rate of survival observed for this sub-set of patients. The present review aims to summarise the most recent promising advances in the understanding of how and why prostate tumours metastasise to the bone, with the ultimate aim of highlighting novel treatment and prognostic targets, which may provide the opportunity to improve the diagnosis and treatment of patients with PCa with bone metastases.

Interobserver variation in clinical target volume (CTV) delineation for stereotactic radiotherapy to non-spinal bone metastases in prostate cancer: CT, MRI and PET/CT fusion

BACKGROUND AND PURPOSE

The use of SBRT for the treatment of oligometastatic prostate cancer is increasing rapidly. While consensus guidelines are available for non-spinal bone metastases practice continues to vary widely. The aim of this study is to look at inter-observer variability in the contouring of prostate cancer non-spinal bone metastases with different imaging modalities.

MATERIALS AND METHODS

15 metastases from 13 patients treated at our centre were selected. 4 observers independently contoured clinical target volumes (CTV) on planning CT alone, planning CT with MRI fusion, planning CT with PET-CT fusion and planning CT with both MRI and PET-CT fusion combined. The mean inter-observer agreement on each modality was compared by measuring the delineated volume, generalized conformity index (CIgen), and the distance of the centre of mass (dCOM), calculated per metastasis and imaging modality.

RESULTS

Mean CTV volume delineated on planning CT with MRI and PET-CT fusion combined was significantly larger compared to other imaging modalities (p = 0.0001). CIgen showed marked variation between modalities with the highest agreement between planning CT + PET-CT (mean CIgen 0.55, range 0.32-0.73) and planning CT + MRI + PET-CT (mean CIgen 0.59, range 0.34-0.73). dCOM showed small variations between imaging modalities but a significantly shorter distance found on planning CT + PET-CT when compared with planning CT + PET-CT + MRI combined (p = 0.03).

CONCLUSIONS

Highest consistency in CTV delineation between observers was seen with planning CT + PET-CT and planning CT + PET-CT + MRI combined.

Conditioned medium of PC‑3 prostate cancer cells affects microRNA and mRNA profiles in mechanically strained osteoblasts

Bone is the main site of metastasis from prostate cancer; therefore, it is important to investigate the microRNAs (miRNAs) and mRNA associated with bone metastases from prostate cancer. Since an appropriate mechanical environment is important in the growth of bone, in the present study, the miRNA, mRNA, and long non-coding RNA (lncRNA) profiles of mechanically strained osteoblasts treated with conditioned medium (CM) from PC-3 prostate cancer cells were studied. MC3T3-E1 osteoblastic cells were treated with the CM of PC-3 prostate cancer cells and were simultaneously stimulated with a mechanical tensile strain of 2,500 µε at 0.5 Hz; the osteoblastic differentiation of the MC3T3-E1 cells was then assessed. In addition, the differential expression levels of mRNA, miRNA and lncRNA in MC3T3-E1 cells treated with the CM of PC-3 cells were screened, and some of the miRNAs and mRNAs were verified by reverse transcription-quantitative PCR (RT-qPCR). The signal molecules and signaling pathways associated with osteogenic differentiation were predicted by bioinformatics analysis. The CM of PC-3 prostate cancer cells suppressed osteoblastic differentiation of MC3T3-E1 cells. A total of seven upregulated miRNAs and 12 downregulated miRNAs were selected by sequencing and further verified using RT-qPCR, and related differentially expressed genes (11 upregulated and 12 downregulated genes) were also selected by sequencing and further verified using RT-qPCR; subsequently, according to the enrichment of differentially expressed genes in signaling pathways, nine signaling pathways involved in osteogenic differentiation were screened out. Furthermore, a functional mRNA-miRNA-lncRNA regulatory network was constructed. The differentially expressed miRNAs, mRNAs and lncRNAs may provide a novel signature in bone metastases of prostate cancer. Notably, some of the signaling pathways and related genes may be associated with pathological osteogenic differentiation caused by bone metastasis of prostate cancer.

Prostate cancer expressing membrane-bound TGF-α induces bone formation mediated by the autocrine effect of prostaglandin E2 in osteoblasts

Prostate cancer highly metastasizes to bone, and such cancer is associated with severe bone resorption and bone formation at the site of metastasis. Prostaglandin E₂ (PGE₂) promotes bone resorption in inflammatory diseases; however, the roles in prostate cancer-induced bone formation are still unclear. In the present study, we investigated the effects of membrane-bound TGF-α on prostate cancer-induced bone formation through autocrine PGE₂ signaling in osteoblasts. In the prostate cancer explant experiment into tibiae, injected prostate cancer cells induced bone formation with the increased expression of osteogenic genes, such as Runx2 and Wnt5a, and prostaglandin synthase Ptgs2. In osteoblasts, PGE₂ increased the number of calcified bone nodules with enhanced expression of Runx2 and Wnt5a. We also screened the factors involved in cancer progression, and 11 EGF family members were found to be expressed in the human prostate cancer cell line PC3. PC3 highly expressed amphiregulin, HB-EGF, and especially TGF-α. Treatment with recombinant TGF-α increased the Ptgs2 expression and PGE₂ production in osteoblasts, which promoted the formation of calcified bone nodules, suggesting that the interaction between PC3 and osteoblasts promoted PGE₂ production. In co-culture of osteoblasts and fixed PC3 cells, the phosphorylation of EGFR and ERK and subsequent Ptgs2 expression and PGE₂ production were increased, an effect that was attenuated by treatment with inhibitors of EGFR and ERK. These results indicate that membrane-bound TGF-α enhances ERK signaling while also inducing PGE₂-mediated bone formation in osteoblasts, thus suggesting that prostate cancer regulates both PGE₂-mediated bone resorption and bone formation at the site of bone metastasis of prostate cancer.

Preparation, Optimisation, and In Vitro Evaluation of [18F]AlF-NOTA-Pamidronic Acid for Bone Imaging PET

[¹⁸F]sodium fluoride ([¹⁸F]NaF) is recognised to be superior to [⁹⁹mTc]-methyl diphosphate ([^99mTc]Tc-MDP) and 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) in bone imaging. However, there is concern that [¹⁸F]NaF uptake is not cancer-specific, leading to a higher number of false-positive interpretations. Therefore, in this work, [¹⁸F]AlF-NOTA-pamidronic acid was prepared, optimised, and tested for its in vitro uptake. NOTA-pamidronic acid was prepared by an N-Hydroxysuccinimide (NHS) ester strategy and validated by liquid chromatography-mass spectrometry analysis (LC-MS/MS). Radiolabeling of [¹⁸F]AlF-NOTA-pamidronic acid was optimised, and it was ensured that all quality control analysis requirements for the radiopharmaceuticals were met prior to the in vitro cell uptake studies. NOTA-pamidronic acid was successfully prepared and radiolabeled with ¹⁸F. The radiolabel was prepared in a 1:1 molar ratio of aluminium chloride (AlCl₃) to NOTA-pamidronic acid and heated at 100 °C for 15 min in the presence of 50% ethanol (v/v), which proved to be optimal. The preliminary in vitro results of the binding of the hydroxyapatite showed that [¹⁸F]AlF-NOTA-pamidronic acid was as sensitive as [¹⁸F]sodium fluoride ([¹⁸F]NaF). Normal human osteoblast cell lines (hFOB 1.19) and human osteosarcoma cell lines (Saos-2) were used for the in vitro cellular uptake studies. It was found that [¹⁸F]NaF was higher in both cell lines, but [¹⁸F]AlF-NOTA-pamidronic acid showed promising cellular uptake in Saos-2. The preliminary results suggest that further preclinical studies of [¹⁸F]AlF-NOTA-pamidronic acid are needed before it is transferred to clinical research.

Diagnostic Significance of 18F-FDG PET/CT Imaging Coupled with Magnetic Resonance Imaging of the Entire Body for Bone Metastases

Objective

To see if 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) imaging paired with MR diffusion imaging can help doctors diagnose bone metastases.

Methods

From September 2020 to December 2021, a total of 30 individuals with probable bone metastases were recruited for the trial. With an average interval of four days, MAGNETIC resonance whole-body diffusion imaging (MR whole-body diffusion imaging) was performed on each of the 30 patients who had 18F-FDG PET/CT. The SUVmax values of the group with bone metastases were compared to those of the group without bone metastases. In this study, 18F-FDG PET/CT imaging, MR whole-body diffusion imaging, and their combination were examined. The researchers compared the results when 18F-FDG PET/CT imaging, whole-body MRI diffusion scans, and their combination indicated abnormal bone lesions. By comparing the diagnostic efficacy of 18F-FDG PET/CT imaging, MR whole-body diffusion imaging, and their combination, as well as accuracy, sensitivity, and specificity, the three techniques for diagnosing bone metastases will be evaluated for diagnostic usefulness. Results: the SUV max values of patients with bone metastases were significantly different from those of patients without bone metastases, as determined by 18F-FDG PET/CT imaging (P < 0.05). Using 18F-FDG PET/CT imaging, MR whole-body diffusion imaging, and their combined detection of aberrant bone lesions in various areas, we found statistically significant differences.

Conclusion

The use of 18F-FDG PET/CT imaging in conjunction with MR whole-body diffusion imaging in the diagnosis of bone metastases can be very helpful.

Overexpression of regucalcin blocks the migration, invasion, and bone metastatic activity of human prostate cancer cells: Crosstalk between cancer cells and bone cells

BACKGROUND

Prostate cancer is a bone metastatic cancer and is the second leading cause of cancer-related death in men. Prolonged progression-free survival of prostate cancer patients is associated with high regucalcin expression in the tumor tissues. This study investigates the underlying mechanism by which regucalcin prevents bone metastatic activity of prostate cancer cells.

METHODS

Human prostate cancer PC-3 or DU-145 wild-type cells or regucalcin-overexpressing PC-3 or DU-145 cells (transfectants) were cultured in Dulbecco's modified Eagle's medium containing 10% fetal bovine serum.

RESULTS

Overexpressed regucalcin suppressed the migration and invasion of bone metastatic human prostate cancer cells in vitro, and it reduced the levels of key proteins in metastasis including Ras, Akt, MAPK, RSK-2, mTOR, caveolin-1, and integrin β1. Invasion of prostate cancer cells was promoted by coculturing with preosteoblastic MC3T3-E1 or preosteoclastic RAW264.7 cells. Coculturing with cancer cells and bone cells repressed the growth of preosteoblastic cells and enhanced osteoclastogenesis of preosteoclastic cells, and these alterations were caused by a conditioned medium from cancer cell culture. Disordered differentiation of bone cells was prevented by regucalcin overexpression. Production of tumor necrosis factor-α (TNF-α) in cancer cells was blocked by overexpressed regucalcin. Of note, the effects of conditioned medium on bone cells were prevented by NF-κB inhibitor. TNF-α may be important as a mediator in the crosstalk between cancer cells and bone cells.

CONCLUSION

Overexpression of regucalcin suppressed the migration, invasion, and bone metastatic activity of human prostate cancer cells. This study may provide a new strategy for therapy with the regucalcin gene transfer.

The marine factor 3,5-dihydroxy-4-methoxybenzyl alcohol suppresses growth, migration and invasion and stimulates death of metastatic human prostate cancer cells: targeting diverse signaling processes

Prostate cancer is metastatic cancer and is the second leading cause of cancer-related death in men. It is needed to develop more effective treatment for metastatic prostate cancer. The present study investigates whether the novel factor 3,5-dihydroxy-4-methoxybenzyl alcohol (DHMBA), which was isolated from marine oyster, suppresses the activity of metastatic human prostate cancer PC-3 or DU-145 cells. Culture of DHMBA (1 or 10 µM) suppressed colony formation and growth of PC-3 or DU-145 cells in vitro. Suppressive effects of DHMBA on cell proliferation were not occurred by culturing with intracellular signaling inhibitors. Mechanistically, DHMBA (10 µM) reduced the levels of key proteins linked to promotion of cell growth, including Ras, PI3K, Akt, MAPK, and mTOR in PC-3 cells. Interestingly, DHMBA increased the levels of cancer suppressor p53, p21, Rb, and regucalcin. Moreover, culture of DHMBA simulated the death of PC-3 and DU-145 cells. This effect was implicated to caspase-3 activation in cells. Interestingly, the effects of DHMBA on cell proliferation and death were blocked by culturing with an inhibitor of aryl hydrocarbon receptor linked to transcriptional regulation. Furthermore, culture of DHMBA inhibited production of reactive oxygen species in PC-3 or DU-145 cells. Of note, DHMBA blocked migration and invasion by diminishing their related protein levels, including NF-κB 65, caveolin-1 and integrin β1. The novel marine factor DHMBA was demonstrated to suppress metastatic prostate cancer cells via targeting diverse signaling pathways. This study may provide a new strategy for prostate cancer therapy with DHMBA.

Niraparib Shows Superior Tissue Distribution and Efficacy in a Prostate Cancer Bone Metastasis Model Compared to Other PARP Inhibitors

Prostate cancer patients whose tumors bear deleterious mutations in DNA-repair pathways often respond to poly (ADP-ribose) polymerase (PARP) inhibitors. Studies were conducted to compare the activity of several PARP inhibitors in vitro, and their tissue exposure and in vivo efficacy in mice bearing PC-3M-luc-C6 prostate tumors grown subcutaneously (SC) or in bone. Niraparib, olaparib, rucaparib, and talazoparib were compared in proliferation assays, using several prostate tumor cell lines, and in a cell-free PARP trapping assay. PC-3M-luc-C6 cells were ~12-20-fold more sensitive to PARP inhibition than other prostate tumor lines, suggesting these cells bear a DNA damage repair defect. The tissue exposure and efficacy of these PARP inhibitors were evaluated in vivo in PC-3M-luc-C6 SC and bone metastasis tumor models. A steady-state pharmacokinetic study in PC-3M-luc-C6 tumor-bearing mice demonstrated that all of the PARP inhibitors had favorable SC tumor exposure, but niraparib was differentiated by superior bone marrow exposure compared with the other drugs. In a PC-3M-luc-C6 SC tumor efficacy study, niraparib, olaparib, and talazoparib inhibited tumor growth and increased survival to a similar degree. In contrast, in the PC-3M-luc-C6 bone metastasis model, niraparib showed the most potent inhibition of bone tumor growth compared to the other therapies (67% vs 40-45% on Day 17), and the best survival improvement over vehicle control (hazard ratio [HR] 0.28 vs HR 0.46-0.59) and over other therapies (HR 1.68-2.16). These results demonstrate that niraparib has superior bone marrow exposure and greater inhibition of tumor growth in bone, compared with olaparib, rucaparib, and talazoparib.

Bone Marrow-Derived Stem Cell Factor Regulates Prostate Cancer-Induced Shifts in Pre-Metastatic Niche Composition

Skeletal metastasis is the leading cause of morbidity and mortality in prostate cancer, with 80% of advanced prostate cancer patients developing bone metastases. Before metastasis, bone remodeling occurs, stimulating pre-metastatic niche formation and bone turnover, and platelets govern this process. Stem cell factor (SCF, Kit Ligand) is increased in advanced prostate cancer patient platelet releasates. Further, SCF and its receptor, CD117/c-kit, correlate with metastatic prostate cancer severity. We hypothesized that bone-derived SCF plays an important role in prostate cancer tumor communication with the bone inducing pre-metastatic niche formation. We generated two cell-specific SCF knockout mouse models deleting SCF in either mature osteoblasts or megakaryocytes and platelets. Using two syngeneic androgen-insensitive murine prostate cancer cell lines, RM1 (Ras and Myc co-activation) and mPC3 (Pten and Trp53 deletion), we examined the role of bone marrow-derived SCF in primary tumor growth and bone microenvironment alterations. Platelet-derived SCF was required for mPC3, but not RM1, tumor growth, while osteoblast-derived SCF played no role in tumor size in either cell line. While exogenous SCF induced proangiogenic protein secretion by RM1 and mPC3 prostate cancer cells, no significant changes in tumor angiogenesis were measured by immunohistochemistry. Like our previous studies, tumor-induced bone formation occurred in mice bearing RM1 or mPC3 neoplasms, demonstrated by bone histomorphometry. RM1 tumor-bearing osteoblast SCF knockout mice did not display tumor-induced bone formation. Bone stromal cell composition analysis by flow cytometry showed significant shifts in hematopoietic stem cell (HSC), mesenchymal stem cell (MSC), and osteoblast cell percentages in mice bearing RM1 or mPC3 tumors. There were no significant changes in the percentage of macrophages, osteoclasts, or osteocytes. Our study demonstrates that megakaryocyte/platelet-derived SCF regulates primary mPC3 tumor growth, while SCF originating from osteoblasts plays a role in bone marrow-derived progenitor cell composition and pre-metastatic niche formation. Further, we show that both the source of SCF and the genetic profile of prostate cancer determine the effects of SCF. Thus, targeting the SCF/CD117 signaling axis with tyrosine kinase inhibitors could affect primary prostate carcinomas or play a role in reducing bone metastasis dependent on the gene deletions or mutations driving the patients' prostate cancer.

Comparison of 68Ga-PSMA PET/CT with fluoride PET/CT for detection of bone metastatic disease in prostate cancer

Background

¹⁸F-NaF positron emission tomography/computed tomography (fluoride PET/CT) is considered the most sensitive technique to detect bone metastasis in prostate cancer (PCa). ⁶⁸Ga-PSMA-11 (PSMA) PET/CT is increasingly used for staging of PCa. This study primarily aimed to compare the diagnostic performance of fluoride PET/CT and gallium-based PSMA PET/CT in identifying bone metastasis followed by a comparison of PSMA PET/CT with contrast-enhanced CT (CE-CT) in identifying soft tissue lesions as a secondary objective.

Methods

Twenty-eight PCa patients with high suspicion of disseminated disease following curative treatment were prospectively evaluated. PET/CT examinations using fluoride and PSMA were performed. All suspicious bone lesions were counted, and the tracer uptake was measured as standardized uptake values (SUV) for both tracers. In patients with multiple findings, ten bone lesions with highest SUV_max were selected from which identical lesions from both scans were considered for direct comparison of SUV_max. Soft tissue findings of local and lymph node lesions from CE-CT were compared with PSMA PET/CT.

Results

Both scans were negative for bone lesions in 7 patients (25%). Of 699 lesions consistent with skeletal metastasis in 21 patients on fluoride PET/CT, PSMA PET/CT identified 579 lesions (83%). In 69 identical bone lesions fluoride PET/CT showed significantly higher uptake (mean SUV_max: 73.1 ± 36.8) compared to PSMA PET/CT (34.5 ± 31.4; p < 0.001). Compared to CE-CT, PSMA PET/CT showed better diagnostic performance in locating local (96% vs 61%, p = 0.004) and lymph node (94% vs 46%, p < 0.001) metastasis.

Conclusion

In this prospective comparative study, PSMA PET/CT detected the majority of bone lesions that were positive on fluoride PET/CT. Further, this study indicates better diagnostic performance of PSMA PET/CT to locate soft tissue lesions compared to CE-CT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41824-022-00127-4.

Role of Epigenetic Therapy in the Modulation of Tumor Growth and Migration in Human Castration-Resistant Prostate Cancer Cells with Neuroendocrine Differentiation

INTRODUCTION

Neuroendocrine transdifferentiation (NED) of prostate cancer (PC) cells is associated with the development of resistance to antiandrogen therapy and poor prognosis in patients with castration-resistant PC (CRPC). Many of the molecular events, involved in NED, appear to be mediated by epigenetic mechanisms. In this study, we evaluated the antitumor activity and epigenetic modulation of 2 epigenetic drugs, such as the demethylating agent 5-aza-2'-deoxycytidine (AZA) and the methyl donor S-adenosylmethionine (SAM), in 2 human CRPC cell lines with NED (DU-145 and PC-3).

METHODS

The effects of AZA and SAM on cell viability, cell cycle, apoptosis, migration, and genome-wide DNA methylation profiling have been evaluated.

RESULTS

Both drugs showed a prominent antitumor activity in DU-145 and PC-3 cells, through perturbation of cell cycle progression, induction of apoptosis, and inhibition of cell migration. AZA and SAM reversed NED in DU-145 and PC-3, respectively. Moreover, AZA treatment modified DNA methylation pattern in DU-145 cells, sustaining a pervasive hypomethylation of the genome, with a relevant effect on several pathways involved in the regulation of cell proliferation, apoptosis, and cell migration, in particular Wnt/β-catenin.

CONCLUSIONS

A relevant antitumor activity of these epigenetic drugs on CRPC cell lines with NED opens a new scenario in the therapy of this lethal variant of PC.

Metastatic Prostate Cancer Cells Secrete Methylglyoxal-Derived MG-H1 to Reprogram Human Osteoblasts into a Dedifferentiated, Malignant-like Phenotype: A Possible Novel Player in Prostate Cancer Bone Metastases

Bone metastases from prostate cancer (PCa) result from a complex cross-talk between PCa cells and osteoblasts (OB). Thus, targeting this interplay has become an attractive strategy to interfere with PCa bone dissemination. The agents currently used in clinical trials have proved ineffective, boosting research to identify additional mechanisms that may be involved in this two-directional talk. Here, we investigated whether and how 5-hydro-5-methylimidazolone (MG-H1), a specific methylglyoxal (MG)-derived advanced glycation end product (AGE), was a novel player in the dialogue between PCa and OB to drive PCa bone metastases. Conditioned medium from osteotropic PC3 PCa cells, pre-treated or not with a specific MG scavenger, was administrated to human primary OB and cell morphology, mesenchymal trans-differentiation, pro-osteogenic determinants, PCa-specific molecules, and migration/invasion were studied by phase-contrast microscopy, real-time PCR, western blot and specific assays, respectively. We found that PC3 cells were able to release MG-H1 that, by binding to the receptor for AGEs (RAGE) on OB, reprogrammed them into a less-differentiate phenotype, endowed with some PCa-specific molecular features and malignant properties, in a mechanism involving reactive oxidative species (ROS) production and NF-kB pathway activation. These findings provide novel insights into the mechanisms of PCa osteoblastic metastases and foster in vivo research toward new therapeutic strategies interfering with PCa/OB cross-talk.

Extracellular Vesicle-Mediated Bone Remodeling and Bone Metastasis: Implications in Prostate Cancer

Bone metastasis is the tendency of certain primary tumors to spawn and dictate secondary neoplasia in the bone. The process of bone metastasis is regulated by the dynamic crosstalk between metastatic cancer cells, cellular components of the bone marrow microenvironment (osteoblasts, osteoclasts, and osteocytes), and the bone matrix. The feed-forward loop mechanisms governs the co-option of homeostatic bone remodeling by cancer cells in bone. Recent developments have highlighted the discovery of extracellular vesicles (EVs) and their diverse roles in distant outgrowths. Several studies have implicated EV-mediated interactions between cancer cells and the bone microenvironment in synergistically promoting pathological skeletal metabolism in the metastatic site. Nevertheless, the potential role that EVs serve in arbitrating intricate sequences of coordinated events within the bone microenvironment remains an emerging field. In this chapter, we review the role of cellular participants and molecular mechanisms in regulating normal bone physiology and explore the progress of current research into bone-derived EVs in directly triggering and coordinating the processes of physiological bone remodeling. In view of the emerging role of EVs in interorgan crosstalk, this review also highlights the multiple systemic pathophysiological processes orchestrated by the EVs to direct organotropism in bone in prostate cancer. Given the deleterious consequences of bone metastasis and its clinical importance, in-depth knowledge of the multifarious role of EVs in distant organ metastasis is expected to open new possibilities for prognostic evaluation and therapeutic intervention for advanced bone metastatic prostate cancer.

EphA2 Is a Clinically Relevant Target for Breast Cancer Bone Metastatic Disease

EphA2 receptor tyrosine kinase (RTK) is highly expressed in breast tumor cells across multiple molecular subtypes and correlates with poor patient prognosis. In this study, the potential role of EphA2 in this clinically relevant phenomenon is investigated as metastasis of breast cancer to bone is a major cause of morbidity and mortality in patients. It was found that the EphA2 function in breast cancer cells promotes osteoclast activation and the development of osteolytic bone disease. Blocking EphA2 function molecularly and pharmacologically in breast tumors reduced the number and size of bone lesions and the degree of osteolytic disease in intratibial and intracardiac mouse models, which correlated with a significant decrease in the number of osteoclasts at the tumor-bone interface. EphA2 loss of function in tumor cells impaired osteoclast progenitor differentiation in coculture, which is mediated, at least in part, by reduced expression of IL-6. EPHA2 transcript levels are enriched in human breast cancer bone metastatic lesions relative to visceral metastatic sites; EphA2 protein expression was detected in breast tumor cells in bone metastases in patient samples, supporting the clinical relevance of the study's findings. These data provide a strong rationale for the development and application of molecularly targeted therapies against EphA2 for the treatment of breast cancer bone metastatic disease. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Exploiting bone niches: progression of disseminated tumor cells to metastasis

Many solid cancers metastasize to the bone and bone marrow (BM). This process may occur even before the diagnosis of primary tumors, as evidenced by the discovery of disseminated tumor cells (DTCs) in patients without occult malignancies. The cellular fates and metastatic progression of DTCs are determined by complicated interactions between cancer cells and BM niches. Not surprisingly, these niches also play important roles in normal biology, including homeostasis and turnover of skeletal and hematopoiesis systems. In this Review, we summarize recent findings on functions of BM niches in bone metastasis (BoMet), particularly during the early stage of colonization. In light of the rich knowledge of hematopoiesis and osteogenesis, we highlight how DTCs may progress into overt BoMet by taking advantage of niche cells and their activities in tissue turnover, especially those related to immunomodulation and bone repair.

Prostate cancer-secreted CCN3 uses the GSK3β and β-catenin pathways to enhance osteogenic factor levels in osteoblasts

Prostate cancer osteoblastic bone metastases are incurable and associated with chronic bone pain and a high mortality rate. Osteoclast-targeting drugs intended to prevent skeletal-related events associated with prostate cancer bone metastases do not prolong overall survival. Improved understanding of the bone-derived factors that contribute to prostate cancer osteoblastic bone metastases is required to design treatments that will improve morbidities and overall survival. Activated osteoblasts stimulate prostate cancer growth in bone. In this study, we report that prostate cancer conditioned medium (CM) promoted bone morphogenetic protein (BMP)-2, -4 and -7 production and the expression of osteogenic transcription factors Runx2 and osterix in osteoblasts. Treating the prostate cancer CM with antibody against CCN3 (nephroblastoma-overexpressed), a cysteine-rich protein that belongs to the CCN family, reduced all of these increases. Incubation of osteoblasts with CCN3 facilitated phosphorylation of GSK3β and β-catenin. GSK3β and β-catenin inhibitors or siRNAs all abolished CCN3-induced promotion of BMPs, Runx2 and osterix expression in osteoblasts. Our results indicate that prostate cancer-secreted CCN3 enhances BMP, Runx2 and osterix expression in osteoblasts via the GSK3β and β-catenin signaling pathways. This understanding of the role played by CCN3 in osteoblastic prostate bone metastasis may lead to more efficient targeted therapies.

Prognostic value of miR-339-5p in patients with prostate cancer and its effects on tumor progression

Prostate cancer places a serious health burden on males. The present study aimed to explore the potential prognostic significance and biological function of microRNA (miR)-339-5p in patients with prostate cancer. The expression of miR-339-5p was detected in prostate cancer tissues and cell lines by using reverse transcription-quantitative PCR. Kaplan-Meier survival curves and Cox regression analyses were used to investigate the prognostic significance of miR-339-5p in prostate cancer. The Cell Counting Kit-8 assay was used to determine the effect of miR-339-5p on prostate cancer cell proliferation. Transwell assays were used to assess the effect of miR-339-5p on cell migration and invasion. The results indicated that the expression of miR-339-5p was downregulated in prostate cancer tissues and cell lines. Downregulation of miR-339-5p was significantly associated with the Gleason score, lymph node metastasis and TNM stage. Patients with high miR-339-5p expression levels had a longer survival time than those with low expression levels. Multivariate Cox regression analysis indicated that miR-339-5p may be an independent prognostic factor for the overall survival of patients with prostate cancer. Overexpression of miR-339-5p inhibited the proliferation, migration and invasion of prostate cancer cells. Taken together, these results indicated that miR-339-5p functions as a suppressor gene in prostate cancer and acts by inhibiting cell proliferation, migration and invasion of prostate cancer cells. miR-339-5p may serve as an independent prognostic biomarker and therapeutic target for the treatment of prostate cancer.

The botanical component p-hydroxycinnamic acid suppresses the growth and bone metastatic activity of human prostate cancer PC-3 cells in vitro

Bone metastatic prostate cancer is one of the most common malignancies in developed countries and the second leading cause of cancer-related death in men. There remains no effective treatment for metastatic prostate cancer. We investigate here the anticancer effects of botanical component p-hydroxycinnamic acid (HCA) on the PC-3 cells in vitro model of bone metastatic human prostate cancer. Culturing with HCA (10-1000 nM) suppressed colony formation and growth of PC-3 cells. Mechanistically, culturing with HCA decreased protein levels of Ras, PI3K, Akt, MAPK, NF-κB p65 and β-catenin related to processes of cell signaling and transcription, and it increased levels of p21, p53, retinoblastoma and regucalcin, which are suppressors in carcinogenesis. These alterations can lead to suppression of cell growth. Furthermore, culturing with HCA increased cell death and caspase-3 levels. The effects of HCA on the growth and death of PC-3 cells were blocked by culturing with CH223191, an antagonist of aryl hydrocarbon receptor (AHR), suggesting that HCA effects are partly involved in AHR signaling. Interestingly, HCA suppressed the stimulatory effects of Bay K 8644, an agonist of L-type calcium channel, on the growth of PC-3 cells. Coculturing of PC-3 cells and preosteoblastic MC-3T3 E1 cells increased osteoblastic mineralization. This increase was not attenuated by treatment of HCA that stimulated mineralization. Notably, osteoclastogenesis from preosteoclastic RAW264.7 cells was enhanced by coculturing with PC-3 cells, and this enhancement was suppressed by treatment with HCA (10-1000 nM). Thus, HCA has anticancer effects on bone metastatic human prostate cancer, potentially providing a novel therapeutic tool.

Urinary proteomic profiles of prostate cancer with different risk of progression and correlation with histopathological features

Prostate cancer (PCa) is the most common tumor in men with extremely variable outcome, varying from latent or indolent form to very aggressive behavior. High grade tumors, expansions exceeding the prostatic capsule into the surrounding soft tissues and spreading through lymph vascular channels, represent the most consistent unfavorable prognostic factors. However, accuracy in the prediction of the disease progression is sometimes difficult. Along with new molecular diagnostic techniques and more accurate histopathological approaches, proteomic studies challenge to identify potential biomarkers predictive of PCa progression. In our study we analyzed the urinary proteomes of 42 patients affected by PCa through two-dimensional electrophoresis associated with mass spectrometry. Proteomic profiles were correlated to histopathological features including pTNM stage and tumor differentiation in order to provide new promising markers able to define more accurately the PCa aggressiveness and driving new therapeutic approaches.

Progression-free survival of prostate cancer patients is prolonged with a higher regucalcin expression in the tumor tissues: Overexpressed regucalcin suppresses the growth and bone activity in human prostate cancer cells

Prostate cancer, which is a bone metastatic cancer, is the second leading cause of cancer-related death in men. There is no effective treatment for metastatic prostate cancer. Regucalcin has been shown to contribute as a suppressor in various types of human cancers. In the present study, furthermore, we investigate an involvement of regucalcin in suppression of prostate cancer. Regucalcin expression was compared in 131 primary tumor tissues and 19 metastatic tumor tissues in prostate cancer patients. Regucalcin expression in the metastatic tumor was found to be reduced as compared with that in primary tumor. The progression-free survival rate was prolonged in patients with a higher regucalcin expression. Translationally, overexpression of regucalcin in bone metastatic human prostate cancer PC-3 and DU-145 cells suppressed colony formation and cell growth in vitro. Mechanistically, overexpressed regucalcin enhanced the levels of p53, Rb, and p21, and decreased the levels of Ras, PI3 kinase, Akt, and mitogen-activated protein kinase, leading to suppression of cell growth. Furthermore, higher regucalcin expression suppressed the levels of nuclear factor-κB p65, β-catenin, and signal transducer and activator of transcription 3, which regulate a transcription activity. Cell growth was promoted by culturing with the calcium agonist Bay K 8644. This effect was blocked by overexpression of regucalcin. Notably, overexpressed regucalcin suppressed bone metastatic activity of PC-3 and DU-145 cells when cocultured with preosteoblastic or preosteoclastic cells. Regucalcin may suppress the development of human prostate cancer, suggesting that gene delivery systems in which its expression is forced may be a novel therapeutic strategy.

A novel miRNA inhibits metastasis of prostate cancer via decreasing CREBBP-mediated histone acetylation

BACKGROUND

To identify novel miRNAs implicated in prostate cancer metastasis.

METHODS

Sixty-five prostate cancer tissues and paired pan-cancer tissues were sequenced. Novel miRNAs were re-analyzed by MIREAP program. Biological functions of miR-N5 were transwell experiment and colony formation. Target genes of miR-N5 were analyzed by bioinformatic analysis. Downstream of target gene was analyzed by The Cancer Genome Atlas (TCGA) and Memorial Sloan Kettering Cancer Center (MSKCC) databases and confirmed by CHIP experiment.

RESULTS

We identified a novel miRNA-miR-N5, which was downregulated in PCa cells, PCa tissue, and in the serum of patients with PCa. Knockout of miR-N5 enhanced migration and invasiveness in vitro. miR-N5 specified targeted CREBBP 3'-UTR and inhibited CREBBP expression, which mediated H3K56 acetylation at the promoter of EGFR, β-catenin and CDH1.

CONCLUSION

This study may shed the light on miR-N5 which influences metastasis via histone acetylation.

Bone, a Secondary Growth Site of Breast and Prostate Carcinomas: Role of Osteocytes

Bone is the primarily preferred site for breast and prostate cancer to metastasize. Bone metastases are responsible for most deaths related to breast and prostate cancer. The bone's particular microenvironment makes it conducive for the growth of cancer cells. Studies on bone metastasis have focused on the interaction between cancer cells and the bone microenvironment. Osteocytes, the most common cell type of bone tissue, have received little attention in bone metastasis, although they are master signal sensors, integrators, and skeleton transducers. They play an important role in regulating bone mass by acting on both osteoblasts and osteoclasts, through the release of proteins such as sclerostin, Dickkopf-1 (DKK-1), and fibroblast growth factor 23 (FGF23). Osteocytes have been extensively re-evaluated, in light of their multiple functions: with different experimental approaches, it has been shown that, indeed, osteocytes are actively involved in the colonization of bone tissue by cancer cells. The present review focuses on recent research on the role that osteocytes play in bone metastasis of breast and prostate cancers. Moreover, the studies here summarized open up perspectives for new therapeutic approaches focused on modulating the activity of osteocytes to improve the condition of the bone metastatic patients. A better understanding of the complex interactions between cancer cells and bone-resident cells is indispensable for identifying potential therapeutic targets to stop tumor progression and prevent bone metastases.

Necroptosis of osteoblasts was induced by breast cancer cells in vitro

Background

Bone metastasis of breast cancer could lead to serious osteolysis and severe pain. This study is aimed to investigate the existence of necroptosis, a new type of programmed cell necrosis pathway, in breast cancer-induced osteoblast cell death.

Methods

In this study, conditioned medium (CM) of breast cancer cells was prepared to simulate the micro-environment of bone metastasis in breast cancer in vitro and co-cultured with osteoblast. Then the percentage of cell survival and death was detected via cell viability and flow cytometry. Western blot and PCR were taken to measure protein and mRNA expression level of RIPK 3, MLKL and caspase 3 respectively.

Results

CM could induce osteoblasts death, including apoptosis and necroptosis and necrostatin-1 plus Z-IETD-FMK could decrease the percentage of death cells significantly in the flow cytometry detection. Moreover, CM could increase cleaved caspase 3, RIPK 3 and p-MLKL significantly, while RIPK 3 and p-MLKL was reduced statistically when osteoblasts were treated with Necrostatin-1 (Nec-1). In addition, the mRNA level of three proteins was not consistent with the change of their corresponding protein level.

Conclusions

In conclusion, the necroptosis pathway exists in osteoblast cell death pathway induced by breast cancer cells and could be inhibited by Necrostatin-1 (Nec-1).

Exploring the key communicator role of exosomes in cancer microenvironment through proteomics

There have been many attempts to fully understand the mechanism of cancer behavior. Yet, how cancers develop and metastasize still remain elusive. Emerging concepts of cancer biology in recent years have focused on the communication of cancer with its microenvironment, since cancer cannot grow and live alone. Cancer needs to communicate with other cells for survival, and thus they secrete various messengers, including exosomes that contain many proteins, miRNAs, mRNAs, etc., for construction of the tumor microenvironment. Moreover, these intercellular communications between cancer and its microenvironment, including stromal cells or distant cells, can promote tumor growth, metastasis, and escape from immune surveillance. In this review, we summarized the role of proteins in the exosome as communicators between cancer and its microenvironment. Consequently, we present cancer specific exosome proteins and their unique roles in the interaction between cancer and its microenvironment. Clinically, these exosomes might provide useful biomarkers for cancer diagnosis and therapeutic tools for cancer treatment.