Prostate cancer and bone: the elective affinities

The role of the methyltransferase METTL3 in prostate cancer: a potential therapeutic target

The incidence of prostate cancer (PCa), the most prevalent malignancy, is currently at the forefront. RNA modification is a subfield of the booming field of epigenetics. To date, more than 170 types of RNA modifications have been described, and N6-methyladenosine (m6A) is the most abundant and well-characterized internal modification of mRNAs involved in various aspects of cancer progression. METTL3, the first identified key methyltransferase, regulates human mRNA and non-coding RNA expression in an m6A-dependent manner. This review elucidates the biological function and role of METTL3 in PCa and discusses the implications of METTL3 as a potential therapeutic target for future research directions and clinical applications.

Functional anti-bone tumor biomaterial scaffold: construction and application

Bone tumors, including primary bone tumors and bone metastases, have been plagued by poor prognosis for decades. Although most tumor tissue is removed, clinicians are still confronted with the dilemma of eliminating residual cancer cells and regenerating defective bone tissue after surgery. Therefore, functional biomaterial scaffolds are considered to be the ideal candidates to bridge defective tissues and restrain cancer recurrence. Through functionalized structural modifications or coupled therapeutic agents, they provide sufficient mechanical strength and osteoinductive effects while eliminating cancer cells. Numerous novel approaches such as photodynamic, photothermal, drug-conjugated, and immune adjuvant-assisted therapies have exhibited remarkable efficacy against tumors while exhibiting low immunogenicity. This review summarizes the progress of research on biomaterial scaffolds based on different functionalization strategies in bone tumors. We also discuss the feasibility and advantages of the combined application of multiple functionalization strategies. Finally, potential obstacles to the clinical translation of anti-tumor bone bioscaffolds are highlighted. This review will provide valuable references for future advanced biomaterial scaffold design and clinical bone tumor therapy.

Association of dynamic change in patient-reported pain with survival in metastatic castrate sensitive prostate cancer-exploratory analysis of LATITUDE study

BACKGROUND

Pain is an important dimension of quality-of-life in patients with metastatic castrate-sensitive prostate cancer (mCSPC). However, it is unclear if dynamic change in pain over time can predict for overall survival (OS) or progression-free survival (PFS) in these patients.

METHODS

This is an exploratory analysis of LATITUDE, a phase III randomized study, in which men with de novo mCSPC were randomized to receive either ADT plus abiraterone versus ADT alone. Information was collected on patient-reported worst pain score (WPS) and pain-interference score (PIS) from the Brief Pain Inventory-Short Form. A Bayesian joint modelling approach was used determine the association of dynamic change in WPS and PIS with OS and PFS.

RESULTS

Overall, 1125 patients with at least 3 measurements on pain scores were eligible. On Cox multivariable regression, increase in baseline WPS was associated with inferior OS (hazard ratio [HR] 1.049 [95% confidence intervals [CI] 1.015-1.085]; time dependent area under curve [tAUC] 0.64) and PFS (HR 1.045 [1.011-1.080]; tAUC: 0.64). Increase in baseline PIS was associated with inferior OS (HR 1.062 [1.020-1.105]; tAUC: 0.63) but not with PFS (HR 1.038 [0.996-1.08]). On independent joint models, an increase in the current value of WPS by 1-unit was associated with inferior OS (HR 1.316 [1.258-1.376]; tAUC 0.74) and PFS (HR 1.319 [1.260-1.382]; tAUC 0.70). Similar association was seen for increase in the current value of PIS with OS (HR 1.319 [1.261-1.381]; tAUC 0.73) and PFS (HR 1.282 [1.224-1.344]; tAUC 0.73).

CONCLUSIONS

The above findings highlight the potential dynamic interplay between patient-reported pain with OS and PFS in mCSPC. Compared to baseline pain, such dynamic assessment of pain was found to have superior predictive ability and thus has the potential to tailor subsequent treatment based on response to initial therapy beyond its role as a very important dimension of quality-of-life.

Chemopreventive Effect of Cinnamon and Its Bioactive Compounds in a Rat Model of Premalignant Prostate Carcinogenesis

Cinnamon and its bioactive compounds inhibit prostate cancer cell proliferation in vitro. The aim of the current study was to assess the chemopreventive efficacy of cinnamon (CN) and its bioactive compounds in vivo using N-methyl-N-nitrosourea (MNU) and testosterone (T) to induce prostate carcinogenesis in male Wistar/National Institute of Nutrition rats. Cancer-induced (CI) rats (n = 10) developed prostatic hyperplasia and prostatic intraepithelial neoplasia. These histopathologic changes were diminished in CI rats fed for 4 months with diets supplemented with either CN (n = 20) or its bioactive compounds (cinnamaldehyde, n = 10 and procyanidin B2, n = 10). Androgen receptor (AR) expression was lower in the prostates of CI rats than in control, but the AR target gene, probasin, was robustly upregulated. Treatment of CI rats with CN or its bioactive compounds upregulated AR expression but inhibited the expression of the 5-alpha reductase genes (Srd5a1 and Srd5a2) and did not further increase probasin expression, suggesting blunted transcriptional activity of AR due to the limited availability of dihydrotestosterone. MNU+T induced an altered oxidant status in rat prostate, which was reflected by an increase in lipid peroxidation and DNA oxidation. These changes were completely or partially corrected by treatment with CN or the bioactive compounds. CN and its active components increased the activity of the apoptotic enzymes caspase-8 and caspase-3 in the prostates of CI rats. In conclusion, our data demonstrate that CN and its bioactive compounds have inhibitory effects on premalignant prostate lesions induced by MNU + T and, therefore, may be considered for the chemoprevention of prostate cancer.

PREVENTION RELEVANCE

The research work presented in this article demonstrates the chemopreventive efficacy of CN and its bioactive compounds in a rat model of premalignant prostate cancer.

Bone morphogenetic protein pathway responses and alterations of osteogenesis in metastatic prostate cancers

BACKGROUND

Prostate cancer is a common cancer in men that annually results in more than 33 000 US deaths. Mortality from prostate cancer is largely from metastatic disease, reflecting on the great strides in the last century of treatments in care for the localized disease. Metastatic castrate resistant prostate cancer (mCRPC) will commonly travel to the bone, creating unique bone pathology that requires nuanced treatments in those sites with surgical, radio and chemotherapeutic interventions. The bone morphogenetic protein (BMP) pathway has been historically studied in the capacity to regulate the osteogenic nature of new bone. New mineralized bone generation is a frequent and common observation in mCRPC and referred to as blastic bone lesions. Less common are bone destructive lesions that are termed lytic.

METHODS

We queried the cancer genome atlas (TCGA) prostate cancer databases for the expression of the BMP pathway and found that distinct gene expression of the ligands, soluble antagonists, receptors, and intracellular mediators were altered in localized versus metastatic disease. Human prostate cancer cell lines have an innate ability to promote blastic- or lytic-like bone lesions and we hypothesized that inhibiting BMP signaling in these cell lines would result in a distinct change in osteogenesis gene expression with BMP inhibition.

RESULTS

We found unique and common changes by comparing these cell lines response and unique BMP pathway alterations. We treated human PCa cell lines with distinct bone pathologic phenotypes with the BMP inhibitor DMH1 and found distinct osteogenesis responses. We analyzed distinct sites of metastatic PCa in the TCGA and found that BMP signaling was selectively altered in commons sites such as lymph node, bone and liver compared to primary tumors.

CONCLUSIONS

Overall we conclude that BMPs in metastatic prostate cancer are important signals and functional mediators of diverse processes that have potential for individualized precision oncology in mCRPC.

Role of the Hypoxic-Secretome in Seed and Soil Metastatic Preparation

During tumor growth, the delivery of oxygen to cells is impaired due to aberrant or absent vasculature. This causes an adaptative response that activates the expression of genes that control several essential processes, such as glycolysis, neovascularization, immune suppression, and the cancer stemness phenotype, leading to increased metastasis and resistance to therapy. Hypoxic tumor cells also respond to an altered hypoxic microenvironment by secreting vesicles, factors, cytokines and nucleic acids that modify not only the immediate microenvironment but also organs at distant sites, allowing or facilitating the attachment and growth of tumor cells and contributing to metastasis. Hypoxia induces the release of molecules of different biochemical natures, either secreted or inside extracellular vesicles, and both tumor cells and stromal cells are involved in this process. The mechanisms by which these signals that can modify the premetastatic niche are sent from the primary tumor site include changes in the extracellular matrix, recruitment and activation of different stromal cells and immune or nonimmune cells, metabolic reprogramming, and molecular signaling network rewiring. In this review, we will discuss how hypoxia might alter the premetastatic niche through different signaling molecules.

Role of Src kinase in regulating protein kinase C mediated phosphorylation of TRPV1

BACKGROUND

Transient receptor potential vanilloid-1 (TRPV1), activated by heat, acidic pH, endogenous vanilloids and capsaicin, is essential for thermal hyperalgesia. Under inflammatory conditions, phosphorylation of TRPV1 by protein kinase C (PKC) can sensitize the channel and decrease the activation threshold. Src kinase also phosphorylates TRPV1, promoting channel trafficking to the plasma membrane. These post-translational modifications are important for several chronic pain conditions. This study presents a previously undescribed relationship between Src and PKC phosphorylation of TRPV1, influencing the thermal hypersensitivity associated with TRPV1 activation.

METHODS

We assessed TRPV1 channel activity using intracellular calcium imaging and patch-clamp electrophysiology in mouse dorsal root ganglion cultures. Additionally, we used behavioural experiments to evaluate plantar thermal sensitivity following intraplantar injections of activators of known modulators of TRPV1 with and without an Src antagonist.

RESULTS

Using calcium imaging and patch-clamp techniques, we demonstrated that pharmacological inhibition of Src kinase or mutation of the Src phosphorylation site on TRPV1 prevented PKC but not PKA-mediated sensitization of TRPV1 in vitro. We found that intraplantar injection of the PKC activator phorbol 12-myristate 13-acetate (PMA) or bradykinin produces thermal hypersensitivity that can be attenuated by pharmacological inhibition of Src. Additionally, complete Freund's Adjuvant (CFA)-induced inflammatory hypersensitivity could also be attenuated by local Src kinase inhibition.

CONCLUSIONS

Our data demonstrate that Src phosphorylation is critical for PKC-mediated sensitization of TRPV1. Further, in a model of inflammatory pain, CFA, Src kinase inhibition could reduce thermal hypersensitivity. Targeting of Src kinase may have analgesic benefits in inflammatory pain conditions.

SIGNIFICANCE

Src kinase-mediated phosphorylation of TRPV1 is a critical regulator of the PKC-induced sensitization induced by multiple inflammatory mediators. This suggest a new regulatory mechanism governing TRPV1 function and a potential therapeutic target for inflammatory type pain, including cancer pain where Src antagonists are currently utilized.

Oral metastasis as the first indication of undiscovered malignancy at a distant site: A systematic review of 413 cases

This systematic review is the first to provide evidence regarding demographic, clinical, and imaging characteristics, as well as information related to survival, of patients with oral and maxillofacial metastases of occult primary tumors. Case reports, case series, and cross-sectional studies were included. Ten databases were searched. The risk of bias was assessed using the Joanna Briggs Institute appraisal tools. Overall, 353 articles (413 patients) were included. Statistically significant associations between survival and multiplicity of metastatic foci, and between each of the main primary sites and some features of the oral lesions were observed. Some clinical and imaging characteristics can help dentists in raising diagnostic suspicions and also in relating to plausible primary sites. Early diagnosis of oral and maxillofacial metastases can positively affect the survival rate when they are the only focus of dissemination, conferring an important role on the dentist.

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.

A Double-Edged Sword Role of Cytokines in Prostate Cancer Immunotherapy

Prostate cancer (PC) is one of the most common malignancies among men and is the second leading cause of cancer death. PC immunotherapy has taken relatively successful steps in recent years, and these treatments are still being developed and tested. Evidence suggests that immunotherapy using cytokines as essential mediators in the immune system may help treat cancer. It has been shown that cytokines play an important role in anti-tumor defense. On the other hand, other cytokines can also favor the tumor and suppress anti-tumor responses. Moreover, the dose of cytokine in cancer cytokine-based immunotherapy, as well as the side effects of high doses, can also affect the outcomes of treatment. Cytokines can also be determinative in the outcome of other immunotherapy methods used in PC. In this review, the role of cytokines in the pathogenesis of cancer and their impacts on the main types of immunotherapies in the treatment of PC are discussed.

Bone Metastases from Gastric Cancer: What We Know and How to Deal with Them

Gastric cancer (GC) is the third cause of cancer-related death worldwide; the prognosis is poor especially in the case of metastatic disease. Liver, lymph nodes, peritoneum, and lung are the most frequent sites of metastases from GC; however, bone metastases from GC have been reported in the literature. Nevertheless, it is unclear how the metastatic sites may affect the prognosis. In particular, knowledge about the impact of bone metastases on GC patients’ outcome is scant, and this may be related to the rarity of bone lesions and/or their underestimation at the time of diagnosis. In fact, there is still a lack of specific recommendation for their detection at the diagnosis. Then, the majority of the evidences in this field came from retrospective analysis on very heterogeneous study populations. In this context, the aim of this narrative review is to delineate an overview about the evidences existing about bone metastases in GC patients, focusing on their incidence and biology, the prognostic role of bone involvement, and their possible implication in the treatment choice.

A duplex probe-directed recombinase amplification assay for detection of single nucleotide polymorphisms on 8q24 associated with prostate cancer

Single nucleotide polymorphisms (SNPs) have important application value in the research of population genetics, hereditary diseases, tumors, and drug development. Conventional methods for detecting SNPs are typically based on PCR or DNA sequencing, which is time-consuming, costly, and requires complex instrumentation. In this study, we present a duplex probe-directed recombinase amplification (duplex-PDRA) assay that can perform real-time detection of two SNPs (rs6983267 and rs1447295) in four reactions in two tubes at 39°C within 30 min. The sensitivity of duplex-PDRA was 2×10³-10⁴ copies per reaction and no cross-reactivity was observed. A total of 382 clinical samples (179 prostate cancer patients and 203 controls) from northern China were collected and tested by duplex-PDRA assay and direct sequencing. The genotyping results were completely identical. In addition, the association analysis of two SNPs with prostate cancer risk and bone metastasis was conducted. We found that the TT genotype of rs6983267 (OR: 0.42; 95%CI: 0.23-0.78; P=0.005) decreased the risk of prostate cancer, while the CA genotype of rs1447295 (OR: 1.89; 95%CI: 1.20-2.96; P=0.005) increased the risk of prostate cancer. However, no association between the two SNPs (rs6983267 and rs1447295) and bone metastasis in prostate cancer was found in this study (P>0.05). In conclusion, the duplex-PDRA assay is an effective method for the simultaneous detection of two SNPs and shows great potential for widespread use in research and clinical settings.

Osteoclast-expanded super-charged NK-cells preferentially select and expand CD8+ T cells

Osteoclasts (OCs) and much less dendritic cells (DCs) induce significant expansion and functional activation of NK cells, and furthermore, the OC-expanded NK cells preferentially increase the expansion and activation of CD8+ T cells by targeting CD4+ T cells. When autologous OCs were used to expand patient NK cells much lower percentages of expanded CD8+ T cells, decreased numbers of expanded NK cells and decreased functions of NK cells could be observed, and the addition of allogeneic healthy OCs increased the patients' NK function. Mechanistically, OC-expanded NK cells were found to lyse CD4+ T cells but not CD8+ T cells suggesting potential selection of CD8+ T cells before their expansion by OC activated NK cells. In agreement, Increased IFN-γ secretion, and NK cell-mediated cytotoxicity and higher percentages of CD8+ T cells, in various tissue compartments of oral tumor-bearing hu-BLT mice in response to immunotherapy by OC-expanded NK cells were observed. Thus, our results indicate an important relationship between NK and CD8+ T cells.

Arginine vasopressin receptor 1a is a therapeutic target for castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) recurs after androgen deprivation therapy (ADT) and is incurable. Reactivation of androgen receptor (AR) signaling in the low androgen environment of ADT drives CRPC. This AR activity occurs through a variety of mechanisms, including up-regulation of AR coactivators such as VAV3 and expression of constitutively active AR variants such as the clinically relevant AR-V7. AR-V7 lacks a ligand-binding domain and is linked to poor prognosis. We previously showed that VAV3 enhances AR-V7 activity to drive CRPC progression. Gene expression profiling after depletion of either VAV3 or AR-V7 in CRPC cells revealed arginine vasopressin receptor 1a (AVPR1A) as the most commonly down-regulated gene, indicating that this G protein-coupled receptor may be critical for CRPC. Analysis of publicly available human PC datasets showed that AVPR1A has a higher copy number and increased amounts of mRNA in advanced PC. Depletion of AVPR1A in CRPC cells resulted in decreased cell proliferation and reduced cyclin A. In contrast, androgen-dependent PC, AR-negative PC, or nontumorigenic prostate epithelial cells, which have undetectable AVPR1A mRNA, were minimally affected by AVPR1A depletion. Ectopic expression of AVPR1A in androgen-dependent PC cells conferred castration resistance in vitro and in vivo. Furthermore, treatment of CRPC cells with the AVPR1A ligand, arginine vasopressin (AVP), activated ERK and CREB, known promoters of PC progression. A clinically safe and selective AVPR1A antagonist, relcovaptan, prevented CRPC emergence and decreased CRPC orthotopic and bone metastatic growth in mouse models. Based on these preclinical findings, repurposing AVPR1A antagonists is a promising therapeutic approach for CRPC.

Cytokines and Chemokines as Mediators of Prostate Cancer Metastasis

The consequences of prostate cancer metastasis remain severe, with huge impact on the mortality and overall quality of life of affected patients. Despite the convoluted interplay and cross talk between various cell types and secreted factors in the metastatic process, cytokine and chemokines, along with their receptors and signaling axis, constitute important factors that help drive the sequence of events that lead to metastasis of prostate cancer. These proteins are involved in extracellular matrix remodeling, epithelial-mesenchymal-transition, angiogenesis, tumor invasion, premetastatic niche creation, extravasation, re-establishment of tumor cells in secondary organs as well as the remodeling of the metastatic tumor microenvironment. This review presents an overview of the main cytokines/chemokines, including IL-6, CXCL12, TGFβ, CXCL8, VEGF, RANKL, CCL2, CX3CL1, IL-1, IL-7, CXCL1, and CXCL16, that exert modulatory roles in prostate cancer metastasis. We also provide extensive description of their aberrant expression patterns in both advanced disease states and metastatic sites, as well as their functional involvement in the various stages of the prostate cancer metastatic process.

METTL3 enhances cell adhesion through stabilizing integrin β1 mRNA via an m6A-HuR-dependent mechanism in prostatic carcinoma

Bone metastasis is the major cause of morbidity and mortality in patients with prostate cancer (PCa). However, the underlying mechanism of bone-specific metastasis remain vague. Recently, with the deep research of N6-methyladenine (m6A) mRNA methylation, many studies directly focus on the role of m6A modification in human diseases, especially in cancers. Here we found that methyltransferase-like 3 (METTL3) expression is higher in PCa than in normal prostate tissues, especially in PCa with bone metastasis. High METTL3 expression was positively correlated with advanced progression and a poor prognosis of PCa. Functional assays demonstrated that METTL3 regulates the expression of Integrin β1 (ITGB1) through m6A-HuR-dependent mechanism, which affects the binding of ITGB1 to Collagen I and tumor cell motility, so as to promote the bone metastasis of PCa. The findings of this study reveal a novel mechanism of PCa osteotropism and suggest METTL3 as a therapeutic target for PCa bone metastasis.

Bufalin suppresses the migration and invasion of prostate cancer cells through HOTAIR, the sponge of miR-520b

Bufalin, the major active component of the traditional Chinese medicine ChanSu obtained from the skin and parotid venom glands of toads, has long been known as an anticancer agent. Recent studies show that microRNAs (miRs) are involved in the anticancer activities of bufalin, while long non-coding RNAs (lncRNAs) are known to interact with miRNAs to regulate various biological functions. In this paper, we investigated the possible network related to the antimetastatic effect of bufalin in prostate cancer (PCa) cells. We demonstrated that bufalin (0.05-10 µM) dose-dependently suppressed the proliferation of prostate cancer DU145 and PC3 cells with IC50 values of 0.89 and 1.28 µM, respectively. Furthermore, bufalin treatment significantly suppressed the cell migration and invasion. To explore the role of lncRNAs in the antimetastatic activity of bufalin, we used an lncRNA microarray and found that HOX transcript antisense RNA (HOTAIR) was the most markedly downregulated lncRNA in bufalin-treated PCa cells. Overexpression of HOTAIR counteracted the suppressing effects of bufalin on DU145 and PC3 cells. We then predicted and verified that HOTAIR upregulated FGFR1 expression by sponging miR-520b in PCa cells. In 40 patients with PCa bone metastasis, we used in situ hybridization or immunohistochemical assay to assess the HOTAIR and FGFR1 expression, which revealed that both HOTAIR and FGFR1 expression were significantly higher in bone metastasis tissues than in the primary PCa tissues. In addition, the level of serum HOTAIR was positively associated with the levels of serum bone metabolic markers (CTx, OST, B-ALP and PINP) and may serve as a reasonable biomarker for PCa bone metastasis. Taken together, this is the first study revealing that HOTAIR promotes PCa bone metastasis, and bufalin may be a promising candidate for the treatment of this disease.

Exosomes from LNCaP cells promote osteoblast activity through miR-375 transfer

Previous studies have revealed that exosomes influence tumour metastasis, diagnosis and treatment. In addition, exosomal microRNAs (miRNAs/miRs) are closely associated with the metastatic microenvironment; however, the regulatory role of exosomal miRNAs from prostate cancer cells on bone metastasis remains poorly understood. In the present study, a series of experiments were performed to determine whether exosomal miR-375 from LNCaP cells promote osteoblast activity. Exosomes were isolated and purified by ultracentrifugation, total RNA from cells and total miRNA from exosomes were then extracted, and miR-375 levels were detected by reverse transcription-quantitative polymerase chain reaction. Exosome libraries from LNCaP and RWPE-1 cells were sequenced and selected using an Illumina HiSeq™ 2500 system. The effects of exosomes on osteoblasts were determined and osteoblast activity was evaluated by measuring the activity of alkaline phosphatase, the extent of extracellular matrix mineralisation and the expression of osteoblast activity-associated marker genes. Morphological observations, particle size analysis and molecular phenotyping confirmed that cell supernatants contained exosomes. Differential expression analysis confirmed high miR-375 expression levels in LNCaP cell-derived exosomes. The ability of exosomes to enter osteoblasts and increase their levels of miR-375 was further analysed. The results demonstrated that exosomal miR-375 significantly promoted osteoblast activity. In conclusion, the present study may lead to further investigation of the function role of exosomal miR-375 in the activation and differentiation of osteoblasts in PCa.

Prostate cancer metastasis and soy isoflavones: a dogfight over a bone

Prostate cancer is a complex, progressive, bone-tropic disease, which is usually associated with skeletal issues, poor mobility and a fatal outcome when it reaches the metastatic phase. Soy isoflavones, steroid-like compounds from soy-based food/dietary supplements, have been found to decrease the risk of prostate cancer in frequent consumers. Herein, we present a systematization of the data on soy isoflavone effects at different stages of metastatic prostate cancer progression, with a particular interest in the context of bone-related molecular events. Specifically, soy isoflavones have been determined to downregulate the prostate cancer cell androgen receptors, reverse the epithelial to mesenchymal transition of these cells, decrease the expressions of prostate-specific antigen, matrix metalloproteinase and serine proteinase, and reduce the superficial membrane fluidity in prostate cancer cells. In addition, soy isoflavones suppress the angiogenesis that follows prostate cancer growth, obstruct prostate cancer cells adhesion to the vascular endothelium and their extravasation in the area of future bone lesions, improve the general bone morphofunctional status, have a beneficial effect on prostate cancer metastasis-caused osteolytic/osteoblastic lesions and possibly affect the pre-metastatic niche formation. The observed, multilevel antimetastatic properties of soy isoflavones imply that they should be considered as promising components of combined therapeutic approaches to advanced prostate cancer.

Parathyroid hormone-related peptide activates and modulates TRPV1 channel in human DRG neurons

Parathyroid hormone-related peptide (PTHrP) is associated with advanced tumor growth and metastasis, especially in breast, prostate and myeloma cancers that metastasize to bones, resulting in debilitating chronic pain conditions. Our recent studies revealed that the receptor for PTHrP, PTH1R, is expressed in mouse DRG sensory neurons, and its activation leads to flow-activation and modulation of TRPV1 channel function, resulting in peripheral heat and mechanical hypersensitivity. In order to verify the translatability of our findings in rodents to humans, we explored whether this signalling axis operates in primary human DRG sensory neurons. Analysis of gene expression data from recently reported RNA deep sequencing experiments performed on mouse and human DRGs reveals that PTH1R is expressed in DRG and tibial nerve. Furthermore, exposure of cultured human DRG neurons to PTHrP leads to slow-sustained activation of TRPV1 and modulation of capsaicin-induced channel activation. Both activation and modulation of TRPV1 by PTHrP were dependent on PKC activity. Our findings suggest that functional PTHrP/PTH1R-TRPV1 signalling exists in human DRG neurons, which could contribute to local nociceptor excitation in the vicinity of metastatic bone tumor microenvironment.

Parathyroid Hormone-Related Peptide Elicits Peripheral TRPV1-dependent Mechanical Hypersensitivity

Bone metastasis in breast, prostate and lung cancers often leads to chronic pain, which is poorly managed by existing analgesics. The neurobiological mechanisms that underlie chronic pain associated with bone-metastasized cancers are not well understood, but sensitization of peripheral nociceptors by tumor microenvironment factors has been demonstrated to be important. Parathyroid hormone-related peptide (PTHrP) is highly expressed in bone-metastasized breast and prostate cancers, and is critical to growth and proliferation of these tumors in the bone tumor microenvironment. Previous studies have suggested that PTHrP could sensitize nociceptive sensory neurons, resulting in peripheral pain hypersensitivity. In this study, we found that PTHrP induces both heat and mechanical hypersensitivity, that are dependent on the pain-transducing transient receptor potential channel family vanilloid, member-1 (TRPV1), but not the mechano-transducing TRPV4 and TRPA1 ion channels. Functional ratiometric Ca²⁺ imaging and voltage-clamp electrophysiological analysis of cultured mouse DRG neurons show significant potentiation of TRPV1, but not TRPA1 or TRPV4 channel activation by PTHrP. Interestingly, PTHrP exposure led to the slow and sustained activation of TRPV1, in the absence of any exogenous channel agonist, and is dependent on the expression of the type-1 parathyroid hormone receptor (PTH1), as well as on downstream phosphorylation of the channel by protein kinase C (PKC). Accordingly, local administration of specific small-molecule antagonists of TRPV1 to mouse hindpaws after the development of PTHrP-induced mechanical hypersensitivity led to its significant attenuation. Collectively, our findings suggest that PTHrP/PTH1-mediated flow activation of TRPV1 channel contributes at least in part to the development and maintenance of peripheral mechanical pain hypersensitivity, and could therefore constitute a mechanism for nociceptor sensitization in the context of metastatic bone cancer pain.

NAC1 promotes the migration of prostate cancer cells and participates in osteoclastogenesis by negatively regulating IFNβ

Nucleus accumbens-associated protein 1 (NAC1), a transcriptional co-regulator, is overexpressed in advanced prostate cancer. However, the NAC1-regulated transcriptome has not been completely explored. In the present study, the functional silencing of NAC1 blocked the migration of prostate cancer cells and suppress osteoclastogenesis. The present study also determined that NAC1 was overexpressed in the highly aggressive prostate cancer cell lines PC-3, DU-145 and LNCaP. NAC1 small interfering RNA treatment of DU-145 cells decreased cell migration, but interestingly had no significant effects on cell proliferation. Furthermore, microarray analysis showed that a group of genes may be associated with the development of prostate cancer after NAC1 knockdown, including interferon-β (IFNβ), which is reported to be involved in osteoclastogenesis, an important factor affecting bone metastasis. The mechanisms of NAC1 function were further explored by co-culture studies using PC-3 and RAW264.7 osteoclast precursor cells, which demonstrated that silencing NAC1 downregulated the genes associated with the activation of osteoclasts. Furthermore, it was revealed that NAC1 had the ability to affect the release of IFNβ into the extracellular environment. Together, these findings indicated that NAC1 promoted cell migration, and that NAC1 may have a key role in osteoclastogenesis.

Anticancer Activity of Ganoderic Acid DM: Current Status and Future Perspective

Ganoderma lucidum is a mushroom that has a long history of medicinal use in the Far East countries as this mushroom is revered for its supposed miracle cures and life improving properties. Recently, this mushroom has come under scientific scrutiny to examine the possibility of finding biologically active compounds that may have an impact on human physiology. The main category of biologically active compounds produced in the G. lucidum, are the triterpenoids, which are known as Ganoderic Acids. In this review, we discuss one Ganoderic Acid in particular known as Ganoderic Acid-DM (GA-DM) that is extracted from the Ganoderma lucidum mushroom. We will discuss GA-DM as a potential therapeutic candidate for treating a number of diseases yet will focus on the potential to be used as an alternative or supplemental therapeutic agent in regards to various cancer types. The urge for this promising therapeutic agent is that GA-DM is capable of inducing cell death in cancer cells while exhibiting minimal toxicity to normal bystander cells. Furthermore, this review will look at GA-DM's ability to stimulate an immune response in the tumor environment to potentially provide long-term protection from the malignant tumors. We will also discuss the known routes of administration of GA-DM and pose the advantages and disadvantages of each route in a comparative manner. Finally, we will cover current status of the roles GA-DM may have as a therapeutic agent in respect to different cancer types as wells as discuss about its future perspective as a therapeutic candidate in other diseases as well.

Integrated and Functional Genomics Analysis Validates the Relevance of the Nuclear Variant ErbB380kDa in Prostate Cancer Progression

The EGF-family of tyrosine-kinase receptors activates cytoplasmic pathways involved in cell proliferation, migration and differentiation in response to specific extracellular ligands. Beside these canonical pathways, the nuclear localization of the ErbB receptors in primary tumours and cancer cell lines led to investigate their role as transcriptional regulators of cancer genes. The nuclear localization of ErbB3 has been reported in various cancer tissues and cell lines but the nuclear functions and the putative correlation with tumour progression and resistance to therapy remain unclear. We first assessed ErbB3 expression in normal and tumour prostate tissues. The nuclear staining was mainly due to an isoform matching the C-terminus domain of the full length ErbB3_185kDa receptor. Nuclear staining was also restricted to cancer cells and was increased in advanced castration-resistant prostate cancer when compared to localized tumours, suggesting it could be involved in the progression of prostate cancer up to the terminal castration-resistant stage. ChIP-on-chip experiments were performed on immortalized and tumour cell lines selected upon characterization of endogenous nuclear expression of an ErbB3_80kDa isoform. Among the 1840 target promoters identified, 26 were selected before ErbB3_80kDa-dependent gene expression was evaluated by real-time quantitative RT-PCR, providing evidence that ErbB3_80kDa exerted transcriptional control on those genes. Some targets are already known to be involved in prostate cancer progression even though no link was previously established with ErbB3 membrane and/or nuclear signalling. Many others, not yet associated with prostate cancer, could provide new therapeutic possibilities for patients expressing ErbB3_80kDa. Detecting ErbB3_80kDa could thus constitute a useful marker of prognosis and response to therapy.

Induction of thermal and mechanical hypersensitivity by parathyroid hormone-related peptide through upregulation of TRPV1 function and trafficking

The neurobiological mechanisms underlying chronic pain associated with cancers are not well understood. It has been hypothesized that factors specifically elevated in the tumor microenvironment sensitize adjacent nociceptive afferents. We show that parathyroid hormone-related peptide (PTHrP), which is found at elevated levels in the tumor microenvironment of advanced breast and prostate cancers, is a critical modulator of sensory neurons. Intraplantar injection of PTHrP led to the development of thermal and mechanical hypersensitivity in both male and female mice, which were absent in mice lacking functional transient receptor potential vanilloid-1 (TRPV1). The PTHrP treatment of cultured mouse sensory neurons enhanced action potential firing, and increased TRPV1 activation, which was dependent on protein kinase C (PKC) activity. Parathyroid hormone-related peptide induced robust potentiation of TRPV1 activation and enhancement of neuronal firing at mild acidic pH that is relevant to acidic tumor microenvironment. We also observed an increase in plasma membrane TRPV1 protein levels after exposure to PTHrP, leading to upregulation in the proportion of TRPV1-responsive neurons, which was dependent on the activity of PKC and Src kinases. Furthermore, co-injection of PKC or Src inhibitors attenuated PTHrP-induced thermal but not mechanical hypersensitivity. Altogether, our results suggest that PTHrP and mild acidic conditions could induce constitutive pathological activation of sensory neurons through upregulation of TRPV1 function and trafficking, which could serve as a mechanism for peripheral sensitization of nociceptive afferents in the tumor microenvironment.

MiRNA 34a: a therapeutic target for castration-resistant prostate cancer

INTRODUCTION

Development of a therapy for bone metastases is of paramount importance for castration-resistant prostate cancer (CRPC). The osteomimetic properties of CRPC confer a propensity to metastasize to osseous sites. Micro-ribonucleic acid (miRNA) is non-coding RNA that acts as a post-transcriptional regulator of multiple proteins and associated pathways. Therefore identification of miRNAs could reveal a valid third generation therapy for CRPC.

AREAS COVERED

miR34a has been found to play an integral role in the progression of prostate cancer, particularly in the regulation of metastatic genes involved in migration, intravasation, extravasation, bone attachment and bone homeostasis. The correlation between miR34a down-regulation and metastatic progression has generated substantial interest in this field.

EXPERT OPINION

Examination of the evidence reveals that miR34a is an ideal target for gene therapy for metastatic CRPC. We also conclude that future studies should focus on the effects of miR34a upregulation in CRPC with respect to migration, translocation to bone micro-environment and osteomimetic phenotype development. The success of miR34a as a therapeutic is reliant on the development of appropriate delivery systems and targeting to the bone micro-environment. In tandem with any therapeutic studies, biomarker serum levels should also be ascertained as an indicator of successful miR34a delivery.

Molecular regulation of bone marrow metastasis in prostate and breast cancer

Metastasis is a multistep process, which refers to the ability to leave a primary tumor through circulation toward the distant tissue and form a secondary tumor. Bone is a common site of metastasis, in which osteolytic and osteoblastic metastasis are observed. Signaling pathways, chemokines, growth factors, adhesion molecules, and cellular interactions as well as miRNAs have been known to play an important role in the development of bone metastasis. These factors provide an appropriate environment (soil) for growth and survival of metastatic tumor cells (seed) in bone marrow microenvironment. Recognition of these factors and determination of their individual roles in the development of metastasis and disruption of cellular interactions can provide important therapeutic targets for treatment of these patients, which can also be used as prognostic and diagnostic biomarkers. Thus, in this paper, we have attempted to highlight the molecular regulation of bone marrow metastasis in prostate and breast cancers.