Parathyroid hormone related peptide and receptor expression in paired primary prostate cancer and bone metastases

Parathyroid hormone related-protein (PTHrP) in tissues with poor prognosis in prostate cancer patients

BACKGROUND

Parathyroid hormone-related peptide (PTHrP) is known to have a pivotal role in the progression of various solid tumors, among which prostate cancer stands out. However, the extent of PTHrP expression and its clinical implications in prostate cancer patients remain shrouded in obscurity. The primary objective of this research endeavor was to shed light on the relevance of PTHrP in the context of prostate cancer patients and to uncover the potential underlying mechanisms.

METHODS

The expression of PTHrP, E-cadherin, and vimentin in tumor tissues of 88 prostate cancer patients was evaluated by immunohistochemical technique. Subsequently, the associations between PTHrP and clinicopathological parameters and prognosis of patients with prostate cancer were analyzed.

RESULTS

Immunohistochemical analysis showed that the expression rates of PTHrP, E-cadherin, and vimentin in prostate cancer tissues were 95.5%, 88.6%, and 84.1%, respectively. Patients with a high level of PTHrP had a decreased expression of E-cadherin (P = .013) and an increased expression of vimentin (P = .010) compared with patients with a low level of PTHrP. Besides, the high expression of PTHrP was significantly correlated with a higher level of initial prostate-specific antigen (P = .026), positive lymph node metastasis (P = .010), osseous metastasis (P = .004), and Gleason score (P = .026). Moreover, patients with a high level of PTHrP had shorter progression-free survival (P = .002) than patients with a low level of PTHrP.

CONCLUSION

The present study indicates that PTHrP is associated with risk factors of poor outcomes in prostate cancer, while epithelial-mesenchymal transition may be involved in this process.

Parathyroid hormone-related protein as a potential prostate cancer biomarker: Promoting prostate cancer progression through upregulation of c-Met expression

Parathyroid hormone-related protein (PTHrP) plays a significant role in various tumor types, including prostate cancer. However, its specific role and underlying mechanisms in prostate cancer remain unclear. This study investigates the role of PTHrP and its interaction with the c-Met in prostate cancer. PTHrP was overexpressed and knocked down in prostate cancer cell lines to determine its effect on cell functions. Xenograft tumor models were employed to assess the impact of PTHrP overexpression on tumor growth. To delve into the interaction between PTHrP and c-Met, rescue experiments were conducted. Clinical data and tissue samples from prostate cancer patients were gathered and analyzed for PTHrP and c-Met expression. PTHrP overexpression in prostate cancer cells upregulates c-Met expression and augments cell functions. In contrast, PTHrP-knockdown diminishes c-Met expression and inhibits cell functions. In vivo experiments further demonstrated that PTHrP overexpression promoted tumor growth in xenograft models.Moreover, modulating c-Met expression in rescue experiments led to concurrent alterations in prostate cancer cell functions. Immunohistochemical analysis of clinical samples displayed a significant positive correlation between PTHrP and c-Met expression. Additionally, PTHrP expression correlated with clinical parameters like prostate-specific antigen (PSA) levels, tumor stage, lymph node involvement, distant metastasis, and Gleason score. PTHrP plays a crucial role in prostate cancer progression by upregulating c-Met expression. These insights point to PTHrP as a promising potential biomarker for prostate cancer.

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.

Parathyroid Hormone-Related Protein/Parathyroid Hormone Receptor 1 Signaling in Cancer and Metastasis

PTHrP exerts its effects by binding to its receptor, PTH1R, a G protein-coupled receptor (GPCR), activating the downstream cAMP signaling pathway. As an autocrine, paracrine, or intracrine factor, PTHrP has been found to stimulate cancer cell proliferation, inhibit apoptosis, and promote tumor-induced osteolysis of bone. Despite these findings, attempts to develop PTHrP and PTH1R as drug targets have not produced successful results in the clinic. Nevertheless, the efficacy of blocking PTHrP and PTH1R has been shown in various types of cancer, suggesting its potential for therapeutic applications. In light of these conflicting data, we conducted a comprehensive review of the studies of PTHrP/PTH1R in cancer progression and metastasis and highlighted the strengths and limitations of targeting PTHrP or PTH1R in cancer therapy. This review also offers our perspectives for future research in this field.

Immunoarray Measurements of Parathyroid Hormone-Related Peptides Combined with Other Biomarkers to Diagnose Aggressive Prostate Cancer

Parathyroid hormone-related peptide (PTHrP) is related to bone metastasis and hypercalcemia in prostate and breast cancers and should be an excellent biomarker for aggressive forms of these cancers. Current clinical detection protocols for PTHrP are immunoradiometric assay and radioimmunoassay but are not sensitive enough to detect PTHrPs at early stages. We recently evaluated a prostate cancer biomarker panel, including serum monocyte differentiation antigen (CD-14), ETS-related gene protein, pigment epithelial-derived factor, and insulin-like growth factor-1, with promise for identifying aggressive prostate cancers. This panel predicted the need for patient biopsy better than PSA alone. In the present paper, we report an ultrasensitive microfluidic assay for PTHrPs and evaluate their diagnostic value and the value of including them with our prior biomarker panel to diagnose aggressive forms of prostate cancer. The immunoarray features screen-printed carbon sensor electrodes coated with 5 nm glutathione gold nanoparticles with capture antibodies attached. PTHrPs are bound to a secondary antibody attached to a polyhorseradish peroxidase label and delivered to the sensors to provide high sensitivity when activated by H₂O₂ and a mediator. We obtained an unprecedented 0.3 fg mL^-1 limit of detection for PTHrP bioactive moieties PTHrP 1-173 and PTHrP 1-86. We also report the first study of PTHrPs in a large serum pool to identify aggressive malignancies. In assays of 130 human patient serum samples, PTHrP levels distinguished between aggressive and indolent prostate cancers with 83-91% clinical sensitivity and 78-96% specificity. Logistic regression identified the best predictive model as a combination of PTHrP 1-86 and vascular endothelial growth factor-D. PTHrP 1-173 alone also showed a high ability to differentiate aggressive and indolent cancers.

PTHLH Predicts the Prognosis of Patients with Oral Leukoplakia

Background

Oral leukoplakia is the most common oral mucosal disease. A proportion of such cases can progress to oral squamous cell carcinoma (OSCC). The mechanism of oral leukoplakia malignant transformation is still unclear. In this study, we analyzed the expression of parathyroid hormone-like hormone (PTHLH) in oral leukoplakia and the effect on prognosis, so as to find reliable molecular markers that can predict oral leukoplakia malignant transformation.

Methods

We measured PTHrP which is coded by PTHLH in oral leukoplakia tissues of 79 cases (30 cases progressed to OSCC and 49 did not) and analyzed the clinical outcomes. Then, PTHLH expression was reduced using lentivirus-mediated small hairpin RNA (shRNA) interference to determine the biological role of PTHLH in DOK cells.

Results

PTHrP was found to be highly expressed in 38% of tissues of oral leukoplakia. There was weak or no PTHrP expression in 25 patients, moderate expression in 24 patients, and strong in 30 patients with oral leukoplakia. The expression level was associated with the degree of atypical hyperplasia and poor prognosis. The cell proliferation, invasion, migration, cell cloning, and cell cycle were affected after reducing PTHLH expression.

Conclusion

Our data suggest that either PTHLH or PTHrP plays a key role in the malignant transformation of oral leukoplakia and might be a reliable biomarker for predicting the carcinogenesis of oral leukoplakia.

Relationship Between the Neutrophil to Lymphocyte Ratio and Parathyroid Adenoma Size in Patients With Primary Hyperparathyroidism

The aim of our study was to evaluate the relationship between neutrophil to lymphocyte ratio (NLR) and adenoma size in parathyroidectomized patients who underwent a parathyroidectomy. The neutrophil to lymphocyte ratio has recently become popular as a biomarker for malignant diseases or for estimating tumor size preoperatively. This study aimed to estimate the relationship between adenoma size and NLR. Furthermore, we assessed whether a higher level of NLR is correlated with the presence of parathyroid carcinoma. A retrospective chart review was performed for patients with parathyroid adenoma who underwent parathyroidectomy between January 2012 and August 2014. Data related to age, sex, NLR, parathyroid hormone level (PTH), preoperative calcium, phosphorus, adenoma size, and pathology reports were collected. The neutrophil to lymphocyte ratio was significantly correlated with calcium levels, PTH levels, parathyroid adenoma size, and the presence of cancer. However, there was no correlation between NLR and age, sex, and phosphorus levels. This study is the first to document a positive correlation between NLR and parathyroid adenoma size, as well as the presence of cancer, in patients who underwent surgery as a result of primary hyperparathyroidism.

Parathyroid Hormone-Like Hormone is a Poor Prognosis Marker of Head and Neck Cancer and Promotes Cell Growth via RUNX2 Regulation

Parathyroid Hormone-Like Hormone (PTHLH) is an autocrine/paracrine ligand that is up-regulated in head and neck squamous cell carcinoma (HNSCC). However, the cellular function and regulatory mechanism in HNSCC remains obscure. We investigated the clinical significance of PTHLH in HNSCC patients, and verified the role of RUNX2/PTHLH axis, which is stimulated HNSCC cell growth. In patients, PTHLH is a poor prognosis marker. PTHLH expression lead to increasing the cell proliferation potential through an autocrine/paracrine role and elevating blood calcium level in Nod-SCID mice. In public HNSCC microarray cohorts, PTHLH is found to be co-expressed with RUNX2. Physiologically, PTHLH is regulated by RUNX2 and also acting as key calcium regulator. However, elevations of calcium concentration also increased the RUNX2 expression. PTHLH, calcium, and RUNX2 form a positive feedback loop in HNSCC. Furthermore, ectopic RUNX2 expression also increased PTHLH expression and promoted proliferation potential through PTHLH expression. Using cDNA microarray analysis, we found PTHLH also stimulated expression of cell cycle regulators, namely CCNA2, CCNE2, and CDC25A in HNSCC cells, and these genes are also up-regulated in HNSCC patients. In summary, our results reveal that PTHLH expression is a poor prognosis marker in HNSCC patients, and RUNX2-PTHLH axis contributes to HNSCC tumor growth.

Sequential culture on biomimetic nanoclay scaffolds forms three-dimensional tumoroids

In recent times, the limitation of two-dimensional cultures and complexity of in vivo models has paved the way for the development of three-dimensional models for studying cancer. Here we report the development of a new tumor model using PCL/HAPClay scaffolds seeded with a sequential culture of human mesenchymal stem cells (hMSCs) followed by human prostate cancer cells (HPCCs). This nanocomposite system is used as a test-bed for studying cancer metastasis and efficacy of anti-cancer drugs using a polymersome delivery method. A novel sequential cell culture system in three-dimensional in vitro bone model provides a unique bone mimetic environment. The hMSCs seeded scaffolds are seeded with prostate cancer cells after the hMSCs have differentiated into osteoblasts. Sequential culture on the scaffolds has shown formation of tumoroids or microtissue consisting of organized, densely packed round cells with hypoxic core regions similar to in vivo tumors. Such tumoroids are not observed on HPCC seeded scaffolds or when HPCCs sequentially cultured with human osteoblast cells. Clearly, the newly differentiated hMSCs play a vital role in the ability of cancer cells to grow into tumoroids and cause disease. The PCL/HAPclay scaffold system seeded with the sequential culture of hMSCs, and HPCCs presents a good model system for study of the interactions between prostate cancer cells and bone microenvironment. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1591-1602, 2016.

Parathyroid hormone-related protein serves as a prognostic indicator in oral squamous cell carcinoma

BACKGROUND

In our previous study, parathyroid hormone-like hormone (PTHLH) which encodes parathyroid hormone-related protein (PTHrP) was revealed to be up-regulated in oral squamous cell carcinoma (OSCC) compared with paired apparently normal surgical margins using microarray method. However, the function and prognostic indicators of PTHLH/PTHrP in OSCC remain obscure.

METHODS

The mRNA levels of PTHLH and its protein levels were investigated in 9 OSCC cell lines and in 36 paired OSCC specimens by real-time PCR and western blotting. The biological function of PTHLH/PTHrP was investigated using small interfering RNA (siRNA) in 3 OSCC cell lines, and immunohistochemistry was used to estimate the prognostic value of PTHrP in 101 patients with head and neck squamous cell carcinoma (HNSCC), including OSCC and oropharyngeal squamous cell carcinoma. Cell cycle was tested by flow cytometry and cell cycle related genes were investigated by western blotting and immunocytochemistry assay.

RESULTS

This study showed that the mRNA and protein levels of PTHLH in 9 OSCC cell lines were much higher than that in normal epithelial cells (P < 0.0001). In 36 paired OSCC tissues, PTHLH mRNA expressions were found higher in 32 OSCC tissues than that of paired apparently normal surgical margins (P = 0.0001). The results revealed that the down-regulation of PTHLH/PTHrP by siRNAs could reduce cell proliferation and inhibit plate and soft agar colony formation as well as affect the cell cycle of OSCC cells. The key proteins related to the cell cycle were changed by anti-PTHLH siRNA. The results showed that cyclin D1 and CDK4 expressions were significantly reduced in the cells transfected with anti-PTHLH siRNA. On the other hand, the expression of p21 was increased. The results also showed that high PTHrP level was associated with poor pathologic differentiation (P = 0.0001) and poor prognosis (P = 0.0003) in patients with HNSCC.

CONCLUSIONS

This study suggests that PTHLH/PTHrP is up-regulated in OSCCs. Therefore, PTHLH/PTHrP could play a role in the pathogenesis of OSCC by affecting cell proliferation and cell cycle, and the protein levels of PTHrP might serve as a prognostic indicator for evaluating patients with HNSCCs.

Paracrine interactions between LNCaP prostate cancer cells and bioengineered bone in 3D in vitro culture reflect molecular changes during bone metastasis

As microenvironmental factors such as three-dimensionality and cell-matrix interactions are increasingly being acknowledged by cancer biologists, more complex 3D in vitro models are being developed to study tumorigenesis and cancer progression. To better understand the pathophysiology of bone metastasis, we have established and validated a 3D indirect co-culture model to investigate the paracrine interactions between prostate cancer (PCa) cells and human osteoblasts. Co-culture of the human PCa, LNCaP cells embedded within polyethylene glycol hydrogels with human osteoblasts in the form of a tissue engineered bone construct (TEB), resulted in reduced proliferation of LNCaP cells. LNCaP cells in both monoculture and co-culture were responsive to the androgen analog, R1881, as indicated by an increase in the expression (mRNA and/or protein induction) of androgen-regulated genes including prostate specific antigen and fatty acid synthase. Microarray gene expression analysis further revealed an up-regulation of bone markers and other genes associated with skeletal and vasculature development and a significant activation of transforming growth factor β1 downstream genes in LNCaP cells after co-culture with TEB. LNCaP cells co-cultured with TEB also unexpectedly showed similar changes in classical androgen-responsive genes under androgen-deprived conditions not seen in LNCaP monocultures. The molecular changes of LNCaP cells after co-culturing with TEBs suggest that osteoblasts exert a paracrine effect that may promote osteomimicry and modulate the expression of androgen-responsive genes in LNCaP cells. Taken together, we have presented a novel 3D in vitro model that allows the study of cellular and molecular changes occurring in PCa cells and osteoblasts that are relevant to metastatic colonization of bone. This unique in vitro model could also facilitate cancer biologists to dissect specific biological hypotheses via extensive genomic or proteomic assessments to further our understanding of the PCa-bone crosstalk.

Parathyroid hormone related-protein promotes epithelial-to-mesenchymal transition in prostate cancer

Parathyroid hormone-related protein (PTHrP) possesses a variety of physiological and developmental functions and is also known to facilitate the progression of many common cancers, notably their skeletal invasion, primarily by increasing bone resorption. The purpose of this study was to determine whether PTHrP could promote epithelial-to-mesenchymal transition (EMT), a process implicated in cancer stem cells that is critically involved in cancer invasion and metastasis. EMT was observed in DU 145 prostate cancer cells stably overexpressing either the 1-141 or 1-173 isoform of PTHrP, where there was upregulation of Snail and vimentin and downregulation of E-cadherin relative to parental DU 145. By contrast, the opposite effect was observed in PC-3 prostate cancer cells where high levels of PTHrP were knocked-down via lentiviral siRNA transduction. Increased tumor progression was observed in PTHrP-overexpressing DU 145 cells while decreased progression was observed in PTHrP-knockdown PC-3 cells. PTHrP-overexpressing DU 145 formed larger tumors when implanted orthoptopically into nude mice and in one case resulted in spinal metastasis, an effect not observed among mice injected with parental DU 145 cells. PTHrP-overexpressing DU 145 cells also caused significant bone destruction when injected into the tibiae of nude mice, while parental DU 145 cells caused little to no destruction of bone. Together, these results suggest that PTHrP may work through EMT to promote an aggressive and metastatic phenotype in prostate cancer, a pathway of importance in cancer stem cells. Thus, continued efforts to elucidate the pathways involved in PTHrP-induced EMT as well as to develop ways to specifically target PTHrP signaling may lead to more effective therapies for prostate cancer.

Signaling between tumor cells and the host bone marrow microenvironment

Tumor cells with high skeletal homing affinity express numerous cell surface receptors that bind ligands produced in bone. Upon arrival, these cells survive in the host environment, encompassed in close proximity to bone marrow cells. Interactions between tumor cells and cells of the host microenvironment are essential to not only tumor cell survival but also their activation and proliferation into environment-modifying tumors. Through the production of RANKL, PTHrP, cytokines, and integrins, activated tumor cells stimulate osteoclastogenesis, enhance bone resorption, and subsequently release matrix-bound proteins that further promote tumor growth and bone resorption. In addition, alterations in the TGF-β/BMP and Wnt signaling pathways via tumor cell growth can either stimulate or suppress osteoblastic bone formation and function, leading to sclerotic or lytic bone disease, respectively. Hence, the presence of tumor cells in bone dysregulates bone remodeling, dramatically impairing skeletal integrity. Furthermore, through complex mechanisms, cells of the immune system interact with tumor cells to further impact bone remodeling. Lastly, with alterations in bone cell activity, the environment is permissive to promoting tumor growth further, suggesting an interdependence between tumor cells and bone cells in metastatic bone disease and multiple myeloma.

A prospective study of total and ionized serum calcium and time to fatal prostate cancer

BACKGROUND

Higher levels of total and ionized serum calcium have been shown to predict fatal prostate cancer in prospective studies. Because the follow-up time in these studies was relatively short, these associations could reflect the effect of clinically significant but occult prostate tumors on serum calcium levels. If this were true, prostate cancer mortality rates among men with higher levels of serum calcium should be higher during the early follow-up period and should decline thereafter.

METHODS

We tested this hypothesis by estimating the relative risk of death from prostate cancer in the National Health and Nutrition Examination Survey III for incremental increases in total and ionized serum calcium using Cox proportional hazards regression with time-dependent effects.

RESULTS

Forty-nine (49) fatal prostate cancers occurred over 204 months of follow-up and 1,069,327 person-months of observation. Men with higher total serum calcium and higher serum ionized calcium had increased risks of fatal prostate cancer during the first 96 months of follow-up [Relative Hazard (RH) = 1.50 per 0.1 mmol/L total serum calcium, 95% confidence interval (CI) = 1.04-2.17; RH = 1.72 per 0.05 mmol/L ionized calcium, 95% CI = 1.11-2.66]. Evidence of an association between total and ionized serum calcium and prostate cancer deaths was not significant after 96 months.

CONCLUSIONS

Our analyses support the hypothesis that the elevated risk for fatal prostate cancer observed in men with high serum calcium is because of the presence of extant, but occult prostate cancer.

IMPACT

These findings have implications for the potential use of serum calcium in the detection of clinically significant prostate cancer.

The role of bone microenvironment, vitamin D and calcium

Starting first from Paget's "seed and soil" to the latest hypothesis about metastatic process involving the concept of a premetastatic niche, a large amount of data suggested the idea that metastatization is a multistep coordinated process with a high degree of efficiency. A specific subpopulation of cells with tumor-initiating and migratory capacity can selectively migrate toward sites that are able to promote survival, and/or proliferation of metastatic tumor cells through a microenvironment modification. Bone plays a pivotal role in this process, acting not only as a preferential site for cancer cells' homing and proliferation, due to a complex interplay between different cellular phenotypes such as osteoblasts and osteoclasts, but also as a source of bone marrow precursors that are able to facilitate the metastatic process in extra-skeletal disease. Moreover, bone microenvironment has the unique capacity to retain cancer stem cells in a quiescent status, acting as a reservoir that is able to cause a metastatic spread also many years after the resection of the primary tumor. To add a further level of complexity, these mechanisms are strictly regulated through the signalling through several soluble factors including PTH, vitamin D or calcium concentration. Understanding this complexity represents a major challenge in anti-cancer research and a mandatory step towards the development of new drugs potentially able not only to reduce the consequences of bone lesions but also to target the metastatization process from the "bone pre-neoplastic niche" to "visceral pre-neoplastic niches".

Physiopathology of spine metastasis

The metastasis is the spread of cancer from one part of the body to another. Two-thirds of patients with cancer will develop bone metastasis. Breast, prostate and lung cancer are responsible for more than 80% of cases of metastatic bone disease. The spine is the most common site of bone metastasis. A spinal metastasis may cause pain, instability and neurological injuries. The diffusion through Batson venous system is the principal process of spinal metastasis, but the dissemination is possible also through arterial and lymphatic system or by contiguity. Once cancer cells have invaded the bone, they produce growth factors that stimulate osteoblastic or osteolytic activity resulting in bone remodeling with release of other growth factors that lead to a vicious cycle of bone destruction and growth of local tumour.

Parathyroid hormone mediates hematopoietic cell expansion through interleukin-6

Parathyroid hormone (PTH) stimulates hematopoietic cells through mechanisms of action that remain elusive. Interleukin-6 (IL-6) is upregulated by PTH and stimulates hematopoiesis. The purpose of this investigation was to identify actions of PTH and IL-6 in hematopoietic cell expansion. Bone marrow cultures from C57B6 mice were treated with fms-like tyrosine kinase-3 ligand (Flt-3L), PTH, Flt-3L plus PTH, or vehicle control. Flt-3L alone increased adherent and non-adherent cells. PTH did not directly impact hematopoietic or osteoclastic cells but acted in concert with Flt-3L to further increase cell numbers. Flt-3L alone stimulated proliferation, while PTH combined with Flt-3L decreased apoptosis. Flt-3L increased blasts early in culture, and later increased CD45⁺ and CD11b⁺ cells. In parallel experiments, IL-6 acted additively with Flt-3L to increase cell numbers and IL-6-deficient bone marrow cultures (compared to wildtype controls) but failed to amplify in response to Flt-3L and PTH, suggesting that IL-6 mediated the PTH effect. In vivo, PTH increased Lin^- Sca-1⁺c-Kit⁺ (LSK) hematopoietic progenitor cells after PTH treatment in wildtype mice, but failed to increase LSKs in IL-6-deficient mice. In conclusion, PTH acts with Flt-3L to maintain hematopoietic cells by limiting apoptosis. IL-6 is a critical mediator of bone marrow cell expansion and is responsible for PTH actions in hematopoietic cell expansion.

Detection of circulating tumor cells in prostate cancer patients: methodological pitfalls and clinical relevance

Disseminated malignancy is the major cause of prostate cancer-related mortality. Circulating tumor cells (CTCs) are essential for the establishment of metastasis. Various contemporary and molecular methods using prostate-specific biomarkers have been applied to detect extraprostatic disease that is undetectable by conventional imaging techniques, assessing the risk for disease recurrence after therapy of curative intent. However, the clinical relevance of CTC detection is still controversial. We review current literature regarding molecular methods used for the detection of CTCs in the peripheral blood and bone marrow biopsies of patients with prostate cancer, and we discuss the methodological pitfalls that influence the clinical significance of molecular staging.

Tumor expressed PTHrP facilitates prostate cancer-induced osteoblastic lesions

Expression of parathyroid hormone-related protein (PTHrP) correlates with prostate cancer skeletal progression; however, the impact of prostate cancer-derived PTHrP on the microenvironment and osteoblastic lesions in skeletal metastasis has not been completely elucidated. In this study, PTHrP overexpressing prostate cancer clones were stably established by transfection of full length rat PTHrP cDNA. Expression and secretion of PTHrP were verified by western blotting and IRMA assay. PTHrP overexpressing prostate cancer cells had higher growth rates in vitro, and generated larger tumors when inoculated subcutaneously into athymic mice. The impact of tumor-derived PTHrP on bone was investigated using a vossicle co-implant model. Histology revealed increased bone mass adjacent to PTHrP overexpressing tumor foci, with increased osteoblastogenesis, osteoclastogenesis and angiogenesis. In vitro analysis demonstrated pro-osteoclastic and pro-osteoblastic effects of PTHrP. PTHrP enhanced proliferation of bone marrow stromal cells and early osteoblast differentiation. PTHrP exerted a pro-angiogenic effect indirectly, as it increased angiogenesis but only in the presence of bone marrow stromal cells. These data suggest PTHrP plays a role in tumorigenesis in prostate cancer, and that PTHrP is a key mediator for communication and interactions between prostate cancer and the bone microenvironment. Prostate cancer-derived PTHrP is actively involved in osteoblastic skeletal progression.

Prostate cancer, serum parathyroid hormone, and the progression of skeletal metastases

Bony metastases from prostate cancer are a significant cause of morbidity and mortality. These metastases are predominantly blastic (bone-forming) and commonly cause increased serum levels of parathyroid hormone (PTH) as calcium ions are transferred from serum into blastic bone. The epidemiologic and clinical significance of secondary hyperparathyroidism in advanced prostate cancer have not been widely appreciated. Prostate cancer bony metastases show increased expression of the PTH receptor (PTH-IR) and PTH promotes the growth and invasiveness of prostate cancer cells in bone. Thus, blastic metastases appear to induce a "vicious cycle" in which PTH resorbs normal bone to support the growth of blastic bone. Recognition of the potential role of PTH in the progression of skeletal metastases suggests novel opportunities for prostate cancer secondary prevention. In particular, we propose that suppressing serum PTH in advanced prostate cancer may reduce morbidity by decreasing fractures and pain caused by bone resorption and may reduce mortality by retarding the progression of metastatic disease.

Skeletal metastasis: Established and emerging roles of parathyroid hormone related protein (PTHrP)

Parathyroid hormone related protein (PTHrP) is a well characterized tumor derived product that also has integral functions in normal development and homeostasis. PTHrP is produced by virtually all tumor types that metastasize to bone and numerous studies have demonstrated a correlation between PTHrP expression and skeletal localization of tumors. PTHrP has prominent effects in bone via its interaction with the PTH-1 receptor on osteoblastic cells. Through indirect means, PTHrP supports osteoclastogenesis by upregulating the receptor activator of NFkappaB ligand (RANKL) in osteoblasts. PTHrP also regulates osteoblast proliferation and differentiation in manners that are temporal and dose dependent. Bone turnover has been implicated in the localization of tumors to bone and PTHrP increases bone turnover. Bone turnover results in the release of growth factors such as TGFbeta and minerals such as calcium, both of which impact tumor cell growth and contribute to continued PTHrP production. PTHrP also has anabolic properties and could be in part responsible for osteoblastic type reactions in prostate cancer. Finally, emerging roles of PTH and PTHrP in the support of hematopoietic stem cell development in the bone marrow microenvironment suggest that an interaction between hematopoietic cells and tumor cells warrants further investigation.

Metastatic bone cancer pain: Etiology and treatment options

Painful metastatic bone disease remains a challenge for physicians. The treatment choices available are wide and varied, with each having its appropriate place in the management of painful bone metastases. Radiotherapy remains the mainstay of treatment with or without surgery. Advances in understanding the intricate pathway responsible for pain generation and the addition of agents such as bisphosphonates to the physician's armamentarium further assist in the management of painful bone metastases.

Bone-Directed Treatments for Prostate Cancer

Maintaining bone health in men who have advanced prostate cancer is an important goal of therapy. Low bone mass is prevalent in men who have prostate cancer, and long-term androgen deprivation therapy causes additional significant decreases in bone mineral density. The adverse effects of the disease and current treatment modalities on bone health are further compounded when patients develop bone metastases,which cause clinically significant skeletal morbidity. Treatment with bone-directed therapies, including intravenous bisphosphonates, radio-nuclides, and endothelin-1 antagonists, can provide palliative and therapeutic benefits for patients who have established bone metastases, and treatment with intravenous bisphosphonates may prevent the development of bone metastases.

Natural history and treatment of bone complications in prostate cancer

Bone metastases are highly prevalent in patients with prostate cancer, and they commonly present a therapeutic challenge. The natural history of prostatic bone metastases is characterized by skeletal morbidity, often producing distressing symptoms for individual patients and reducing patient autonomy and mobility. These bone metastases are usually radiologically osteoblastic, but there is also a strong osteolytic component as evidenced by marked increases in bone resorption markers. Malignant bone lesions can reduce the structural integrity of the skeleton, resulting in skeletal complications such as pathologic fracture, spinal cord compression, and severe bone pain, which adversely affect quality of life. Preclinical and clinical studies have provided insight into the pathophysiology of malignant bone disease from prostate cancer and suggest that bone-directed therapies, including radionuclides, endothelin-1 antagonists, and bisphosphonates, may provide both palliative and therapeutic benefits. Clinical investigations with these agents are underway in patients with prostate cancer to gain insight into the pathophysiology of bone metastases and to evaluate the role of bone-specific therapies in treating and preventing bone metastases.

Direct evidence that PTHrP expression promotes prostate cancer progression in bone

Parathyroid hormone-related protein (PTHrP) is an oncoprotein that is expressed in many malignancies as well as normal tissues. At essentially every site of expression, PTHrP regulates cell growth and proliferation. We and other investigators have previously reported that PTHrP is widely expressed by prostate cancer. For this tumor, there are substantial in vitro and correlative data that PTHrP expression regulates the progression of the tumor, especially in bone, but little direct data. We studied the effects of PTHrP expression on prostate cancer behavior directly in a mouse model of human prostate cancer cells that were transfected to express different forms of the polypeptide and then injected intraskeletally. Skeletal progression of the prostate cancer cells was evaluated radiologically and by measurement of serum tumor markers. PTHrP transfection converted a non-invasive cell line into one that progressed in the skeleton: Injection of the PTHrP transfected cells resulted in greater tumor progression in bone when compared to non-transfected cells, and this effect was also influenced by non-amino terminal peptides of PTHrP. Serum measurements of PTHrP, IL-6, IL-8, and calcium reflected tumor burden. Our experiments provide direct in vivo evidence that PTHrP expression results in the skeletal progression of prostate cancer cells.

Targeting multiple signaling pathways as a strategy for managing prostate cancer: multifocal signal modulation therapy

The aberrant behavior of cancer reflects upregulation of certain oncogenic signaling pathways that promote proliferation, inhibit apoptosis, and enable the cancer to spread and evoke angiogenesis. Theoretically, it should be feasible to decrease the activity of these pathways-or increase the activity of pathways that oppose them-with noncytotoxic agents. Since multiple pathways are dysfunctional in most cancers, and cancers accumulate new oncogenic mutations as they progress, the greatest and most durable therapeutic benefit will likely be achieved with combination regimens that address several targets. Thus, a multifocal signal modulation therapy (MSMT) of cancer is proposed. This concept has already been documented by researchers who have shown that certain combinations of signal modulators-of limited utility when administered individually-can achieve dramatic suppression of tumor growth in rodent xenograft models. The present essay attempts to guide development of MSMTs for prostate cancer. Androgen ablation is a signal-modulating measure already in standard use in the management of delocalized prostate cancer. The additional molecular targets considered here include the type 1 insulin-like growth factor receptor, the epidermal growth factor receptor, mammalian target of rapamycin, NF-kappaB, hypoxia-inducible factor-1alpha, hsp90, cyclooxygenase-2, protein kinase A type I, vascular endothelial growth factor, 5-lipoxygenase, 12-lipoxygenase, angiotensin II receptor type 1, bradykinin receptor type 1, c-Src, interleukin-6, ras, MDM2, bcl-2/bclxL, vitamin D receptor, estrogen receptor-beta, and PPAR-. Various nutrients and phytochemicals suspected to have potential utility in prostate cancer prevention and therapy, but whose key molecular targets are still unknown, might reasonably be incorporated into MSMTs for prostate cancer; these include lycopene, selenium, green tea polyphenols, genistein, and silibinin. MSMTs can be developed systematically by testing various combinations of signal-modulating agents, in concentrations that can feasibly be achieved and maintained clinically, on human prostate cancer cell lines; combinations that appear promising can then be tested in xenograft models and, ultimately, in the clinic. Some signal modulators can increase response to cytotoxic drugs by upregulating effectors of apoptosis. When MSMTs fail to raise the spontaneous apoptosis rate sufficiently to achieve tumor stasis or regression, incorporation of appropriate cytotoxic agents into the regimen may improve the clinical outcome.

Calcium-sensing receptor activation stimulates parathyroid hormone-related protein secretion in prostate cancer cells: role of epidermal growth factor receptor transactivation

We have previously reported that high extracellular Ca2+ stimulates parathyroid hormone-related protein (PTHrP) release from human prostate and breast cancer cell lines as well as from H-500 rat Leydig cancer cells, an action mediated by the calcium-sensing receptor (CaR). Activating the CaR leads to phosphorylation of mitogen-activated protein kinases (MAPKs) that participate in PTHrP synthesis and secretion. Because the CaR is a G protein-coupled receptor (GPCR), it is likely to transactivate the epidermal growth factor receptor (EGFR) or the platelet-derived growth factor receptor (PDGFR). In this study, we hypothesized that activation of the CaR transactivates the EGFR or PDGFR, and examined whether transactivation affects PTHrP secretion in PC-3 human prostate cancer cells. Using Western analysis, we observed that an increase in extracellular Ca2+ resulted in delayed activation of extracellular signal-regulated kinase (ERK) in PC-3 cells. Pre-incubation with AG1478 (an EGFR kinase inhibitor) or an EGFR neutralizing antibody inhibited the high Ca2+ -induced phosphorylation of ERK1/2. GM6001, a pan matrix metalloproteinase (MMP) inhibitor, also partially suppressed the ERK activation, but AG1296 (a PDGFR kinase inhibitor) did not. High extracellular Ca2+ stimulates PTHrP release during a 6-h incubation (1.5- to 2.5- and 3- to 4-fold increases in 3.0 and 7.5 mM Ca2+, respectively). When cells were preincubated with AG1478, GM6001, or an antihuman heparin-binding EGF (HB-EGF) antibody, PTHrP secretion was significantly inhibited under basal as well as high Ca2+ conditions, while AG1296 had no effect on PTHrP secretion. Taken together, these findings indicate that activation of the CaR transactivates the EGFR, but not the PDGFR, leading to phosphorylation of ERK1/2 and resultant PTHrP secretion, although CaR-EGFR-ERK might not be the only signaling pathway for PTHrP secretion. This transactivation is most likely mediated by activation of MMP and cleavage of proheparin-binding EGF (proHB-EGF) to HB-EGF.

Cancer metastasis therapeutic targets and drug discovery: emerging small-molecule protein kinase inhibitors

Cancer metastasis is a significant problem and a tremendous challenge to drug discovery relative to identifying key therapeutic targets as well as developing breakthrough medicines. Recent progress in unravelling the complex molecular circuitry of cancer metastasis, including receptors, intracellular proteins and genes, is highlighted. Furthermore, recent advances in drug discovery to provide novel proof-of-concept ligands, in vivo effective lead compounds and promising clinical candidates, are summarised. Such drug discovery efforts illustrate the integration of functional genomics, cell biology, structural biology, drug design, molecular/cellular screening and chemical diversity (e.g., small molecules, peptides/peptidomimetics, natural products, antisense, vaccines and antibodies). Promising therapeutic targets for cancer metastasis have been identified, including Src, focal adhesion kinase, the integrin receptor, the vascular endothelial growth factor receptor, the epidermal growth factor receptor, Her-2/neu, c-Met, Ras/Rac GTPases, Raf kinase, farnesyl diphosphate synthase (i.e., amino-bisphosphonate therapeutic target) and matrix metalloproteases within the context of their implicated functional roles in cancer growth, invasion, angiogenesis and survival at secondary sites. Clinical and preclinical drug discovery is described and emerging small-molecule inhibitors of protein kinases are highlighted.

Clinical approaches to osseous metastases in prostate cancer

BACKGROUND

Prostate cancer is unique among solid tumors in its proclivity to metastasize primarily to bone. Osseous metastases pose a formidable health threat to patients with metastatic disease, putting them at risk for pain, marrow crowding, fracture, and other sequelae. Treatments directed against bone disease have the potential both to palliate pain and to increase survival.

CONCLUSIONS

A number of agents exist that have the potential to palliate the effects of osseous metastases and should be routinely applied in the clinical care of the patient with advanced prostate cancer. These include hormones, bone-seeking radiopharmaceuticals, chemotherapy, and bisphosphonates. Strategies under investigation aim to eradicate bone disease, and not merely palliate symptoms. These approaches combine those listed above with tumor-directed targeting of osseous disease and manipulation of the biology that underlies the cancer's relationship to bone.

The use of zoledronic acid in the management of metastatic bone disease and hypercalcaemia

Zoledronic acid is a potent, third generation, nitrogen-containing bisphosphonate, licensed for the management of skeletal metastases and hypercalcaemia of malignancy, both of which cause considerable morbidity. In the preclinical setting, zoledronic acid has demonstrated superior potency regarding inhibition of osteolysis and reduction of hypercalcaemia as compared with other bisphosphonates. Clinical trials have indicated that zoledronic acid is superior to pamidronate in suppressing osteolysis and in reducing hypercalcaemia of malignancy. Its main mechanism of action is induction of osteoclast apoptosis through inhibition of the mevalonate pathway. Zoledronic acid has also demonstrated direct anti-tumour activity both in vitro and in animal models, suggesting it may be of benefit in preventing the formation of bone metastases. Clinical trials are in progress, assessing the benefit of zoledronic acid in the adjuvant setting in both breast and prostate cancer.

Prognostic value of immunocytochemical determination of parathyroid hormone-related peptide expression in cells of mammary ductal carcinoma. Analysis of 7 years of the disease course

Parathyroid hormone-related peptide (PTHrP) participates in the development of humoral hypercalcaemia of malignancy. The peptide is thought to affect growth and differentiation of normal and neoplastic cells. The present study aimed at evaluation of the relationship between survival time and development of distant metastases in patients with ductal mammary carcinoma on the one hand and PTHrP expression on the other. Immunocytochemical reactions using mouse monoclonal (clone 212-10.7) anti-PTHrP (38-64) antibodies were performed in paraffin sections originating from 47 patients with ductal mammary carcinoma. Expression of the protein was quantified employing a scale, considering the number of positive cells and intensity of the reaction (immunoreactive score, IRS). Survival time of the patients, determined during the course of a 7-year observation was also analysed. The obtained results demonstrated a relationship between intensity of PTHrP expression and the survival time. Patients with high expression of PTHrP (IRS>6) manifested longer survival than patients with lower PTHrP expression (IRS< or =6; Cox'es F test, P<0.05). Moreover, in the group with the lower PTHrP expression, a negative relationship was detected between expression of the protein and the survival time (Cox'es model, P<0.05). No relationship was detected between PTHrP expression and the development of distant metastases.

Prostate carcinoma: defining therapeutic objectives and improving overall outcomes

The development and progression of a prostate carcinoma from prediagnosis to death can be characterized as a series of clinical states. The states are milestones that can be used to assess prognosis, define therapeutic objectives, and assess outcomes. The antitumor effects of hormone therapies and cytotoxic agents in patients with prostate carcinoma are placed in context along with the bidrectional tumor-host interactions that contribute to the growth and resistance of osseous lesions. Identifying the factors that contribute to the growth of the disease at different points in the illness has lead to novel, systemic approaches. Proving the benefit of these approaches requires a series of unique trials with unique endpoints relevant to the clinical state of the patients and the specific therapy under evaluation.

Metastasis to bone: causes, consequences and therapeutic opportunities

The most common human cancers --lung, breast and prostate -- have a great avidity for bone, leading to painful and untreatable consequences. What makes some cancers, but not others, metastasize to bone, and how do they alter its physiology? Some of the molecular mechanisms that are responsible have recently been identified, and provide new molecular targets for drug development.

Role of proteolytic enzymes in human prostate bone metastasis formation: in vivo and in vitro studies

Prostate cancers ability to invade and grow in bone marrow stroma is thought to be due in part to degradative enzymes. The formation of prostate skeletal metastases have been reproduced in vitro by growing co-cultures of prostatic epithelial cells in bone marrow stroma. Expression of urokinase plasminogen activator, matrix metalloproteinase 1 and 7 by prostatic epithelial cells were identified using immunocytochemistry. Also, in vivo tissue sections from human prostatic bone marrow metastases were stained. To establish the role of these enzymes on colony formation, inhibitory antibodies directed against urokinase plasminogen activator, matrix metalloproteinase 1 and matrix metalloproteinase 7 were added into primary prostatic epithelial cells and bone marrow stroma co-cultures. All prostatic epithelial cell cultures stained positively for matrix metalloproteinase 1, matrix metalloproteinase 7 and urokinase plasminogen activator. Generally prostatic epithelial cells derived from malignant tissues showed increased staining in comparison to epithelia derived from non-malignant tissue. In agreement with in vitro co-cultures, the in vivo tissue sections of prostate bone marrow metastases showed positive staining for all three enzymes. Inhibition studies demonstrated that blocking matrix metalloproteinase 1, matrix metalloproteinase 7 and urokinase plasminogen activator function reduced the median epithelial colony area significantly in bone marrow stroma co-cultures in vitro. Using a human ex-vivo model we have shown that matrix metalloproteinase 1, matrix metalloproteinase 7 and urokinase plasminogen activator play an important role in the establishment of prostatic epithelial cells within bone marrow.