Expression of parathyroid hormone-related protein and its receptor in bone metastases from prostate cancer

High Expression of Parathyroid Hormone-related Protein and Tumor Necrosis Factor-α in Cancer Cells as Risk Factors for Hypercalcemia in Bone Metastases Lytic Lesions

BACKGROUND: Cancer mortality is more commonly due to metastases of the tumor to other organs and the complications that accompany it than the tumor growth itself. Until recently, metastasis has been an insurmountable problem. AIM: As the most frequent site of metastases, apart from the lungs and liver, tumor metastases to bone are associated with hypercalcemia which is fatal for the affected patient. METHODS: This study used a case-control study design. The case group consisted of paraffin block samples derived from bone metastatic cancer cell biopsies of patients with hypercalcemic lytic lesions. The control group consisted of paraffin block samples derived from bone metastatic cancer cell biopsies of patients with non-hypercalcemic lytic lesions. Radiological examination was performed to examine the presence of lytic lesions, followed by data collection of serum calcium levels. The data obtained from the histopathological examination was confirmed along with the availability of paraffin blocks of bone metastasis cancer cell biopsy samples, and immunohistochemical analysis was performed to determine the expression of tumor necrosis factor-α _(TNF-α) and parathyroid hormone-related protein (PTHrP). A Mann–Whitney test was performed to determine the expression of TNF-α _and PTHrP between hypercalcemia and non-hypercalcemia groups. To identify the cut-off point, Youden index on receiver operating characteristic was used, then the optimal cut-off point was determined where the sensitivity and specificity curves intersect. Analysis of risk factor assessment was done by creating a 2 × 2 cross-tabulations and calculating the association size in the form of odds ratio (OR). RESULTS: The expression of PTHrP and TNF-α _in the case group was significantly different from the control group with p < 0.05. The cut-off point for PTHrP expression was 267.5 with an area under the curve of 0.93, indicating a high accuracy value. The cut-off point for TNF-α _expression was 227.5 with an area under the curve of 0.68, indicating a moderate accuracy value. The OR between hypercalcemia and non-hypercalcemia to PTHrP expression was 110.3 (Fisher’s exact statistical test obtained p < 0.05), while the OR between hypercalcemia and non-hypercalcemia to TNF-α _expression was 7.27 (Fisher’s exact test statistical obtained p = 0.01). CONCLUSION: Significant differences in the expression of PTHrP and TNF-α _were found between patients with bone metastases lytic lesions with hypercalcemia compared to those without hypercalcemia. We can conclude that either a high level of PTHrP expression and/or TNF-α _expression in cancer cells can serve as risk factors for hypercalcemia in patients with bone metastatic lytic lesions.

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.

Intermittent Administration of Parathyroid Hormone Enhances Odonto/Osteogenic Differentiation of Stem Cells from the Apical Papilla via JNK and P38 MAPK Pathways

Objective

Parathyroid hormone (PTH) is considered to be essential during the tooth development. Stem cells from the apical papilla (SCAPs) are responsible for dentine formation. However, the interaction between PTH and SCAPs remains unclear. This study was aimed at investigating the effects of PTH on odonto/osteogenic differentiation capacity of SCAPs and elucidating the underlying molecular mechanisms. Materials and Methods. Here, SCAPs were isolated and identified in vitro. Effects of PTH on the proliferation of SCAPs were determined by Cell Counting Kit-8 (CCK-8), flow cytometry (FCM), and EdU. Alkaline phosphatase (ALP) activity, alizarin red staining, Western blot, and RT-PCR were carried out to detect the odonto/osteogenic differentiation of PTH-treated SCAPs as well as the participation of the MAPK signaling pathway.

Results

An ALP activity assay determined that 10^-8 mol/L PTH was the optimal concentration for the induction of SCAPs with no significant influence on the proliferation of SCAPs as indicated by CCK-8, FCM, and EdU. The expression of odonto/osteogenic markers was significantly upregulated in mRNA levels and protein levels. Moreover, intermittent treatment of PTH also increased phosphorylation of JNK and P38, and the differentiation was suppressed following the inhibition of JNK and P38 MAPK pathways.

Conclusion

PTH can regulate the odonto/osteogenic differentiation of SCAPs via JNK and P38 MAPK pathways.

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.

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.

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.

The osteoblastic and osteoclastic interactions in spinal metastases secondary to prostate cancer

Prostate cancer (PC) is one of the most common cancers arising in men and has a high propensity for bone metastasis, particularly to the spine. At this stage, it often causes severe morbidity due to pathological fracture and/or metastatic epidural spinal cord compression which, if untreated, inevitably leads to intractable pain, neurological deficit, and paralysis. Unfortunately, the underlying molecular mechanisms driving growth of secondary PC in the bony vertebral column remain largely unknown. Further investigation is warranted in order to identify therapeutic targets in the future. This review summarizes the current understanding of PC bone metastasis in the spine, highlighting interactions between key tumor and bone-derived factors which influence tumor progression, especially the functional roles of osteoblasts and osteoclasts in the bone microenvironment through their interactions with metastatic PC cells and the critical pathway RANK/RANKL/OPG in bone destruction.

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.

Nuclear localization of parathyroid hormone-related peptide confers resistance to anoikis in prostate cancer cells

Prostate cancer remains a leading cause of cancer-related death in men, largely attributable to distant metastases, most frequently to bones. Despite intensive investigations, molecular mechanisms underlying metastasis are not completely understood. Among prostate cancer-derived factors, parathyroid hormone-related peptide (PTHrP), first discovered as an etiologic factor for malignancy-induced hypercalcemia, regulates many cellular functions critical to tumor growth, angiogenesis, and metastasis. In this study, the role of PTHrP in tumor cell survival from detachment-induced apoptosis (i.e. anoikis) was investigated. Reduction of PTHLH (encoding PTHrP) gene expression in human prostate cancer cells (PC-3) increased the percentage of apoptotic cells when cultured in suspension. Conversely, overexpression of PTHrP protected prostate cancer cells (Ace-1 and LNCaP, both typically expressing low or undetectable basal PTHrP) from anoikis. Overexpression of nuclear localization signal (NLS)-defective PTHrP failed to protect cells from anoikis, suggesting that PTHrP-dependent protection from anoikis is an intracrine event. A PCR-based apoptosis-related gene array showed that detachment increased expression of the TNF gene (encoding the proapoptotic protein tumor necrosis factor-α) fourfold greater in PTHrP-knockdown PC-3 cells than in control PC-3 cells. In parallel, TNF gene expression was significantly reduced in PTHrP-overexpressing LNCaP cells, but not in NLS-defective PTHrP overexpressing LNCaP cells, when compared with control LNCaP cells. Subsequently, in a prostate cancer skeletal metastasis mouse model, PTHrP-knockdown PC-3 cells resulted in significantly fewer metastatic lesions compared to control PC-3 cells, suggesting that PTHrP mediated antianoikis events in the bloodstream. In conclusion, nuclear localization of PTHrP confers prostate cancer cell resistance to anoikis, potentially contributing to prostate cancer metastasis.

Immunohistochemical identification of the PTHR1 parathyroid hormone receptor in normal and neoplastic human tissues

BACKGROUND

Parathyroid hormone (PTH) is a crucial regulator of calcium homoeostasis in humans. Although it is well known that PTH acts primarily on kidney and bone, the precise cellular and subcellular sites of PTH action have not been visualised in human tissues.

METHOD

We developed and characterised a novel anti-peptide antibody to the carboxy-terminal region of the human PTH receptor type 1 (PTHR1). Specificity of the antiserum was demonstrated by i) detection of a broad band migrating at M(r) 85,000-95,000 in western blots of membranes from human kidney and PTHR1-transfected cells; ii) cell surface staining of PTHR1-transfected cells; iii) translocation of PTHR1 receptor immunostaining after agonist exposure; and iv) abolition of tissue immunostaining by preadsorption of the antibody with its immunising peptide. The distribution of PTHR1 receptors was investigated in 320 human tumours and their tissues of origin.

RESULTS

In the kidney, PTHR1 receptors were predominantly detected at the basolateral plasma membrane of epithelial cells in the proximal and distal tubules but not in the thin limbs of Henle, collecting ducts or glomeruli. In bone, PTHR1 receptors were detected as discrete plasma membrane staining of osteocytes and osteoblasts, whereas osteoclasts remained unstained. In addition, PTHR1 was found in the gut and in a number of neoplastic tissues including colorectal carcinoma, prostate cancer, renal cell carcinoma and osteosarcoma.

CONCLUSION

This is the first localisation of PTHR1 receptors in human tissues at the cellular level. The overexpression of PTHR1 receptors may provide a molecular basis for efficient targeting of human tumours with radiolabelled PTH analogues.

Parathyroid hormone-related peptide and parathyroid hormone-related peptide receptor type 1 expression in human lung adenocarcinoma

BACKGROUND

In many primary tumors, parathyroid hormone-related peptide (PTHrP) and PTHrP type 1 receptor (PTH1R) are coexpressed, supporting the possibility that PTHrP/PTH1R system can mediate important signals for tumor progression through paracrine/autocrine mechanisms. In non-small cell lung carcinoma the clinical relevance of the expression of PTH1R remains to be investigated.

METHODS

Fifty-four lung adenocarcinomas of mixed histologic type from patients with stage I and II cancer were assayed by quantitative immunohistochemistry for the expression of PTHrP and PTH1R.

RESULTS

PTHrP and PTH1R were expressed in a wide range of intensity in the cytoplasm of tumor cells, and their values showed a positive correlation. PTH1R, but not PTHrP, was expressed by plasma cells infiltrating the tumor stroma. PTHrP and PTH1R were not associated with age, tumor diameter, or histopathologic grading, whereas they were directly associated with lymph node involvement at presentation. Cox regression analysis, using PTHrP and PTH1R as continuous covariates, showed that the covariate levels were directly associated with the risk of death and metastasis. Patients whose tumors coexpressed high levels of PTHrP and PTH1R showed the highest risk of metastasis (relative risk, 5.89; 95% CI, 2.1-16.6; P = .0003) and death (relative risk, 6.24; 95% CI, 1.6-23.9; P = .0033). The presence of PTH1R-positive plasma cells in the tumor stroma was associated with a more favorable survival rate independently from the PTHrP status of the tumor.

CONCLUSION

The paracrine/autocrine signaling through PTHrP/PTH1R could be important in early-stage lung adenocarcinoma progression.

The neuroendocrine-derived peptide parathyroid hormone-related protein promotes prostate cancer cell growth by stabilizing the androgen receptor

During progression to an androgen-independent state following androgen ablation therapy, prostate cancer cells continue to express the androgen receptor (AR) and androgen-regulated genes, indicating that AR is critical for the proliferation of hormone-refractory prostate cancer cells. Multiple mechanisms have been proposed for the development of AR-dependent hormone-refractory disease, including changes in expression of AR coregulatory proteins, AR mutation, growth factor-mediated activation of AR, and AR protein up-regulation. The most prominent of these progressive changes is the up-regulation of AR that occurs in >90% of prostate cancers. A common feature of the most aggressive hormone-refractory prostate cancers is the accumulation of cells with neuroendocrine characteristics that produce paracrine factors and may provide a novel mechanism for the regulation of AR during advanced stages of the disease. In this study, we show that neuroendocrine-derived parathyroid hormone-related protein (PTHrP)-mediated signaling through the epidermal growth factor receptor (EGFR) and Src pathways contributes to the phenotype of advanced prostate cancer by reducing AR protein turnover. PTHrP-induced accumulation of AR depended on the activity of Src and EGFR and consequent phosphorylation of the AR on Tyr(534). PTHrP-induced tyrosine phosphorylation of AR resulted in reduced AR ubiquitination and interaction with the ubiquitin ligase COOH terminus of Hsp70-interacting protein. These events result in increased accumulation of AR and thus enhanced growth of prostate cancer cells at low levels of androgen.

Phytoestrogen modulation of bone-related cytokines and its impact on cell viability in human prostate cancer cells

AIMS

Prostate cancer (PCa) has a high propensity to metastasize to the bone. PCa cells produce several bone-related factors, namely parathyroid hormone related protein (PTHrP), its PTH type 1 receptor (PTH1R), osteoprotegerin (OPG), and receptor activator of NF-kappa B ligand (RANKL). The effects of these factors might explain, at least in part, the ability of PCa cells to grow in and interact with bone.

MAIN METHODS

We first analyzed the expression of the aforementioned factors (by western blot and flow cytometry), and their modulation by the phytoestrogens genistein and daidzein (as potential anti-tumoral agents), in human PCa cells in vitro. We also assessed the impact of these osteomimetic factors on PCa cell viability (by propidium iodide staining and flow cytometry, and trypan blue staining).

KEY FINDINGS

Genistein and daidzein, at nM range, increased both the PTHrP/PTH1R system and the OPG/RANKL protein ratio, while genistein and, to a lesser extent, daidzein, at >microM doses, inhibited cell viability in PCa cells. Both N- and C-terminal domains of PTHrP inhibited genistein-induced cell death by modulating transcription factor Runx-2 and the Bcl-2/Bax protein ratio in PCa cells.

SIGNIFICANCE

Our findings indicate that high doses of genistein and daidzein cause PCa cell death. On the other hand, low doses of these phytoestrogens induce some osteomimetic features in PCa cells with putative impact on PCa development.

Osteotropic cancers: from primary tumor to bone

It has long been recognized that primary cancers spread to distant organs with characteristic preference. Bone metastases occur in approximately 70% of patients with advanced breast and prostate cancer, causing severe morbidity and hospitalization. In the last decade, we have gained a better understanding of the mechanisms by which certain tumor types tend to metastasize specifically to bone. It appears that the interaction between the organ microenvironment and cancer cells is fundamental for establishing metastatic growth. Accordingly, Stephen Paget's 'seed and soil' hypothesis - stating that circulating cancer cells (the 'seeds') disperse in all directions, but can accomplish metastases only in organs where the microenvironment (the 'soil') is permissive for their growth - still holds forth today. For this reason, this review uses the 'seed and soil' hypothesis as a template to discuss novel insight and developments in the bone metastasis field.

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.

Immunohistochemical analysis of low-grade and high-grade prostate carcinoma: relative changes of parathyroid hormone-related protein and its parathyroid hormone 1 receptor, osteoprotegerin and receptor activator of nuclear factor-kB ligand

AIM

To investigate multiple bone cytokines produced by prostate carcinoma (PCa) as a novel strategy to differentiate potential aggressiveness in localised PCa using immunohistochemical analysis.

METHODS

A total of 47 cases of PCa undergoing radical prostatectomy or transurethral prostatic resection at our institution (Fundación Jiménez Díaz (Grupo Capio), Madrid, Spain) between January 1991 and June 1998 were identified as low-grade (< or =4; n = 22) or high-grade (> or =7, excluding 7 (3+4) cases; n = 25) PCa according to Gleason grade. PCa specimens were immunostained for: parathyroid hormone (PTH)-related protein (PTHrP), the PTH1 receptor, osteoprotegerin and receptor activator of nuclear factor-kappa B ligand (RANKL), as well as Ki67 (a proliferation marker) and CD34 (an angiogenesis marker).

RESULTS

PCa samples showed an increased immunostaining for both osteoprotegerin and RANKL, associated with tumour grade and PTHrP positivity, in the tumoral epithelium. Using a score value of 4-corresponding to moderate staining - as cut-off, the best sensitivity value was for PTHrP (with C-terminal antiserum C6; 100 %); wheras the best specificity value was for RANKL (95 %).

CONCLUSIONS

All the evaluated factors are overexpressed mainly in the high-grade tumours. Our findings indicate that, in most patients with PCa (with Ki67 values between 1% and 9%), sequential determination of C-terminal PTHrP and RANKL immunoreactivities is a useful approach to discriminate low-grade and high-grade tumours.

Epidermal growth factor receptor expression and activation in neuroendocrine tumours

Epidermal growth factor receptor (EGFR) is expressed in many cancers and is associated with poor prognosis. EGFR activation pathways have been well characterised using tumour cell lines and are known to involve EGFR activation through autophosphorylation. Phosphorylation of downstream signalling molecules, such as ERK1/2 (extra-cellular regulated kinase 1 and 2) and PKB/Akt (protein kinase B), leads to enhanced tumour cell survival and proliferation. Although EGFR expression has been determined in neuroendocrine tumour tissue, its activation and subsequent effects on the downstream signalling molecules, ERK1/2 and Akt, have not been studied. We therefore planned to determine the role of EGFR in neuroendocrine tumours (NETs) by determining its pattern of expression and activation, and the subsequent activation of downstream signalling molecules ERK1/2 and Akt. Paraffin-embedded tumour tissue was available from 98 patients with NETs (39 foregut, 42 midgut, four hindgut, five paragangliomas, and four of unknown origin). Immunohistochemical evaluation was performed for the expression of EGFR, p-EGFR, p-Akt, and p-ERK1/2. Ninety-six percent of tumour samples were positive for EGFR expression; 63% were positive for activated EGFR; 76% were positive for activated Akt; and 96% were positive for activated ERK1/2. Importantly, the histological score for the activation of Akt and ERK1/2 correlated with the histological score for activated EGFR. These data provide a rationale for considering EGFR inhibitors in the treatment of NETs. Additionally, direct inhibition of Akt and ERK1/2 may provide further therapeutic options in the treatment of NETs in the future.

Differential expression of G-protein coupled receptor 56 in human esophageal squamous cell carcinoma

Herein, we describe the identification of GPCR56, an orphan G-protein coupled receptor, to be differentially expressed in esophageal squamous cell carcinoma. Although, GPCRs have been demonstrated to be altered in various human cancers, much is still unknown about GPCR56 expression in tumors. To evaluate the expression of these genes in esophageal tissues, we performed semi-quantitative Reverse-Transcription Polymerase Chain Reaction in ESCCs, dysplasia and matched normal esophageal epithelium. Increased transcript levels of GPCR56 were detected in 48% of ESCCs, while the adjacent non-malignant esophageal tissue did not show the expression of this transcript. Interestingly, most of the dysplastic tissues analyzed also exhibited increased expression of GPCR56 suggesting that alteration in GPCR56 expression is an early event in esophageal tumorigenesis. In depth analysis of GPCR56 in different stages of development and progression of esophageal tumorigenesis is warranted to explore its utility as potential early diagnostic marker and its function in esophageal cancer.

Prostate secretory protein of 94 amino acids (PSP-94) and its peptide (PCK3145) as potential therapeutic modalities for prostate cancer

This review focuses on the promising roles of prostate secretory protein of 94 amino acids (PSP-94) and one of its derived peptides (PCK3145) as potential therapeutic modalities for prostate cancer and its associated complications. Evaluation of these compounds was carried out in vitro and in vivo using syngeneic models of rat prostate cancer. Overproduction of parathyroid hormone-related protein (PTHrP) results in the development of hypercalcemia of malignancy in several malignancies including prostate cancer. In order to evaluate the effect of PSP-94 and PCK3145 on prostate cancer progression, the rat Dunning R3227 MatLyLu cell line transfected with full-length cDNA encoding PTHrP (MatLyLu-PTHrP) was used. As the main pathogenetic factor of hypercalcemia of malignancy, overexpression of PTHrP was aimed at mimicking the hypercalcemic nature seen in patients suffering from late-stage cancer. In vitro studies showed that PSP-94 and PCK3145 can cause a dose-dependent inhibition in the growth of MatLyLu-PTHrP cells. For in vivo studies, male Copenhagen rats were inoculated either s.c. into the right flank or directly into the left ventricle via intracardiac (i.c.) inoculation with MatLyLu-PTHrP cells. In these models, s.c. injection of MatLyLu cells results in the development of primary tumor growth, whereas i.c. inoculation routinely results in the development of experimental skeletal metastases in the lumbar vertebrae causing hind-limb paralysis. Administration of PSP-94 and PCK3145 into tumor-bearing animals resulted in a dose-dependent inhibition of primary tumor growth, and tumoral and plasma PTHrP levels, and in the reduction of plasma calcium levels. Additionally, treatment with PSP-94 or PCK3145 caused an inhibition of skeletal metastases resulting in a significant delay in the development of hind-limb paralysis. Interestingly, equimolar concentrations of PCK3145 were shown to be more effective in delaying the development of experimental skeletal metastases as compared to PSP-94. One of the possible mechanisms of action of these modalities is through the induction of apoptosis which was observed by both in-vitro and in-vivo analyses of MatLyLu-PTHrP cells and tumors. Several intracellular mechanisms can also be involved in inhibiting PTHrP production and anti-tumor effects of PSP-94 and PCK3145. Collectively, these studies warrant the continued clinical development of these agents as therapeutic agents for patients with hormone-refractory prostate cancer.

Bone neoplasms in F344 rats given teriparatide [rhPTH(1-34)] are dependent on duration of treatment and dose

A long-term study was conducted in female F344 rats to determine the relative importance of dose, treatment duration, and age at initiation of treatment on the incidence of teriparatide [rhPTH[1-34)]-induced bone proliferative lesions. Treatment groups consisted of different combinations of dose (0, 5, or 30 microg/kg/d), treatment duration (6, 20, or 24 months) and age at initiation of treatment (2 or 6 months of age). The primary endpoints were the incidence of bone neoplasms and effects on bone mass and structure as evaluated by quantitative computed tomography and histomorphometery. Significant increases in the incidence of bone tumors (osteoma, osteoblastoma, and osteosarcoma) occurred in rats treated with 30 microg/kg for 20 or 24 months. No neoplasms were found when the 5 microg/kg treatment was initiated at 6 months of age and continued for either 6 or 20 months (up to 70% of life span). This treatment regimen defined a "no-effect" dose for neoplasm formation that nevertheless resulted in substantial increases in bone mass. These results demonstrate that treatment duration and administered dose are the most important factors in the teriparatide-induced bone tumors in rats.

A synthetic 15-mer peptide (PCK3145) derived from prostate secretory protein can reduce tumor growth, experimental skeletal metastases, and malignancy-associated hypercalcemia

In previous studies, we have shown that prostate secretory protein (PSP-94) can reduce prostate cancer growth in vivo. In the current study, we identified the amino acid sequence of PSP-94 that is required for eliciting this response. For these studies, we used rat prostate cancer Mat Ly Lu cells overexpressing parathyroid hormone-related protein (PTHrP), which is the main pathogenetic factor responsible for hypercalcemia of malignancy. Synthetic peptides corresponding to amino acids 7-21 (PCK721), 31-45 (PCK3145), and 76-94 (PCK7694) of PSP-94 were synthesized. Only PCK3145 showed a significant reduction in tumor cell proliferation. For in vivo studies, syngenic male Copenhagen rats were inoculated s.c. with Mat Ly Lu cells overexpressing PTHrP into the right flank or into the left ventricle via intracardiac injection, which results in experimental metastases to the lumbar vertebrae causing hind-limb paralysis. Animals were infused with different doses (1, 10, and 100 microg/kg/day) of peptides for 15 days, and the effect of these treatments on tumor volume, skeletal metastases, or development of hind-limb paralysis was determined. Treatment with PCK3145 resulted in a dose-dependent decrease in tumor volume and delay in the development of skeletal metastases. Bone histomorphometry showed that after intracardiac inoculation of tumor cells, the highest dose of PCK3145 (100 microg/kg/day) resulted in reducing skeletal tumor burden, which delayed the development of hind-limb paralysis. Treatment with PCK3145 led to reduction of plasma calcium and PTHrP levels and a significant decrease in PTHrP levels in the primary tumors and in vertebrae of experimental animals. These effects of PCK3145 were due to its ability to promote tumor cell apoptosis. Collectively, the results of these studies have demonstrated the ability of a small peptide derived from PSP-94 to reduce tumor volume and experimental skeletal metastases-results that will be highly beneficial in the continued development of this peptide as a novel therapeutic agent for patients with hormone refractory, late-stage prostate cancer.

Parathyroid hormone-related peptide: expression in prostate cancer bone metastases

Parathyroid hormone-related peptide (PTHrP) is a regulatory protein associated with cell growth in non-osseous tissues and with osteoclast stimulation in bone. It has been implicated in the pathogenesis of bone metastases, particularly in breast carcinoma. PTHrP is widely expressed in primary prostate cancers, but there are few reports of its expression in prostatic metastases. The aim of this study was to examine the expression of PTHrP in bone metastases from patients with untreated adenocarcinoma of the prostate. Ten bone biopsies containing metastatic deposits of untreated prostatic cancer were identified. These were immunohistochemically stained for PTHrP using a murine monoclonal antibody (PTHLP[Ab1]) and the streptavidin-biotin complex technique. Intensity of staining for PTHrP was graded by two observers. In total, PTHrP expression was positive in 5/10 specimens. This was graded as moderate in four and weak in one. In those specimens with positive staining, the expression varied between cells. There was no obvious association between expression of PTHrP and tumour differentiation. PTHrP is expressed in prostatic bone metastases and may have a role in their pathogenesis and pathophysiology. However, expression is not universal.

A moderately low phosphate intake may provide health benefits analogous to those conferred by UV light - a further advantage of vegan diets

Although exposure to ultraviolet light is often viewed as pathogenic owing to its role in the genesis of skin cancer and skin aging, there is growing epidemiological evidence that such exposure may decrease risk for a number of more serious cancers, may have a favorable impact on blood pressure and vascular health, and may help to prevent certain autoimmune disorders - in addition to its well-known influence on bone density. Most likely, these health benefits are reflective of improved vitamin D status. Increased synthesis or intake of vitamin D can be expected to down-regulate parathyroid hormone (PTH), and to increase autocrine synthesis of its active metabolite calcitriol in certain tissues; these effects, in turn, may impact cancer risk, vascular health, immune regulation, and bone density through a variety of mechanisms. Presumably, a truly adequate supplemental intake of vitamin D - manyfold higher than the grossly inadequate current RDA - could replicate the benefits of optimal UV exposure, without however damaging the skin. Diets moderately low in bioavailable phosphate - like many vegan diets - might be expected to have a complementary impact on disease risks, inasmuch as serum phosphate suppresses renal calcitriol synthesis while up-regulating that of PTH. A proviso is that the impact of dietary phosphorus on bone health is more equivocal than that of vitamin D. Increased intakes of calcium, on the other hand, down-regulate the production of both PTH and calcitriol - the latter effect may explain why the impact of dietary calcium on cancer risk (excepting colon cancer), hypertension, and autoimmunity is not clearly positive. An overview suggests that a vegan diet supplemented with high-dose vitamin D should increase both systemic and autocrine calcitriol production while suppressing PTH secretion, and thus should represent a highly effective way to achieve the wide-ranging health protection conferred by optimal UV exposure.

Assessment and management of patients with abnormal calcium

Calcium is essential for homeostasis, and normocalcemia should be maintained strictly during the perioperative period. The biochemistry of calcium equilibrium results from the calcium-sensing receptors on the parathyroid glands, which detect changes in calcium concentrations and initiate the proper response. Asymptomatic hypercalcemia is a common metabolic derangement that is often discovered on routine serum screening. The most common etiologies are primary hyperparathyroidism and cancer. Increasingly, parathyroidectomy is the preferred therapy for primary hyperparathyroidism. Severe hypercalcemia ("hypercalcemic crisis") should be managed aggressively with a combination of intravenous fluids, steroids, bisphosphonates, and calcitonin. Some of these patients may require an urgent parathyroidectomy for calcium control. Hypocalcemia needs to be verified, as many cases of hypocalcemia are the artifact of hypoalbuminemia. Severe hypocalcemia occurs after subtotal or total parathyroidectomy with auto transplantation as well as after massive resuscitation or blood transfusion. Strategies aimed at correcting calcium concentrations depend on the severity of symptomatology. If symptoms are mild, oral calcium supplementation can be given; otherwise, intravenous calcium should be administered.

Pulmonary adenocarcinoma with osteoblastic bone metastases in a cat

A 12-year-old male cat with depression and dyspnoea was presented for investigation. Radiography and computed tomography revealed hydrothorax and solid masses involving the sternum, ribs and thoracic vertebrae. The cat died two days after first presentation, and postmortem examination revealed lung masses and proliferative bony lesions. Histologically, a neoplastic proliferation of epithelial cells was seen in the lungs, with a large amount of collagen and deposits of cholesterin. The bone lesions were also composed of neoplastic epithelial cells and abundant calcified osteoid, without atypia. A diagnosis of pulmonary adenocarcinoma with osteoblastic bone metastases was made. This is the first reported case of osteoblastic metastases in the cat.

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.

New bone formation in nude mouse calvaria induced by canine prostate tissue

Osteoblastic metastases are common in patients with advanced prostate cancer. The pathophysiology of the new bone formation at metastatic sites is not currently known, but it is hypothesized that growth factors secreted by the prostate may be involved. Unfortunately, most rodent models of prostate cancer with metastasis to bone are osteolytic and not osteoblastic. Significant osteolysis by tumor cells at metastatic sites also may lead to fractures or bone instability. Misinterpretation of new periosteal bone due to bone instability as tumor-cell osteo-induction is another disadvantage of the osteolytic models. To circumvent these problems, we have developed a model system of new bone formation in the calvaria of nude mice stimulated by normal canine prostate tissue. Collagenase-digested normal prostate tissue was implanted adjacent to the calvaria of nude mice. Calvaria were examined at 2 weeks post-implantation for changes in the bone microenvironment by histology, calcein uptake at sites of bone mineralization, and tartrate-resistant acid phosphatase staining for osteoclasts. The prostate tissue remained viable and induced abundant new woven bone formation on the adjacent periosteal surface. In some cases new bone formation also was induced on the distant or concave calvarial periosteum. The new bone stained intensely with calcein, which demonstrated mineralization of the bone matrix. The new bone formation on prostate-implanted calvaria significantly increased (1.7-fold) the thickness of the calvaria compared with control calvaria. New bone formation was not induced in calvaria of mice implanted with normal canine kidney, urinary bladder, spleen, or skeletal muscle tissue, or mice with surgically-induced disruption of the periosteum. Osteoclast numbers in the medullary spaces and periosteum of calvaria were mildly increased (61%) in mice with implanted prostate tissue. In conclusion, this animal model will be useful for investigating the roles of prostate-derived growth factors on new bone formation in vivo.

Transforming growth factor-beta stimulates parathyroid hormone-related protein and osteolytic metastases via Smad and mitogen-activated protein kinase signaling pathways

Transforming growth factor (TGF)-beta promotes breast cancer metastasis to bone. To determine whether the osteolytic factor parathyroid hormone-related protein (PTHrP) is the primary mediator of the tumor response to TGF-beta, mice were inoculated with MDA-MB-231 breast cancer cells expressing a constitutively active TGF-beta type I receptor. Treatment of the mice with a PTHrP-neutralizing antibody greatly decreased osteolytic bone metastases. There were fewer osteoclasts and significantly decreased tumor area in the antibody-treated mice. TGF-beta can signal through both Smad and mitogen-activated protein (MAP) kinase pathways. Stable transfection of wild-type Smad2, Smad3, or Smad4 increased TGF-beta-stimulated PTHrP secretion, whereas dominant-negative Smad2, Smad3, or Smad4 only partially reduced TGF-beta-stimulated PTHrP secretion. When the cells were treated with a variety of protein kinases inhibitors, only specific inhibitors of the p38 MAP kinase pathway significantly reduced both basal and TGF-beta-stimulated PTHrP production. The combination of Smad dominant-negative blockade and p38 MAP kinase inhibition resulted in complete inhibition of TGF-beta-stimulated PTHrP production. Furthermore, TGF-beta treatment of MDA-MB-231 cells resulted in a rapid phosphorylation of p38 MAP kinase. Thus, the p38 MAP kinase pathway appears to be a major component of Smad-independent signaling by TGF-beta and may provide a new molecular target for anti-osteolytic therapy.

Nerve growth factor expression and innervation of the painful intervertebral disc

Following a previous description of nociceptive nerve fibre growth into usually aneural inner parts of painful intervertebral disc (IVD), this study has investigated whether nociceptive nerve ingrowth into painful IVD is stimulated by local production of neurotrophins. Immunohistochemistry and in situ hybridization have been used to investigate expression of the candidate neurotrophin, nerve growth factor (NGF), and its high- and low-affinity receptors trk-A and p75, respectively, in painful IVD excised for the management of low back pain. IVD from patients with back pain were of two types: those that when examined by discography reproduced the patient symptoms (pain level IVD) and those that did not (non-pain level IVD). Microvascular blood vessels accompanied nerve fibres growing into pain level IVD and these expressed NGF. The adjacent nerves expressed the high-affinity NGF receptor trk-A. These vessels entered the normally avascular IVD through the discal end plates. NGF expression was not identified in non-pain level or control IVD. Some non-pain level IVD had vessels within them, which entered through the annulus fibrosus. These did not express NGF nor did nerves accompany them. These findings show that nociceptive nerve ingrowth into painful IVD is causally linked with NGF production by blood vessels growing into the IVD, from adjacent vertebral bodies.

Co-expression of parathyroid hormone-related protein (PTHrP) and PTH/PTHrP receptor in cartilaginous tumours: a marker for malignancy?

AIM

Parathyroid hormone-related protein (PTHrP) is one of the critical factors for the differentiation and growth of chondrocytes. We examined the correlation between the co-expression of PTHrP and PTH/PTHrP receptor and the grade of malignancy in cartilaginous tumours.

METHODS

We analysed PTHrP and PTH/PTHrP receptor expression in chondrosarcoma by immunohistochemistry and compared specific staining with the expression in benign cartilaginous tumours. There were 38 cartilaginous bone tumours consisting of 26 chondrosarcoma, six enchondroma and six osteochondroma. Chondrosarcoma were composed of 20 conventional chondrosarcoma (10 grade 1, seven grade 2, and three grade 3), two dedifferentiated chondrosarcoma, two clear cell chondrosarcoma, and two myxoid chondrosarcoma. We performed the standard peroxidase-labelled streptavidin-biotin detection method for immunohistochemistry using an antibody raised against PTHrP (1-14) and PTH/PTHrP receptor. The magnitude of receptor positivity of PTHrP and PTH/ PTHrP in each tumour was assessed as a percentage of PTHrP and PTH/PTHrP-positive cells per thousand tumour cells in the most histologically aggressive area of the tumour.

RESULTS

All chondrosarcoma, five of six enchondroma, and four of six osteochondroma showed PTHrP-positive cells, and all chondrosarcoma, five of six enchondroma and five of six osteochondroma showed PTHrP receptor-positive cells. The grade of malignancy correlated with the percentage of both PTHrP and PTH/PTHrP receptor-positive tumour cells (P < 0.0001, either). Each grade of chondrosarcoma showed statistically higher expression of both PTHrP and PTH/PTHrP receptor than benign cartilaginous tumour.

CONCLUSION

This is the first report of the co-expression of PTHrP and PTH/PTHrP receptor in chondrosarcoma. PTHrP and PTH/PTHrP receptor positivity may be valuable for differentiating between benign and malignant cartilaginous tumours.

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

Parathyroid hormone-related peptide is a regulatory protein implicated in the pathogenesis of bone metastases, particularly in breast carcinoma. Parathyroid hormone-related peptide is widely expressed in primary prostate cancers but there are few reports of its expression in prostatic metastases. The aim of this study was to examine the expression of parathyroid hormone-related peptide and its receptor in matched primary and in bone metastatic tissue from patients with untreated adenocarcinoma of the prostate. Eight-millimetre trephine iliac crest bone biopsies containing metastatic prostate cancer were obtained from 14 patients from whom matched primary tumour tissue was also available. Histological grading was performed by an independent pathologist. The cellular location of mRNA for parathyroid hormone-related peptide and parathyroid hormone-related peptide receptor was identified using in situ hybridization with (35)S-labelled probe. Expression of parathyroid hormone-related peptide and its receptor was described as uniform, heterogenous or negative within the tumour cell population. Parathyroid hormone-related peptide expression was positive in 13 out of 14 primary tumours and in all 14 metastases. Receptor expression was evident in all 14 primaries and 12 out of 14 metastases. Co-expression of parathyroid hormone-related peptide and parathyroid hormone-related peptide receptor was common (13 primary tumours, 12 metastases). The co-expression of parathyroid hormone-related peptide and its receptor suggest that autocrine parathyroid hormone-related peptide mediated stimulation may be a mechanism of escape from normal growth regulatory pathways. The high frequency of parathyroid hormone-related peptide expression in metastases is consistent with a role in the pathogenesis of bone metastases.

Mechanisms governing bone metastasis in prostate cancer

Why does prostate cancer metastasize to bone? Why is there increased turnover of the bone matrix in the presence of prostate cancer? A recent autopsy study supports a traditional hypothesis that gross, anatomic patterns of blood flow influence the distribution of metastatic deposits. On the other hand, recent developments in animal models of prostate cancer bone metastasis have renewed interest in the traditional 'seed and soil' hypothesis: several studies point to specific biological interactions between prostate cancer cells and the bone microenvironment that can explain the tendency of prostate cancer cells to colonize bone and grow into clinically relevant metastatic deposits. Some studies implicate mechanisms including chemoattraction and enhanced adherence to bone endothelium. Additional data suggest that prostate cancer cells are 'osteomimetic', that is, they take on the properties and behaviors of osteoblasts or osteoclasts upon arrival in bone. These activities lead to enhanced turnover of the bone matrix and may explain the propensity of prostate cancer to grow in bone. Finally, a series of studies have implicated other molecular markers as distinguishing characteristics of bone-metastatic prostate cancer tissue.