Parathyroid hormone related peptide can function as an autocrine growth factor in human renal cell carcinoma

6-Shogaol Suppresses 2-Amino-1-Methyl-6-Phenylimidazo [4,5-b] Pyridine (PhIP)-Induced Human 786-O Renal Cell Carcinoma Osteoclastogenic Activity and Metastatic Potential

2-Amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP) which can be detected in processed meats and red meats, is a potential carcinogen for renal cell carcinoma (RCC). Approximately 30% of patients with metastatic RCC have bone metastases, and the prognosis of RCC with bone metastases is poor. Thus, the aim of the present study was to investigate whether PhIP induced bone metastases and to develop novel therapeutic agents. Our data revealed that PhIP pre-treatment increased the production of parathyroid hormone-related protein (PTHrP) in human 786-O renal cell carcinoma cells. Subsequently, the cultures of human osteoblasts with PhIP-stimulated condition medium of 786-O increased the expression of the macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor kappa-B ligand (RANKL), and decreased the expression of osteoprotegerin (OPG). In addition, PhIP-mediated PTHrP up-regulated as well as increased IL-8 secretion in 786-O cells, and then contributed to 786-O-mediated bone resorption. Furthermore, 6-shogaol, which is an active ingredient in ginger, showed suppressive effects on PhIP-mediated bone resorption. In summary, this is the first study to demonstrate that PhIP pre-treatment increases the stimulatory effect of human renal cell carcinoma 786-O on osteoclastogenesis activity directly by PTHrP. In addition, 6-shogaol treatment reverses PhIP-mediated bone resorption. It suggests that 6-shogaol treatment results in bone resorption activity in the RCC model in vitro.

Bone Metastasis from Renal Cell Carcinoma

About one-third of patients with advanced renal cell carcinoma (RCC) have bone metastasis that are often osteolytic and cause substantial morbidity, such as pain, pathologic fracture, spinal cord compression and hypercalcemia. The presence of bone metastasis in RCC is also associated with poor prognosis. Bone-targeted treatment using bisphosphonate and denosumab can reduce skeletal complications in RCC, but does not cure the disease or improve survival. Elucidating the molecular mechanisms of tumor-induced changes in the bone microenvironment is needed to develop effective treatment. The “vicious cycle” hypothesis has been used to describe how tumor cells interact with the bone microenvironment to drive bone destruction and tumor growth. Tumor cells secrete factors like parathyroid hormone-related peptide, transforming growth factor-β and vascular endothelial growth factor, which stimulate osteoblasts and increase the production of the receptor activator of nuclear factor κB ligand (RANKL). In turn, the overexpression of RANKL leads to increased osteoclast formation, activation and survival, thereby enhancing bone resorption. This review presents a general survey on bone metastasis in RCC by natural history, interaction among the immune system, bone and tumor, molecular mechanisms, bone turnover markers, therapies and healthcare burden.

TRPM3 and miR-204 establish a regulatory circuit that controls oncogenic autophagy in clear cell renal cell carcinoma

Autophagy promotes tumor growth by generating nutrients from the degradation of intracellular structures. Here we establish, using shRNAs, a dominant-negative mutant, and a pharmacologic inhibitor, mefenamic acid (MFA), that the Transient Receptor Potential Melastatin 3 (TRPM3) channel promotes the growth of clear cell renal cell carcinoma (ccRCC) and stimulates MAP1LC3A (LC3A) and MAP1LC3B (LC3B) autophagy. Increased expression of TRPM3 in RCC leads to Ca(2+) influx, activation of CAMKK2, AMPK, and ULK1, and phagophore formation. In addition, TRPM3 Ca(2+) and Zn(2+) fluxes inhibit miR-214, which directly targets LC3A and LC3B. The von Hippel-Lindau tumor suppressor (VHL) represses TRPM3 directly through miR-204 and indirectly through another miR-204 target, Caveolin 1 (CAV1).

Involvement of ERK1/2, p38 MAPK, and PI3K/Akt signaling pathways in the regulation of cell cycle progression by PTHrP in colon adenocarcinoma cells

Parathyroid hormone-related peptide (PTHrP) is distributed in most fetal and adult tissues, and its expression correlates with the severity of colon carcinoma. Recently we obtained evidence that in Caco-2 cells, a cell line from human colorectal adenocarcinoma, exogenous PTHrP increases the number of live cells, via ERK1/2, p38 MAPK, and PI3-kinase and induces the expression of cyclin D1, a cell cycle regulatory protein. In this study, we further investigated the role of PTHrP in the regulation of the cell cycle progression in these intestinal cells. Flow cytometry analysis revealed that PTHrP treatment diminishes the number of cells in the G0/G1 phase and increases the number in both S and G2/M phases. The hormone increases the expression of CDK6 and diminishes the amount of negative cell cycle regulators p27Kip1, p15INK4B, and p53. However, PTHrP does not modify the expression of cyclin D3, CDK4, and p16INK4A. In addition, inhibitors of ERK1/2 (PD98059), p38 MAPK (SB203580), and PI3Kinase (LY294002) reversed PTHrP response in Caco-2 cells. Taken together, our results suggest that PTHrP positively modulates cell cycle progression and changes the expression of proteins involved in cell cycle regulation via ERK1/2, p38 MAPK, and PI3K signaling pathways in Caco-2 cells.

Tumor signatures of PTHLH overexpression, high serum calcium, and poor prognosis were observed exclusively in clear cell but not non clear cell renal carcinomas

High serum calcium (Ca) due to aberrant secretion of tumor parathyroid hormone-like hormone (PTHLH) is a well-known paraneoplastic sign and is associated with poor prognosis in patients with renal cell carcinoma (RCC). However, the status of serum Ca and tumor PTHLH expression have not been verified using the 2004 World Health Organization (WHO) renal tumor classification. We retrospectively reviewed corrected serum Ca levels at initial onset (n = 683) and/or as of recurrence (n = 71) in patients with RCC. We also examined a total of 623 renal parenchymal tumor samples for PTHLH mRNA expressions by quantitative real-time PCR. High serum Ca concomitant with PTHLH overexpression in tumors was observed exclusively in clear cell RCC but not in other non clear cell subtype tumors, including papillary, chromophobe, collecting-duct, unclassified, and other rare subtype RCCs or in benign oncocytomas and angiomyolipomas. In clear cell RCC, PTHLH expression was significantly high in male patients, and was associated with a symptomatic presentation, higher grade, and higher stage cases, whereas it was not associated with VHL gene status. Univariate analyses demonstrated that high PTHLH expression was strongly associated with poor outcome both in overall survival (OS) and disease-free survival (DFS) for patients who underwent standard nephrectomy. Further multivariate Cox analyses revealed that the PTHLH expressions remained as independent prognostic parameters for OS but not for DFS. These data suggest that the previously characterized tumor signatures of high serum Ca due to high PTHLH expression and poor prognosis are clear cell RCC-specific features, whereas these characteristics are rare in non clear cell RCCs.

Combined hepatocellular-cholangiocarcinoma producing parathyroid hormone-related protein: report of a case

Combined hepatocellular-cholangiocarcinoma (CHCC) is an uncommon form of primary liver cancer. A 57-year-old man was readmitted to our hospital for treatment of recurrent CHCC, 12 months after central bisegmentectomy and 4 months after limited hepatic resection. Magnetic resonance imaging (MRI) revealed multiple hepatic nodules. Laboratory data showed increased serum levels of α-fetoprotein (AFP), calcium, and parathyroid hormone-related protein (PTH-rP), to 5,571 ng/mL, 17.0 mg/dL, and 16.1 pmol/L, respectively. Palliative mass reduction surgery was indicated by the fact that the hypercalcemia was difficult to manage medically. Thus, we performed lateral segmentectomy with partial resection of segment 7 and the caudate lobe, and microwave coagulation therapy for multiple recurrent CHCC. Thereafter, the serum PTH-rP and AFP levels decreased remarkably and the hypercalcemia was controlled for the next 3 months. He died of disease progression 9 months after the last hepatic surgery. To our knowledge, this is only the second reported case of CHCC producing PTH-rP in the English-language literature.

The multifaceted actions of PTHrP in skeletal metastasis

PTHrP, identified during the elucidation of mediators of malignancy-induced hypercalcemia, plays numerous roles in normal physiology as well as pathological conditions. Recent data support direct functions of PTHrP in metastasis, particularly from tumors with strong bone tropism. Bone provides a unique metastatic environment because of mineralization and the diverse cell populations in the bone marrow. PTHrP is a key regulator of tumor-bone interactions and regulates cells in the bone microenvironment through proliferative and prosurvival activities that prime the 'seed' and the 'soil' of the metastatic lesion. This review highlights recent findings regarding the role of PTHrP in skeletal metastasis, including direct actions in tumor cells, as well as alterations in the bone microenvironment and future perspectives involving the potential roles of PTHrP in the premetastatic niche, and tumor dormancy.

Parathyroid Hormone-Related Protein (PTHrP): A Key Regulator of Life/Death Decisions by Tumor Cells with Potential Clinical Applications

Parathyroid hormone-related protein (PTHrP), classically regarded as the mediator of the humoral hypercalcemia of malignancy syndrome, is a polyhormone that undergoes proteolytic processing into smaller bioactive forms. These bioactive forms comprise an N-terminal- as well as midregion- and C-terminal peptides, which have been shown to regulate various biological events, such as survival, proliferation and differentiation, in diverse cell model systems, both normal and pathological. A number of experimental data have demonstrated that PTHrP is also able to modulate tumor-relevant phenotypic expressions, thereby playing a role in early and advanced tumorigenesis, and in the response to treatment. In particular, interest has mainly been focused on the effects of PTHrP on cell proliferation/apoptosis, migration and invasion, which are the main roles involved in cancer development in vivo. The objective of this review is to discuss collectively the literature data on the molecular and biochemical basis of the mechanisms underlying the different, and sometimes opposite, effects exerted by PTHrP on various neoplastic cytotypes, with some final comments on both present and potential utilization of PTHrP as a target for anti-cancer therapy.

Cancer genomics identifies regulatory gene networks associated with the transition from dysplasia to advanced lung adenocarcinomas induced by c-Raf-1

BACKGROUND

Lung cancer is a leading cause of cancer morbidity. To improve an understanding of molecular causes of disease a transgenic mouse model was investigated where targeted expression of the serine threonine kinase c-Raf to respiratory epithelium induced initially dysplasia and subsequently adenocarcinomas. This enables dissection of genetic events associated with precancerous and cancerous lesions.

METHODOLOGY/PRINCIPAL FINDINGS

By laser microdissection cancer cell populations were harvested and subjected to whole genome expression analyses. Overall 473 and 541 genes were significantly regulated, when cancer versus transgenic and non-transgenic cells were compared, giving rise to three distinct and one common regulatory gene network. At advanced stages of tumor growth predominately repression of gene expression was observed, but genes previously shown to be up-regulated in dysplasia were also up-regulated in solid tumors. Regulation of developmental programs as well as epithelial mesenchymal and mesenchymal endothelial transition was a hall mark of adenocarcinomas. Additionally, genes coding for cell adhesion, i.e. the integrins and the tight and gap junction proteins were repressed, whereas ligands for receptor tyrosine kinase such as epi- and amphiregulin were up-regulated. Notably, Vegfr- 2 and its ligand Vegfd, as well as Notch and Wnt signalling cascades were regulated as were glycosylases that influence cellular recognition. Other regulated signalling molecules included guanine exchange factors that play a role in an activation of the MAP kinases while several tumor suppressors i.e. Mcc, Hey1, Fat3, Armcx1 and Reck were significantly repressed. Finally, probable molecular switches forcing dysplastic cells into malignantly transformed cells could be identified.

CONCLUSIONS/SIGNIFICANCE

This study provides insight into molecular pertubations allowing dysplasia to progress further to adenocarcinoma induced by exaggerted c-Raf kinase activity.

Human parathyroid hormone-related protein and human parathyroid hormone receptor type 1 are expressed in human medulloblastomas and regulate cell proliferation and apoptosis in medulloblastoma-derived cell lines

Human parathyroid hormone-related protein (hPTHrP), identified in patients with paraneoplastic hypercalcemia and expressed by different cell types during development and adult life, plays important roles in many human neoplasms. Immunohistochemical and RT-PCR analyses of hPTHrP and human parathyroid hormone receptor type 1 (PTHR-1) in primary medulloblastoma confirmed their expression in both classic and desmoplastic variants at RNA and protein levels. To evaluate the functional role of hPTHrP, DAOY and D283 medulloblastoma and U87MG glioma cells, expressing high levels of hPTHrP and PTHR-1, were treated with anti-sense oligonucleotides for hPTHrP. Anti-sense treatment produced in all cell lines a decrease of cell proliferation and clonogenic activity and an increase of apoptosis, while addition of exogenous hPTHrP (1-37) prevented these effects. Anti-sense induced the increase of Caspase-3, Fas (CD95) mRNAs and Bax/Bcl-2 mRNA ratio after 12 h of cell treatment. Exogenous hPTHrP (1-37) increased intracellular Ca(2+) concentration in DAOY cells as revealed by FURA. Anti-sense treated cells showed a significant decrease of steady-state levels of intracellular Ca(2+), which was reverted by addition of exogenous hPTHrP (1-37). This study indicates that hPTHrP and PTHR-1 are expressed in medulloblastoma and could promote tumor growth, protecting cells from apoptosis.

Paraneoplastic Syndromes: Elements of Interest for the Urologist

A paraneoplastic syndrome is a clinical condition in a patient affected by tumor which occurs distally from the primary neoplasia or its metastases, and is assessed via the humoral mediators. The uncommon secretion of peptide hormones is the most frequent cause of paraneoplastic syndromes. Although the symptoms are strongly varied, paraneoplastic endocrine syndromes are characterized by several functional features that differentiate them from the endocrine glands hyper-function related disorders. Based on the field's literature, the article presents the pathogenetic mechanisms, the laboratory and imaging features, and the essential therapeutic measures for humoral hypercalcemia of malignancy, hypercortisolism from ectopic ACTH/CRH production and water intoxication syndrome due to inadequate ADH secretion. Moreover, neuroendocrine differentiation in some urogenital cancers (prostate, bladder, kidney etc.), occurring as pure endocrine malignancy or as focal lesion, can develop a paraneoplastic carcinoid-like syndrome. On the other hand, some patients with urogenital tumors have increased serum levels of IGF-2 resulting in paraneoplastic hypoglycemia.

Class II G protein-coupled receptors and their ligands in neuronal function and protection

G protein-coupled receptors (GPCRs) play pivotal roles in regulating the function and plasticity of neuronal circuits in the nervous system. Among the myriad of GPCRs expressed in neural cells, class II GPCRs which couples predominantly to the Gs-adenylate cyclase-cAMP signaling pathway, have recently received considerable attention for their involvement in regulating neuronal survival. Neuropeptides that activate class II GPCRs include secretin, glucagon-like peptides (GLP-1 and GLP-2), growth hormone-releasing hormone (GHRH), pituitary adenylate cyclase activating peptide (PACAP), corticotropin-releasing hormone (CRH), vasoactive intestinal peptide (VIP), parathyroid hormone (PTH), and calcitonin-related peptides. Studies of patients and animal and cell culture models, have revealed possible roles for class II GPCRs signaling in the pathogenesis of several prominent neurodegenerative conditions including stroke, Alzheimer's, Parkinson's, and Huntington's diseases. Many of the peptides that activate class II GPCRs promote neuron survival by increasing the resistance of the cells to oxidative, metabolic, and excitotoxic injury. A better understanding of the cellular and molecular mechanisms by which class II GPCRs signaling modulates neuronal survival and plasticity will likely lead to novel therapeutic interventions for neurodegenerative disorders.

Parathyroid hormone-related protein in human renal cell carcinoma

Parathyroid hormone-related protein (PTHrP), a polyprotein discovered in 1987, plays crucial roles not only in development and in various physiological events associated with normal life, but also in a number of pathological conditions such as cancer. PTHrP appears as the major causative agent in humoral hypercalcemia of malignancy (HHM) associated to a broad range of tumors. However, this is only one aspect of the multiple facets of PTHrP in cancer biology. Indeed, the complex growth factor-like properties of PTHrP has shed new light onto potential roles of this peptide in the regulation of tumor growth and invasion. Initial studies in breast, prostate and lung cancer and recent results in renal cell carcinoma (RCC) suggest such roles and highlight the therapeutic potential of PTHrP-targeting strategies in human cancer including RCC. In this review, the role of PTHrP in RCC tumorigenesis and its potential as a therapeutic target will be discussed.

Transcriptional regulation of parathyroid hormone-related protein promoter P3 by ETS-1 in adult T-cell leukemia/lymphoma

Parathyroid hormone-related protein (PTHrP) plays a primary role in the development of humoral hypercalcemia of malignancy seen in the majority of adult T-cell leukemia/lymphoma (ATLL) patients with human T-cell lymphotropic virus type-1 (HTLV-1) infection. HTLV-1 Tax has been shown to complex with ETS-1 and SP1 to transactivate the PTHrP P3 promoter. Previously, we established a SCID/bg mouse model of human ATL with RV-ATL cells and showed that PTHrP expression was independent of Tax. In this study, we report an inverse correlation of PTHrP with tax/rex mRNA in multiple HTLV-1-positive cell lines and RV-ATL cells. Stimulation of Jurkat T cells with PMA/ionomycin upregulated the PTHrP P3 promoter by a previously characterized Ets binding site and also induced protein/DNA complex formation identical to that observed in RV-ATL cells. Further, we provide evidence that cotransfection with Ets-1 and constitutively active Mek-1 in HTLV-1-negative transformed T cells with stimulation by PMA/ionomycin not only resulted in a robust induction of PTHrP P3 but also formed a complex with ETS-1/P3 EBS similar to that in ATLL cells. Our data demonstrate that transcriptional regulation of PTHrP in ATLL cells can be controlled by T-cell receptor signaling and the ETS and MAPK ERK pathway in a Tax-independent manner.

Antitumor effect of parathyroid hormone-related protein neutralizing antibody in human renal cell carcinoma in vitro and in vivo

Functional inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene occurs in 40-80% of human conventional renal cell carcinomas (RCCs). We showed recently that VHL-deficient RCCs expressed large amounts of parathyroid hormone-related protein (PTHrP), and that PTHrP, acting through the PTH1 receptor (PTH1R), plays an essential role in tumor growth. We also showed that PTHrP expression is negatively regulated by the VHL gene products (pVHL). Our goal was to determine whether blocking the PTHrP/PTH1R system might be of therapeutic value against RCC, independent of VHL status and PTHrP expression levels. The antitumor activity of PTHrP neutralizing antibody and of PTH1R antagonist were evaluated in vitro and in vivo in a panel of human RCC lines expressing or not pVHL. PTHrP is upregulated compared with normal tubular cells. In vitro, tumor cell growth and viability was decreased by up to 80% by the antibody in all cell lines. These effects resulted from apoptosis. Exogenously added PTHrP had no effect on cell growth and viability, but reversed the inhibitory effects of the antibody. The growth inhibition was reproduced by a specific PTH1R antagonist in all cell lines. In vivo, the treatment of nude mice bearing the Caki-1 RCC tumor with the PTHrP antibody inhibited tumor growth by 80%, by inducing apoptosis. Proliferation and neovascularization were not affected by the antiserum. Anti-PTHrP treatment induced no side effects as assessed by animal weight and blood chemistries. Current therapeutic strategies are only marginally effective against metastatic RCC, and adverse effects are common. This study provides a rationale for evaluating the blockade of PTHrP signaling as therapy for human RCC in a clinical setting.

Parathyroid hormone-related protein and lung biology

Parathyroid hormone-related protein (PTHrP) is expressed in normal and malignant lung and has roles in development, homeostasis, and pathophysiology of injury and cancer. Its effects in developing lung include regulation of branching morphogenesis and type II cell maturation. In adult lung, PTHrP stimulates disaturated phosphatidylcholine secretion, inhibits type II cell growth, and sensitizes them to apoptosis. In lung cancer, PTHrP may play a role in carcinoma progression, or metastasis. The protein could be a useful marker for assessing lung maturity or type II cell function, predicting risk of injury, and detecting lung cancer. PTHrP-based therapies could also prove useful in lung injury and lung cancer.

Parathyroid hormone-related protein is an essential growth factor for human clear cell renal carcinoma and a target for the von Hippel-Lindau tumor suppressor gene

Clear cell renal carcinoma (CCRC) is responsible for 2% of cancer-related deaths worldwide and is resistant to virtually all therapies, indicating the importance of a search for new therapeutic targets. Parathyroid hormone-related protein (PTHrP) is a polyprotein derived from normal and malignant cells that regulates cell growth. In the current study, we show that blocking PTHrP with antibodies or antagonizing the common parathyroid hormone (PTH)/PTHrP receptor, the PTH1 receptor, dramatically blunts the expansion of human CCRC in vitro by promoting cell death. Importantly, in nude mice, anti-PTHrP antibodies induced complete regression of 70% of the implanted tumors by inducing cell death. In addition, we demonstrate that the von Hippel-Lindau tumor suppressor protein, which functions as a gatekeeper for CCRC, negatively regulates PTHrP expression at the post-transcriptional level. These studies indicate that PTHrP is an essential growth factor for CCRC and is a novel target for the von Hippel-Lindau tumor suppressor protein. Taken together, these results strongly suggest that targeting the PTHrP/PTH1 receptor system may provide a new avenue for the treatment of this aggressive cancer in humans.

The parathyroid hormone-related protein system: more data but more unsolved questions

PURPOSE OF REVIEW

The present review focuses on recent studies that might be considered as the most relevant advances in the parathyroid hormone-related protein field, with special emphasis on proven functions in renovascular and cardiovascular systems, in physiological as well as pathological conditions. Thus, the questions as to whether and how parathyroid hormone-related protein intervenes in vascular development and homeostasis and in vascular diseases such as hypertension, atherosclerosis, restenosis and heart failure have begun to be unraveled.

RECENT FINDINGS

Since its discovery from hypercalcemia-associated tumors in 1987, it has become clear that parathyroid hormone-related protein is a ubiquitously expressed poly-hormone and plays crucial roles in normal life. The early lethality to parathyroid hormone-related protein knockout mice emphasizes the crucial roles of the protein in development but has limited the use of these models. However, data accumulated from transgenic animals overexpressing the protein in particular cells have provided considerable support to its physiological and pathological relevance. The recent demonstration that nascent parathyroid hormone-related protein not only follows the secretory pathways, but also directly translocates to the nucleus, is beginning to uncover new actions for the protein in a number of physiological systems such as bone, mammary gland and vascular smooth muscle, as well as in pathological situations, such as cancer, osteoporosis, sepsis, atherosclerosis and hypertension.

SUMMARY

The development of mice with conditionally deleted parathyroid hormone-related protein or parathyroid hormone-1 receptor alleles will allow the creation of cell- or tissue-specific parathyroid hormone-related protein knockout mice which will greatly facilitate the determination of the biological relevance of this protein in a specific cell or tissue type, particularly in the cardiovascular system.

Effect of parathyroid hormone related protein, and dihydrotestosterone on proliferation and ornithine decarboxylase mRNA in human prostate cancer cell lines

OBJECTIVES

Parathyroid hormone related protein (PTHrP) has been identified as the major hormone responsible for the syndrome of humoral hypercalcemia of malignancy (HHM). Recent studies have shown that a large number of prostate tumors demonstrate the presence of PTHrP despite the fact that prostate cancer is rarely associated with the HHM syndrome. Other studies have indicated that PTHrP behaves as an early response gene, which stimulates ornithine decarboxylase (ODC) enzyme activity, an enzyme, involved in the biosynthesis of polyamines. It is therefore possible that PTHrP regulates prostate tumor cell proliferation via ODC gene expression.

METHODS

In the present study, we evaluated the effects of PTHrP and/or dihydrotestosterone (DHT) treatment on DNA synthesis by thymidine incorporation in androgen-dependent (LnCaP) and androgen-independent (PC3) human prostate adenocarcinoma cell lines. In addition, we utilized Northern blot analysis to investigate the effect of PTHrP [1-34] alone or in combination with DHT on ODC mRNA.

RESULTS

PTHrP [1-34] treatment resulted in an increase in thymidine uptake in PC3 cells by 50%, whereas no such increase was seen in LnCaP cells. However, in the LnCaP cells, in the presence of DHT, PTHrP stimulated DNA synthesis to a level greater than that seen with DHT alone. DHT (10 nM) treatment resulted in an induction of PTHrP as well as ODC mRNAs in the androgen-dependent (LnCaP) but not in androgen-independent (PC3) cell line. PTHrP [1-34] treatment resulted in induction of ODC mRNA in the LnCaP cells. Addition of DHT resulted in a further increase in the ODC mRNA expression.

CONCLUSIONS

These data suggest that PTHrP may play a role in prostate cancer cell proliferation and the increased ODC gene expression may be one possible mechanisms responsible for this phenomenon.

Guanosine nucleotides inhibit different syndromes of PTHrP excess caused by human cancers in vivo

There are two well-described syndromes caused by tumor production of parathyroid hormone-related peptide (PTHrP), namely osteolytic bone disease associated with breast cancer and humoral hypercalcemia of malignancy (HHM) that occurs with or without bone metastasis. Both syndromes have been shown experimentally to be inhibited by neutralizing antibodies to PTHrP. In a search for small-molecule inhibitors of PTHrP production or effects, we have identified guanine-nucleotide analogs as compounds that inhibit PTHrP expression by human tumor cells associated with these syndromes. We show in nude athymic murine models that these compounds reduce PTHrP-mediated osteolytic lesions associated with metastatic human breast-cancer cells as well as the degree of hypercalcemia caused by excessive PTHrP production by a squamous-cell carcinoma of the lung. These results suggest that the PTHrP gene promoter may be a suitable target for treating the skeletal effects of malignancy.

Local secretion of parathyroid hormone-related protein by an osteoblastic osteosarcoma (UMR 106-01) cell line results in growth inhibition

Parathyroid hormone-related protein (PTHrP) has been implicated as being important in the growth of tumor cells responsive to the peptide. We utilized a rat osteoblastic osteosarcoma cell line, UMR 106-01, which has PTHrP receptors and a PTHrP-responsive adenylate cyclase/cAMP messenger system, to produce a modified cell line that overexpresses PTHrP. The human PTHrP cDNA sequence was transfected by electroporation into UMR 106-01 cells and the stable cell lines UMR-36 and UMR-34 were established. The modified cell line, UMR-36, had increased levels of PTHrP mRNA compared with control cell lines and secreted PTHrP into the culture medium at levels of 0.01-0.1 pmol/10(7) cells in 12 h. The secreted peptide was biologically active as indicated by its ability to activate adenylate cyclase. The number of UMR-36 cells following 9 days in culture was reduced by up to 80% compared with control lines, which was associated with decreased (3)H-thymidine incorporation into genomic DNA. Addition of 1000-fold excess of the PTHrP antagonist, PTHrP(7-34), to UMR-36 cells resulted in the escape of growth inhibition and increased rate of growth. In vivo, tumors derived from UMR-36 cells were smaller in size compared with tumors derived from control cells. In conclusion, increased autocrine secretion of, and responsiveness to, PTHrP results in inhibited growth kinetics of an osteoblast-like bone tumor cell line in vitro and in vivo.

Treatment of malignant hypercalcaemia

Hypercalcaemia is a common paraneoplastic syndrome caused by the production by tumours of several factors which affect bone resorption and/or tubular calcium reabsorption. Antihypercalcaemic therapy in cancer patients involves rehydration manoeuvres, as well as the use of a variety of available drugs which inhibit bone resorption, namely plicamycin, calcitonin, bisphosphonates and gallium nitrate. While plicamycin is currently out of use because of its considerable toxicity, bisphosphonates have become the standard therapy in hypercalcaemia of malignancy (HM). These compounds are potent inhibitors of bone resorption but they do not affect tubular calcium reabsorption, which limits their efficacy in humoral HM (HHM) cases. In these patients, gallium nitrate should be the therapy of choice. Among the available bisphosphonates, pamidronate administered in a single infusion of 90 mg, normalises serum calcium levels in > 90% of HM patients. A recently introduced bisphosphonate, zoledronate, is likely to replace pamidronate as a first-line therapy in these patients. The effectiveness of calcitonin in HM treatment is limited, although it seems to be useful at the outset in cases with severe symptomatic hypercalcaemia. Future treatment options of HM are likely to include new bone resorption inhibitors, for example, naturally-occurring osteoprotegerin, or alternate approaches aimed at reducing the tumour production of parathyroid hormone-related protein with noncalcaemic analogues of calcitriol or ras-isoprenylation inhibitors. The development of putative therapeutic agents targeted to inhibit distal calcium reabsorption should be valuable in the management of HHM cases.

Parathyromatosis as cause of recurrent secondary hyperparathyroidism: a cytologic diagnosis

Parathyromatosis is a rare cause of hyperparathyroidism. It can be divided into two types: primary and secondary. The pathologic lesion consists of multiple small nodules of hypercellular parathyroid tissue strewn in soft tissue (fat, skeletal muscle, fibrous tissue) of the neck. We present a case of parathyromatosis occurring in a patient with recurrent secondary hyperparathyroidism 4 yr after parathyroidectomy. The diagnosis was confirmed preoperatively by fine-needle aspiration of one of several neck masses.

Higher expression of K-ras is associated with parathyroid hormone-related protein-induced hypercalcaemia in renal cell carcinoma

OBJECTIVES

To determine whether the K-ras oncogene is associated with parathyroid hormone-related protein (PTHrP) production in renal cell carcinoma (RCC) and whether the serum value of PTHrP is related to the patients' survival.

PATIENTS AND METHODS

The serum levels of PTHrP and corrected serum calcium levels were analysed in 51 consecutive patients (29 men and 22 women, mean age 63.7 years, range 33-82) with newly diagnosed RCC. Matched pairs were analysed of the mRNA levels of K-ras and PTHrP in tumour and in corresponding non-tumour tissue originating from the same patient, using the polymerase chain reaction after reverse transcription.

RESULTS

Seven patients had elevated serum PTHrP values at the diagnosis of RCC. The mRNA expression of K-ras and PTHrP were detected in both tumour and non-tumour tissues, with K-ras mRNA levels being higher in the former than the latter (P < 0.05), and correlated with tumour stage (P < 0.05). There were no differences in PTHrP mRNA levels between the tissues. Furthermore, the mRNA levels of K-ras and PTHrP in seven tumours from patients with high serum values of PTHrP were higher than in tumours from those with normal values (both P < 0.01). The expression of mRNAs of K-ras and PTHrP was positively correlated (r = 0.771, P < 0.001). In seven patients with high serum PTHrP values the mRNA levels of PTHrP correlated with serum values of PTHrP and calcium (r = 0.875, P < 0.01 and r = 0.762, P < 0.05, respectively). Kaplan-Meier plots of survival rate in patients with elevated or normal serum PTHrP showed that high serum PTHrP was associated with a shorter overall survival (P < 0.05). The Cox proportional hazards model showed that serum PTHrP was an independent predictor of overall survival (P < 0.05).

CONCLUSIONS

These findings suggest that K-ras may be associated with PTHrP-induced hypercalcaemia and that PTHrP levels may reflect the aggressiveness of tumour cells through the K-ras oncogene in RCC.

Parathyroid hormone-related protein regulates the growth of orthotopic human lung tumors in athymic mice

BACKGROUND

Parathyroid hormone-related protein (PTHrP) has growth regulatory effects for many malignant cells and may influence the progression of carcinomas of the breast, prostate, and lung. In the current study, the authors investigated the in vivo and in vitro effects of PTHrP neutralizing antibody and PTHrP treatment on the growth of BEN cells, a human lung squamous cell carcinoma line that expresses PTHrP and its receptor.

METHODS

Orthotopic lung tumors were produced in 20 athymic mice with BEN-GFP cells (a clonal line that stably expresses green fluorescent protein [GFP]) by instilling suspensions of 3 x 10(6) cells per mouse into the lungs of anesthetized animals. The mice were divided into 2 groups receiving either subcutaneous mouse antihuman PTHrP antibodies or irrelevant mouse immunoglobulin (Ig) G (150 microg) twice weekly.

RESULTS

After 30 days, 6 of 10 mice receiving anti-PTHrP antibodies had lung tumors visible on macroscopic inspection, but only 1 of the 10 mice treated with irrelevant IgG had a lung tumor that was of that size (P < 0.01). GFP fluorescence was significantly greater in lung homogenates of the PTHrP antibody-treated mice than in the mice treated with IgG (6006 +/- 411 vs. 2907 +/- 282 relative fluorescent units, respectively; P < 0.001). Although neutralizing antibodies stimulated BEN cell lung tumor growth, exogenous PTHrP 1-34 treatment (0.01-1 nM) inhibited the growth of cultured BEN cells by approximately 40%.

CONCLUSIONS

Although PTHrP expression has been reported to be associated with more aggressive malignancies, the data from the current study suggest that PTHrP 1-34 was a paracrine growth inhibitor in BEN human lung carcinoma cells. The growth-related effects of PTHrP are complex, and can be both stimulatory and inhibitory.

Humoral hypercalcemia of malignancy: severe combined immunodeficient/beige mouse model of adult T-cell lymphoma independent of human T-cell lymphotropic virus type-1 tax expression

The majority of patients with adult T-cell leukemia/lymphoma (ATL) resulting from human T-cell lymphotropic virus type-1 (HTLV-1) infection develop humoral hypercalcemia of malignancy (HHM). We used an animal model using severe combined immunodeficient (SCID)/beige mice to study the pathogenesis of HHM. SCID/beige mice were inoculated intraperitoneally with a human ATL line (RV-ATL) and were euthanized 20 to 32 days after inoculation. SCID/beige mice with engrafted RV-ATL cells developed lymphoma in the mesentery, liver, thymus, lungs, and spleen. The lymphomas stained positively for human CD45RO surface receptor and normal mouse lymphocytes stained negatively confirming the human origin of the tumors. The ATL cells were immunohistochemically positive for parathyroid hormone-related protein (PTHrP). In addition, PTHrP mRNA was highly expressed in lymphomas when compared to MT-2 cells (HTLV-1-positive cell line). Mice with lymphoma developed severe hypercalcemia. Plasma PTHrP concentrations were markedly increased in mice with hypercalcemia, and correlated with the increase in plasma calcium concentrations. Bone densitometry and histomorphometry in lymphoma-bearing mice revealed significant bone loss because of a marked increase in osteoclastic bone resorption. RV-ATL cells contained 1.5 HTLV-1 proviral copies of the tax gene as determined by quantitative real-time polymerase chain reaction (PCR). However, tax expression was not detected by Western blot or reverse transcriptase (RT)-PCR in RV-ATL cells, which suggests that factors other than Tax are modulators of PTHrP gene expression. The SCID/beige mouse model mimics HHM as it occurs in ATL patients, and will be useful to investigate the regulation of PTHrP expression by ATL cells in vivo.

Parathyroid hormone-related peptide producing cholangiocellular carcinoma with a marked psammoma formation

Humoral hypercalcemia caused by parathyroid hormone-related peptide (PTHrP), associated with cholangiocellular carcinoma (CCC), has rarely been documented. There have been no reports of CCC associated with extensive calcification of the tumor with psammoma body formation. A 66-year-old man was admitted with a large calcified tumor in the liver detected on an abdominal X-ray. An ultrasound-guided fine needle biopsy specimen of the liver tumor showed evidence of adenocarcinoma. He had hypercalcemia with an elevated PTHrP level. The patient died because of disseminated intravascular coagulation and progressive hepatic failure. A postmortem examination revealed a large poorly differentiated CCC in the liver. Immunohistochemical examination showed the presence of PTHrP-positive tumor cells. The calcified lesion consisted of a number of accumulated psammoma bodies. We present a case of PTHrP producing CCC with a marked psammoma formation.

Parathyroid hormone-related protein is an independent prognostic factor for renal cell carcinoma

BACKGROUND

Parathyroid hormone-related protein (PTHrP) has been shown to be the principal cause of humoral hypercalcemia associated with renal cell carcinoma (RCC). Recent studies have demonstrated that the amino-terminal region of PTHrP has growth factor-like activities, suggesting it may play a role in the development of RCC. In this study, expression of the carboxy-terminal region of PTHrP was assessed immunohistochemically and its significance in predicting the prognosis of RCC was studied.

METHODS

Forty radical nephrectomy specimens were immunostained with a murine monoclonal antibody (9H7) against the carboxy-terminal region (amino acids 109-141) of PTHrP using the streptavidin-peroxidase enzyme conjugate method. Staining intensity was evaluated semiquantitatively and compared with clinicopathologic features of the corresponding RCC.

RESULTS

Immunoreactivity to 9H7 was observed to be localized to the cytosol of tumor cells at various staining intensities. There were 30 cases (75.0%) with strong staining and 10 cases (25.0%) in which staining was weak or nonexistent. Staining intensity showed no significant correlation with gender, tumor greatest dimension, stage, or grade. Tumors of the clear cell type expressed PTHrP to a significantly greater extent than tumors of the granular cell type. Tumor recurrence was significantly greater in the weakly stained or unstained group compared with the strongly stained group (P = 0.035). Multivariate analysis indicated that PTHrP expression and tumor stage were equally significant prognostic indicators in RCCs measuring <10 cm in greatest dimension.

CONCLUSIONS

Evident PTHrP(109-141) expression is present in the majority of RCCs. The results of the current study indicate PTHrP(109-141) may be a possible marker of cellular differentiation and may be useful for predicting recurrence free survival in RCC patients after radical nephrectomy.

Expression and role of parathyroid hormone-related protein in human renal proximal tubule cells during recovery from ATP depletion

Parathyroid hormone (PTH)-related protein (PTHrP) is widely expressed in normal fetal and adult tissues and regulates growth and differentiation in a number of organ systems. Although various renal cell types produce PTHrP, and PTHrP expression in rat proximal renal tubules is upregulated in response to ischemic injury in vivo, the role of PTHrP in the kidney is unknown. To study the effects of injury on PTHrP expression and its consequences in more detail, the immortalized human proximal tubule cell line HK-2 was used in an in vitro model of ATP depletion to mimic in vivo renal ischemic injury. These cells secrete PTHrP into conditioned medium and express the type I PTH/PTHrP receptor. Treatment of confluent HK-2 cells for 2 h with substrate-free, glucose-free medium containing the mitochondrial inhibitor antimycin A (1 microM) resulted in 75% depletion of cellular ATP. After an additional 2 h in glucose-containing medium, cellular ATP levels recovered to approximately 75% of baseline levels. PTHrP mRNA levels, as measured in RNase protection assays, peaked at 2 h into the recovery period (at four times baseline expression). The increase in PTHrP mRNA expression was correlated with an increase in PTHrP protein content in HK-2 cells at 2 to 6 h into the recovery period. Heat shock protein-70 mRNA expression was not detectable under baseline conditions but likewise peaked at 2 h into the recovery period. Treatment of HK-2 cells during the recovery period after injury with an anti-PTHrP(1-36) antibody (at a dilution of 1:250) resulted in significant reductions in cell number and uptake of [3H]thymidine, compared with nonimmune serum at the same titer. Similar results were observed in uninjured HK-2 cells. It is concluded that this in vitro model of ATP depletion in a human proximal tubule cell line reproduces the pattern of gene expression previously observed in vivo in rat kidney after ischemic injury and that PTHrP plays a mitogenic role in the proliferative response after energy depletion.

Over-production of parathyroid hormone-related peptide results in increased osteolytic skeletal metastasis by prostate cancer cells in vivo

Prostate carcinoma is one of the most common malignancies affecting males, resulting in a high rate of morbidity and mortality. This hormone-dependent malignancy is characteristically associated with a high incidence of osteoblastic skeletal lesions. However, osteolytic lesions invariably accompany blastic ones. In the current study, we assessed the role of parathyroid hormone-related peptide (PTHRP), a potent bone-resorbing agent, in contributing to bone breakdown and prostatic skeletal metastasis using a syngeneic rat prostate cancer model. The full-length cDNA encoding rat PTHRP was subcloned as a Hind III insert in the sense orientation into the mammalian expression vector pRc-CMV to generate the expression vector pRc-PTHRP-S. Both control and experimental plasmids were stably transfected into low PTHRP-producing Dunning R3227, Mat Ly Lu rat prostate cancer cells. Following antibiotic selection, monoclonal cell lines expressing the highest amount of PTHRP mRNA and immunoreactive PTHRP were selected as experimental tumor cells for further analysis. Increased PTHRP production by these cells had no significant effect in vitro on the invasive capacity of these cells. Control and experimental cells were inoculated s.c. into the right flank or by the intracardiac (i.c.) route into the left ventricle of inbred male Copenhagen rats. No skeletal metastases occurred after s.c. injection with either cells. In contrast, i.c. inoculation led to lumbar vertebra metastasis and consequent hind-limb paralysis. Furthermore, histological examination of skeletal metastases in experimental animals showed a marked increase in osteoclastic activity. Our results demonstrate that PTHRP can increase osteoclastic osteolysis in the presence of focal osseous prostate cancer metastases and may contribute to the lytic lesions which generally accompany osteoblastic lesions in prostate cancer.

Renal expression of parathyroid hormone-related protein (PTHrP) and PTH/PTHrP receptor in a rat model of tubulointerstitial damage

BACKGROUND

PTHrP, which appears to act as a growth/differentiation factor in a variety of tissues, is present in the kidney; however, its role is unclear.

METHODS

The expression of PTHrP and the PTH/PTHrP receptor were investigated by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry in the remnant kidney of uninephrectomized (UNX) rats after protein overloading [1 g/day of bovine serum albumin (BSA)].

RESULTS

Compared with UNX-control rats, proteinuria in BSA-overloaded animals was detected within the first 24 hours and increased during the entire study period (28 days). Kidney examination by light microscopy showed no significant renal lesions at day 1 of BSA treatment, whereas at days 8 and 28, tubular lesions, infiltration of mononuclear cells, and mesangial expansion were observed. PTHrP mRNA expression in the renal cortex was already increased at day 1 (fourfold) and plateaued between days 8 and 28 (12- and 15-fold, respectively) in BSA-overloaded animals compared with UNX-control rats. At day 8, immunohistochemical analysis with two different anti-PTHrP antibodies showed a dramatic increase of PTHrP staining in the damaged proximal and distal tubules from BSA-overloaded rats with respect to UNX-control rats. Moreover, intense PTHrP immunostaining was also observed in glomerular mesangial and endothelial cells in BSA-overloaded rats, but not in the UNX-control rats. A reciprocal decrease of PTH/PTHrP receptor mRNA and immunostaining, without significant changes in the cellular localization (proximal and distal tubule, and glomerular mesangial and epithelial cells) of the PTH/PTHrP receptor positivity was found to occur in the renal cortex of BSA-overloaded rats. At day 8, coinciding with the up-regulation of PTHrP, an increase in the angiotensin converting enzyme and preproendothelin-1 gene expression was observed in the renal cortex of BSA-overloaded rats compared with UNX-control rats.

CONCLUSIONS

These results indicate that PTHrP can be added to the group of genes that are up-regulated in proximal tubular cells in response to intense proteinuria. Our results, together with previous findings, suggest that the vasoactive hormones angiotensin II and endothelin-1 could participate in the PTHrP production in the renal cortex of BSA-overloaded rats. Further experiments are required to clarify the mechanisms of PTHrP up-regulation and its possible role in the response to renal damage in this animal model.

Clinicopathological implications of parathyroid hormone-related protein in human colorectal tumours

The purpose of the present study was to clarify the relationship of parathyroid hormone-related protein (PTHrP) to the oncogenesis and progression of colorectal adenocarcinoma. A total of 108 colorectal tumours, including 12 adenomas, six adenocarcinomas in adenomas, and 90 adenocarcinomas, were studied. Immunohistochemistry, in situ hybridization, and reverse transcription-polymerase chain reaction (RT-PCR) techniques were used to evaluate the expression of PTHrP. Positivity of immunostaining for PTHrP was defined as highly positive (++), slightly positive (+), and negative (-). None of the adenomas of background non-neoplastic mucosal epithelia showed immunostaining of PTHrP. In contrast, PTHrP was expressed in 85 (94.4 per cent) of 90 colorectal adenocarcinomas. Immunoreactivity of PTHrP was greater in poorly differentiated adenocarcinomas than in well-differentiated ones. Furthermore, advancing margins of primary tumours stained more intensely than other sites. Highly positive immunoreactivity of PTHrP, classified by histological invasiveness, was 22.6 per cent within the muscularis propria and 69.5 per cent beyond the muscularis propria. PTHrP expression was significantly correlated with differentiation, depth of invasion, lymphatic invasion, lymph node metastasis, hepatic metastases, and Dukes' classification. In carcinoma, PTHrP mRNA expression was evident in tumour cells by in situ hybridization. PTHrP transcripts were also detected in two resected human colorectal adenocarcinomas by RT-PCR. These findings suggest that PTHrP is related to carcinogenesis, differentiation, progression, and prognosis of colorectal adenocarcinomas.

Characterization of the cell-specific expression of parathyroid hormone-related protein in normal and neoplastic prostate tissue

OBJECTIVES

Parathyroid hormone-related protein (PTHrP) is a primary factor in the pathogenesis of malignancy-associated hypercalcemia. By alternative splicing, the human PTHrP gene can generate three different species of mRNA that encode three initial translational isoforms of 139, 173, and 141 amino acids. We recently reported that PTHrP was present in normal prostatic neuroendocrine cells and was overexpressed in prostate cancer tissue as demonstrated by immunostaining. This study was undertaken to further clarify the complex expression of PTHrP gene in normal prostate tissue and prostate cancer.

METHODS

PTHrP mRNA in samples prepared from normal prostate tissue, prostate cancer, and three prostate cancer cell lines, PC3, LNCaP, and DU145 was assessed using Northern hybridization. Expressed PTHrP isoforms were deduced from differential reverse transcription-polymerase chain reaction (RT-PCR) assays with exon-specific primers. Further localization of different species of PTHrP mRNA was performed using nonradioactive in situ hybridization with exon-specific probes on consecutive sections of normal and neoplastic prostate tissue.

RESULTS

Northern hybridization showed that the PTHrP expression level was higher in prostate cancer than in normal prostate tissue. All three PTHrP isoforms could be detected in normal prostate tissues and prostate cancer with differential RT-PCR. Further analysis using in situ hybridization with exon-specific probes revealed that all three PTHrP isoforms were present in prostatic neuroendocrine cells and only PTHrP-1-139 isoform could be clearly detected in prostate cancer tissue. Two androgen-insensitive cell lines, PC3 and DU145, derived from a bone metastasis and a brain metastasis, respectively, expressed all three mRNA species encoding for the three isoforms, but DU145 cells expressed less than PC3 cells. Androgen-sensitive LNCaP cells exhibited a low level of expression of mRNA species encoding for PTHrP-1-139 and PTHrP-1-173, and no expression of PTHrP1-141 isoform.

CONCLUSIONS

All three initial translational isoforms of PTHrP are produced by prostatic neuroendocrine cells. The mature products of PTHrP might exert their effects on other prostatic epithelial cells in a paracrine fashion and also participate in the homeostatic regulation of the ejaculate. In prostate cancer, differential expression of these three isoforms is evident and PTHrP-1-139 isoform is more abundant than the other two forms. These findings are valuable for designing future research studies to further elucidate the biological functions of PTHrP in normal prostatic glands and prostate cancer.

Hypercalcaemia in patients with cancer: aetiology and treatment

Hypercalcaemia is one of the most common disorders occurring in patients with cancer and may have disabling symptoms. The mechanisms underlying hypercalcaemia associated with malignant disease, the symptoms attributable to and the treatment of this disorder are discussed in this paper.

Expression of the receptor for parathyroid hormone-related protein in normal and malignant breast tissue

Parathyroid hormone-related protein (PTHrP) is the cause of humoral hypercalcaemia of malignancy and interacts with parathyroid hormone (PTH) receptors. Breast cancer cells produce PTHrP in vitro and in vivo. The breast cancer cell line MCF-7, which products PTHrP and expresses PTHrP receptors, proliferates in response to PTHrP. The aim of these studies was to determine the tissue location of PTHrP/PTH receptors (PTHrPR) in primary breast carcinomas and to establish whether they had the potential to respond to PTHrP. The cellular location of mRNA for the PTHrP/PTH receptor was identified using in situ hybridization in primary breast carcinomas and normal breast tissue. Immunohistochemistry for PTHrP was carried out on the same specimens. Tumours were assessed and scored by two observers using the product of intensity of signal and number of positive tumour cells (possible range 0-9). Tumours were also assessed for Ki-67 expression by counting positive nuclei. Non-malignant ductular epithelium expressed mRNA for the PTHrP receptor (mean score 2.6, range 1-4). Breast carcinomas (mean score 4.4, range 0-9) showed variable expression of PTHrP receptor mRNA: eight tumours were negative, 50 had scores similar to normal breast tissue, and 49 had higher scores for the receptor. Levels of expression of the receptor within the primary breast carcinomas were unrelated to immunohistochemical detection of PTHrP or to any standard prognostic factor. There was a significant (P = 0.05) relationship between Ki-67 and PTHrPR expression in individual tumours. The presence of PTHrP and its receptor in normal breast epithelium and breast carcinomas demonstrates that most breast tumours are able to respond to PTHrP. The Ki-67 data suggest that PTHrP is a potential autocrine growth factor in primary breast carcinoma.

Expression and characterization of recombinant rat parathyroid hormone-related peptide (1-141) and an amino-terminally-truncated analogue (38-141)

We have synthesized and purified recombinant parathyroid hormone related peptide (PTHrP (1-141)) and PTHrP (38-141) using an E. coli system that requires minimal purification. The cDNAs encoding PTHrP (1-141) and PTHrP (35-141) respectively were inserted into the multiple cloning site of the pTrcHis-B bacterial expression plasmid. The PTHrP encoded sequences were thereby fused at their NH2-termini to six histidine residues within the fusion protein. The recombinant plasmids were transfected into E. coli cells and PTHrP synthesis was induced by addition of 1 mM isopropyl-beta-D-thiogalactopyranoside (IPTG) at 37 degrees C. The recombinant fusion proteins were purified by binding of the histidine residues to a nickel column followed by gradient elusion and dialysis. PTHrP (1-141) was released from its fusion protein by cyanogen bromide cleavage, whereas PTHrP (38-141) was released by enzymatic digestion with enterokinase. This rapid isolation method resulted in pure PTHrP (1-141) and (38-141) as judged by SDS-polyacrylamide gel electrophoresis and NH2-terminal sequence analysis. PTHrP (1-141) stimulated cAMP accumulation and mobilized intracellular calcium ([Ca2+]i) in UMR106 osteoblast-like cells, and stimulated phosphate transport in OK/E renal cells, whereas PTHrP (38-141) was inert in these bioassays. Availability of PTHrP and its NH2-terminally truncated analogue, which lacks the sequence necessary for its hypercalcemic actions, will enable their biological activities to be examined in greater detail.

Gastric cancer associated with overexpression of parathyroid hormone-related peptide (PTHrP) and PTH/PTHrP receptor in relation to tumor progression

Parathyroid hormone-related peptide (PTHrP) is involved in cell proliferation in both neoplastic and non-neoplastic tissues. We describe an autopsy case of gastric cancer in a patient who showed serum hypercalcemia and overexpression of PTHrP and PTH/PTHrP receptor in the metastatic tumor cells. The primary gastric tumor was poorly differentiated adenocarcinoma, and multiple metastases were present in the bone, multiple visceral organs, peritoneum, and lymph nodes. PTHrP and its mRNA were detected only in the metastatic tumor cells, but not in primary gastric tumor. PTH/PTHrP receptor was also demonstrated immunohistologically in metastatic tumor cells. This case suggests that the expression of PTHrP is related to tumor progression and the poor prognosis in tumors associated with humoral hypercalcemia.

Interaction of human T-cell lymphotropic virus type I Tax, Ets1, and Sp1 in transactivation of the PTHrP P2 promoter

We have previously shown that the parathyroid hormone-related protein (PTHrP) promoter contains binding sites for transcription factors Ets1 and Sp1 and that human T-cell lymphotropic virus type I (HTLV-I) Tax cooperates with Ets1 to transactivate the PTHrP P2 promoter. Using the yeast two-hybrid interaction system, we now provide evidence that Tax interacts with Ets1. Moreover, a double mutation (D22A,C23S) in the Tax protein that abrogated the Tax/Ets1 interaction also inhibited the Tax/Ets1 cooperative effect, suggesting that the interaction between Tax and Ets1 is important for transactivation of the PTHrP promoter. In coimmunoprecipitation assays, we find that Tax facilitates the interaction between Ets1 and Sp1, forming a ternary complex. When the Sp1 site in the PTHrP promoter was mutated, the Tax/Ets1 cooperative effect was dramatically decreased. This suggests that Sp1 plays an important role in the Ets1-dependent Tax transactivation of the PTHrP P2 promoter. Finally, we demonstrate that Gal4-Tax is a strong activator of the Gal PTHrP promoter, implying that Tax contributes directly to the transcriptional activation of the promoter. We propose a model in which the Tax/Ets1 cooperative effect on the PTHrP P2 promoter is based on the ability of Tax, Ets1, and Sp1 to form a ternary complex on the template DNA. Tax facilitates the interaction of Ets1/Sp1 and participates directly in the transcription initiation process.

Enhanced expression of parathyroid hormone-related protein in prostate cancer as compared with benign prostatic hyperplasia

Parathyroid hormone-related protein (PTHrP) has been shown to be the primary factor responsible for humoral hypercalcemia of malignancy. Recently PTHrP has been shown to be an early-response gene that may be involved in cellular proliferation or differentiation. In addition, PTHrP has been implicated in the pathogenesis of bone metastases. Bone metastases are a significant complication in patients with prostate cancer. We compared the expression of PTHrP by immunohistochemical staining using a monoclonal antibody directed against epitope between amino acids [53-64] in benign prostatic hyperplasia (BPH) with that in various stages of prostate cancer. Tissue sections were obtained on formalin-fixed paraffin-embedded blocks from BPH, well-differentiated prostate cancer, poorly differentiated prostate cancer, lymph node metastases (n = 15 each), and normal prostate (n = 2). In the normal prostate tissue there was no staining observed. In BPH, 13 of 15 tissue samples were positive for PTHrP immunoreactivity. An average of 33% of the cells stained positive with 1+ intensity. All samples from prostate cancer stained positive for PTHrP. In the samples from well-differentiated prostate cancer, an average of 87% of cells stained positive for PTHrP, whereas 100% of cells were positive in poorly differentiated and metastatic tumors. The intensity of staining was 3+ in well-differentiated tumors and 4+ in poorly differentiated tumors. Therefore, the expression of PTHrP is enhanced in prostate cancer as compared with BPH and is greater in poorly differentiated carcinoma as compared with the well-differentiated tumors. The role of PTHrP in the pathogenesis of prostate cancer deserves further study.

Increased PTHRP production by a tyrosine kinase oncogene, Tpr-Met: role of the Ras signaling pathway

We have used the Tpr-Met oncogene as a model to examine signaling pathways of growth factors and tyrosine kinase oncogenes that can increase parathyroid hormone-related peptide (PTHRP) production. PTHRP production in Tpr-Met transfected cells, when assessed by Northern blot analysis and radioimmunoassay, was increased four- to eightfold. Treatment of these cells with the transcriptional inhibitor actinomycin D and nuclear run-off assays showed that the major cause of increased PTHRP mRNA was enhanced gene transcription. To analyze the intracellular signaling molecules involved in PTHRP production, stable cell lines expressing a Tyr489 Phe mutant of the Tpr-Met oncoprotein were examined. The mutant fails to activate phosphatidylinositol (PI)-3 kinase or associate with the Grb-2 adaptor protein and caused a significant reduction in PTHRP production. Treatment of wild-type Tpr-Met transfected cells with wortmannin, a PI-3 kinase inhibitor, had no effect on PTHRP production; however, treatment of these cells with lovastatin, an inhibitor of p21ran isoprenylation, significantly reduced PTHRP expression. These results show that PTHRP is a downsteam target of the Tpr-Met oncogene and indicate that the PTHRP stimulating activity is mediated via the Ras signaling pathway.

Plasma parathyroid hormone related-protein levels in patients with cancer, normocalcemic and hypercalcemic

Hypercalcemia in patients with cancer may reflect the synthesis and secretion into circulation of parathyroid hormone-related protein (PTHrP) produced by the tumor. In the present study, we have measured circulating PTHrP concentrations in healthy subjects and patients using a new immunoradiometric assay (IRMA) that is specific for the 1-86 amino acid sequence of molecule, and in plasma collected with protease inhibitors. Plasma concentrations of PTHrP(1-86) were greater than the detection limit of the assay (0.3 pmol/l) in healthy subjects. All patients with hypercalcemia-associated cancer had PTHrP(1-86) levels significantly greater (median 7.74 pmol/l, P < 0.05) than healthy subjects or patients with cancer and normal serum calcium, primary hyperparathyroidism and hyperparathyroidism secondary to chronic renal failure. Plasma PTHrP and corrected serum calcium were correlated in patients with hypercalcemia-associated cancer. In one patient, a marked decrease in PTHrP and calcium levels was observed following surgery. Our results suggest that this IRMA for PTHrP(1-86) may be useful for diagnosis and monitoring of PTHrP-producing tumors induced hypercalcemia.

Parathyroid hormone-related peptide: immunolocalisation in normal salivary glands and in pleomorphic adenomas

Parathyroid hormone-related peptide (PTHrP) has been shown to be produced as an early step in the differentiation sequence and is considered to be a marker of some progenitor cells. We investigated the presence and distribution of PTHrP in 7 normal parotid glands and in 18 salivary pleomorphic adenomas (PA). Localisation of PTHrP was studied by immunohistochemistry with a three-step unlabelled peroxidase-antiperoxidase method. In the normal glands PTHrP is found mainly in the basal and dark cells, and to a lesser extent in the light cells of the ducts. In PA the inner layer of tubulo-ductal structures and all cells of the cyst-like structures show strong positivity for PTHrP. Scattered cells in the dense clusters also stain strongly. Virtually all tumour cells in myxoid and chondroid areas are devoid of staining. In clusters of squamous metaplasia, most cells are slightly positive and scattered cells are stained strongly. PTHrP contributes to cellular differentiation and is also related to keratinisation. We suggest that the PTHrP-positive inner layer cells in pleomorphic adenomas represent a step in the squamous differentiation and in the further elaboration of the tubulo-ductal structures.

Distribution and functions of parathyroid hormone-related protein in vertebrate cells

Parathyroid hormone-related protein (PTHrP) was isolated from tumors and identified as the agent of humoral hypercalcemia of malignancy (HHM) in 1987. Since then its gene structure in several mammalian and an avian species has been analyzed and its gene expression demonstrated in many adult and embryonic tissues derived from all three germ layers. The composition and structure of PTHrP peptide depends on both differential gene splicing and posttranslational processing, which result in a range of peptides of potentially diverse functions. This chapter describes the distribution of PTHrP in both normal and neoplastic adult and embryonic tissues. PTHrP is of fundamental importance to cell survival because the absence of the gene is fatal; this aspect of PTHrP function in cell physiology becomes overwhelmingly important in neoplasia. Intracrine or paracrine actions for PTHrP seem to be most likely in mammalian and avian physiology, but in fishes high circulating levels suggest classic endocrine functions as well. Much remains to be learned of the biology of this fascinating protein.

Parathyroid hormone-related protein is an autocrine modulator of rabbit proximal tubule cell growth

Parathyroid hormone-related protein (PTHrP), a likely mediator for humoral hypercalcemia of malignancy, is also synthesized in various normal tissues. In the kidney, PTHrP, mainly detected in proximal and distal tubules, has been shown to stimulate proliferation of rat mesangial cells in culture. Experiments were carried out to investigate the possible mitogenic effect of PTHrP in cultures of rabbit proximal tubule cells (PTC). Immunocytochemical analysis, using antihuman (h)PTHrP antibodies to (38-64) and (107-111) epitopes in the PTHrP molecule, showed strong cytoplasmic staining in PTC and proximal tubule-like LLC-PK1 cells. PTC secreted immunoreactive PTHrP (54.8 +/- 7.0 fmol/10(6) cells) into the culture medium. Human PTHrP(1-141) stimulated proliferation in subconfluent cultures of these cells dose-dependently. This effect was similar to that induced by [Tyr34]hPTHrP(1-34) amide (hPTHrP[1-34]), hPTHrP(1-86), and bovine (b)PTH(1-34), while hPTHrP(38-64) amide, hPTHrP9107-111) amide, and hPTHrP(107-139) amide were ineffective. Addition of anti-hPTHrP neutralizing antibodies to (1-34), (38-64), and (107-111) epitopes of PTHrP decreased PTC growth. The mitogenic effect of these agonists was abolished in confluent PTC. In contrast, [Nle8,18, Tyr34]bPTH(3-34)amide (bPTH[3-34]) increased DNA synthesis in either subconfluent or confluent PTC. In LLC-PK1 cells, which also secreted PTHrP and are devoid of PTH receptors, none of these peptides affected proliferation. Forskolin (10 microM) or H-8 (2 microM), a protein kinase A inhibitor, did not affect basal or hPTHrP(1-34)-stimulated DNA synthesis, respectively, in subconfluent PTC. On the other hand, 10 nM staurosporine and 100 nM calphostin C, protein kinase C (PKC) inhibitors, blunted the effects of hPTHrP(1-34) or bPTH(3-34) on DNA synthesis in these cells. These studies suggest that PTHrP may function as an autocrine factor in the regulation of proximal tubule cell growth by a PKC-mediated mechanism.

Identification of Metallothionein- and parathyroid hormone-related peptide (PTHrP)-positive cells in salivary gland tumours

Ductal basal cells and myoepithelial cells (MEC) of normal salivary gland share metallothionein (MT)-positivity, while PTHrP positivity is restricted to ductal basal cells. We studied 21 benign and 4 malignant tumours in which MEC are thought to play a role using immuno-histochemical methods for detecting the presence of MT and PTHrP positive cells. In benign tumours, a shared positivity for MT and PTHrP is found in the inner layer of tubulo-ductal and trabecular structures, in part of the cells in the myxoid and chondroid matrices of pleomorphic adenoma, and in the basal epithelial lining of Warthin's tumours. In myoepithelioma almost all tumour cells demonstrate MT reactivity and a restricted positivity for PTHrP. MT-positive cells in oncocytoma were demonstrated in the periphery of some oncocytic islets, while PTHrP positivity was restricted to a few oncocytic cells. In malignant tumours, positivity for MT is found in the periphery of epithelial clusters of mucoepidermoid carcinomas, while PTHrP-positive cells are seen in cyst-like structures and scattered cells in solid arrangements of squamous cells. Although the biologic significance of the presence of MT in neoplastic cells is not yet clearly understood, MT may be necessary for the growth and differentiation in actively growing cells. The variability of MT expression in salivary gland tumours could be a reflection of the morphological heterogeneity and correlate with the degree of differentiation and maturation of the tumour cells. The observations suggest that MT may be considered an oncodevelopmental product.