The parathyroid hormone-related protein

Uncovering Hypercalcemia of Malignancy Following Parathyroidectomy for Hyperparathyroidism

Hypercalcemia is a common complication of malignancy, often attributed to elevated PTH-related protein levels mimicking the effects of PTH and promoting bone resorption. We present the case of a 67-year-old Hispanic female with a history of hypertension, type 2 diabetes mellitus, hyperlipidemia, and chronic kidney disease, who initially underwent parathyroidectomy for suspected primary hyperparathyroidism resulting from persistent hypercalcemia. Despite surgery, the patient continued to experience hypercalcemia and was subsequently diagnosed with diffuse large B-cell lymphoma with hypercalcemia as a rare but life-threatening complication. This case highlights the importance of considering malignancy as a potential cause of hypercalcemia, particularly in the context of hematologic malignancies such as diffuse large B-cell lymphoma. Prompt recognition and management are crucial to prevent severe complications associated with hypercalcemia. A multidisciplinary approach involving oncologists, endocrinologists, and supportive care teams is essential for effective management in such cases.

Gli1-labeled adult mesenchymal stem/progenitor cells and hedgehog signaling contribute to endochondral heterotopic ossification

Heterotopic ossification (HO), acquired or hereditary, endochondral or intramembranous, is the formation of true bone outside the normal skeleton. Since perivascular Gli1+ progenitors contribute to injury induced organ fibrosis, and CD133 is expressed by a variety of populations of adult stem cells, this study utilized Cre-lox based genetic lineage tracing to test the contribution to endochondral HO of adult stem/progenitor cells that expressed either Gli1 or CD133. We found that both lineages contributed broadly to different normal tissues with distinct patterns, but that only Gli1-creERT labeled stem/progenitor cells contributed to all stages of endochondral HO in a BMP dependent, injury induced, transgenic mouse model. Hedgehog (Hh) signaling was abnormal at endochondral HO lesion sites with increased signaling surrounding the lesion but diminished signaling within it. Thus, local dysregulation of Hh signaling participates in the pathophysiology of endochondral HO. However, unlike a previous report of intramembranous HO, systemic inhibition of Hh signaling was insufficient to prevent the initiation of the endochondral HO process or to treat the existing endochondral HO, suggesting that Hh participates in, but is not essential for endochondral HO in this model. This could potentially reflect the underlying difference between intramembranous and endochondral HO. Nevertheless, identification of this novel stem/precursor cell population as a HO-contributing cell population provides a potential drugable target.

Malignant hypercalcaemia related to parathyroid hormone-related peptide (PTHrP) secretion from a metastatic pancreatic neuroendocrine tumour (NET)

A 54-year-old woman presented to our centre with acute abdominal pain and vomiting. Routine blood tests showed severe hypercalcaemia (>4 mmol/L). Serum parathyroid hormone (PTH) was suppressed. CT scan detected a pancreatic mass and some liver lesions, initially suspicious for metastatic pancreatic adenocarcinoma. Liver biopsy however revealed the presence of a well-differentiated, grade 1, metastatic neuroendocrine tumour (NET) where prognosis is considerably better. Serum PTHrP was raised, indicating paraneoplastic hypercalcaemia, most likely secondary to the pancreatic NET. Following injection of a short-acting somatostatin analogue octreotide, serum PTHrP levels normalised within 24 hours, causing a rapid drop of serum calcium below the lower limit of normal and an immediate compensatory rise of serum PTH. Ongoing treatment with long-acting somatostatin analogues together with replacement with calcium carbonate, vitamin D3 and once weekly alendronic acid resulted in stable normal adjusted calcium levels over a 3-month follow-up period.

TGF-β Induces Degradation of PTHrP Through Ubiquitin-Proteasome System in Hepatocellular Carcinoma

Both transforming growth factor-β (TGF-β) and parathyroid hormone-related protein (PTHrP) regulate important cellular processes, such as apoptosis in the development of hepatocellular carcinoma. However, the mechanisms of regulation of PTHrP by TGF-β are largely unknown. We hypothesized that TGF-β regulates the expression of PTHrP protein through a post-translational mechanism. Using hepatocellular carcinoma cell lines as the in vitro model, we investigated the effects of TGF-β on protein expression and post-translational processing of PTHrP. We found that TGF-β treatment led to protein degradation of PTHrP through the ubiquitin-proteasome-dependent pathway. We also provided evidence to show that Smurf2 was the E3 ligase responsible for the ubiquitination of PTHrP. Furthermore, using immunohistochemistry on human hepatocellular carcinoma specimens and a tissue array, we found that the expression of PTHrP was predominantly in the cancer cells, whereas the expression of TGF-β was present in non-neoplastic liver tissue adjacent to hepatocellular carcinoma. Our findings reveal a novel mechanism whereby TGF-β may regulate PTHrP in hepatocellular carcinogenesis and lack of TGF-β in hepatocellular carcinoma may promote cancer progression. Promotion of PTHrP degradation provides a novel target of therapeutic intervention to sensitize hepatocellular carcinoma cells to cytostatic and/or pro-apoptotic signals.

Parathyroid hormone-related peptide (PTHrP) secretion by gastroenteropancreatic neuroendocrine tumors (GEP-NETs): clinical features, diagnosis, management, and follow-up

CONTEXT

Only a small number of case reports has been published on patients with PTHrP-hypersecreting metastatic gastroenteropancreatic (GEP) neuroendocrine tumors (NETs).

OBJECTIVE

The objective of this study was to evaluate the clinical, biochemical, and radiological features, management, and treatment outcome of patients with PTHrP-hypersecreting GEP-NETs.

DESIGN

Retrospective case series.

SETTING

Tertiary referral hospital.

MAIN OUTCOME MEASURES

Clinical, biochemical, and radiological features were measured, as well as response to therapy and survival.

PATIENTS

Ten patients with PTHrP-secreting GEP-NETs (nine pancreatic and one unknown primary) with a median age of 50.4 years (range, 38.3-61.1) were studied. Multiple endocrine neoplasia type 1 patients were excluded.

RESULTS

The median follow-up was 57.2 months (range, 11.6-204.5 mo). Median overall survival was 86.0 months. In total, 51 different treatment interventions and combinations were applied. In seven of the 10 patients, somatostatin analog (SSA) treatment resulted in a temporary normalization of serum calcium levels with a long-term response observed in two patients (up to 35.2 mo). Peptide receptor radiotherapy (PRRT) with radiolabeled SSAs induced long-term responses ranging from 9.0-49.0 months in four of six patients treated with PRRT.

CONCLUSIONS

Hypersecretion of PTHrP by metastatic GEP-NETs is very rare and seems to be exclusively associated with metastatic pancreatic NETs. PTHrP production has major clinical impact because poorly controllable hypercalcemia is associated with increased morbidity and mortality. The most successful treatment options for PTHrP-producing GEP-NETs are SSAs and PRRT using radiolabeled SSAs. Isotonic saline and bisphosphonates can be considered as supportive therapies.

New concepts of breast cell communication to bone

Lactation is the most extreme case of normal physiological bone loss during a lifetime, and breast cancers have a strong tendency to metastasize to bone. In both the physiological and pathological circumstances, parathyroid hormone-related peptide (PTHrP) plays a central role. Until recently there were no regulatory mechanisms to explain the induction of endocrine PTHrP secretion from breast cells during lactation. The mammary epithelium possesses a local serotonin signaling system which drives PTHrP expression during lactation and in breast cancer cells. The mammary gland serotonin system is highly induced in response to alveolar dilation due to milk secretion. Discovery of serotonergic control of PTHrP suggests that it may be possible to manipulate the breast-to-bone axis by targeting serotonin signaling.

PTHrP is a novel mediator for TGF-β-induced apoptosis

Parathyroid hormone-related protein (PTHrP) is a polyhormone secretory protein that plays fundamental roles in the development and function of various tissues. Transforming growth factor (TGF)-β is an important tumor suppressor that induces cell cycle arrest and apoptosis. Increased PTHrP expression has been implicated in TGF-β-induced growth inhibition in human hepatocellular carcinoma cells. However, whether PTHrP is involved in TGF-β-induced apoptosis remains unknown. Using Hep3B and HuH-7, two human hepatocellular carcinoma cell lines, the current study examined the hypothesis that TGF-β-induced apoptosis is mediated by the induction of PTHrP expression. We found that (1) TGF-β induces PTHrP mRNA expression, protein expression and secretion in a time-dependent fashion; (2) knockdown of PTHrP gene expression or neutralization of secreted PTHrP isoforms blocks TGF-β-induced apoptosis; and (3) TGF-β-induced PTHrP expression is Smad3-dependent. Thus, we have identified PTHrP as a novel mediator for TGF-β-induced apoptosis in Hep3B cells. Our findings provide further insights into the mechanisms through which TGF-β conveys tumor suppression activity.

Parathyroid hormone-related protein: an unusual mechanism for hypercalcemia in sarcoidosis

OBJECTIVE

To describe parathyroid hormone-related protein (PTHrP) as a mediator of hypercalcemia in sarcoidosis.

METHODS

We present a detailed case report including history, physical, laboratory testing, pathology findings, and follow-up data over 2 years. We also propose a possible mechanism for PTHrP-mediated hypercalcemia in sarcoidosis.

RESULTS

A 56-year-old man presented with abdominal pain, fatigue, and excess thirst. Routine laboratory testing demonstrated severe hypercalcemia. The patient was admitted for treatment and work-up. Inpatient work-up was significant for suppressed parathyroid hormone, low 25-hydroxyvitamin D, normal 1,25-dihydroxyvitamin D, and elevated PTHrP. The patient was treated for hypercalcemia and discharged for follow-up. Malignancy screening included computed tomography of the chest, which revealed parenchymal nodules and diffuse lymphadenopathy. Biopsy revealed nonnecrotizing granulomatous inflammation with positive PTHrP staining by immunohistochemistry. After treatment with intravenous hydration and glucocorticoids, the hypercalcemia resolved and on subsequent follow-up, PTHrP levels had normalized to 0.5 pmol/L.

CONCLUSION

PTHrP may be a possible mediator of hypercalcemia in sarcoidosis. The differential diagnosis of PTHrP-induced hypercalcemia should include sarcoidosis, and further research is needed to establish the incidence and source of PTHrP in sarcoidosis.

Hypercalcemia and huge splenomegaly presenting in an elderly patient with B-cell non-Hodgkin's lymphoma: a case report

INTRODUCTION

Hypercalcemia is the major electrolyte abnormality in patients with malignant tumors. It can be due to localized osteolytic hypercalcemia or elaboration of humoral substances such as parathyroid hormone-related protein from tumoral cells. In hematological malignancies, a third mechanism of uncontrolled synthesis and secretion of 1-25(OH)2D3 from tumoral cells or neighboring macrophages may contribute to the problem. However, hypercalcemia is quite unusual in patients with B-cell non-Hodgkin's lymphoma.

CASE PRESENTATION

An 85-year-old Caucasian woman presented with low grade fever, anorexia, abdominal discomfort and fullness in her left abdomen for the last six months. She was mildly anemic and complained of fatigability. She had huge splenomegaly and was hypercalcemic. After correction of her hypercalcemia, she had a splenectomy. Microscopic evaluation revealed a malignant lymphoma. Her immunohistochemistry was positive for leukocyte common antigen, CD20 and parathyroid hormone-related peptide.

CONCLUSION

Immunopositivity for parathyroid hormone-related peptide clearly demonstrates that hypersecretion of a parathyroid hormone-like substance from the tumor had led to hypercalcemia in this case. High serum calcium is seen in only seven to eight percent of patients with B-cell non-Hodgkin's lymphoma, apparently due to different mechanisms. Evaluation of serum parathyroid hormone-related protein and 1-25(OH)2D3 can be helpful in diagnosis and management. It should be noted that presentation with hypercalcemia has a serious impact on prognosis and survival.

New insights into granin-derived peptides: evolution and endocrine roles

The granin protein family is composed of two chromogranin and five secretogranin members that are acidic, heat-stable proteins in secretory granules in cells of the nervous and endocrine systems. We report that there is little evidence for evolutionary relationships among the granins except for the chromogranin group. The main granin members, including chromogranin A and B, and secretogranin II are moderately conserved in the vertebrates. Several small bioactive peptides can be generated by proteolysis from those homologous domains existing within the granin precursors, reflecting the conservation of biological activities in different vertebrates. In this context, we focus on reviewing the distribution and function of the major granin-derived peptides, including vasostatin, bovine CgB(1-41) and secretoneurin in vertebrate endocrine systems, especially those associated with growth, glucose metabolism and reproduction.

Humoral hypercalcemia of malignancy in a patient with large cell carcinoma of the lung: report of case and review of literature

OBJECTIVE

To report a case of hypercalcemia associated with parathyroid hormone-related protein (PTHrP) in large cell carcinoma of the lung.

METHODS

We present a case of PTHrP-mediated hypercalcemia in a patient with a large cell carcinoma of the lung and review the related literature.

RESULTS

A 43-year-old African American man required medical attention because of lethargy, confusion, and poor oral intake. He had bullous emphysema attributable to a 50-pack-year smoking history. On physical examination, vital signs were normal, he was oriented to place and person but not time, and he had cachexia. Breath sounds were decreased in the left lower lung field. Findings on cardiac and abdominal examination were normal. Results of laboratory studies (and corresponding reference ranges) were as follows: calcium 12.1 mg/dL (8.5 to 10.5), albumin 2.0 g/dL (3.5 to 5.0), phosphorus 2 mg/dL (2.5 to 4.5), alkaline phosphatase 68 U/L (40 to 150), intact parathyroid hormone 5 pg/mL (10 to 60), PTHrP 7.0 pmol/L (0.0 to 1.5), 1,25-dihydroxyvitamin D 20.8 pg/mL (25.1 to 66.1), and 25-hydroxyvitamin D 3.7 ng/mL (10 to 60). Computed tomographic scans of the chest showed a large complex lesion in the left lower hemithorax, a small right pleural effusion, and extensive pulmonary emphysema bilaterally. Open lung biopsy revealed a large cell undifferentiated carcinoma. Abdominal and pelvic computed tomographic scans showed no evidence of metastatic involvement. A bone scan was negative for osseous metastatic lesions.

CONCLUSION

Although the finding is rare, patients with large cell carcinoma of the lung and hypercalcemia may have humoral hypercalcemia mediated by PTHrP.

Somatostatin receptor expression in a parathyroid hormone-related peptide-secreting pancreatic neuroendocrine tumour causing severe hypercalcaemia

BACKGROUND

Humoral hypercalcaemia is a common complication of malignancy with parathyroid hormone-related protein (PTHrP) as a major cause. Breast and lung cancer are relatively common sources of ectopic PTHrP secretion leading to increased osteoclastic bone resorption.

CASE REPORT

We report the rare case of a 40-year-old man with severe hypercalcaemia due to a PTHrP-secreting poorly differentiated endocrine carcinoma of the pancreas. On immunohistochemistry, the tumour was positive for PTHrP and somatostatin receptors sst1, sst2, and sst3, whereas sst4 and sst5 were not detected. We demonstrate the transient improvement of hypercalcaemia after adding octreotide to the treatment mainstays in hypercalcaemia of malignancy (fluid repletion, administration of bisphosphonates, loop diuretics, and glucocorticoids).

CONCLUSION

To the best of our knowledge, this is the first report showing somatostatin receptor expression in a PTHrP-secreting pancreatic neuroendocrine tumour.

Expression of parathyroid hormone-related protein (PTHrP) mRNA in mammary gland of periparturient cows

The expression of parathyroid hormone-related protein (PTHrP) mRNA was examined in mammary gland with or without lactation, and during periparturient period in a Holstein cow and a Jersey cow. In the lactating mammary gland, PTHrP was detected in alveolar epithelial cells and the lumen by immunohistochemical analysis. The relative expression levels of PTHrP mRNA in mammary gland from lactating cows were significantly higher than those from non-lactating cows (P<0.05). During periparturient period, relative PTHrP mRNA level was remarkably low before the parturition in a Jersey and a Holstein cow, however, both levels were gradually increased and reached a peak level at 5-6 weeks after the parturition. In addition, the peak level in a Jersey cow was approximately 3-fold higher than that in a Holstein cow. From these results, PTHrP was synthesized and secreted in alveolar epithelial cells in mammary gland and increased subsequently with the lactation, suggesting a possible mechanism for the regulation of local calcium homeostasis.

The role and regulation of the nuclear factor kappa B signalling pathway in human labour

Within the discipline of reproductive biology, our understanding of one of the most fundamental biological processes is lacking--the cellular and molecular mechanisms that govern birth. This lack of understanding limits our ability to reduce the incidence of labour complications. The incidence of labour complications including: preterm labour; cervical incompetence; and post-date pregnancies has not diminished in decades. The key to improving the management of human labour and delivery is an understanding of how the multiple processes that are requisite for a successful labour and delivery are coordinated to achieve a timely birth. Processes of human labour include the formation of: contraction associated proteins; inflammatory mediators (e.g. cytokines); uterotonic phospholipid metabolites (e.g. prostaglandins); and the induction of extracellular matrix (ECM) remodelling. Increasingly, it is becoming evident that labour onset and birth are the result of cross-talk between multiple components of an integrated network. This hypothesis is supported by recent data implicating various upstream regulatory pathways in the control of key labour-associated processes, including the activity of enzymes involved in the formation of prostaglandins and extracellular matrix remodelling, and mediators of inflammation. Clearly, the biochemical pathways involved in the formation of these mediators represent potential sites for intervention that may translate to therapeutic interventions to delay or prevent preterm labour and delivery. Available data strongly implicate the nuclear factor-kappaB (NF-kappaB) family as candidate upstream regulators of multiple labour-associated processes. Not only do these data warrant further detailed analysis of the involvement of these pathways in the process of human labour but also promise new insights into the key mechanisms that trigger birth and the identification of new therapeutic interventions that will improve the management of labour.

Expression of bovine parathyroid hormone/parathyroid hormone- related protein (PTH/PTHrP) receptor mRNA in the mammary gland of cows

To examine the PTH/PTHrP receptor in the mammary gland, molecular cloning of bovine PTH/PTHrP receptor and measurement of its mRNA expression were carried out in cows during the periparturient period. The PTH/PTHrP receptor gene was partially cloned, and expression of bovine PTH/PTHrP receptor mRNA was detected in various tissues of the cow. In the mammary gland, PTH/PTHrP receptor mRNA expression was constantly low during the periparturient period, whereas PTHrP mRNA expression dramatically increased after parturition. This suggested that expression of PTH/PTHrP receptor mRNA in the mammary gland is not affected by lactation in cows.

The parathyroid polyhormone hypothesis revisited

The parathyroid polyhormone hypothesis holds that peptides derived from the metabolism of parathyroid hormone (PTH) (so-called C-terminal fragments) are themselves biologically active and that their effects are mediated by a novel 'C-terminal receptor.' The evidence supporting these assertions is extensive but remains inconclusive. This Commentary focuses on in vivo pharmacology studies that provide information relevant to understanding the physiological significance of C-terminal fragments. The more recent studies of this sort provide compelling evidence that the bioactivity of C-terminal fragments is likely to become physiologically relevant in settings of secondary hyperparathyroidism. In this condition, circulating levels of C-terminal fragments greatly exceed those of PTH. There is convincing evidence that the hypocalcemic effect of C-terminal fragments results from direct actions on the skeleton that inhibit bone resorption. On the other hand, there are few if any results of in vivo studies suggesting a role for C-terminal fragments in more physiological settings, at least when parameters associated with systemic calcium homeostasis are assessed.

Persistent and moderate hypercalcemia related to an ovarian clear cell adenocarcinoma: Pre- and postoperative parathyroid hormone related-peptide and 1,25-dihydroxyvitamin D3 levels

OBJECTIVE

To evaluate the role of PTH-related peptide (PTH-rP) and 1,25-dihyhydroxyvitamin D3 in a case of hypercalcemia related to an ovarian adenocarcinoma.

DESIGN

We report a case of humoral hypercalcemia in a patient aged 74 yr with a clear cell adenocarcinoma of the right ovary at an early stage of its development (stage T1aN0M0) revealed by moderate and persistent hypercalcemia (variable level between 2.7 and 3.2 mmol/l without any treatment) over six months.

METHODS

PTH-rP and 1,25-dihydroxyvitamin D3 were measured in blood samples taken before and after hysterectomy and bilateral salpingooophorectomy and in blood samples taken intraoperatively from the right ovarian vein and a peripheral vein.

RESULTS

High levels of plasma PTH-rP and 1,25-dihydroxyvitamin D3 concomitant with high serum calcium and low PTH levels were found before surgery, which was followed by normalisation of all parameters studied. A concentration gradient was found regarding plasma PTHrP (right ovarian vein 60.4 pmol/l, peripheral vein 4.5 pmol/l), not 1,25-dihydroxyvitamin D3.

CONCLUSION

1) moderate and persistent hypercalcemia can be observed at an early stage of an ovarian carcinoma; 2) the gradient of PTH-rP concentration between the samples taken from the right ovarian vein and a peripheral vein provides evidence for a direct secretion of PTH-rP by the ovarian tumor; 3) the increased 1,25-dihydroxyvitamin D3 level is not related to a direct ovarian production, but is a consequence of PTH-rP secretion.

Parathyroid hormone secretion and action: evidence for discrete receptors for the carboxyl-terminal region and related biological actions of carboxyl- terminal ligands

PTH is a major systemic regulator of the concentrations of calcium, phosphate, and active vitamin D metabolites in blood and of cellular activity in bone. Intermittently administered PTH and amino-terminal PTH peptide fragments or analogs also augment bone mass and currently are being introduced into clinical practice as therapies for osteoporosis. The amino-terminal region of PTH is known to be both necessary and sufficient for full activity at PTH/PTHrP receptors (PTH1Rs), which mediate the classical biological actions of the hormone. It is well known that multiple carboxyl-terminal fragments of PTH are present in blood, where they comprise the major form(s) of circulating hormone, but these fragments have long been regarded as inert by-products of PTH metabolism because they neither bind to nor activate PTH1Rs. New in vitro and in vivo evidence, together with older observations extending over the past 20 yr, now points strongly to the existence of novel large carboxyl-terminal PTH fragments in blood and to receptors for these fragments that appear to mediate unique biological actions in bone. This review traces the development of this field in the context of the evolution of our understanding of the "classical" receptor for amino-terminal PTH and the now convincing evidence for these receptors for carboxyl-terminal PTH. The review summarizes current knowledge of the structure, secretion, and metabolism of PTH and its circulating fragments, details available information concerning the pharmacology and actions of carboxyl-terminal PTH receptors, and frames their likely biological and clinical significance. It seems likely that physiological parathyroid regulation of calcium and bone metabolism may involve receptors for circulating carboxy-terminal PTH ligands as well as the action of amino-terminal determinants within the PTH molecule on the classical PTH1R.

Substrates of the prostate-specific serine protease prostase/KLK4 defined by positional-scanning peptide libraries

BACKGROUND

Prostase/KLK4 is a member of the human kallikrein (KLK) gene family that is expressed in prostate epithelial cells under the regulation of androgenic hormones. In this study, we sought to characterize the substrate specificity of KLK4 in order to gain insight into potential physiological roles of the enzyme.

METHODS

A chimeric form of KLK4 was constructed in which the pro-region of KLK4 was replaced with the signal and propeptide sequence of trypsinogen (proT-KLK4) to create an activation site susceptible to enterokinase cleavage. proT-KLK4 was expressed in Drosophila S2 cells, purified, and activated with enterokinase to generate mature KLK4. The extended substrate specificity of KLK4 was defined by screening tetrapeptide positional scanning synthetic combinatorial libraries (PS-SCL).

RESULTS

The preferred P1-P4 positions as determined by PS-SCL were: P1-Arg; P2-Gln/Leu/Val; P3-Gln/Ser/Val; P4-Ile/Val. The trypsin-like specificity of KLK4 was further confirmed using synthetic chromogenic peptides. Based upon the optimal cleavage site residues, a database search for potential KLK4 substrates identified several proteins with potential roles mediating normal prostate physiology or neoplastic growth including KLK3/PSA, parathyroid hormone-related peptide (PTHrP), and members of the bone morphogenetic protein (BMP) family. Recombinant KLK4 was able to activate pro-PSA/KLK3 and degrade members of the insulin-like growth factor (IGF) binding protein (IGFBP) family.

CONCLUSIONS

These results identify potential KLK4 substrates that may serve to define the role of this protease in normal prostate physiology, and facilitate studies of the consequences of KLK4 expression in pathological conditions.

Effect of nuclear factor-kappa B inhibitors and peroxisome proliferator-activated receptor-gamma ligands on PTHrP release from human fetal membranes

Parathyroid hormone-related protein (PTHrP) has been implicated in many processes during normal and pathological pregnancies. In the human fetal membranes, PTHrP exhibits cytokine-like actions. We have recently shown that inhibitors of the nuclear factor-kappa B (NF-kappaB) and activators of the peroxisome proliferator-activated receptor (PPAR)-gamma signalling pathways down-regulate cytokine release from human gestational tissues. Therefore, the aim of this study was to determine whether NF-kappaB and PPAR-gamma also regulate PTHrP release from human fetal membranes. Human amnion and choriodecidua explants were incubated in the absence (control) or presence of two known NF-kappaB inhibitors (1, 5 and 10 mM sulphasalazine (SASP) or 5, 10 and 15 mM N-acetyl-cysteine (NAC)), and two PPAR-gamma ligands (15 and 30 microM 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) or 15 and 30 microM troglitazone), under basal conditions. After 18 h incubation, the tissues were collected and NF-kappaB p65 DNA binding activity in nuclear extracts was assessed by ELISA, and the incubation medium was collected and the release of PTHrP was quantified by RIA. Treatment of amnion and choriodecidual tissues with SASP concentrations greater than 5 mM, 15 mM NAC, 30 microM 15d-PGJ(2) and 30 microM troglitazone significantly reduced the release of PTHrP (p < 0.05). This study demonstrates that PTHrP release from human fetal membranes is regulated by inhibitors of NF-kappaB, and ligands of PPAR-gamma.

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.

Disorders of calcium homeostasis

To ensure a multitude of essential cellular functions, the extracellular concentration of calcium is maintained within a narrow physiological range. This depends on integrated regulation of calcium fluxes with respect to the intestine, kidneys and bone. The precise regulation of serum calcium is controlled by calcium itself, through a calcium receptor and several hormones, the most important of which are parathyroid hormone and 1,25(OH)(2) vitamin D. This balance can be disturbed by mutations in the calcium-sensing receptor, inappropriately high or low levels of parathyroid hormone, resistance to parathyroid hormone effects, insufficient intake or production of 1,25(OH)(2) vitamin D and inactivation of the vitamin D receptor. Mineral homeostasis is moreover influenced by many other systemic factors (e.g. sex steroid, thyroid and glucocorticoid hormones) or humoral factors (e.g. cytokines and growth factors). A specific example is the major abnormalities of mineral homeostasis in case of malignancy by excessive production of parathyroid hormone-related peptide resulting in hypercalcaemia. Several new drugs have been developed based on factors in this axis, including calcimimetics, calcilytics, vitamin D analogues and parathyroid hormone-related peptide inhibitors.

Widespread expression of parathyroid hormone-related peptide in melanocytic cells

BACKGROUND

Parathyroid hormone-related peptide (PTH-rP) was associated with the syndrome of hypercalcaemia of malignancy. An increased serum level of PTH-rP could occur in patients with advanced melanoma.

OBJECTIVES

We examined PTH-rP expression in cultured melanocytic cell lines and in lesions of melanocytic origin for associations with clinicopathological variables of disease progression. We measured the supernatant and cell lysate level of PTH-rP in cultured melanoma cells to clarify whether melanoma cells secrete PTH-rP.

METHODS

PTH-rP expression was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) in cultured melanocytic cell lines and by immunoperoxidase staining in 18 melanocytic naevi, 40 primary melanoma and 19 metastatic melanoma lesions. The supernatant level of PTH-rP was measured with an immunoradiometric assay.

RESULTS

RT-PCR products of PTH-rP mRNA were detected in six of eight melanoma cell lines; however, neither naevus cells nor melanocytes showed positive products. On the other hand, immunohistochemical analysis showed that PTH-rP was widely expressed both in benign and malignant melanocytic lesions. In addition, PTH-rP expression was not associated with any clinicopathological variables. Cell lysate but not the supernatant of melanoma cells showed high PTH-rP levels.

CONCLUSIONS

These results suggest that PTH-rP was widely expressed in melanocytic cells; however, the cells did not secrete PTH-rP.

Transforming growth factor beta regulates parathyroid hormone-related protein expression in MDA-MB-231 breast cancer cells through a novel Smad/Ets synergism

The majority of breast cancers metastasizing to bone secrete parathyroid hormone-related protein (PTHrP). PTHrP induces local osteolysis that leads to activation of bone matrix-borne transforming growth factor beta (TGF beta). In turn, TGF beta stimulates PTHrP expression and, thereby, accelerates bone destruction. We studied the mechanism by which TGF beta activates PTHrP in invasive MDA-MB-231 breast cancer cells. We demonstrate that TGF beta 1 up-regulates specifically the level of PTHrP P3 promoter-derived RNA in an actinomycin D-sensitive fashion. Transient transfection studies revealed that TGF beta 1 and its effector Smad3 are able to activate the P3 promoter. This effect depended upon an AGAC box and a previously described Ets binding site. Addition of Ets1 greatly enhanced the Smad3/TGF beta-mediated activation. Ets2 had also some effect, whereas other Ets proteins, Elf-1, Ese-1, and Erf-1, failed to cooperate with Smad3. In comparison, Ets1 did not increase Smad3/TGF beta-induced stimulation of the TGF beta-responsive plasminogen activator inhibitor 1 (PAI-1) promoter. Smad3 and Smad4 were able to specifically interact with the PTHrP P3-AGAC box and to bind to the P3 promoter together with Ets1. Inhibition of endogenous Ets1 expression by calphostin C abrogated TGF beta-induced up-regulation of the P3 transcript, whereas it did not affect the TGF beta effect on PAI expression. In TGF beta receptor II- and Ets1-deficient, noninvasive MCF-7 breast cancer cells, TGF beta 1 neither influenced endogenous PTHrP expression nor stimulated the PTHrP P3 promoter. These data suggest that TGF beta activates PTHrP expression by specifically up-regulating transcription from the PTHrP P3 promoter through a novel Smad3/Ets1 synergism.