Presence Of Parathyroid Hormone-related Protein Research Articles

Parathyroid hormone-related protein (107-111) improves the bone regeneration potential of gelatin–glutaraldehyde biopolymer-coated hydroxyapatite

Biopolymer-coated nanocrystalline hydroxyapatite (HA) made as macroporous foams which are degradable and flexible are promising candidates as orthopaedic implants. The C-terminal (107-111) epitope of parathyroid hormone-related protein (PTHrP) exhibits osteogenic properties. The main aim of this study was to evaluate whether PTHrP (107-111) loading into gelatin–glutaraldehyde biopolymer-coated HA (HAGlu) scaffolds would produce an optimal biomaterial for tissue engineering applications. HAGlu scaffolds with and without PTHrP (107-111) were implanted into a cavitary defect performed in both distal tibial metaphysis of adult rats. Animals were sacrificed after 4weeks for histological, microcomputerized tomography and gene expression analysis of the callus. At this time, bone healing occurred only in the presence of PTHrP (107-111)-containing HAGlu implant, related to an increase in bone volume/tissue volume and trabecular thickness, cortical thickness and gene expression of osteocalcin and vascular cell adhesion molecule 1, but a decreased gene expression of Wnt inhibitors, SOST and dickkopf homolog 1. The autonomous osteogenic effect of the PTHrP (107-111)-loaded HAGlu scaffolds was confirmed in mouse and human osteoblastic cell cultures. Our findings demonstrate the advantage of loading PTHrP (107-111) into degradable HAGlu scaffolds for achieving an optimal biomaterial that is promising for low load bearing clinical applications.

The N- and C-terminal domains of parathyroid hormone-related protein affect differently the osteogenic and adipogenic potential of human mesenchymal stem cells

Parathyroid hormone-related protein (PTHrP) is synthesized by diverse tissues, and its processing produces several fragments, each with apparently distinct autocrine and paracrine bioactivities. In bone, PTHrP appears to modulate bone formation in part through promoting osteoblast differentiation. The putative effect of PTH-like and PTH-unrelated fragments of PTHrP on human mesenchymal stem cell (MSCs) is not well known. Human MSCs were treated with PTHrP (1-36) or PTHrP (107-139) or both (each at 10 nM) in osteogenic or adipogenic medium, from the start or after 6 days of exposure to the corresponding medium, and the expression of several osteoblastogenic and adipogenic markers was analyzed. PTHrP (1-36) inhibited adipogenesis in MSCs and favoured the expression of osteogenic early markers. The opposite was observed with treatment of MSCs with PTHrP (107-139). Moreover, inhibition of the adipogenic differentiation by PTHrP (1-36) prevailed in the presence of PTHrP (107-139). The PTH/PTHrP type 1 receptor (PTH1R) gene expression was maximum in the earlier and later stages of osteogenesis and adipogenesis, respectively. While PTHrP (107-139) did not modify the PTH1R overexpression during adipogenesis, PTHrP (1-36) did inhibit it; an effect which was partially affected by PTHrP (7-34), a PTH1R antagonist, at 1 microM. These findings demonstrate that both PTHrP domains can exert varying effects on human MSCs differentiation. PTHrP (107-139) showed a tendency to favor adipogenesis, while PTHrP (1-36) induced a mild osteogenic effect in these cells, and inhibited their adipocytic commitment. This further supports the potential anabolic action of the latter peptide in humans.

Cell cycle actions of parathyroid hormone-related protein in non-small cell lung carcinoma

Parathyroid hormone-related protein (PTHrP), a paraneoplastic protein expressed by two-thirds of human non-small cell lung cancers, has been reported to slow progression of lung carcinomas in mouse models and to lengthen survival of patients with lung cancer. This study investigated the effects of ectopic expression of PTHrP on proliferation and cell cycle progression of two human lung adenocarcinoma cell lines that are normally PTHrP negative. Stable transfection with PTHrP decreased H1944 cell DNA synthesis, measured by thymidine incorporation, bromodeoxyuridine uptake, and MTT proliferation assay. A substantial fraction of PTHrP-positive cells was arrested in or slowly progressing through G1. Cyclin D2 and cyclin A2 protein levels were 60-70% lower in PTHrP-expressing cells compared with control cells (P < 0.05, N = 3 independent clones per group), while expression of p27(Kip1), a cyclin-dependent kinase inhibitor, was increased by 35 +/- 9% (mean +/- SE, P < 0.05) in the presence of PTHrP. Expression of other cyclins, including cyclins D1 and D3, and cyclin-dependent kinases was unaffected by PTHrP. PTHrP did not alter the phosphorylation state of Rb, but decreased cyclin-dependent kinase (CDK) 2-cyclin A2 complex formation. Ectopic expression of PTHrP stimulated ERK phosphorylation. In MV522 cells, PTHrP had similar effects on DNA synthesis, cyclin A2 expression, pRb levels, CDK2-cyclin A2 association, and ERK activation. In summary, PTHrP appears to slow progression of lung cancer cells into S phase, possibly by decreasing activation of CDK2. Slower cancer cell proliferation could contribute to slower tumor progression and increased survival of patients with PTHrP-positive lung cancer.

Parathyroid hormone-related protein production in the lamprey Geotria australis: developmental and evolutionary perspectives

This study explored the distribution of parathyroid hormone-related protein (PTHrP) and its mRNA in tissues of the lamprey Geotria australis, a representative of one of the two surviving groups of an early and jawless stage in vertebrate evolution. For this purpose, antibodies to N-terminal and mid-molecule human PTHrP were used to determine the locations of the antigen. Sites of mRNA production were demonstrated by in situ hybridisation with a digoxigenin-labelled riboprobe to exon VI of the human PTHrP gene. The results revealed that antigen and its mRNA were widely distributed among similar sites of tissue localisation to those described for mammalian and avian species. However, some novel sites of localisation, such as in the gill and notochord, were also found. Some differences in PTHrP localisation were noted among individuals at different intervals of the life cycle, indicating that the distributions of PTHrP, and possibly its roles, change with the stage of development in this species. The widespread tissue distribution in G. australis implies diverse physiological roles for this protein. The presence of PTHrP in the lamprey, a representative of a group of vertebrates, which apparently evolved over 540 million years ago, strongly suggests that it is a protein of ancient origin. In addition, the successful use of antibodies and probes based on the human sequence in the lamprey also provides evidence that the PTHrP molecule may have been conserved from lampreys through to humans.

Parathyroid hormone-related protein (PTHrp) expression in human bone metastases (BM)

9696 Background: Substantial animal data support a major role for PTHrp in tumor induced osteolysis. However, the presence of PTHrp in BM in humans has not yet been established. The purpose of this study was to determine the presence and frequency of PTHrp expression in BM from different types of cancer. Methods: Bone pathologic fractures or BM biopsies from 64 patients, median age 63 (36–85), 36 female, were analysed. Thirty-two had breast carcinoma, 10-gastrointestinal, 6-lung, 6-prostate, and 10 several other types of cancer. The lesions were lytic in 48 patients, blastic in 10 and mixed in 6. Nineteen patients had pathologic fractures (PF). Formalin fixed, decalcified, paraffin embedded sections of metastatic lesions were stained by an immunohistochemical (IHC) method using a mouse monoclonal antibody (Chugai Pharmaceutical Co., Ltd.) to human PTHrp. The expression of PTHrp in cancer cells was graded according to the percentage of stained cells (0; 1: < 25%; 2: 25–75%; 3: > 75%) and the intensity of staining (1, 2 or 3). A final IHC score (0–9) was obtained for each patient. The Mann-Whitney test and the Kruskal-Wallis test were employed to analyse the correlation among clinical factors and the IHC score. Results: 56/64 (87.5%) of patients showed PTHrp expression in the cancer cells in bone. There was no statistically significant difference in PTHrp expression regarding the primary tumor site (breast versus non-breast; p= 0.22), the x-ray pattern of BM (lytic versus blastic, or mixed lesions, p=0.85), or ER/PR expression in breast cancer cells in bone (p= 0.35). There was a statistically significant difference in PTHrp expression in patients who had PF (median score= 6) compared to patients without PF (median score=2.5), p=0.0007. Conclusions: The expression of PTHrp in BM was high and independent of the primary tumor origin or the x-ray pattern of the bone lesions. PTHrp expression was significantly higher in patients who had PF. This study suggests that therapies targeting PTHrp to treat BM should be tried in different types of cancer and may be useful to prevent PF. No significant financial relationships to disclose.

Parathyroid hormone-related protein (PTHrp) expression in human bone metastases (BM)

9696 Background: Substantial animal data support a major role for PTHrp in tumor induced osteolysis. However, the presence of PTHrp in BM in humans has not yet been established. The purpose of this study was to determine the presence and frequency of PTHrp expression in BM from different types of cancer. Methods: Bone pathologic fractures or BM biopsies from 64 patients, median age 63 (36–85), 36 female, were analysed. Thirty-two had breast carcinoma, 10-gastrointestinal, 6-lung, 6-prostate, and 10 several other types of cancer. The lesions were lytic in 48 patients, blastic in 10 and mixed in 6. Nineteen patients had pathologic fractures (PF). Formalin fixed, decalcified, paraffin embedded sections of metastatic lesions were stained by an immunohistochemical (IHC) method using a mouse monoclonal antibody (Chugai Pharmaceutical Co., Ltd.) to human PTHrp. The expression of PTHrp in cancer cells was graded according to the percentage of stained cells (0; 1: < 25%; 2: 25–75%; 3: > 75%) and the intensity of staining (1, 2 or 3). A final IHC score (0–9) was obtained for each patient. The Mann-Whitney test and the Kruskal-Wallis test were employed to analyse the correlation among clinical factors and the IHC score. Results: 56/64 (87.5%) of patients showed PTHrp expression in the cancer cells in bone. There was no statistically significant difference in PTHrp expression regarding the primary tumor site (breast versus non-breast; p= 0.22), the x-ray pattern of BM (lytic versus blastic, or mixed lesions, p=0.85), or ER/PR expression in breast cancer cells in bone (p= 0.35). There was a statistically significant difference in PTHrp expression in patients who had PF (median score= 6) compared to patients without PF (median score=2.5), p=0.0007. Conclusions: The expression of PTHrp in BM was high and independent of the primary tumor origin or the x-ray pattern of the bone lesions. PTHrp expression was significantly higher in patients who had PF. This study suggests that therapies targeting PTHrp to treat BM should be tried in different types of cancer and may be useful to prevent PF. No significant financial relationships to disclose.

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

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. 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. 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. 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.

Parathyroid hormone-related protein (PTHrP) in cartilaginous and bony fish tissues

Tissues from a range of fish were examined for the presence of parathyroid hormone-related protein (PTHrP) to investigate PTHrP protein distribution and PTHrP gene expression in jawless fish, cartilaginous fish, and bony fish. Immunoreactive PTHrP was localized using antisera to N-terminal and mid-molecule regions of human PTHrP and PTHrP gene expression examined using a digoxigenin labeled riboprobe to a conserved region of the mammalian PTHrP gene. In all of the fish studied, PTHrP protein and messenger RNA (mRNA) were localized to the skin, kidney, and skeletal muscle, following the pattern seen in higher vertebrates. Additional sites of localization for both protein and mRNA included gill, nerve cord, and pituitary, as well as developing dermal denticles and rectal gland in the elasmobranch species. The sites of PTHrP distribution indicate that PTHrP may have roles in ionoregulation as well as growth and differentiation in fish, as has been suggested in higher vertebrates. The results imply that the distribution of PTHrP is widespread in fish and that there is homology between the PTHrP molecules found in humans and fish. The conservation of localization and possible similarity of the PTHrP molecules between tetrapods and fish suggests that PTHrP has a number of fundamental roles in vertebrates. J. Exp. Zool. 284:541–548, 1999. © 1999 Wiley-Liss, Inc.

Bone morphogenetic protein-6 and parathyroid hormone-related protein coordinately regulate the hypertrophic conversion in mouse clonal chondrogenic EC cells, ATDC5

We evaluated the roles of bone morphogenetic protein (BMP)-6, BMP-4 and parathyroid hormone-related protein (PTHrP) in the hypertrophic conversion using mouse chondrogenic EC cells, ATDC5. In ATDC5 cells, the expression of BMP-6 and PTHrP receptor mRNAs increased in parallel with the progression of chondrogenic differentiation of these cells, exhibiting a time course similar to that of type II collagen, a phenotypic marker of proliferating chondrocytes, while BMP-4 mRNA was continuously expressed throughout the differentiation processes. The expression of type X collagen mRNA, a phenotypic marker of hypertrophic chondrocytes, was upregulated by BMP-6 and BMP-4, and downregulated by PTHrP(1–141). The expression of BMP-6 mRNA was upregulated while that of BMP-4 mRNA was downregulated by both BMP-6 and BMP-4. Moreover, the expression of BMP-6 mRNA was downregulated by PTHrP(1–141). Furthermore, even in the presence of PTHrP(1–141), BMP-6 increased the transcript level of type X collagen in a dose-dependent manner. These results indicate that transiently expressed BMP-6 promotes the hypertrophic conversion in association with the augmentation of BMP-6 gene expression by BMP signals and that both BMP-6 and PTHrP coordinately regulate the rate of the hypertrophic conversion of ATDC5 cells.

BMP-6 is an autocrine stimulator of chondrocyte differentiation.

While parathyroid hormone-related protein (PTHrP) has been characterized as an important negative regulator of chondrocyte maturation in the growth plate, the autocrine or paracrine factors that stimulate chondrocyte maturation are not well characterized. Cephalic sternal chondrocytes were isolated from 13-day embryos, and the role of bone morphogenetic protein-6 (BMP-6) as a positive regulator of chondrocyte maturation was examined in monolayer cultures. Progressive maturation, which was accelerated in the presence of ascorbate, occurred in the cultures. During maturation, the cultures expressed high levels of BMP-6 mRNA which preceded the induction of type X collagen mRNA. Treatment of the cultures with PTHrP (10(-7) M) at the time of plating completely abolished BMP-6 and type X collagen mRNA expression. Removal of PTHrP after 6 days was followed by the rapid (within 24 h) expression of BMP-6 and type X collagen mRNA, with BMP-6 again preceding type X collagen expression. The addition of exogenous BMP-6 (100 ng/ml) to the cultures accelerated the maturation process both in the presence and absence of ascorbate and resulted in the highest levels of type X collagen. When exogenous BMP-6 was added to PTHrP containing cultures, maturation occurred with the expression of high levels of type X collagen, despite the presence of PTHrP in the cultures. Furthermore, BMP-6 did not stimulate expression of its own mRNA in the PTHrP treated cultures, but it did stimulate the expression of Indian hedgehog (Ihh) mRNA. These latter findings suggest that while PTHrP directly inhibits BMP-6, it indirectly regulates Ihh expression through BMP-6. Other phenotypic changes associated with chondrocyte differentiation were also stimulated by BMP-6, including increased alkaline phosphatase activity and decreased proliferation. The results suggest that BMP-6 is an autocrine factor that initiates chondrocyte maturation and that PTHrP may prevent maturation by inhibiting the expression of BMP-6.

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.

Immunohistochemical localization of parathyroid hormone-related protein in canine mammary tumors.

Parathyroid hormone-related protein (PTHrP) was localized immunohistochemically in 58 canine mammary tumors (31 malignant, 27 benign) and adjacent normal or hyperplastic mammary tissue. PTHrP immunoreactivity was significantly enhanced by pretreatment with microwave heating in normal and neoplastic tissues. Epithelial cells of hyperplastic and neoplastic mammary tissues, myoepithelial cells, and metaplastic osteoblasts in mammary tumors stained moderately to strongly positive for PTHrP No significant difference between staining intensity for PTHrP and histologic pattern of mammary tumors was found. The presence of PTHrP in normal and neoplastic canine mammary tissues supports a pathophysiological role for PTHrP as a paracrine or autocrine hormone in the mammary gland.

Parathyroid hormone-related protein detection and interaction with NO and cyclic AMP in the renovascular system

The presence of parathyroid hormone-related protein (PTHrP) in human kidney vasculature and the signal transduction pathways stimulated during PTHrP-induced vasodilation of the rabbit kidney were investigated. Immunostaining of human kidney revealed the abundant presence of PTHrP in media and intima of all microvessels as well as in macula densa. In isolated perfused rabbit kidney preconstricted with noradrenaline, 10(-5) M Rp-cAMPS, a direct inhibitor of protein kinase A, produced comparable inhibition of 2.5 x 10(-7) M forskolin- and 10(-7) M PTHrP-induced vasorelaxations. Renal vasorelaxation and renal microvessel adenylyl cyclase stimulation underwent comparable desensitization following exposure to PTHrP. Nitric oxide (NO)-synthase inhibition by L-NAME (10(-4) M), NO scavenging by an imidazolineoxyl N-oxide (10(-4) M) and guanylyl cyclase inhibition by methylene blue (10(-4) M) decreased PTHrP-induced vasorelaxation by 27 to 53%, abolished bradykinin-induced vasorelaxation and did not affect forskolin-induced vasorelaxation. The effects of Rp-cAMPS and L-NAME were not additive on PTHrP-induced vasorelaxation. Damaging endothelium by treating the kidney with either anti-factor VIII-related antibody and complement, gossypol or detergent, did not affect PTHrP- or forskolin-induced vasorelaxations but reduced bradykinin-induced vasorelaxation by 53 to 92%. Conversely, endothelial damage did not alter the inhibitory action of L-NAME on PTHrP-induced vasorelaxation. In conclusion, PTHrP is present throughout the human renovascular tree and juxtaglomerular apparatus. Activation of both adenylyl cyclase/protein kinase A and NO-synthase/guanylyl cyclase pathways are directly linked to the renodilatory action of PTHrP in a way that does not require an intact endothelium in the isolated rabbit kidney.

Immunohistochemical detection of parathyroid hormone-related protein in a rare variant of hepatic neoplasm (sclerosing hepatic carcinoma)

Sclerosing hepatic carcinoma represents an uncommon subtype of hepatic malignancy, frequently associated with hypercalcemia. We applied immunohistochemistry using the avidin-biotin-complex technique to examine the presence of parathyroid hormone-related protein (PTHrP) in formalin-fixed and paraffin-embedded sections of tissue from a case of sclerosing hepatic carcinoma obtained at autopsy. Two polyclonal antibodies against the regions 24 to 35 and 107 to 111 of human PTHrP, and a monoclonal antibody that recognizes the human sequence 38 to 64 of this protein, were used. Preabsortion tests using the corresponding synthetic peptide as antigen were done with these antibodies. The neoplastic tissue displayed cytoplasmic immunostaining, diffuse with the antibodies against the amino- or carboxy-terminal regions of PTHrP, and with a predominant peripheral pattern when using the antibody to the midregion of the molecule. Tumor cells positive for PTHrP were also positive for hepatocellular markers cytokeratins 10, 17, and 18, but negative for chromogranin A. Our findings provide the first evidence for PTHrP production in the sclerosing subtype of hepatic carcinoma.

Immunohistochemical detection of parathyroid hormone related protein in the primary tumours of hypercalcaemic breast cancer patients

Abstract Recent studies in patients with breast cancer have implicated parathyroid hormone related protein (PTHrP) in the development of bone metastases and hypercalcaemia. The aim of this study was to investigate in breast cancer patients who developed hypercalcaemia, the relationship between immunohistochemically detectable PTHrP in the primary tumour with common prognostic factors and the pattern of metastatic spread. The primary tumours of 33 breast cancer patients who subsequently developed hypercalcaemia were examined for the presence of PTHrP using an immunohistochemical technique. 76% of primary tumours were found to contain PTHrP. A relationship between positive progesterone receptor status and the presence of PTHrP was observed but no association with oestrogen receptor status, nodal status, tumour size or age was discernible. All but two patients developed bone metastases. No relationship between the presence of PTHrP in the primary tumour and pattern of metastases in this group of patients was found.

Parathyroid hormone‐related protein antigen localization distinguishes between mesothelioma and adenocarcinoma of the lung

The distinction between pleural malignant mesothelioma and pulmonary adenocarcinoma remains a problem in diagnostic histopathology. Parathyroid hormone-related protein (PTHrP) has been demonstrated in the neoplastic cells of malignant mesotheliomata, using a polyclonal antiserum raised to synthetic PTHrP(1-16). In a series of 44 malignant mesotheliomata and 44 cases of pleural adenocarcinomata, PTHrP was localized immunohistochemically in 84 per cent of the mesotheliomata and in 11 per cent of the pleural adenocarcinomata. Normal and reactive mesothelium did not contain detectable PTHrP. The presence of PTHrP in a very high percentage of malignant mesotheliomata indicates the value of including it in the panel of antibodies utilized in the differential diagnosis of mesothelioma.

Human parathyroid hormone-related protein in ovarian small cell carcinoma. An immunohistochemical study

Small cell carcinomas (SCC) are the most common ovarian tumors associated with hypercalcemia. Parathyroid hormone-related protein (PTHrp) is the most frequent cause of hypercalcemia of malignancy. The presence of PTHrp in SCC has been studied by immunohistochemistry in formalin fixed, paraffin embedded tissues. A polyclonal antibody against a synthetic peptide corresponding to the first 36-N terminal amino acid residues of PTHrp was used. Normal dog skin, which is rich in PTHrp, was used as a positive control. Absorption tests using the synthetic peptide as antigen were done in all the cases. Immunoreactivity for PTHrp was found in five of seven cases of SCC. The serum calcium levels were elevated in two of these cases, normal in two, and unknown in one. The two negative cases were associated with high serum calcium levels. The lack of correlation between immunoreactivity and serum calcium levels can be explained on the basis that immunohistochemistry is dependent on the peptide content of cells rather than on the capability for hormone production and/or release. The results suggest that PTHrp plays a role in the development of hypercalcemia in patients with SCC of the ovary.

Parathyroid hormone-related protein and human papillomavirus in gynecological tumors.

The presence of parathyroid hormone-related protein (PTHrP) and human papillomavirus (HPV) in a series of gynecological tumors from 131 unselected patients was examined. PTHrP was localized immunohistochemically using a highly specific rabbit polyclonal anti-serum against PTHrP(1-16). The results confirmed that gynecological malignancies, although rarely associated with humoral hypercalcemia of malignancy (HHM), stained for PTHrP in a majority of the squamous-cell carcinomas (SCC) at all sites, but only in a minority of adenocarcinomas, and then in areas of squamous metaplasia. This included a series of endometrial tumors. Detection of HPV types was achieved using a polymerase-chain-reaction (PCR) detection system enabling the detection of HPV types 6, 11, 16, 18, 31, 33 and 45. PTHrP production was not directly related to HPV infection, but correlated with the type of tumor.

Actions of parathyroid hormone-related protein on the renal glomerulo-vascular bed

Parathyroid hormone (PTH)-related protein (PTHrP) is the main factor responsible for the syndrome of humoral hypercalcemia of malignancy. In addition, PTHrP is produced by a multitude of normal as well as malignant cells and exerts both classic PTH-like and PTH-unlike effects despite limited sequence homology between the two peptides. Thereby, PTHrP has been detected in a wide variety of smooth muscle, both of vascular and nonvascular origin, under normal physiological conditions and exhibits potent smooth muscle relaxation especially in vessels by interacting with PTH receptors supporting the possibility that PTHrP act in an autocrine or paracrine fashion to regulate vascular tone. These observations have prompted intense inquiry into its biological function in this tissue area. The present review focusses on what we know about PTHrP actions and mechanisms of actionin vitro andin vivo in a special vascular bed, namely the intra-renal vascular, where PTHrP has been shown to be expressed.In vitro, PTHrP and PTH bind to glomerular arterioles and tubules in a sanrable and specific manner by interacting with single-class common receptors and stinulate adenylyl cyclase (AC) activity. PTHrP also stimulates AC activity in glomeruli by interaction with PTH receptors. Furthermore, PTHrP, like PTH, vasodilates isolated afferent and efferent arterioles and perfused kidney by nitric oxide-dependent and independent pathways and stimulates directly renal renin release.In vivo, localization of PTH/PTHrP dilatory effects along the renal arterial tree has been investigated on the split hydronephrotic rat kidney showing that peptides specifically and markedly dilate the preglomerular side and thas an efferent dilation is masked by preglomerular production of amgiotensin II through PTHrP-induced renin release. These properties of PTHrP with the recently discovered presence of PTHrP in glomeruli and afferent arteriole argument favorably a role for this peptide as a vascular relaxant and filtration regulator in kidney, yet a thorough understanding of its role in normal renovascular homeostasis will require further investigation.

Parathyroid hormone-related protein in gastric cancers with heterotopic ossification

Parathyroid hormone-related protein (PTHrP) has been regarded as one of the substances causing humoral hypercalcemia of malignancy. The immunohistochemical localization of PTHrP was investigated in 33 cases of gastric cancer (4 with heterotopic ossification and 29 without heterotopic ossification) to clarify the role of PTHrP in heterotopic ossification by using the anti-PTHrP monoclonal antibody, 4B3. The four cases with heterotopic ossification showed positive staining at primary or metastatic sites, and in one case fibroblasts in the stroma surrounding the heterotopic ossifying foci also showed positive. On the other hand, of the 29 cases without heterotopic ossification, only 5 showed positive staining. The presence of PTHrP in ossifying gastric carcinomas at a relatively high rate indicates that PTHrP also might be related to heterotopic ossification associated with malignancies. It is speculated that PTHrP would contribute to heterotopic ossification by facilitating the process of mineralization.