Expression of parathyroid hormone related protein in normal skin and in tumours of skin and skin appendages

Risk of keratinocyte carcinomas with vitamin D and calcium supplementation: a secondary analysis of a randomized clinical trial

BACKGROUND

It is unknown whether dietary supplementation with vitamin D or calcium prevents keratinocyte carcinomas, also known as nonmelanoma skin cancers.

OBJECTIVES

This study aimed to determine whether daily vitamin D or calcium supplementation alters the risk of basal cell carcinoma (BCC) or invasive cutaneous squamous cell carcinoma (SCC).

METHODS

The Vitamin D/Calcium Polyp Prevention Study is a completed multicenter, double-blind, placebo-controlled, partial 2 × 2 factorial, randomized clinical trial of vitamin D, calcium, or both for the prevention of colorectal adenomas. During 2004-2008, a total of 2259 men and women, 45-75 y of age, recently diagnosed with a colorectal adenoma, were randomly assigned to 1000 IU/d of vitamin D3 or placebo and 1200 mg/d of calcium carbonate or placebo for 3 or 5 y, and followed after treatment ended. Reports of incident BCC or SCC were confirmed from pathology records.

RESULTS

During a median follow-up of 8 y, 200 (9%) participants were diagnosed with BCC and 68 (3%) participants were diagnosed with SCC. BCC incidence was unrelated to treatment with vitamin D compared with no vitamin D (HR: 0.96; 95% CI: 0.73, 1.26), calcium compared with no calcium (HR: 1.01; 95% CI: 0.74, 1.39), and both agents compared with neither (HR: 0.99; 95% CI: 0.65, 1.51). SCC incidence was unrelated to treatment with vitamin D compared with no vitamin D (HR: 0.79; 95% CI: 0.49, 1.27), but there was suggestive evidence of beneficial treatment effects for calcium compared with no calcium (HR: 0.60; 95% CI: 0.36, 1.01) and both agents compared with neither (HR: 0.42; 95% CI: 0.19, 0.91).

CONCLUSIONS

Calcium alone or in combination with vitamin D may reduce the risk of SCC, but not BCC. This trial was registered at clinicaltrials.gov as NCT00153816.

Translational Neuroendocrinology of Human Skin: Concepts and Perspectives

Human skin responds to numerous neurohormones, neuropeptides, and neurotransmitters that reach it via the vasculature or skin nerves, and/or are generated intracutaneously, thus acting in a para- and autocrine manner. This review focuses on how neurohormones impact on human skin physiology and pathology. We highlight basic concepts, major open questions, and translational research perspectives in cutaneous neuroendocrinology and argue that greater emphasis on neuroendocrine human skin research will foster the development of novel dermatological therapies. Furthermore, human skin and its appendages can be used as highly accessible and clinically relevant model systems for probing nonclassical, ancestral neurohormone functions. This calls for close interdisciplinary collaboration between dermatologists, skin biologists, neuroendocrinologists, and neuropharmacologists.

The effect of parathyroid hormones on hair follicle physiology: implications for treatment of chemotherapy-induced alopecia

Parathyroid hormone (PTH) and parathyroid hormone-related protein (PTHrP) influence hair follicles through paracrine and intracrine routes. There is significant evidence that PTH and PTHrP influence the proliferation and differentiation of hair follicle cells. The PTH/PTHrP receptor signalling plays an important role in the hair follicle cycle and may induce premature catagen-telogen transition. Transgenic mice with an overexpression or blockade (PTH/PTHrP receptor knockout mice) of PTHrP activity revealed impaired or increased hair growth, respectively. Some findings also suggest that PTHrP may additionally influence the hair cycle by inhibiting angiogenesis. Antagonists of the PTH/PTHrP receptor have been shown to stimulate proliferation of hair follicle cells and hair growth. A hair-stimulating effect of a PTH/PTHrP receptor antagonist applied topically to the skin has been observed in hairless mice, as well as in mice treated with cyclophosphamide. These data indicate that the PTH/PTHrP receptor may serve as a potential target for new (topical) hair growth-stimulating drugs, especially for chemotherapy-induced alopecia.

Hormones and the pilosebaceous unit

Hormones can exert their actions through endocrine, paracrine, juxtacrine, autocrine and intracrine pathways. The skin, especially the pilosebaceous unit, can be regarded as an endocrine organ meanwhile a target of hormones, because it synthesizes miscellaneous hormones and expresses diverse hormone receptors. Over the past decade, steroid hormones, phospholipid hormones, retinoids and nuclear receptor ligands as well as the so-called stress hormones have been demonstrated to play pivotal roles in controlling the development of pilosebaceous units, lipogenesis of sebaceous glands and hair cycling. Among them, androgen is most extensively studied and of highest clinical significance. Androgen-mediated dermatoses such as acne, androgenetic alopecia and seborrhea are among the most common skin disorders, with most patients exhibiting normal circulating androgen levels. The "cutaneous hyperandrogenism" is caused by in stiu overexpression of the androgenic enzymes and hyperresponsiveness of androgen receptors. Regulation of cutaneous steroidogenesis is analogous to that in gonads and adrenals. More work is needed to explain the regional difference within and between the androgn-mediated dermatoses. The pilosebaceous unit can act as an ideal model for studies in dermato-endocrinology.

Oral propylthiouracil for the treatment of resistant plaque psoriasis

BACKGROUND

Propylthiouracil (PTU) has been used in the treatment of hyperthyroidism for many years and inhibits the enzyme 5'-deiodinase, which converts thyroxine to triiodothyronine. Several studies have reported PTU as an effective treatment for plaque psoriasis. PTU exhibits immunomodulatory effects; however, its exact mechanism of action in psoriasis is unknown. Few patients were studied in these reports and treatment with PTU was continued for no longer than 8 weeks.

METHODS

In this study we report on four patients with resistant plaque psoriasis who had treatment with oral PTU for 4-32 weeks (mean 18.4).

RESULTS

Three of the four patients exhibited moderate clinical improvement with reductions in psoriasis severity observed within 4-6 weeks of commencing PTU therapy. The side effects noted were subclinical hypothyroidism in two patients and worsening of muscle aches in one patient. Monitoring included regular thyroid function, full blood count, and liver and renal function tests.

CONCLUSION

This study illustrates that oral PTU can be a useful addition to the therapy of resistant cases of plaque psoriasis and shows that this treatment can be continued for longer than 8 weeks with few side effects occurring secondary to PTU.

Immunohistochemical localization of parathyroid hormone-related protein (PTHrP) and serum PTHrP in normocalcemic patients with oral squamous cell carcinoma

Cancer cells produce parathyroid hormone-related protein (PTHrP) in the early phase of malignancy development, before hypercalcemia occurs. The relationship between PTHrP and the clinicopathologic features of oral squamous cell carcinoma is poorly understood. We studied 60 patients (43 men, 17 women; mean age, 64.8 +/- 11.2 years) with primary oral squamous cell carcinoma, from whom pretreatment biopsy specimens were obtained. We examined the relationship among immunohistochemical PTHrP expression, serum PTHrP levels, clinical characteristics of the tumor, and histopathologic aspects of the tumor. The mean calcium concentration for the 60 patients was 9.1 +/- 0.4 mg/dl. No patients had laboratory evidence of hypercalcemia before treatment. Six patients had serum levels of C-terminal (C)-PTHrP higher than the normal level of 55.3 pmol/l. There were no significant differences in serum C-PTHrP levels according to TNM stages. Abundant positive immunoreactivity for anti-PTHrP (1-34) antibody was recognized diffusely in the whole cytoplasm of many tumor cells. Anti-PTHrP (38-64) antibody staining tended to localize as small granules in the cytoplasm, especially close to the nuclear periphery. There was no correlation between the serum C-PTHrP concentration and the intensity of either immunostain. The intensity of PTHrP was proportionally related to the degree of differentiation or extent of keratinization (P < 0.05) and the histologic malignancy grade of the tumor (P < 0.05), when using antibody against PTHrP (1-34), but not when using antibody against PTHrP (38-64). Serum C-PTHrP levels did not correlate with the intensity of cellular PTHrP expression and characteristics of the tumor at the initial patient visit. The fragment that includes PTHrP (1-34) may be involved in the differentiation of oral squamous cell carcinoma. The differences between immunoreactivities may have been due to differing tissue malignancies and the use of different antibodies. The results suggest the need for caution when interpreting immunoreactivities of PTHrP in malignancies.

Initial characterization of PTH-related protein gene-driven lacZ expression in the mouse

The PTHrP gene generates low-abundance mRNA and protein products that are not easily localized by in situ hybridization histochemistry or immunohistochemistry. We report here a PTHrP-lacZ knockin mouse in which beta-gal activity seems to provide a simple and sensitive read-out of PTHrP gene expression.

INTRODUCTION

PTH-related protein (PTHrP) is widely expressed in fetal and adult tissues, typically as low-abundance mRNA and protein products that maybe difficult to localize by conventional methods. We created a PTHrP-lacZ knockin mouse as a means of surveying PTHrP gene expression in general and of identifying previously unrecognized sites of PTHrP expression.

MATERIALS AND METHODS

We created a lacZ reporter construct under the control of endogenous PTHrP gene regulatory sequences. The AU-rich instability sequences in the PTHrP 3' untranslated region (UTR) were replaced with SV40 sequences, generating products with lacZ/beta gal kinetics rather than those of PTHrP. A nuclear localization sequence was not present in the construct.

RESULTS

We characterized beta-galactosidase (beta-gal) activity in embryonic whole mounts and in the skeleton in young and adult animals. In embryos, we confirmed widespread PTHrP expression in many known sites and in several novel epidermal appendages (nail beds and footpads). In costal cartilage, beta-gal activity localized to the perichondrium but not the underlying chondrocytes. In the cartilaginous molds of forming long bones, beta-gal activity was first evident at the proximal and distal ends. Shortly after birth, the developing secondary ossification center formed in the center of this PTHrP-rich chondrocyte population. As the secondary ossification center developed, it segregated this population into two distinct PTHrP beta-gal+ subpopulations: a subarticular subpopulation immediately subjacent to articular chondrocytes and a proliferative chondrocyte subpopulation proximal to the chondrocyte columns in the growth plate. These discrete populations remained into adulthood. beta-gal activity was not identified in osteoblasts but was present in many periosteal sites. These included simple periosteum as well as fibrous tendon insertion sites of the so-called bony and periosteal types; the beta-gal-expressing cells in these sites were in the outer fibrous layer of the periosteum or its apparent equivalents at tendon insertion sites. Homozygous PTHrP-lacZ knockin mice had the expected chondrodysplastic phenotype and a much expanded region of proximal beta-gal activity in long bones, which appeared to reflect in large part the effects of feedback signaling by Indian hedgehog on proximal cell proliferation and PTHrP gene expression.

CONCLUSIONS

The PTHrP-lacZ mouse seems to provide a sensitive reporter system that may prove useful as a means of studying PTHrP gene expression.

Hair-cycle-dependent expression of parathyroid hormone-related protein and its type I receptor: evidence for regulation at the anagen to catagen transition

The humoral hypercalcemia factor parathyroid hormone-related protein is a paracrine-signaling molecule that regulates the development of several organ systems, including the skin. In pathologic circumstances such as hypercalcemia and in development, parathyroid hormone-related protein signaling appears to be mediated by the type I parathyroid hormone/parathyroid hormone-related protein receptor. In order to clarify the role of the ligand and receptor pair in cutaneous biology, gene expression was monitored in a series of murine skin samples ranging from embryonic day 14 to 2 y with in situ hybridization and RNase protection. In all samples, high levels of parathyroid hormone-related protein transcripts were exclusively expressed in the developing and adult hair follicle but were not observed in the interfollicular epidermis. In the adult, parathyroid hormone-related protein mRNA expression was dynamically regulated as a function of the murine hair cycle in a way similar to other signaling molecules that regulate the anagen to catagen transition. PTH receptor transcripts were abundantly expressed in the developing dermis. In the adult skin, PTH receptor mRNA was markedly reduced, but again demonstrated hair-cycle-dependent expression. The dorsal skin of the keratin 14-parathyroid hormone-related protein mouse was used to evaluate the impact of overexpression of the peptide on the murine hair cycle. All types of hair were 30-40% shorter in adult keratin 14-parathyroid hormone-related protein mice as compared with wild-type littermates. This appeared to result from a premature entry into the catagen phase of the hair cycle. Finally, the relationship between parathyroid hormone-related protein signaling and other growth factors that regulate the hair cycle was examined by cross-breeding experiments employing keratin 14-parathyroid hormone-related protein mice and fibroblast growth factor-5-knockout mice. It appears that parathyroid hormone-related protein and fibroblast growth factor-5 regulate the anagen to catagen transition by independent pathways.

Functional type I PTH/PTHrP receptor in freshly isolated newborn rat keratinocytes: identification by RT-PCR and immunohistochemistry

The presence of identical or distinct type I parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) receptors in keratinocytes is still a matter of debate. We studied the expression and functionality of PTHrP receptors in freshly isolated keratinocytes from newborn rat skin. Four overlapping primers, amplifying different regions in the rat PTH receptor, were used for reverse transcriptase-polymerase chain reaction (RT-PCR). The first region corresponded to the N-terminal extracellular region and the first transmembrane domain (S/M1), the second region amplified the connecting intracellular and extracellular loops transmembrane domain (E2/M5), the third spanned the range from the transmembrane to the intracellular domain (M4/T), and the fourth region amplified the C-terminal tail (M6/7/T). The PCR products from the keratinocyte RNA were identical to those from kidney RNA of the same rats. The cloned four transcripts showed 100% of homologies with the cDNA sequence from bone ROS cells. Keratinocytes, freshly isolated or present in situ in the epidermis, recognized an anti-PTH receptor antibody (PTH-II) directed against the receptor extracellular domain. Western blotting showed the same protein patterns in keratinocytes, kidney, and ROS cell extracts. Low doses of PTHrP(1-34) (10(-12)-10(-9) M) increased the cell number studied by [3H]thymidine incorporation and DNA content. Treatment with the PTH/PTHrP receptor antagonist [Asn10, Leu11, D Trp12] PTHrP(7-34) or two different PTH receptor antibodies inhibited the increase in cell proliferation induced by PTHrP(1-34). All these findings indicate that newborn rat epidermis and keratinocytes express functional PTHrP receptors, which are identical to type I PTH/PTHrP receptor and are recognized by PTHrP(1-34).

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.

Messenger RNA stability of parathyroid hormone-related protein regulated by transforming growth factor-beta1

Humoral hypercalcemia of malignancy (HHM), a paraneoplastic syndrome associated with epithelial cancers, including squamous cell carcinoma (SCC), is due to expression and secretion of parathyroid hormone-related protein (PTHrP). Transforming growth factor-beta1 (TGFbeta1), expressed by many tumors, has been demonstrated in vitro to increase the half-life of PTHrP mRNA. In this study, oral squamous carcinoma cells (SCC2/88) had a two-fold increase in PTHrP mRNA stability (from 45 to 90 min) in response to treatment with TGFbeta1. In order to examine the mechanism of TGFbeta1-mediated PTHrP mRNA stability, a cell-free assay of mRNA degradation was utilized in which the degradation of in vitro-transcribed mRNA incubated with cytoplasmic protein extracts from SCC2/88 treated with vehicle or TGFbeta1 was measured. In this assay, full-length PTHrP mRNA was not significantly stabilized in TGFbeta1-treated samples when compared to vehicle treated samples. However, there was a striking (>5-fold) increase in PTHrP mRNA half-life in TGFbeta1-treated samples when PTHrP mRNA lacked the 3'-untranslated region (3'-UTR). In contrast, the degradation of 3'-UTR-truncated PTHrP mRNA using the cell-free assay was not altered in vehicle-treated samples. UV cross-linking of PTHrP mRNA and cytoplasmic proteins from cells treated with either vehicle or TGFbeta1 revealed numerous mRNA-binding proteins. TGFbeta1 treatment resulting in decreased binding of 33, 31, 27, 20 and 18 kDa binding proteins to the terminal coding region. These studies revealed that TGFbeta1-induced PTHrP mRNA stability might be, in part, the result of cis-acting sequences within the coding region of the PTHrP mRNA.

Head and neck squamous cell carcinoma: measurement of plasma parathyroid hormone-related protein and serum and urine calcium concentrations

OBJECTIVES

Parathyroid hormone-related protein (PTHrP) is expressed by squamous cell carcinomas. Our first objective was to examine the stability of PTHrP in normal human plasma. Our second objective was to determine whether plasma PTHrP could be used in patients with head and neck squamous cell carcinoma (HNSCC) as an indicator of tumor burden or relapse.

STUDY DESIGN AND SETTING

Blood and urine samples from 55 HNSCC patients undergoing tumor resection at The Ohio State University were measured for plasma PTHrP (1-86) concentration, serum ionized calcium concentration, and urine calcium/creatinine ratio.

RESULTS

Two of 55 HNSCC patients had detectable levels of plasma PTHrP. Serum ionized calcium concentrations and urinary calcium/creatinine ratios were within normal limits in all patients.

CONCLUSIONS

Plasma PTHrP was not a valuable indicator of tumor presence or recurrence in our patient population.

SIGNIFICANCE

Plasma PTHrP is not a useful marker of tumor presence or recurrence in patients with stage II to IV or recurrent HNSCC.

The parathyroid hormone-related protein

Many physiologic roles of PTHrP are emerging. The protein functions locally in diverse tissues, often regulating the entry of cells into a differentiation pathway or acting as an epithelial signal in epithelial-mesenchymal interactions. To carry out these functions, PTHrP uses the receptor it shares with PTH or one of several PTHrP receptors that have evolved to recognize selectively the PTH-like region of PTHrP or other domains. Thus, PTHrP is a polyhormone. An exquisite selectivity barrier allows PTHrP to carry out its local tissue functions at the same time PTH uses their shared receptor to regulate systemic calcium homeostasis. This barrier is breached under pathologic circumstances, such as when malignant tumors secrete enough PTHrP into blood to cause PTH-like effects, including hypercalcemia. Powerful genetic models that have been developed in the past 7 years promise to give continuing insights into the physiology and pathophysiology of PTHrP.

Regulation of parathyroid hormone-related protein expression in a canine squamous carcinoma cell line by colchicine

The regulation of parathyroid hormone-related protein expression by colchicine, vinblastine, nocodazole, taxol, transforming growth factor-beta1 (TGFbeta1), and epidermal growth factor (EGF) was investigated in a canine squamous carcinoma cell line (SCC 2/88 cells). SCC 2/88 cells were stably transfected with a human P2/P3 PTHrP promoter-luciferase reporter gene construct and gene expression was measured after chemical treatments. The greatest increase in reporter gene expression was observed after colchicine treatment and small increases occurred after treatment with vinblastine, taxol, TGFbeta1, or EGF. Nocodazole had no significant effect on reporter gene expression. Colchicine also increased PTHrP steady state mRNA expression and PTHrP secretion by SCC 2/88 cells. These results demonstrated that PTHrP production was increased in SCC 2/88 cells by colchicine and suggested that factors or events during mitosis are capable of stimulating PTHrP production. An increase in PTHrP production during mitosis of malignant epithelial cells may be important in the pathogenesis of humoral hypercalcemia of malignancy.

Human keratinocytes express transcripts for three isoforms of parathyroid hormone-related protein (PTHrP), but not for the parathyroid hormone/PTHrP receptor: effects of 1,25(OH)2 vitamin D3

Parathyroid hormone-related protein (PTHrP) is strongly expressed in the epidermis and has been implicated in the regulation of growth and differentiation of keratinocytes. PTHrP has N-terminal sequence homology with parathyroid hormone (PTH) and binds to the type I PTH/PTHrP receptor, but earlier reports suggest that keratinocytes do not possess this cell surface receptor. In order to determine which PTHrP mRNA isoforms are expressed by keratinocytes and whether the type I receptor mRNA is present, we designed specific primers for reverse transcriptase-polymerase chain reaction. The interaction of PTHrP with other promoters of keratinocyte differentiation is unclear. In particular, 1,25(OH)2D3 is also fundamental in calcium homeostasis and induces changes in intracellular calcium. We therefore investigated the effect of 1,25(OH)2D3 on PTHrP mRNA expression and protein production in cultured human keratinocytes. Cells were incubated for 3 days at concentrations of 1.25(OH)2D3 of 10(-10)-10(-6) mol/L. PTHrP in culture supernatant, measured by two site immunoradiometric assay, was 915 +/- 98 PTHrP fmol/mg of cell layer protein in untreated cultures decreasing to 570 +/- 113 with 10(-8) mol/L and 402 +/- 24 with 10(-6) mol/L 1,25(OH)2D3 (mean +/- SEM, P < 0.01, n = 6). Transcripts for all three PTHrP isoforms (139, 141 and 173 amino acids) were detectable in keratinocyte mRNA. Corresponding to the decrease in PTHrP protein we demonstrated a reduction in all three PTHrP mRNA transcripts after 3 days' incubation with 1,25(OH)2D3 over a concentration range 10(-10)-10(-6) mol/L. Repeated studies failed to detect type I PTH/PTHrP receptor mRNA in human keratinocytes, either in control cultures or in the presence of 1,25(OH)2D3. We have shown that keratinocytes produce abundant PTHrP and that this is modulated by 1,25(OH)2D3, suggesting a physiological role. Further studies are required to investigate the relative expression of PTHrP isoforms, their role in keratinocyte signalling and the receptors involved.

PTHrP and cell division: expression and localization of PTHrP in a keratinocyte cell line (HaCaT) during the cell cycle

Parathyroid hormone-related protein (PTHrP) is highly expressed in normal skin keratinocytes, and its involvement in growth and differentiation processes in these cells has been implicated by several lines of evidence which include the use of antisense PTHrP (Kaiser et al., 1994, Mol. Endocrinol., 8:139-147). In this study, we have investigated whether PTHrP expression and its subcellular localization is linked to cell cycle progression in a human keratinocyte cell line (HaCat), which constitutively expresses and secretes PTHrP. PTHrP mRNA and immunoreactive PTHrP were assessed in asynchronous dividing cells and in cells blocked at G1 or G2 + M phases of the cell cycle using several different protocols. The response of PTHrP mRNA expression was examined following readdition of serum in the continued presence of cycle blockers, and after release from cell cycle block, or from cell synchronization by serum deprivation. PTHrP expression was greatest in actively dividing cells when cells were in S and G2 + M phases of the cell cycle and were lowest in quiescent G1 cells. Most notable were the high levels of PTHrP mRNA and protein in cells at G2 + M phase of the cell cycle at division. Furthermore, PTHrP was localized to the nucleolus in quiescent cells, but redistributed to the cytoplasm when cells were actively dividing. Taken together, these results support a role for PTHrP in cell division in keratinocytes. In asynchronously growing cells, PTHrP expression fell as cells became confluent at a time when cell growth is inhibited and cells begin to differentiate. Mitogen stimulation of HaCaT cells resulted in a rapid increase in PTHrP mRNA expression, but was dependent upon cells being in the G1 phase of the cell cycle. Cells blocked in G1 responded to mitogen both in the continued presence of aphidicolin or when released from block. Cells blocked at G2 + M with colcemid expressed high levels of PTHrP mRNA and protein, and PTHrP mRNA did not respond further to mitogen in the continued presence of blocker. However, in cells released from block at G2 + M by addition of serum, an increase in PTHrP expression was seen coincident with the progression of cells into G1. In contrast, in a squamous cancer cell line (COLO16), basal PTHrP expression was high and was not altered during the cell cycle or by cell cycle block, consistent with association of its dysregulated expression in malignant cells. The results of this study suggest that PTHrP may have two roles in the cell cycle; one in G1 in response to mitogen, and a second at cell division when its expression is high and it is relocated from the nucleolus to the cytoplasm.

Effects of excess PTH on nonclassical target organs

The classical target organs for parathyroid hormone (PTH) are the bone and kidneys. In uremia, however, numerous studies have shown that PTH may also affect the function of a number of nonclassical organs and tissues besides the bone and kidney, including the brain, heart, smooth muscles, lungs, erythrocytes, lymphocytes, pancreas, adrenal glands, and testes. Most of these effects do not apply to the generally accepted actions or normal regulatory mechanisms of PTH. Thus, the potential role of PTH as one of the possibly many toxins in uremia is of current interest. The molecular basis for the actions of elevated PTH levels on various nonrenal and nonskeletal organs or tissues might be mediated via the widespread distribution of the classical PTH/PTH-related peptide (PTHrP) receptors and via the novel PTH2 receptors. The present survey deals with an evaluation of the nonrenal and nonskeletal effects of excess PTH in uremia, taking into consideration the presently available information on the organ-specific expression of the classical and novel PTH receptors, and of the expression and function of PTHrP.

Association of hypercalcemia, PTHrP expression and disease progression in a woman with primary squamous cell carcinoma of the breast

This paper describes humoral hypercalcemia of malignancy (HHM) associated with squamous cell carcinoma (SCC) of the breast and its association with assayed levels of parathyroid hormone related protein (PTHrP). A 57-year-old woman presented with locally advanced SCC of the breast. The diagnosis was supported by serum analysis and histological and immunohistochemical findings. She was initially treated with chemotherapy to reduce the tumor bulk but developed symptomatic hypercalcemia after on course. The hypercalcemia was effectively treated with intravenous amino hydroxy propildene diphosphonate. Subsequently the tumor progressed despite multimodality therapy and was associated with recurrent hypercalcemia. The patient died nine months after presentation.

Control of hair growth with parathyroid hormone (7-34)

Parathyroid hormone (PTH) related peptide (PTHrP) is thought to influence the proliferation and differentiation of the epidermis and hair follicle. As a means of elucidating the biologic function of PTHrP on the hair follicle, a PTHrP analog PTH (7-34), which is a PTH/PTHrP receptor antagonist, was given intraperitoneally twice daily to C57 BL/6 mice at different stages of the hair cycle. PTH (7-34) induced 99 +/- 4.5% (mean +/- SEM) of resting telogen hair follicles into a proliferative (anagen) state, whereas 100% of the hair follicles in the control group remained in telogen. To determine whether this peptide influenced the progression of the hair follicles from anagen to catagen (hair follicle maturation and regression), groups of mice that were either spontaneously in or induced to anagen received either PTH (7-34) or placebo. Morphometric analysis of the hair follicles from the middle back region of the spontaneous anagen mice that received PTH (7-34) revealed that 19 +/- 4% (mean +/- SEM) of the follicles were in anagen VI, whereas none (0%) were in anagen in the control group. Similarly, in induced anagen mice treated with PTH (7-34), 22.3 +/- 1.4 (mean +/- SEM) of the follicles were in anagen VI compared to only 1.3 +/- 0.7% in the control mice. Together these observations suggest that PTHrP is a hair follicle morphogen that may be a major factor responsible for controlling the hair cycle. These studies provide a new insight for development of PTHrP analogs for a wide variety of disorders related to disturbances of hair cycling.

Parathyroid hormone-related protein is not an autocrine growth factor for normal prostatic epithelial cells

BACKGROUND

Parathyroid hormone-related protein (PTHrP) is the primary factor responsible for humoral hypercalcemia of malignancy. The hypercalcemic actions of PTHrP occur via stimulation of renal distal tubular calcium reabsorption and increased osteoclastic bone resorption. These effects of PTHrP are thought to be mediated through a common parathyroid hormone (PTH)/PTHrP receptor. In addition to the well-established role of PTHrP in bone remodeling, PTHrP is believed to be an important mediator of cellular growth and differentiation in a number of nonbony tissues. We recently demonstrated abundant expression of PTHrP in normal and malignant human prostatic tissues, and in cultured prostatic epithelial cells.

METHODS

In vitro assays were used to test growth-regulatory activity of synthetic and endogenous PTHrP peptides on normal prostatic epithelial cells.

RESULTS

No growth-regulatory activity could be demonstrated.

CONCLUSIONS

PTHrP is not an autocrine growth factor for normal prostatic epithelial cells.

Hair follicle growth controls

Research in hair biology has embarked in the pursuit for molecules that control hair growth. Many molecules already have been associated with the controls of hair patterning, hair maturation, and hair cycling and differentiation. Knowing how these molecules work gives us the tools for understanding and treating patients with hair disorders.

Humoral hypercalcemia of malignancy with elevated plasma PTHrP, TNF alpha and IL-6 in cutaneous squamous cell carcinoma

A case of humoral hypercalcemia of malignancy in cutaneous squamous cell carcinoma is reported. An 82-year-old male underwent surgery for cutaneous squamous cell carcinoma (SCC) of the left hand in 1992. He subsequently developed clouding of consciousness with remarkable hypercalcemia, a high parathyroid hormone related protein (PTHrP) level, and elevated plasma cytokine levels [tumor necrosis factor alpha (TNF alpha), interleukin-6 (IL-6)]. Diagnosis of humoral hypercalcemia of malignancy (HHM) was made on the basis of these findings. He died of renal insufficiency due to this hypercalcemia in spite of several replacement therapies and chemotherapies. The PTHrP might have derived from the SCC and have been responsible for the HHM in conjunction with IL-6 and TNF alpha.

Parathyroid hormone--related protein (PTHrP) is an epidermal growth factor-regulated secretory product of human prostatic epithelial cells

Parathyroid hormone-related protein (PTHrP) has previously been shown to be expressed in human prostatic tissue and in prostatic cancer cell lines. In the present study, PTHrP immunoreactivity was detected in the glandular epithelium of normal prostate and benign prostatic hyperplasia (BPH), as well as in prostatic adenocarcinoma (CaP). Epithelial cell cultures derived from normal, BPH, and CaP tissues were also stained by antibodies against PTHrP, and northern analysis revealed multiple transcripts of PTHrP in the cellular RNA. PTHrP (1-34) was measurable by radioimmunoassay (RIA) in media conditioned by the prostatic epithelial cell cultures, and PTHrP accumulated in conditioned media during a 72 hr time course. Addition of complete growth medium to starved cells resulted in increased PTHrP mRNA levels by 1 hr, with maximal stimulation at 8-24 hr. Several individual factors contained in the complete growth medium were tested for their ability to regulate PTHrP expression. Epidermal growth factor (EGF) was the major inducer of PTHrP expression, while cholera toxin, bovine pituitary extract, hydrocortisone, and insulin had minimal or no effect on PTHrP transcript levels. Since each of these factors is growth stimulatory, the unique ability of EGF to induce PTHrP is apparently unrelated to mitogenicity. 1,25-Dihydroxyvitamin D3[1,25(OH)2D3], an inhibitor of PTHrP expression in several other cell types, had no effect on steady-state levels of PTHrP mRNA expressed by epithelial cells in complete growth medium, although prostate cells have vitamin D receptors and are responsive to 1,25(OH)2D3 in other ways. Our results indicate that PTHrP expression is not confined to the neuroendocrine cells of the human prostate and that our culture system can be used as a model to investigate the role of PTHrP in the prostate.

Lung tumours immunoreactive for parathyroid hormone related peptide: analysis of serum calcium levels and tumour type

Secretion by tumours of parathyroid hormone-related peptide (PTHrP) in quantities sufficient to raise circulating levels results in the syndrome of humoral hypercalcaemia of malignancy (HHM). Since HHM is commonly associated with squamous carcinoma of lung and rarely with adenocarcinoma or lung neuroendocrine tumours, immunopositivity was related to tumour type, to assess whether this difference was due to a low general incidence of PTHrP expression in the latter two groups. Seventy-six of 82 tumours were immunopositive: 22 of 22 squamous carcinomas, 21 of 25 small cell lung carcinomas, 14 of 15 carcinoids, and 19 of 20 adenocarcinomas. These data confirm and extend previous observations on squamous and neuroendocrine tumours but are in contrast with previous findings in adenocarcinoma, which have suggested that only a small proportion of cases express the peptide. They suggest that the differences in incidence of HHM in the various tumour types are due to patterns of secretion, rather than differences in expression of PTHrP. The second aim of this study was therefore to assess whether tumours immunopositive for PTHrP, but not associated with HHM, might secrete PTHrP at levels which might result in more subtle changes in calcium metabolism. Preoperative calcium levels were analysed in a series of 56 patients with immunopositive lung tumours of all types. One small cell carcinoma was associated with hypercalcaemia, but there was no evidence of any other alteration in serum calcium. These data indicate that the majority of tumours expressing PTHrP do not secrete it in amounts sufficient to alter calcium metabolism.

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.

C-terminal fragment of parathyroid hormone-related protein, PTHrP-(107-111), stimulates membrane-associated protein kinase C activity and modulates the proliferation of human and murine skin keratinocytes

Low concentrations of the C-terminal parathyroid hormone-related protein (PTHrP) fragments, PTHrP-(107-111) and PTHrP-(107-139), stimulated membrane-associated protein kinase Cs (PKCs), but not adenylyl cyclase or an internal Ca2+ surge, in early passage human skin keratinocytes and BALB/MK-2 murine skin keratinocytes. The fragment maximally stimulated membrane-associated PKCs in BALB/MK-2 cells at 5 x 10(-9) to 10(-8) M. The maximally PKC-stimulating concentrations of PTHrP-(107-111) also stopped or stimulated BALB/MK-2 keratinocyte proliferation depending on whether the cells were, respectively, cycling or quiescent at the time of exposure. Thus, just one brief (30-minute) pulse of 10(-8) M PTHrP-(107-111) stopped the proliferation of BALB/MK-2 keratinocytes for at least 5 days. On the other hand, daily 30-minute pulses of 10(-8) M PTHrP-(107-111) started and then maintained the proliferation of initially quiescent BALB/MK-2 cells. Similarly PTHrP-(107-111) inhibited DNA synthesis by cycling primary adult human keratinocytes, but it stimulated DNA synthesis by quiescent human keratinocytes.

In vitro production of parathyroid hormone-related protein by cholesteatoma and normal skin

Severe inflammation and infection of the middle ear occasionally results in clinical evidence of bone resorption but with the addition of the cholesteatoma epithelium it becomes inevitable. This study examined production by the cholesteatoma epithelium of a bone resorbing factor, namely parathyroid hormone-related protein (PTH-rP), which would not be expected in inflammatory states alone. PTH-rP was detected in the conditioned medium of primary and secondary cell cultures derived from 12 cholesteatoma biopsies. The levels of PTH-rP were significantly greater than in control cultures of cells derived from normal scalp tissue. Production by the cholesteatoma epithelium may explain the increased incidence of bone resorption in this disease, particularly in cases where inflammation is minimal.

Parathyroid hormone-related peptide is expressed and rapidly inducible in human liver cell cultures that have a bile duct phenotype

Parathyroid hormone-related peptide is the major factor responsible for hypercalcemia of malignancy. There is increasing evidence that parathyroid hormone-related peptide also plays an important role in the growth and differentiation of both neoplastic and non-neoplastic cells. Recently we found that reactive human bile ductules and cholangiocarcinomas, but not normal bile ducts, human hepatocytes nor hepatocellular carcinomas, express parathyroid hormone-related peptide and we speculated that parathyroid hormone-related peptide may function as a growth and differentiation factor for bile ductular epithelial cells. Using a specific polyclonal antibody for immunostaining and a digoxigenin-random prime-labeled probe for in situ hybridization assay, we found that only cell lines with a bile duct phenotype expressed parathyroid hormone-related peptide and its mRNA. HepG2 cells with hepatocellular phenotype (CK19-, CK7-, CK8+, CK18+, albumin+) do not express parathyroid hormone-related peptide. However, A16 (HepG2 derived cell line) expressing bile duct marker CK19, also expressed parathyroid hormone-related peptide, while hepatocyte markers CK8, CK18, CALLA and albumin were negative. In addition, the H1 cell line (adult human hepatocytes immortalized in our laboratory by SV40 DNA transfection, passaged at least 40 times and cultured for 13 months) expressed bile duct marker CK7 and parathyroid hormone-related peptide, while hepatocyte markers CK8, CK18, CALLA and albumin were negative. Previous studies demonstrated that parathyroid hormone-related peptide gene expression in keratinocytes can be modulated by serum, growth factors and cycloheximide although there is a species and cellular specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Epidermal growth factor-stimulated parathyroid hormone-related protein expression involves increased gene transcription and mRNA stability

Epidermal growth factor (EGF) produced rapid and striking effects on parathyroid hormone-related protein (PTHrP) gene expression in the immortalized human keratinocyte cell line, HaCaT. Steady-state levels of PTHrP mRNA and secreted PTHrP were increased 10-fold by maximally effective concentrations of EGF. EGF increased both PTHrP gene transcription and PTHrP mRNA stability. Nuclear run-on assays demonstrated a 4-fold increase in transcriptional rate in EGF-stimulated cells while transient transfection analysis indicated that the action of EGF on transcription involved both the GC-rich promoter, P2, and the downstream TATA promoter, P3, but apparently not the upstream TATA promoter, P1. In experiments where EGF treatment produced more stable PTHrP transcripts, the half-life of c-fos mRNA was unaltered, suggesting a relatively specific effect of EGF. Moreover, only those species of PTHrP mRNA containing two of the alternative 3' exons (exons VII and VIII) were stable, those containing exon IX were not. Reverse-transcription PCR demonstrated that EGF produced differential increases in the abundance of PTHrP mRNA species initiated by the three PTHrP promoters. The major effect was seen on the abundance of transcripts initiated by P1 and P2, with less marked regulation of P3-initiated transcripts. Thus EGF regulation of PTHrP gene expression in HaCaT cells is multifactorial and the combination of its actions at the 5' and 3' ends of the gene favours the accumulation of subpopulations of PTHrP mRNA containing exons I, VII and VIII.

Parathyroid hormone-related protein

We review the current state of knowledge of the molecular properties and actions of parathyroid hormone-related protein (PTHrP) both in cancer patients and in normal physiology. PTHrP is a common product of squamous cancers and is the major mediator of the syndrome of humoral hypercalcemia of malignancy (HHM) by its actions through parathyroid hormone receptors in bone and kidney. Recently developed radioimmunoassays and tissue localization techniques indicate that PTHrP is produced by many more cancers than was originally indicated by clinical studies and that it contributes significantly to malignancy-related hypercalcemia associated with other etiologies, for example, cancers metastatic to bone and hematological malignancies. The gene encoding PTHrP is complex, with multiple exons coding for up to 12 alternate transcripts and three different length proteins, potentially in a tissue-specific manner, by the use of three promoters. Its expression is regulated by hormones and growth factors, and the untranslated exons display features in common with many cytokine genes. Although potential endocrine actions of PTHrP are evident in fetal development, further evidence suggesting that the normal physiological role of PTHrP is predominantly as a locally produced regulator/cytokine comes from localization studies and investigations of its actions in a variety of tissues. Such studies indicate that in addition to its parathyroid hormone-like actions, PTHrP has multiple activities, including those in fetal development, placental calcium transfer, lactation, smooth muscle relaxation, and on epithelial cell growth. Although PTHrP was discovered because of its production by cancers, evidence for its actions as a local regulator highlights the importance of understanding its roles not only in the etiology of HHM in cancer patients but also in normal tissues.

Fatal parathyroid hormone-related protein-induced humoral hypercalcemia of malignancy in a 3-month-old infant

Parathyroid hormone-related protein (PTHrP) is the factor responsible for the syndrome of humoral hypercalcemia of malignancy (HHM). The syndrome is well documented in adult cancer patients, but has not previously been described in young children. We report the case of a 3-month-old infant who developed refractory hypercalcemia (peak total calcium 13.8 mg/dl; normal 8.5-10.5, ionized calcium 3.3 meq/l; normal 2.0-2.5) associated with a high-grade, poorly differentiated malignant hepatic sarcoma. Parathyroid hormone (intact) levels were suppressed (7.5 pg/ml; normal 10-65). Fractional excretion of phosphate was markedly elevated (73.5%; normal 8%-20%) as were urinary cAMP levels (12.48 nmol/dl glomerular filtrate; normal 1.83-4.47) suggesting a PTH-like effect. Increased levels of PTHrP were present both in the serum (4.9 pmol/l; normal for adults < 1.5) and ascitic fluid (6.1 pmol/l). Since previous studies have demonstrated a potential role for PTHrP in the regulation of embryonal tissue differentiation and transmembrane calcium flux, our observation of elevated PTHrP levels associated with the development of a poorly differentiated hepatic sarcoma in a young infant may provide insight into the molecular mechanisms underlying HHM. We suggest that serum or plasma PTHrP levels be determined in all children with hypercalcemia of malignancy in whom the hypercalcemia cannot otherwise be explained.

A parathyroid hormone antagonist stimulates epidermal proliferation and hair growth in mice

The biologic action of parathyroid hormone (PTH)-related peptide (PTHrP) in normal skin was investigated in cultured human keratinocytes and in SKH-1 hairless mice. The results indicate that the PTHrP agonists human PTHrP-(1-34) and PTH(1-34) are potent inhibitors of epidermal cell proliferation. [Nle8,18,Tyr34]bovine PTH-(7-34)-amide, an antagonist of the PTH/PTHrP receptor, blocked the inhibitory effect of PTH-(1-34) in cultured keratinocytes. In the SKH-1 mice, PTH-(7-34) caused a 244% increase of [3H]thymidine incorporation into isolated epidermal DNA and 246% and 180% increases in the number and length of hair shafts, respectively. Thus, PTH and PTHrP may play an important role in the normal physiology of skin, and their agonists and antagonists have potentially wide therapeutic applications in the treatment of hyperproliferative skin disorders and aging skin and could also be effective in stimulating and maintaining hair growth.

Parathyroid hormone-related protein in normal and neoplastic canine tissues: immunohistochemical localization and biochemical extraction

Two polyclonal antibodies, directed against N-terminal amino acids (1-36) or the midregion (amino acids 34-53) of parathyroid hormone-related protein (PTHrP), were used to localize PTHrP in a variety of normal and neoplastic canine tissues. Parathyroid hormone (PTH) immunoreactivity was demonstrated using anti-bovine PTH (amino acids 14-34). The following tissues (among others) stained strongly positive for PTHrP: all layers of epidermal keratinocytes, with the most intense staining of the basal layer; hair follicle keratinocytes; myoepithelial cells of dermal apocrine glands, mammary glands, and apocrine glands of the anal sac; anal sac epithelium; mammary duct epithelium; and thyroid C cells. Adenocarcinomas of the anal sac stained moderately positive (5/22 dogs), weakly positive (11/22 dogs), or did not stain (6/22 dogs). Most parathyroid gland adenomas stained moderately (2/6 dogs) or weakly positive (3/6 dogs) for PTHrP. Squamous cell carcinomas (6/6 dogs) stained strongly positive. Lymphomas stained weakly positive (2/10 dogs) or did not stain (8/10 dogs). There was no consistent relationship between the staining intensity of the tumors and serum calcium concentrations of the dogs. The anti-PTH antibodies stained only parathyroid chief cells strongly positive. Concentrations of PTHrP were measured by radioimmunoassay in protein extracts from an adenocarcinoma derived from the apocrine glands of the anal sac, pancreas, kidney, liver, heart, thyroid, adrenal, and parathyroid glands. PTHrP concentrations varied from undetectable up to 150 pg/mg in normal tissues as compared with 2,000 pg/mg in apocrine adenocarcinoma of the anal sac.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Parathyroid hormone-related peptide expression in primary and metastatic liver tumours

Parathyroid hormone-related peptide (PTHrP) is a major factor in the pathophysiology of hypercalcaemia of malignancy. Recent evidence suggests that PTHrP may play an important role in the growth and differentiation of neoplastic as well as non-neoplastic cells. PTHrP was originally detected in normal fetal, but not adult, liver. We have used immunocytochemistry to show that reactive human bile ductules expressing a neuroendocrine phenotype contain immunoreactive PTHrP. These observations raised the possibility that PTHrP immunoreactivity may be useful in the differential diagnosis of primary liver tumours and metastases of adenocarcinoma. A total of 24 primary liver tumours and 22 metastases of adenocarcinoma were studied. All cholangiocarcinomas showed immunopositivity for PTHrP and chromogranin A, while all hepatocellular carcinomas were negative for PTHrP and showed only focal and weak positivity for chromogranin A. Mixed types of primary liver tumour contained PTHrP immunoreactivity only in the areas of cholangiocellular differentiation. Moreover, all metastatic adenocarcinomas were negative for PTHrP and chromogranin A except for two out of five metastatic breast adenocarcinomas. These two patients had bone metastases and hypercalcaemia and thus did not yield differential diagnostic problems with cholangiocarcinoma. None of the patients with cholangiocarcinoma and hepatocellular carcinoma had hypercalcaemia. We conclude that PTHrP is a useful marker for primary cholangiocarcinoma, especially in the differential diagnosis of hepatocellular carcinoma and metastatic adenocarcinoma.

Parathyroid hormone-related protein in gastric cancers with heterotopic ossification

BACKGROUND

Parathyroid hormone-related protein (PTHrP) has been regarded as one of the substances causing humoral hypercalcemia of malignancy.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Reactive human bile ductules express parathyroid hormone-related peptide

Various cholestatic liver diseases as well as regeneration after submassive necrosis are accompanied by a striking increase in the number of bile ductules. These reactive bile ductules are thought to arise either from proliferation of pre-existing bile ductules or bile ductule-related facultative stem cells, or from ductular metaplasia of hepatocytes. Recently, we found that reactive bile ductules display neuro-endocrine features, and speculated that the substance(s), produced in the neuro-endocrine granules, might play a role in their growth and/or differentiation through an autocrine or paracrine pathway. Parathyroid hormone-related peptide has been shown to be encoded by a growth factor-regulated gene that may play a role in cell growth and differentiation. We studied the immunohistochemical expression of this peptide in human liver, including three normal biopsies, 11 cases of cholestatic liver disease, six cases of focal nodular hyperplasia and three cases of regenerating liver. In regenerating liver, primary biliary cirrhosis, primary sclerosing cholangitis and partial or intermittent obstruction, the majority of reactive ductular cells expressing neuro-endocrine markers also expressed parathyroid hormone-related peptide. In focal nodular hyperplasia, a smaller number of bile ductular cells expressed the peptide. These findings suggest that parathyroid hormone-related peptide is localized in bile ductular cells and may indicate a role for this hormone in the growth and/or differentiation of human reactive bile ductules.

Physiology of endocrine skin interrelations

Hormones influence the skin and play a role in normal biologic processes. Keratinocytes can convert and synthesize endocrine hormones. Endocrine dysregulation of the skin and abnormalities of endocrine functions of keratinocytes may produce abnormal changes in the skin. Knowledge of the cutaneous metabolism of thyroid hormones, steroids, peptide hormones, and vitamin A derivatives is being rapidly updated. Skin manifestations of endocrine disorders result from imbalance in feedback loops maintaining endocrine homeostasis. Define molecular mechanisms of hormonal action on target cells underlie functional agonism and antagonism of hormonal signals aimed at governing epidermal turnover. The molecular synergism between vitamin A and other hormones may explain the therapeutic efficiency of combining retinoids with other therapies.

Common expression of parathyroid hormone-related protein and no correlation of calcium level in renal cell carcinomas

BACKGROUND

Parathyroid hormone-related protein (PTHrP) is the predominant cause of humoral hypercalcemia of malignancy (HHM).

METHODS

Using a PTHrP-specific monoclonal antibody (MoAb), 4B3, the authors investigated the immunohistochemical localization of PTHrP in formalin-fixed and paraffin-embedded sections of normal human kidney tissues and tissues from 42 human renal cell carcinomas obtained at operation or autopsy.

RESULTS

In normal renal tissues, the distal tubules and collecting ducts showed positive immunostaining. PTHrP was detected in 40 of 42 renal cell carcinoma tissues (95%). Histopathologically, the granular cell subtypes of renal cell carcinomas tended to be more strongly positive than the clear cell subtypes. There was no significant correlation between the level of immunostaining and each patient's serum calcium level.

CONCLUSION

PTHrP was commonly observed in renal cell carcinomas, and no significant correlation was seen between the intensity of PTHrP staining and the serum calcium level.

Transforming growth factor beta stimulation of parathyroid hormone-related protein (PTHrP): a paracrine regulator?

The regulation of PTHrP expression and production by transforming growth factor-beta (TGF beta) has been investigated in an epidermal squamous cancer cell line COLO 16. TGF beta 1 treatment increased steady-state levels of PTHrP mRNA and concentrations of PTHrP immunoreactivity in conditioned medium in a time- and dose-dependent manner with a half-maximal effect at 40 pM. An effect of TGF beta 1 on PTHrP mRNA was observed first after 4 h treatment and continued to increase up to 48 h with a concomitant increase in PTHrP immunoreactivity in the culture medium. TGF beta 1 was found to stabilize PTHrP mRNA as assessed by actinomycin C1 experiments. In addition, a direct effect of TGF beta to increase PTHrP transcription was indicated by nuclear run-on and transient transfection experiments using a CAT promoter/expression construct encompassing the region -1100 bp to -20 bp from the initiating AUG of the human PTHrP gene. The conditioned medium from COLO 16 cells was also shown to contain both latent and active TGF beta at concentrations of 160 pM and 16 pM, respectively, in 72 h conditioned medium. A neutralizing antibody to TGF beta 1 (and TGF beta 2) decreased the level of immunoassayable PTHrP in the medium.

Studies on chicken polyclonal anti-peptide antibodies specific for parathyroid hormone-related protein (1-36)

Chicken polyclonal antibodies were prepared against a synthetic peptide corresponding to the first 36 N-terminal amino acids of parathyroid hormone-related protein (PTHrP) by immunizing laying hens. Significant increases of antibodies to PTHrP were first detected after the second immunization. Production of anti-PTHrP egg yolk antibodies peaked 1-2 weeks after the second through sixth immunizations and declined over a period of 2-4 weeks. Polyclonal IgG (IgY) to PTHrP was purified from the egg yolks with high levels of PTHrP specific binding. The anti-PTHrP IgG was used to develop a radioimmunoassay for PTHrP that was able to detect 100 pg PTHrP ml-1 (23 pM) in conditioned cell culture medium. The anti-PTHrP IgG was bound to a solid phase and utilized to immunopurify iodinated [Tyr36]-PTHrP (1-36). Anti-PTHrP IgG inhibited the in vitro biologic activity of PTHrP as demonstrated by the inhibition of adenylate cyclase stimulation in a rat osteoblast-like cell line (ROS 17/2.8). The anti PTHrP IgG was immunopurified and utilized for immunohistochemical localization of PTHrP in canine skin. Chickens were advantageous in producing large amounts of high affinity, neutralizing antibodies to a highly conserved mammalian protein such as PTHrP. The antibodies will be useful to investigate the function and metabolism of PTHrP in vivo and in vitro.

Expression of mRNA of parathyroid hormone-related peptide in fetal bones of the rat

Previous studies have indicated that 19-day-old fetal long bones of the rat contain an adenylyl cyclase-stimulating activity antigenically related to parathyroid hormone-related peptide. To ascertain its origin, Northern blotting and in situ hybridization histochemistry were performed. Results demonstrate that mRNA of parathyroid hormone-related peptide is present in RNA extracted from fetal long bones of the rat and that cells responsible for its production are localized in the periosteum. These cells are not mature osteoblasts because they do not synthesize mRNA of osteocalcin. Thus the present study shows that parathyroid hormone-related peptide could be produced locally, at least in part, in the skeleton of fetal rats.

Parathyroid hormone-related protein: a possible endocrine function in lactation

OBJECTIVE

Parathyroid hormone-related protein (PTHrP), initially discovered as the factor responsible for the syndrome of humoral hypercalcaemia of malignancy, has also been found to be expressed in placenta, in pregnant uterus, in the fetus at many locations, and in the lactating mammary gland. This study sought to establish whether PTHrP reaches the maternal circulation when it is expressed in mammary tissue during lactation or in the maternal reproductive tract during gestation.

DESIGN

Blood samples were collected from 53 subjects: 18 pregnant women in all stages of gestation, 19 lactating mothers and 16 non-lactating post-partum controls.

MEASUREMENTS

PTHrP was measured using a specific and validated radioimmunoassay. Parathyroid hormone was measured by two-site immunoradiometric assay. Total calcium was measured by atomic absorption spectrophotometry.

RESULTS

Circulating levels of PTHrP were readily detectable in 12 of 19 nursing mothers (range 2.7-7.8 pmol/l) but in none of the mothers who were bottle feeding. PTHrP was also detected in one of 18 pregnant subjects. Parathyroid hormone concentrations were lower in lactating mothers (2.3 +/- 1.0 pmol/l), than in non-lactating mothers (3.5 +/- 1.2 pmol/l) (P < 0.01).

CONCLUSION

PTHrP reaches the maternal circulation during lactation in amounts which could produce a systemic effect.

Hypercalcemia in cancer

Hypercalcemia may occur as a complication of haematological malignancies, in association with solid tumors with bone metastases, and with solid tumors in the absence of bone metastases. The latter syndrome, known as the humoral hypercalcemia of malignancy (HHM) shares many features with primary hyperparathyroidism. A parathyroid hormone-related protein (PTHrP) has been identified, isolated and cloned, which is most likely responsible for the calcium disturbances in HHM, PTHrP is a previously unrecognized hormone which has limited amino-terminal sequence homology with PTH and is the product of a separate gene. Tissue localization studies have identified PTHrP in squamous cell carcinomata, renal cortical carcinomata, in a proportion of breast cancers and in adult T-cell leukemia/lymphoma. In normal tissues, PTHrP has been immunohistochemically localized in keratinocytes, placenta and fetal parathyroid glands. In addition to its role in mediating hypercalcemia in cancer, PTHrP is likely to have an important endocrine role in the fetus, and perhaps a paracrine function in several organs.