Production of 1,25-dihydroxyvitamin D3 by human T cell lymphotrophic virus-I-transformed lymphocytes

Lung tumor cells inhibit bone mineralization and osteoblast activity

Patients with non-small cell lung cancer (NSLC) often develop skeletal complications and fractures. To understand mechanisms of bone loss, we developed a murine model of non-metastatic NSLC. Decreased bone mineral density, trabecular thickness and mineralization, without an increase in bone resorption, were observed in vivo in mice injected with Lewis lung adenocarcinoma (LLC1) cells in the absence of tumor cell metastases. A decrease in trabecular bone mineral density was observed in mice injected with cell-free LLC1 CM. Plasma osteoblast biomarkers and PTH-related peptide (PTHrP) were reduced, and parathyroid hormone (PTH), 1,25-dihydroxyvitamin D, calcium and phosphate concentrations were normal in tumor-bearing mice. LLC1 cell conditioned medium (CM) inhibited alkaline phosphatase activity, osteoblast mineralization, and expression of Alpl and Ocn/Bglap mRNA in MC3T3 osteoblast cultures, whereas non-CM or CM from NIH/3T3 fibroblasts did not induce similar changes. LLC1 CM reduced Wnt3a-stimulated Tcf/Lef reporter plasmid activity and Wnt5A, Tcf1 and Lef1 mRNA expression in MC3T3 cells. Although concentrations of the Wnt inhibitor, DKK2, were increased in LLC1 CM compared to non-CM, depletion of DKK2 from LLC1 CM did not completely restore Wnt3a activity in MC3T3 cultures, and recombinant DKK2 failed to inhibit osteoblast mineralization. The data indicate that in a model of lung adenocarcinoma without bone metastases, tumor cells elaborate a secreted factor(s) that reduces bone mass, bone formation and osteoblast Wnt signaling without increases in bone resorption or calcium-regulating hormone concentrations. The factor(s) mediating this inhibition of osteoblast mineralization require further characterization.

Mechanisms of Hypercalcemia in Non-Hodgkin Lymphoma and Associated Outcomes: A Retrospective Review

INTRODUCTION

The etiology of hypercalcemia in non-Hodgkin lymphoma (NHL) has been most often attributed to either elevated serum levels of 1,25-dihydroxycholecalciferol (calcitriol) or parathyroid-related protein (PTHrP). In a single-center retrospective review, we evaluated the incidence of, and outcomes associated with, hypercalcemia in NHL.

PATIENTS AND METHODS

The medical records of patients with a histologically confirmed diagnosis of NHL and ≥ 1 episode of hypercalcemia were evaluated for demographic and lymphoma-specific factors, including the response to therapy and overall survival.

RESULTS

Fifty-four patients with NHL met the inclusion criteria. Most patients (57.4%) had diffuse large B-cell lymphoma, of which, 70% were the nongerminal center subtype. Approximately one half (42.6%) of the included patients had undergone serologic investigation into the etiology of hypercalcemia; however, only 17 patients (31.5%) had both a serum PTHrP and a calcitriol level properly collected. Of the 17 cases for which both a serum calcitriol and a PTHrP were collected, most (61.1%) were found to have neither an elevation of serum calcitriol nor an elevation of PTHrP. The degree of calcitriol elevation correlated with worse progression-free survival (P = .04) but not overall survival.

CONCLUSION

The major mechanism by which NHL patients develop hypercalcemia is not mediated by calcitriol or PTHrP. Hypercalcemia is most prevalent in patients with diffuse large B-cell lymphoma of the nongerminal cell subtype. Patients with calcitriol-mediated hypercalcemia showed a trend toward worse outcomes, suggesting that calcitriol might be a marker of high-grade lymphoma, transformation to such, or a surrogate for more advanced disease.

Liquid Chromatography-Mass Spectrometry Metabolic and Lipidomic Sample Preparation Workflow for Suspension-Cultured Mammalian Cells using Jurkat T lymphocyte Cells

Metabolomics is the comprehensive study of metabolism as it pertains to an organism or biological system. Lipidomics, a subset discipline of metabolomics, encompasses the study of cellular lipid functions: including pathways, networks, and interactions. The abundance of metabolites and lipids, along with their contribution to health and disease, makes metabolomics a valuable tool for biomarker research. Disease biomarker identification requires a reproducible, sensitive, and accurate analytical platform. Although transcriptomic and proteomic areas have well-established protocols for sample preparation and data processing, the metabolomics field is still developing comparable standardized conventions. Furthermore, of the few comparative LC-MS metabolomic studies that have been applied to mammalian cell cultures, most are targeted to adherent cell lines. The purpose of this work was to optimize a sample preparation workflow for the cellular metabolomic analysis of suspension-cultured mammalian cells using commercially available Jurkat T lymphocytes as a model system. The current investigation evaluated commonly used sample preparation techniques for reproducibility, accuracy, and applicability to untargeted biomarker discovery. Results show ammoniated cell rinsing solutions to be an effective means to remove extracellular components present in the media without causing ion suppression or affecting the integrity of the cellular membrane. Additionally, a novel workflow was designed to allow for the combined analysis of metabolites and lipids from mammalian suspension cells from a single cell pellet. The Folch lipid extraction protocol was coupled to an 80% MeOH metabolite isolation to ensure high extraction efficiency for phospholipids and triacylglycerides. While the workflow was tailored to cells in suspension, it could also be applied to adherent cell lines.

Mechanisms and treatment of hypercalcemia of malignancy

PURPOSE OF REVIEW

Hypercalcemia of malignancy is a common paraneoplastic syndrome and a frequent complication of advanced breast and lung cancer, and multiple myeloma. The development of this malignancy complication often purports a poor prognosis. Thorough evaluation to establish the cause of hypercalcemia is essential because some patients may actually have undiagnosed primary hyperparathyroidism.

RECENT FINDINGS

Production of humoral factors by the primary tumor, collectively known as humoral hypercalcemia of malignancy (HHM), is the mechanism responsible for 80% of cases. The vast majority of HHM is caused by tumor-produced parathyroid hormone-related protein followed by infrequent tumor production of 1,25-dihydroxyvitamin D and parathyroid hormone. The remaining 20% of cases are caused by bone metastasis with consequent bone osteolysis and release of skeletal calcium. Key therapies are saline hydration to promote calciuresis and bisphosphonates to reduce pathologic osteoclastic bone resorption. Calcitonin and glucocorticoids, especially in 1,25-dihydroxyvitamin D-mediated HHM, also have calcium-lowering effects.

SUMMARY

Recent discoveries on mechanisms of malignancy-associated hypercalcemia highlight the critical role of the osteoclast. Bisphosphonates and other novel therapies being evaluated in clinical trial target this bone-resorbing cell type and provide effective and durable serum calcium reduction.

HTLV-1-associated adult T cell leukemia lymphoma presenting as granulomatous pneumocystis jiroveci pneumonia (PJP) and hypercalcemia

BACKGROUND

Since the initial description of human T cell lymphotropic virus (HTLV-1), clusters of this infection have been detected globally. Unlike HIV infection, most patients infected with HTLV-1 remain asymptomatic throughout their lifetime.

CASE REPORT

We report the case of a 39-year-old Afro-Caribbean man with HTLV-1 infection presenting as hypercalcemia and granulomatous pneumocystis jiroveci pneumonia.

RESULTS

Interestingly, the hypercalcemia presented with normal parathyroid hormone-related protein and low 1,25 dihydroxyvitamin D levels, and the presence of pneumocystis jiroveci in the granulomas was diagnosed with transbronchial biopsy taken during bronchoscopy. HTLV-1-associated adult T cell leukemia lymphoma (ATLL) was diagnosed in this patient by bone marrow and lymph node biopsy.

CONCLUSION

Increased bone resorption, likely cytokine-mediated, is the most likely mechanism of hypercalcemia in this patient. This is believed to be the first description of this type of reaction to pneumocystis jiroveci in a HTLV-1-infected ATLL patient.

ApaI polymorphism of vitamin D receptor gene is associated with susceptibility to HTLV-1-associated myelopathy/tropical spastic paraparesis in HTLV-1 infected individuals

HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is one outcome of human T-cell lymphotropic virus type-1 (HTLV-1) infection. It remains unknown why the majority of infected people remain healthy, whereas only approximately 2-3% of infected individuals develop the disease. The active form of vitamin D has immunomodulatory effects, and allelic variants of the vitamin D receptor (VDR) appear to be associated with differential susceptibility to several infectious diseases. To investigate whether VDR single nucleotide polymorphisms (SNPs) are associated with the development of HAM/TSP, we studied four VDR SNPs in a group of 207 HAM/TSP patients and 224 asymptomatic HTLV-1 seropositive carriers (HCs) in Kagoshima, Japan, by using PCR-RFLP analysis. We found that ApaI polymorphism of VDR is associated with the risk of HAM/TSP, although this polymorphism did not affect the provirus load of HTLV-1 in either HAM/TSP patients or HCs.

Hypercalcemia complicating leukemic transformation of agnogenic myeloid metaplasia-myelofibrosis

Hypercalcemia is a common and potentially life-threatening metabolic derangement associated with many malignancies, especially solid tumors and multiple myeloma. Hypercalcemia has been reported only rarely with acute myelogenous leukemia. We describe a patient who developed hypercalcemia in association with transformation of agnogenic myeloid metaplasia into M7 acute myelogenous leukemia. Laboratory investigation revealed low levels of serum parathyroid hormone, undetectable levels of parathyroid hormone-related peptide, and normal levels of 25-hydroxyvitamin D. These observations suggest that another mediator was responsible for hypercalcemia in this patient. Awareness of this rare complication of acute myelogenous leukemia is essential for prompt diagnosis and management.

Vitamin D differentially regulates B7.1 and B7.2 expression on human peripheral blood monocytes

The hormonal active form of vitamin D3, 1,25-dihydroxyvitamin D3 (1, 25(OH)2D3), inhibits (through an unknown mechanism) the ability of monocytes/macrophages to induce T-cell activation. For T cells to be optimally activated, recognition of antigen/major histocompatibility complexes (MHC) by the T-cell receptor (TCR) must be accompanied by a second costimulatory signal. Considerable experimental data now suggest that this costimulatory signal is predominantly generated by B7.1 and/or B7.2 molecules, expressed on antigen-presenting cells (APC), when engaged to their counter-receptor, CD28, present on T cells. To determine whether the inhibitory effect of 1,25(OH)2D3 on monocytes/macrophages might involve modulation of the expression of B7.1 and B7.2 molecules, we analysed (by flow cytometry) the influence of 1,25(OH)2D3 and an analogue, KH 1060, on the expression of these two molecules at the surface of resting human peripheral blood monocytes. In parallel, we tested the effect of these two agents on human monocyte expression of cell-surface markers (CD14 and CD4) and antigen-presenting molecules (MHC class I and MHC class II). Our results showed that both 1,25(OH)2D3 and KH 1060 inhibited the basal expression of B7.2 in a dose- and time-dependent manner, without affecting B7.1. Moreover, these two compounds increased CD14 and reduced MHC class II and CD4 expression. Furthermore, the effect of 1,25(OH)2D3 on B7 molecule expression in combination with lipopolysaccharide (LPS) or cytokines, including interleukin-10 (IL-10), interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha), was studied. The 1,25(OH)2D3-induced B7.2 down-regulation was still detectable when monocytes were activated by IL-10, IFN-gamma and TNF-alpha but not with LPS. Moreover, the induction of B7.1 by TNF-alpha was inhibited by addition of 1, 25(OH)2D3. We conclude that the ability of 1,25(OH)2D3 to decrease B7.2 expression on human monocytes might contribute to its inhibitory effect on APC-dependent T-cell activation and to its immunosuppressive properties observed in autoimmune diseases and organ transplantation.

Parathyroid hormone-related protein in hypercalcemia associated with hematological malignancy

Hypercalcemia is an important complication in multiple myeloma as well as T-cell leukemia/lymphoma, and is moderately common in high and intermediate grade non-Hodgkin's lymphoma. The underlying mechanism has been unclear because the neoplastic cells are usually present in the bone marrow, where they are in a position to produce short range effects on bone resorption which are difficult to identify. This contrasts with the situation in hypercalcemia associated with non-metastatic carcinoma, where it has been clearly demonstrated that the most common cause is release from the tumor of a humoral mediator, Parathyroid Hormone-related Protein (PTHrP). Roles have been advocated in multiple myeloma for release of a number of other cytokines with osteolytic capacity on the basis of their enhancement of osteolytic activity in cultured fetal rat bone, although a causal relationship in patients has not been established. PTHrP has more recently been implicated in the genesis of hypercalcemia in patients with hematological malignancies by the demonstration in a proportion of cases of increased circulating levels of PTHrP, comparable to those in hypercalcemia due to cancer. Immunohistochemical studies indicate neoplastic hemopoietic cells can contain PTHrP, and thus have the capacity to act in a paracrine manner to enhance local bone resorption and contribute to the development of hypercalcemia.

Hypercalcaemia in B cell chronic lymphocytic leukaemia

Hypercalcaemia is common in some lymphoproliferative disorders such as myeloma or T-cell leukaemia-lymphoma, but is rarely described in B cell chronic lymphocytic leukaemia (BCLL). We report the case of a patient with BCLL, hypercalcaemia and osteolytic bone lesions. Parathyroid hormone-related protein (PTHrP) mRNA was identified by Northern blot analysis of liver, spleen and lymph node tumour samples. Serum levels of tumour necrosis factor alpha (TNF alpha) were increased.

Lymphomatous presentation of CD4+/CD8+ HTLV-1-related adult T-cell leukemia/lymphoma in an Iranian woman

Adult T-cell leukemia/lymphoma (ATLL) remains an uncommon disorder outside well-defined risk groups. We describe the case of an Iranian woman, who presented with isolated meningeal relapse of diffuse large-cell lymphoma. The malignant cells coexpressed CD4 and CD8 and HTLV-1 seropositivity was confirmed. Despite combination chemotherapy disseminated lymphoma developed. Preterminally the characteristic features of ATLL were noted; hypercalcemia, with normal parathyroid hormone-related protein and vitamin D levels, and peripheral blood leukemic involvement.

1,25-Dihydroxyvitamin D3 exerts opposing effects to IL-4 on MHC class-II antigen expression, accessory activity, and phagocytosis of human monocytes

To investigate the differentiation and activation of monocytes, the combined effects of 1,25-dihydroxyvitamin D3 (D3) and IL-4 on human blood monocytes were examined with respect to expression of MHC class-II antigens, accessory activity, and phagocytic capacity. IL-4 was reported to upregulate the expression of MHC class-II antigens and accessory activity of monocytes. The experiments described here demonstrate that D3 inhibits the expression of all three subtypes of MHC class-II antigens (HLA-DR, -DP and -DQ) as well as the accessory activity of monocytes, both in a dose- and time-dependent manner. However, D3 enhances the immunoglobulin- and complement-dependent phagocytosis by monocytes in a dose- and time-dependent manner. When monocytes are treated with both IL-4 and D3, the effects of D3 are reverted by IL-4, suggesting that IL-4 induces the development of monocytes into accessory cells, whereas D3 stimulates differentiation of monocytes into classical macrophages. These findings provide further evidence for the contention that, depending on defined stimuli, monocytes may develop either into accessory cells or into classical macrophages.

Lower affinity for substrate for extrarenal synthesis of calcitriol in chronic uremia

Previous studies from our laboratory have shown that anephric patients have very low, but detectable, levels of 1,25(OH)2D3 (calcitriol) that can be increased to normal by administration of large doses of 25(OH)D3. The report of 1 alpha-hydroxylase activity in pig liver with an affinity for substrate significantly lower than that of the renal enzyme, led us to use the rat as an experimental model to further clarify the need of supraphysiological levels of 25(OH)D3 to correct calcitriol deficiency in chronic uremia. We have measured 1,25(OH)2D3 production by rat liver. Cytosol free liver homogenates (CFH) from normal rats were incubated with 25(OH)D3 and the production of 1,25(OH)2D3 was measured using the thymus radioreceptor assay after solid phase C18 extraction and HPLC purification of the samples. 1,25(OH)2D3 production was linear up to 30 minutes and a CFH protein concentration up to 20 mg. Saturability was attained for a substrate concentration of approximately 60 microM. Ketoconazole, a cytochrome P450 inhibitor, blocked calcitriol production in a dose dependent fashion. Total inhibition of the liver 1 alpha-hydroxylase was achieved with 180 microM ketoconazole. We next compared the kinetics of the 1 alpha-hydroxylases of normal and uremic rat livers. Maximal velocities were not statistically different (139.6 +/- 22.3 pg/mg/min for normals and 217.1 +/- 73.3 pg/mg/min for uremic rats). However, the apparent Km was 35.9 +/- 3.2 microM for uremic animals, significantly higher (P < or = 0.001) than that of normal rats (16.6 +/- 0.7 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated serum parathyroid hormone related protein and 1,25-dihydroxycholecalciferol in hypercalcaemia associated with adult T-cell leukaemia-lymphoma

Hypercalcaemia occurs in up to 80% of patients with adult T-cell leukaemia-lymphoma (ATLL) associated with human T-cell leukaemia virus-1 infection. Elevated serum levels of 1,25-dihydroxycholecalciferol, implicated in the pathogenesis of hypercalcaemia in lymphoma, and of parathyroid hormone-related protein (PTHrP), which is associated with hypercalcaemia of several solid malignancies, were demonstrated in a patient with ATLL hypercalcaemia. Treatment with bisphosphonates reduced the serum calcium but had no significant effect on the serum PTHrP levels. This case supports recent in vitro evidence for enhanced PTHrP expression in ATLL tumour cells and suggests that more than one tumour cell product may be involved in the pathogenesis of ATLL hypercalcaemia.

Calcium and vitamin D metabolism in granulomatous diseases

Overproduction of the active metabolite of vitamin D 1,25-dihydroxyvitamin D (1,25(OH)2D) has been described in sarcoidosis and other granulomatous diseases. High circulating concentrations of 1,25(OH)2D lead to increased intestinal absorption of calcium, possibly to enhanced bone resorption, and may result in hypercalcaemia and/or hypercalciuria. Data obtained in vivo and in vitro demonstrated that the unregulated production of 1,25(OH)2D lies within the granulomatous tissue and is controlled by glucocorticoids. This abnormal production of 1,25(OH)2D seems to be a general phenomenon of granulomatous processes, which is not exceptional in sarcoidosis, but appears seldom in tuberculosis. These abnormalities, however, are not pathognomonic of granulomatous processes, since they have been described in other diseases such as lymphomas.

1,25-Dihydroxyvitamin D3 down-regulation of HLA-DR on human peripheral blood monocytes

The regulatory activity of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on human leucocyte antigen (HLA)-DR (MHC class II) antigen expression in monocytes from normal human peripheral blood was examined. Using forward light and side scatter by flow cytometry most cells within the discrete monocyte area expressed high levels of HLA-DR antigens following 4-day culture in medium alone (culture-enhanced HLA-DR) and expression was further up-regulated in the presence of interferon-gamma (IFN-gamma) (IFN-gamma-enhanced HLA-DR). Treatment with 1,25-(OH)2D3 markedly inhibited both culture and IFN-gamma-enhanced HLA-DR but not HLA-ABC (MHC class I). This 1,25-(OH)2D3 inhibition was as effective as PGE2 and hydrocortisone. To ascertain if HLA-DR was specifically down-regulated on monocytes, the effect of vitamin D3 analogues in CD33+ cells was examined. Incubation of the CD33+ cells with 1,25-(OH)2D3, 24-25-(OH)2D3 and 25-OHD3 resulted in dose-dependent inhibition of culture-enhanced HLA-DR paralleling the vitamin D3-receptor affinities of these compounds. Northern analysis also demonstrated that 1,25-(OH)2D3 treatment markedly decreased both expression of culture-enhanced and IFN-gamma-enhanced HLA-DR beta chain messenger RNA (mRNA) in monocyte-enriched populations. In total, our findings are consistent with the proposal that vitamin D3 analogues can contribute to down-regulating immune responses as a consequence of inhibiting class II expression.

Management of disorders of calcium homoeostasis

Severe hypercalcaemia may be life-threatening and requires prompt management. Whatever the cause, the aim of therapy should obviously be to eradicate the source of hypercalcaemic factors. After rehydration, which is an essential first step in the management strategy, and after evaluation of the prevailing pathogenetic mechanism, the acute treatment will be aimed at increasing urinary Ca excretion and inhibiting bone resorption. Among the various pharmacological agents, bisphosphonates appear to be the drugs of first choice, because of their efficacy and their virtual absence of side-effects. The decision to treat hypocalcaemia is determined by the extent of the symptoms and the risk of complications. The treatment of acute hypocalcaemia comprises the parenteral administration of Ca or magnesium, when magnesium deficiency can be suspected. Then, chronic hypocalcaemia may require the use of 1,25-dihydroxyvitamin D, once the replenishments of vitamin D stores have been assured.

Hypercalcemia of malignancy: pathophysiology, diagnosis and treatment

Malignancy is the most frequent cause of hypercalcemia in hospitalized patients. The pathophysiology of hypercalcemia of malignancy (HM) is complex. Increased bone resorption is involved in most cases caused either by extensive local bone destruction or by humoral factors. Tumor extracts from patients with humoral hypercalcemia of malignancy (HHM) often contain PTH-like bioactivity. Recently, cDNAs coding for a PTH-related protein (PTH-rP) has been cloned. The N-terminal amino acid sequence of this protein shows a considerable homology with human PTH. However, other bone resorbing factors including prostaglandins, transforming growth factors, colony stimulating factors, leucocyte cytokines and 1,25-dihydroxyvitamin D may be involved in different types of malignancy. HM is usually progressive with troublesome symptoms and a high mortality. Several treatment alternatives are available including rehydration, bisphosphonates, calcitonin, plicamycin, phosphate, and glucocorticoids. Others are under investigation. Treatment should be individualized taking into account the pathophysiological mechanisms involved, the extent of hypercalcemia and renal failure, and the prognosis related to the malignant disease.

Hypercalcemia with excess serum 1,25 dihydroxyvitamin D in lymphomatoid granulomatosis/angiocentric lymphoma

Hypercalcemia has been described in a variety of granulomatous and lymphoproliferative disorders in association with elevated serum levels of 1,25-dihydroxyvitamin D. In such cases, hypercalcemia appears to be the consequence of excessive production of 1,25(OH)2D by the lymphocyte/macrophage line. The authors report a patient with lymphomatoid granulomatosis/angiocentric lymphoma who developed hypercalcemia with extreme elevation in serum 1,25(OH)2D. Therapy with steroids reduced the serum calcium and 1,25(OH)2D levels to normal. Hypercalcemia has not previously been reported in lymphomatoid granulomatosis/angiocentric lymphoma. The distinctive features of this malignancy, and the derangement in the metabolism of 1,25(OH)2D in lymphoproliferative disorders in general, are discussed.

Intermittent hypercalcaemia and vitamin D sensitivity in Hodgkin's disease

A patient with Hodgkin's disease spontaneously developed steroid-responsive hypercalcaemia during two consecutive summers. Administration of 3000 U/day of vitamin D, while he was normocalcaemic, caused a sharp increase in serum 1,25(OH)2D3 (from 59 pg/ml to 142 pg/ml) and subsequently hypercalcaemia while serum 25(OH)D3 rose moderately within the normal range (from 2.8 ng/ml to 10 ng/ml). During a spontaneous episode of hypercalcaemia which was accompanied by increased circulating 1,25(OH)2D3 concentrations, administration of hydrocortisone decreased serum 1,25(OH)2D3 rapidly (from 115 pg/ml to 62 pg/ml) and eventually led to normocalcaemia while serum 25(OH)D3 remained unchanged. Thus the disturbances of mineral metabolism found in this patient with Hodgkin's disease are very similar to those previously described in sarcoidosis.

Immune system and bone remodeling

The skeleton undergoes continuous cellular remodeling in a manner similar to that of replacement of a wall, brick by brick. Products of immune cells are likely to modulate all of the cellular events involved in bone remodeling. The local factors that modulate bone cell function and bone remodeling-osteotropic cytokines or growth-regulatory factors-are similar to those involved in other body processes such as wound healing, immune function, oncogenesis, angiogenesis, and embryogenesis.

1,25(OH)2D2 production by T lymphocytes and alveolar macrophages recovered by lavage from normocalcemic patients with tuberculosis

To compare extra-renal 1,25(OH)2D3 production in different types of granulomatous disease, and to identify the cell types responsible, we have evaluated the conversion of 25(OH)D3 in 1,25(OH)2D3 by uncultured cells recovered by bronchoalveolar lavage and blood mononuclear cells from normocalcemic patients with sarcoidosis and tuberculosis. 1,25(OH)2D3 was produced both by lavage cells (12/12 tuberculosis patients, 2/6 sarcoidosis patients) and blood mononuclear cells (3/5 tuberculosis patients, 0/3 sarcoidosis patients) from patients but not controls, but significantly greater amounts were produced by lavage cells from tuberculosis patients than those of sarcoidosis patients (P less than 0.001). 1,25(OH)2D3 production by lavage cells from tuberculosis patients correlated with the number of CD8+ T lymphocytes present but not other cell types. T lymphocytes appeared to be an important source of 1,25(OH)2D3 production, since purified T lymphocytes from all patients with tuberculosis produced 1,25(OH)2D3, and 1,25(OH)2D3 production by these cells correlated closely with that produced by unseparated lavage cells. Because 1,25(OH)2D3 can improve the capacity of macrophages to kill mycobacteria, our results support the conclusion that macrophage-lymphocyte interactions, mediated at least in part by 1,25(OH)2D3, may be an important component of a successful antituberculous immune response.

Incidence and pathophysiology of hypercalcemia

Hypercalcemia occurs for various reasons in patients with malignant diseases. Most of these patients show a relative increase in bone resorption over bone formation. Increased renal tubular calcium reabsorption is also important for maintaining hypercalcemia in the majority of patients. Calcium absorption from the gut is usually decreased. In a few patients, fixed impairment of glomerular filtration contributes to hypercalcemia. Because the pathophysiology of hypercalcemia is heterogeneous, it may be considered as three separate syndromes: the humoral hypercalcemia of malignancy caused by systemic mediators; the hypercalcemia associated with localized osteolytic disease; and the hypercalcemia associated with myeloma and related hematologic malignancies. Increased bone resorption is a key feature in each of these syndromes. In malignant disease, bone resorption is enhanced because osteoclast activity is increased by the production of humoral mediators. These mediators are often produced by the tumor cells but are also produced by normal host cells that have been activated by the presence of the tumor. some of these mediators of hypercalcemia are systemic factors, but some act only locally. They include parathyroid hormone-related protein, transforming growth factor alpha, lymphotoxin, tumor necrosis factor, interleukin-1 alpha and 1,25-dihydroxyvitamin D.

Hypercalcaemia of malignancy

Hypercalcaemia in malignancy is a major clinical problem. It contributes significantly to morbidity and mortality and can present difficult diagnostic and management dilemmas. Direct bony invasion by tumour cells rather than humorally mediated hypercalcaemia is probably the most common cause of malignant hypercalcaemia. Yet even in this situation the mechanism of bone resorption or the reason that the normal homeostatic mechanisms cannot cope with the calcium load are poorly understood. It is likely that the humoral and paracrine factors produced by tumours which result in hypercalcaemia or in osteosclerotic bone metastases, are interposing themselves into the normal regulatory processes and deranging them. Humoral hypercalcaemia of malignancy is an important model for studying these questions, and it also provides some insight into the normal regulation of bone turnover. This review will examine the animal models and human syndromes of malignant hypercalcaemia and show how animal models, although helpful, fail to delineate the relative importance of the various potential humoral factors. A most interesting recent development in this area is the description of a new hormone, the parathyroid hormone-related peptide, which may explain many of the cases of humoral hypercalcaemia of malignancy. It is also a useful model with multiple sites of action within the bone and calcium homeostatic process. The active hormonal form of vitamin D3, 1,25-dihydroxyvitamin D3, may also be involved in a small proportion of cases, but again it is a useful model of some of the factors that may operate. Of considerable interest are the tumour derived factors, such as the transforming growth factors, and the cytokines, such as tumour necrosis factors, interleukins, and haemopoietic colony stimulating factors. Prostanoids are seldom of major importance, but may be important in certain tumour types. Osteosclerotic metastases, although seldom associated with hypercalcaemia, may provide insight into osteoblast regulating factors. Treatment of hypercalcaemia is discussed to show ways in which response to treatment may shed light on underlying pathophysiological mechanisms. Most effective treatments have many potential modes of action, and further study of the interactions of these agents and tumour types may help to unravel some of the enigmas in this human syndrome. The major advances in this complex problem involve the realisation of the necessity of multiple sites of action, including renal calcium handling as well as relative increases in bone resorption and/or intestinal calcium absorption.(ABSTRACT TRUNCATED AT 400 WORDS)

Hypercalcemia and vitamin D metabolism in Hodgkin's disease. Is there an underlying immunoregulatory relationship?

Hypercalcemia is not common in Hodgkin's disease, but in reported cases is often unassociated with bone involvement. A case is presented demonstrating a mechanism involving elevated levels of 1,25-dihydroxy vitamin D3 (calcitriol). Similar cases in the literature are reviewed. Data implicating calcitriol as a hematolymphoid regulatory hormone are discussed as they may relate to lymphomas, leukemias, and paraneoplastic lymphocyte and monocyte/macrophage activity.

Expression of parathyroid hormone-related protein in a human T cell lymphotrophic virus type I-infected T cell line

We analyzed human T cell lymphotrophic virus type I (HTLV-I)-infected T cells for the presence of mRNA coding for parathyroid hormone-related protein (PTHrP) by Northern blotting using synthetic DNA probes. We report here that PTHrP mRNAs were detected in a HTLV-I-infected T cell line, MT-2, but not in uninfected T cell or B cell lines, and that PTH-like bioactivity was detected only in the conditioned medium of MT-2 cells. Our study suggests that the pathophysiology of hypercalcemia in patients with adult T cell leukemia/lymphoma may resemble that which occurs with solid tumors.

Current management of malignant hypercalcaemia

The pathogenic mechanisms causing malignant hypercalcaemia are primarily increased bone calcium mobilisation and renal calcium retention. In some reticuloendothelial malignancies, enhanced intestinal calcium absorption may also play a role. Malignant hypercalcaemia is a life-threatening condition, and there are many patients with malignancy in whom suppression of this complication is most desirable. In such cases, successful management of the hypercalcaemia will enable the overall treatment aims, such as tumour removal or ablation, to be achieved. Acute treatment involves the rapid lowering of serum calcium from potentially fatal concentrations, and comprises the use of intravenous rehydration, calcitonin and diphosphonates. In the longer term, other measures may be introduced to maintain and control the calcium concentration while specific antitumour therapy is instituted.

Recurrent hypercalcemia and elevated 1,25-dihydroxyvitamin D levels in Hodgkin's disease

Hypercalcemia has been infrequently associated with Hodgkin's disease. When seen, most cases have been attributable to skeletal invasion by disease. Herein is described a 40-year-old man with a 15-year history of Hodgkin's disease. Each of four disease recurrences was heralded by hypercalcemia occurring in the absence of bone disease or elevation of parathyroid hormone levels. Marked elevations of 1,25-dihydroxyvitamin D levels were observed that paralleled his disease course and response to therapy. The repetitive association of hypercalcemia with an elevation of 1,25-dihydroxyvitamin D in this case provides further evidence of lymphoma-associated production of this vitamin.

1,25-Dihydroxyvitamin D3-mediated inhibition of human B cell differentiation

We have examined the mechanisms of 1,25-dihydroxyvitamin D3 (D3)-mediated inhibition of human B cell differentiation to immunoglobulin (Ig) secreting cells. B lymphocytes were purified from human tonsils and peripheral blood mononuclear cells. Mononuclear cells were separated into adherent cells and nonadherent cells. Cells were stimulated with Staphylococcus aureus Cowen I (SAC) or pokeweed mitogen (PWM) for 7 days and immunoglobulin production was measured by ELISA assay, 1,25-dihydroxyvitamin D3 was added at different times during cultures. 1,25-Dihydroxyvitamin D3, in a dose-dependent manner, inhibited both SAC and PWM-induced Ig production by mononuclear cells. The maximum inhibition was observed when 1,25-dihydroxyvitamin D3 was added at the beginning of culture, but inhibition could still be observed when 1,25-dihydroxyvitamin D3 was added on day 4 of cultures. The inhibitory effect of 1,25-dihydroxyvitamin D3 on Ig production was significantly greater on mononuclear cells than on nonadherent cells. Addition of in vitro purified IL-1 to nonadherent cells enhanced 1,25-dihydroxyvitamin D3-induced inhibition of Ig production. 1,25-Dihydroxyvitamin D3 also inhibited the expression of IL-2 receptors on B cells activated with SAC. 1,25-dihydroxyvitamin D3 did not inhibit Ig production by SAC preactivated B cell blasts in response to T cell supernatants. These data suggest that vitamin D3 inhibits Ig production by inhibiting IL-2 receptor expression on B cells and via its effect on adherent macrophages. Vitamin D3 does not influence the effect of differentiation factors on activated B cells that have already expressed growth/differentiation factor receptors.

Production of lymphotoxin, a bone-resorbing cytokine, by cultured human myeloma cells

Myeloma cells destroy bone by producing an osteoclast-stimulating factor that has chemical and biological characteristics similar to the bone-resorbing activity present in the supernatants of activated leukocyte cultures. Recently, a number of bone-resorbing leukocyte cytokines have been identified, including interleukin-1, lymphotoxin, and tumor necrosis factor. We have examined the products of human myeloma cells for the presence of these bone-resorbing cytokines. In a tumor cell line derived from a patient who had myeloma with osteolytic bone lesions and hypercalcemia, we found that the myeloma cells induced bone-resorbing activity and cytotoxic activity in vitro. Most of the bone-resorbing activity and all cytotoxic activity were suppressed by neutralizing antibodies to lymphotoxin. The myeloma cells expressed both lymphotoxin and tumor necrosis factor mRNA, but no tumor necrosis factor could be detected in the cell-culture medium. Interleukin-1 mRNA was not detected in the myeloma cells, and biologic activity of interleukin-1 was not measurable in the medium harvested from the cultured cells. The bone-resorbing activity induced by recombinant tumor necrosis factor and recombinant interleukin-1 was not affected by treatment with the lymphotoxin antibodies. When lymphotoxin was infused subcutaneously into normal mice (10 micrograms per day for three days), their plasma calcium levels increased. We also evaluated four established cell lines derived from three other patients with myeloma, and found a similar pattern of lymphotoxin expression in each. It appears that production of the bone-resorbing cytokine lymphotoxin is related to osteoclastic bone destruction and hypercalcemia in patients with myeloma.

The hypercalcemia of malignancy

The hypercalcemia of malignancy is mediated by complex and heterogeneous mechanisms. Once thought of as a simple paraneoplastic syndrome mediated by the effects of tumor production of PTH, it is now clear that multiple mechanisms are involved and that these mechanisms involve abnormalities in calcium transport in bone, kidney, and gut. Calcium homeostasis in normal individuals is complex and tightly regulated. Although much has been learned over the last 20 years about the effects of individual hormones on target organs, much remains to be understood about how these hormonal systems interact to control extracellular fluid calcium. Future studies on disturbances in calcium homeostasis, such as that occurring in association with malignant disease, should do much to clarify how these complex hormonal mechanisms function in the normal individual.