Malignancy-associated hypercalcemia

Hypercalcemia is the most frequent paraneoplastic syndrome observed in cancer patients. This morbidity can be divided into two categories: one is hypercalcemia induced by severe bone metastases; the other the elaboration of hypercalcemic factors by solid tumors, termed humoral hypercalcemia of malignancy (HHM). With regard to humoral factors responsible for HHM, a protein with parathyroid hormone (PTH)-like activity, designated PTH-related protein (PTHrP), was isolated from a cancer cell line established from a hypercalcemic patient's lung cancer tissue, and the structure of PTHrP mRNA was identified. Since the biological activity of PTHrP explained most of the clinical and laboratory findings of HHM patients and recent clinical studies indicated the very close relationship between the development of HHM and the production of PTHrP by tumor, PTHrP is now regarded to be the primary candidate for the actual factor responsible for HHM.     

Expression of parathyroid hormone-related protein mRNA in tumors obtained from patients with humoral hypercalcemia of malignancy

Human parathyroid hormone-related protein (PTHrP) mRNA was detected in all fresh cancer tissues consecutively obtained from 6 patients with humoral hypercalcemia of malignancy (HHM). The primary sites of the cancers in these cases were distributed among different organs including the lung, esophagus, kidney and ovary. PTHrP mRNA was undetectable in all 10 fresh cancer tissues obtained from normocalcemic patients. These results suggest PTHrP as a major cause of HHM.     

EXPRESSION OF PARATHYROID HORMONE-RELATED PROTEIN mRNA IN TUMORS OBTAINED FROM PATIENTS WITH HUMORAL HYPERCALCEMIA OF MALIGNANCY

Human parathyroid hormone-related protein (PTHrP) mRNA was detected in all fresh cancer tissues consecutively obtained from 6 patients with humoral hypercalcemia of malignancy (HHM). The primary sites of the cancers in these cases were distributed among different organs including the lung, esophagus, kidney and ovary. PTHrP mRNA was undetectable in all 10 fresh cancer tissues obtained from normocalcemic patients. These results suggest PTHrP as a major cause of HHM.     

Humoral hypercalcemia in patients with colorectal carcinoma: report of two cases and review of the literature

BACKGROUND: Humoral hypercalcemia rarely is associated with colorectal carcinoma; to the authors' knowledge only nine cases have been reported to date. METHODS: Two cases of advanced colorectal carcinoma with humoral hypercalcemia of malignancy (HHM) are presented. RESULTS: The two patients had severe hypercalcemia without bone metastases. The diagnosis of HHM was based on findings of hypercalcemia, hypophosphoremia, elevated serum parathyroid hormone-related peptide (PTHrP), and positive tumor immunoreactivity to monoclonal PTHrP antiserum. One patient had a colonic adenocarcinoma with a neuroendocrine component and the other patient had rectal adenocarcinoma. Immunoreactive PTHrP was found in both tumor components. Bisphosphonate treatment normalized the hypercalcemia within a few days but it recurred in the patients 2 weeks and 3 weeks later, respectively. The prognosis was extremely poor. CONCLUSIONS: To the authors' knowledge the two cases presented in the current study are the first to be reported with HHM-associated colorectal carcinoma with positive tumor immunoreactivity to PTHrP monoclonal antiserum.     

Hypercalcemia in patients with esophageal carcinoma. The pathophysiologic role of parathyroid hormone-related protein

To elucidate the actual incidence of hypercalcemia in patients with esophageal carcinoma, 382 consecutive cases admitted to the National Cancer Center Hospital (Tokyo, Japan) from 1983 to 1988 were investigated. Hypercalcemia was detected in 5 patients of 376 (1.3%) at the time of primary detection of cancer, and in 45 patients of 120 (38%) patients with recurrent or unresectable cancer who were monitored within 2 months of death. These observations demonstrated that this electrolyte imbalance is a frequent paraneoplastic syndrome observed in patients with advanced esophageal carcinoma. With regard to the etiology, bone metastases were detected in 13 of 49 patients with hypercalcemia; the remaining 36 patients were assumed to be induced by the production of hypercalcemic substance(s) by tumor tissues. Parathyroid hormone-related protein (PTHrP) is a newly discovered factor which increases serum calcium in vivo. The detection of PTHrP mRNA in tumor tissues as well as the production of PTHrP-like immunoreactivity by tumor tissues were closely associated with the development of hypercalcemia, suggesting that PTHrP is the major cause of hypercalcemia in patients with esophageal carcinoma.     

PTHrP and breast cancer]

Parathyroid hormone-related peptide (PTHrP) has a high homology with the N-terminal portion of the parathyroid hormone (PTH). The gene of PTHrP is complex and can generate by alternative splicing at least three mature peptides containing 139, 141 and 173 amino acids. PTHrP acts via a common receptor with PTH but also via specific receptors. In physiological circumstances, PTHrP is produced locally in many normal tissues where it has autocrine/paracrine functions, particularly during embryonic development, growth regulation and differentiation of many cellular types. PTHrP has endocrine action on bone and kidney. The humoral hypercalcemia of malignancy is mainly mediated by PTHrP. Most hypercalcemic patients with solid tumors have increased plasma PTHrP, whereas PTHrP is not detectable in healthy subjects. During treatment with bisphosphonates, elevated plasma levels of PTHrP are associated with a weak response. PTHrP has also a significant role in the pathophysiology of bone metastases. PTHrP can induce a local osteolysis near the bone metastases, which favours their progression and thus participates in the autocrine regulation of tumor growth. In breast cancer, PTHrP is detected in about 60% of primary tumors and in more than 70% of bone metastases, whereas only 17% of nonbone metastases express PTHrP. A higher expression of PTHrP and its mRNA 1-139, is positively correlated with an invasive tumor phenotype and the development of bone metastases. PTHrP is an effector of transforming growth factor (TGFbeta) in the development and progression of osteolytic bone metastases. TGFbeta, which is released in bone matrix during osteolytic resorption, enhances tumor cells PTHrP production. Then, PTHrP stimulates bone resorption and develops tumor cells metastatic potential. Thus a feedback loop exists between carcinoma cells and the bone microenvironment, leading to a vicious circle.     

Immunohistochemical localization of parathyroid hormone-related protein in human breast cancer

Parathyroid hormone-related protein (PTHrP) is known to be a causative factor in humoral hypercalcemia of malignancy. A polyclonal rabbit antiserum directed against the amino-terminal region of the protein and immunoperoxidase methods have been used to locate the presence of PTHrP in a series of 102 consecutive invasive breast tumors removed surgically from normocalcemic women. Positive PTHrP staining was detected in 60% of the tumors but not in the accompanying normal breast tissue. Positive staining was related to the progesterone receptor status of the tumor (P = 0.039) and to the prognostic index of the patient (P = 0.046) and not to estrogen receptor status, patient age, tumor size, histological grade, or nodal status.     

Parathyroid hormone-related protein-secreting uterine endometrioid adenocarcinoma

The diagnosis of parathyroid hormone-related protein (PTHrP)-secreting metastatic uterine endometrioid cancer was made in a 32-year-old Japanese woman with humoral hypercalcemia of malignancy. The primary endometrial cancer had been removed, and the tumor was diagnosed as Grade 1 endometrioid adenocarcinoma with shallow myometrial invasion. Salvage chemotherapy (paclitaxel and calboplatin) was started from 5 months after surgery when recurrent tumors were detected in the peritoneum and liver. Despite the salvage chemotherapy, the tumor progressed and hypercalcemia became evident with elevated PTHrP whereas no bone metastasis was identified. To the best of our knowledge, this is the first reported case of hypercalcemia due to PTHrP secretion in uterine endometrioid adenocarcinoma.     

A case of leiomyosarcoma associated with humoral hypercalcemia of malignancy: demonstration of biological and immunological activities of parathyroid hormone-related protein in the tumor extract

Hypercalcemia occurred in a patient with leiomyosarcoma when multiple lung metastases developed. Despite normal plasma parathyroid hormone (PTH) levels and low 1,25-dihydroxyvitamin D, this hypercalcemic patient had a marked hypercalciuria and phosphaturia associated with an increased excretion of nephrogenous cyclic AMP (NcAMP). Administration of cisplatin ameliorated both the hypercalcemia and hypercalciuria without any reduction in tumor size of NcAMP excretion. Terminally, acute pancreatitis occurred producing a profound hypocalcemia. In the extract of tumor tissue obtained post mortem, bioactivity stimulating the generation of cyclic AMP in osteogenic cells was demonstrated along with the immunoreactive PTH-related protein (PTH-rP). the first report of a solid non-epithelial malignancy producing PTH-rP and associated with humoral hypercalcemia of malignancy. The hypercalcemia in this case caused acute pancreatitis, which led to a profound hypocalcemia.     

A Case of Leiomyosarcoma Associated with Humoral Hypercalcemia of Malignancy: Demonstration of Biological and Immunological Activities of Parathyroid Hormone-related Protein in the Tumor Extract

Hypercalcemia occurred in a patient with leiomyosarcoma when multiple lung metastases developed. Despite normal plasma parathyroid hormone (PTH) levels and low 1,25-dihydroxyvitamin D, this hypercalcemic patient had a marked hypercakiuria and phosphatnria associated with an increased excretion of nephrogenous cyclic AMP (NcAMP). Administration of cisplatin ameliorated both the hypercalcemia and hypercalciuria without any reduction in tumor size or NcAMP excretion. Terminally, acute pancreatitis occurred producing a profound hypocalcemia. In the extract of tumor tissue obtained post mortem, bioactivity stimulating the generation of cyclic AMP in osteogenic cells was demonstrated along with the immunoreactive PTH-related protein (PTH-rP). This is the first report of a solid non-epithelial malignancy producing PTH-rP and associated with humoral hypercalcemia of malignancy. The hypercalcemia in this case caused acute pancreatitis, which led to a profound hypocalcemia     

Osteoprotegerin prevents and reverses hypercalcemia in a murine model of humoral hypercalcemia of malignancy

Osteoprotegerin (OPG), a novel, secreted tumor necrosis factor receptor family member that inhibits osteoclast formation and activity was examined for its activity in a syngeneic tumor model of humoral hypercalcemia of malignancy. Normal mice bearing Colon-26 tumors develop increases in both parathyroid hormone-related protein (PTHrP) expression and plasma PTHrP, marked hypercalcemia, and increased bone resorption. OPG, given either at the onset of hypercalcemia or after it had occurred, blocked tumor-induced increases in bone resorption and hypercalcemia and rapidly normalized blood ionized calcium. In tumor-bearing mice, OPG treatments reduced osteoclast activity from approximately 2-fold above normal into the subphysiological range but had no effects on tumor size, tumor-induced cachexia, or PTHrP levels. The potent effects of OPG in this humoral hypercalcemia of malignancy model suggest a potential therapeutic role for OPG in the prevention and treatment of this disorder.     

Therapeutic efficacy of a soluble receptor activator of nuclear factor kappaB-IgG Fc fusion protein in suppressing bone resorption and hypercalcemia in a model of humoral hypercalcemia of malignancy

Receptor activator of nuclear factor kappaB (RANK) is a membrane-bound tumor necrosis factor receptor homologue that mediates signals obligatory for osteoclastogenesis as well as osteoclast activation and survival in vivo. The present study was undertaken to evaluate the efficacy of a soluble murine RANK-human immunoglobulin fusion protein (muRANK.Fc) as a bone resorption inhibitor in vitro and in vivo. The in vitro studies demonstrated the ability of muRANK.Fc to inhibit human parathyroid hormone-related protein (PTHrP)-induced resorption in fetal rat long bone cultures. Short-term administration of muRANK.Fc to normal growing mice resulted in a complete disappearance of osteoclasts from metaphyses of long bones associated with a pronounced increase in calcified trabeculae and bone radiodensity. In a model of humoral hypercalcemia of malignancy in which PTHrP secreted by s.c. xenografts of human lung cancer in nude mice induces extensive osteolysis and severe hypercalcemia, daily administration of muRANK.Fc from time of tumor implantation profoundly inhibited osteoclastic bone resorption and prevented hypercalcemia. muRANK.Fc had no effect on tumor production of PTHrP, because there was no significant difference between circulating human PTHrP levels in muRANK.Fc-treated and vehicle-treated tumor-bearing mice. Moreover, even when treatment was initiated after hypercalcemia was established, muRANK.Fc significantly attenuated further increases in blood ionized calcium. These data demonstrate the potent antiresorptive effects of muRANK.Fc in vivo as well as highlight the potential utility of disrupting RANK signaling as a novel therapeutic approach in humoral hypercalcemia of malignancy and possibly multiple myeloma and skeletal metastases associated with osteolysis.     

Retroperitoneal neurilemoma presenting with humoral hypercalcemia associated with markedly elevated plasma prostaglandin levels

A 72-year-old woman complaining of somnolence and thirst was diagnosed to have a hypercalcemic crisis (corrected serum calcium level, 17.4 mg/dl) associated with encephalopathy and nephropathy. Imaging diagnostic techniques demonstrated a retroperitoneal tumor at the median site of right renal pelvis. Hormonal studies revealed that plasma levels of thromboxane B2, prostaglandin (PG) E2, 6-keto prostaglandin F1 alpha (PGF1 alpha) and prostaglandin F2 alpha (PGF2 alpha) were markedly elevated. The tumor was successfully removed by operation; her serum calcium level and PG levels normalized without any treatment indicating that this case belongs to the category of humoral hypercalcemia of malignancy (HHM). Pathologically, this tumor was diagnosed to be a benign neurilemoma. Parathyroid hormone-related protein (PTHrP) radioimmunoassay and Northern blot hybridization for PTHrP mRNA were negative. The current case demonstrates that hypercalcemic crisis could be induced by a curable benign neurilemoma, and suggests that this HHM-like morbidity was associated with markedly elevated plasma PG levels.     

Immunocytochemical demonstration of PTHrP protein in neoplastic tissue of HTLV-1 positive human adult T cell leukaemia/lymphoma: implications for the mechanism of hypercalcaemia

The infiltrated tissues from seven West Indian patients with HTLV-1 positive adult T cell lymphoma/leukaemia (ATLL) have been analysed by immunocytochemical techniques for the presence of immunoreactive parathyroid hormone-related protein (PTHrP), a hormonal mediator of humoral hypercalcaemia of malignancy. Six of the seven were hypercalcaemic at some stage of the course of their disease. Four of the six evaluable patients showed evidence of specific cellular and extracellular expression of PTHrP protein in neoplastic tissues. This finding suggests that PTHrP may be involved in the production of hypercalcaemia in at least some cases of T cell lymphoma - proof of a causal relationship however must await the demonstration of tissue release of PTHrP resulting in raised circulating hormone levels.     

L’hypercalcémie associée au cancer

Hypercalcemia of malignancy is the most common metabolic complication associated with cancer. It can be classified into four types: humoral hypercalcemia caused by an increased secretion of tumor parathyroid hormonerelated protein (PTHrP), local malignant osteolysis, increased production of vitamin D or ectopic secretion of parathyroid hormone (PTH). Malignant hypercalcemia causes a series of symptoms affecting quality of life of the patients, especially if they suffer from bone pain. The management of malignant hypercalcemia includes general measures of support, hydration and treatment with bisphosphonates. These potent inhibitors of bone resorption (particularly the zoledronic acid) have revolutionized the treatment of malignant hypercalcemia with their bioavailability, tolerance and especially their effectiveness.     

Parathyroid hormone-related protein in human renal cell carcinoma

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

Calcium metabolism in cancer. Studies using calcium isotopes and immunoassays for parathyroid hormone and calcitonin.

Studies of calcium metabolism in 38 patients with cancer indicated that: 1) intestinal absorption of calcium was reduced in patients with skeletal metastases and in those with hypercalcemia; 2) calcium-47 space (a measurement of bone turnover rate) was high in the patients with skeletal metastases; 3) hypercalcemic patients had higher urinary and endogenous fecal excretion of calcium than those who were normocalcemic; 4) levels of plasma immunoreactive parathyroid hormone were similar in normo- and hypercalcemic patients, but the levels for a given serum calcium in malignant disease were lower than those in primary hyperparathyroidism; and 5) some patients had elevated calcitonin levels. Hypercalcemia complicating malignant disease is therefore not due to hyperabsorption or diminished excretion of calcium, and a low calcium diet is unlikely to benefit these patients. Measurement of 47Ca space could be of use in monitoring therapy of patients with skeletal metastases, and measurement of plasma parathyroid hormone could be useful in the differential diagnosis of hypercalcemia.     

Abnormal bone and parathyroid histology in carcinoma patients with pseudohyperparathyroidism

Postmortem bone and parathyroid gland histology in nine hypercalcemic cancer patients without bone metastases was compared to bone and parathyroid histology in ten normocalcemia patients. Parameters of parathyroid function, including serum immunoreactive parathyroid hormone, acid base status, serum phosphate, and nephrogenous cyclic AMP were measured in the hypercalcemic group and compared to normals and to patients with primary hyperparathyroidism. Bone histology in all nine hypercalcemic cancer patients showed increased osteoclastic bone resorption and increased fibrous connective tissue in the bone marrow. Parathyroid glands were of normal size in all nine patients but contained little or no fat, one criterion of parathyroid hyperplasia. In the normocalcemic cancer patients only 2/10 had minimally increased bone resorption while 7/10 had decreased or absent stromal fat in the parathyroid glands. Despite the hyperplastic appearance of the parathyroid glands, serum biochemical parameters in the hypercalcemic cancer patients indicate a state of suppressed parathyroid function suggesting that the osteoclastic bone resorption is related to a humoral substance elaborated by the tumors which is distinct from parathyroid hormone.     

Paraneoplastic hypercalcemia in endometrial carcinoma

Humoral hypercalcemic syndrome associated with tumors of the female reproductive system is believed to be uncommon, and only 27 such cases have been identified prior to 1980. We describe 2 patients with humoral hypercalcemia in clear cell adenocarcinoma of the uterus, and review the literature on previously published cases. Both our patients fulfilled the criteria for humoral hypercalcemic syndrome, namely: hypercalcemia without bone metastases ranging from 12.8 to 14.1 mg/dl in the presence of normal serum parathyroid hormone levels, reduced tubular reabsorption of phosphate, and reduced serum albumin. We propose that humoral hypercalcemia is perhaps not a rare complication of uterine malignancy and, that increased awareness may result in early diagnosis of this important metabolic problem.     

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.