Parathyroid hormone-related protein mRNA and protein expression in multiple myeloma: a case report

Treatment of malignancy-associated hypercalcemia with cinacalcet: a paradigm shift

Palliation of symptoms related to malignancy-associated hypercalcemia (MAH) is essential and clinically meaningful for patients, given the continued poor prognosis, with high morbidity and mortality associated with this disease process. Historically, agents have been temporizing, having no impact on patient morbidity nor survival. We suggest that cinacalcet can be an efficacious agent to be taken orally, reducing patients' time in the hospital/clinic settings. It is well-tolerated and maintains serum calcium levels in the normal range, while targeted cancer treatments can be employed. This has a direct, major impact on morbidity. Maintaining eucalcemia can increase quality of life, while allowing targeted therapies time to improve survival. Given that our case (and others) showed calcium reduction in MAH, there is promising evidence that cinacalcet can be more widely employed in this setting. Future consideration should be given to studies addressing the efficacy of cinacalcet in calcium normalization, improvement of quality of life, and impact on survival in patients with MAH. Though the exact mechanism of action for cinacalcet's reduction in calcium in this setting is not currently known, we can still afford patients the possible benefit from it.

Increase in serum 1,25-dihydroxyvitamin D and hypercalcaemia in a patient with inflammatory myofibroblastic tumour

Hypercalcaemia complicates the clinical course of a substantial number of patients with advanced cancer. This report describes a patient with an inflammatory myofibroblastic tumour in soft tissue who developed an inflammatory reaction, hypercalcaemia, and a high serum concentration of 1,25 dihydroxyvitamin D. Serum concentrations of 25-hydroxyvitamin D, parathyroid hormone, and parathyroid hormone related protein were normal. Histological examination of the tumour revealed fibrosarcoma with abundant macrophage infiltration. mRNA for 25-hydroxyvitamin D-1alpha-hydroxylase was identified in the tumoral tissue. In view of this case, inflammatory myofibroblastic tumour should be added to the list of diseases that are responsible for vitamin D mediated hypercalcaemia.

Expression of parathyroid hormone-related protein (PTHrP) in multiple myeloma

Multiple myeloma is a plasma cell neoplasia often associated with multiple skeletal lesions and hypercalcemia. Several cytokines, including interleukin (IL)-1, IL-6 and tumor necrosis factor-beta (TNF-beta), derived from myeloma cells are thought to accelerate osteoclastic bone resorption and cause hypercalcemia through a paracrine mechanism. We report on a case of a 69-year-old man with multiple myeloma associated with hypercalcemia and advanced osteolytic lesions. After bisphosphonate treatment and MP (melphalan and prednisolone) therapy, the patient's serum calcium level was successfully but transiently recovered to the normal range. Biochemical analysis showed a remarkable increase in serum parathyroid hormone-related protein (PTHrP; 3.7 pmol/L) and IL-6 (22.0 pg/mL). On the other hand, parathyroid hormone and 1alpha,25(OH)2 vitamin D3 were suppressed. By immunohistochemistry and in situ hybridization on aspiration-biopsied bone marrow clot sections, PTHrP mRNA and protein were detected in the cytoplasm of myeloma cells. The rate of PTHrP-positive myeloma cells was estimated to be at least one-third. Since PTHrP can, as an endocrine factor, systemically act on bone and kidney, hypercalcemia in this case might have been caused through both local osteolytic hypercalcemia and humoral hypercalcemia of malignancy mechanisms.

Receptor activator of nuclear factor-kappaB ligand and osteoprotegerin: potential implications for the pathogenesis and treatment of malignant bone diseases

BACKGROUND

The current review summarizes the roles of the ligand, receptor activator of nuclear factor-kappaB ligand (RANKL), its receptor, receptor activator of nuclear factor-kappaB (RANK), and its decoy receptor, osteoprotegerin (OPG), on osteoclast biology and bone resorption. Furthermore, it highlights the impact of these compounds on the pathogenesis of malignant bone diseases, including tumor metastasis, humoral hypercalcemia of malignancy, and multiple myeloma. Finally, the authors discuss the therapeutic potential of OPG in the management of malignancies involving the skeleton.

METHODS

After its discovery and cloning, the biologic effects of RANKL, RANK, and OPG have been characterized by in vitro experiments and in vivo studies. The generation of knock-out mice and transgenic mice has produced animal models with absent or excessive production of these cytokine components that display opposite abnormal skeletal phenotypes (osteoporosis or osteopetrosis). The potential effect of RANKL and OPG has been assessed by evaluating these compounds in various animal models of metabolic and malignant bone disease and by administering OPG to humans.

RESULTS

Abnormal bone resorption due to local or systemic stimulation of osteoclast differentiation and activation is a hallmark of various benign and malignant bone diseases. RANKL, RANK, and OPG form an essential cytokine system that is capable of regulating all aspects of osteoclast functions, including proliferation, differentiation, fusion, activation, and apoptosis. The balance of bone resorption depends on the local RANKL-to-OPG ratio, which is enhanced in bone metastases and humoral hypercalcemia of malignancy. The exogenous administration of OPG to tumor-bearing animals corrects the increased RANKL-to-OPG ratio, and reverses the skeletal complications of malignancies.

CONCLUSIONS

Abnormalities of the RANKL/OPG system have been implicated in the pathogenesis of various primary and secondary bone malignancies. The systemic administration of OPG appears to be a potent novel therapeutic agent for treatment of these disorders.

Macrophage inflammatory protein-1alpha is an osteoclastogenic factor in myeloma that is independent of receptor activator of nuclear factor kappaB ligand

A complementary DNA expression library derived from marrow samples from myeloma patients was recently screened and human macrophage inflammatory protein-1alpha (hMIP-1alpha) was identified as an osteoclastogenic factor expressed in these samples. hMIP-1alpha enhanced osteoclast (OCL) formation in human marrow cultures and by highly purified OCL precursors in a dose-dependent manner (5-200 pg/mL). Furthermore, hMIP-1alpha enhanced OCL formation induced by human interleukin-6 (IL-6), which is produced by marrow stromal cells when they interact with myeloma cells. hMIP-1alpha also enhanced OCL formation induced by parathyroid hormone-related protein (PTHrP) and receptor activator of nuclear factor kappaB ligand (RANKL), factors also implicated in myeloma bone disease. Time-course studies revealed that the hMIP-1alpha acted during the last 2 weeks of the 3-week culture period. Reverse transcription-polymerase chain reaction analysis showed that the chemokine receptors for hMIP-1alpha (CCR1 and CCR5) were expressed by human bone marrow and highly purified early OCL precursors. Furthermore, hMIP-1alpha did not increase expression of RANKL. These data demonstrate that hMIP-1alpha is an osteoclastogenic factor that appears to act directly on human OCL progenitors and acts at the later stages of OCL differentiation. These data further suggest that in patients with myeloma, MIP-1alpha produced by myeloma cells, in combination with RANKL and IL-6 that are produced by marrow stromal cells in response to myeloma cells, enhances OCL formation through their combined effects on OCL precursors. (Blood. 2001;97:3349-3353)

Hypercalcemia after High-Dose Chemoradiotherapy for Refractory Multiple Myeloma; Subject Heading

A 43-year-old man with refractory myeloma underwent allogeneic bone marrow transplantation from his HLA-matched sibling. He was conditioned with TBI (12 Gy) followed by melphalan (140 mg/m(2) ). Immediately after conditioning was initiated, he began complaining of severe lumbago, and the level of serum calcium rose from 2.25 to 3.34 mmol / l. However, the biochemical markers for tumor-lysis syndrome such as potassium, uric acid, and lactic dehydrogenase remained unchanged. Hydration with saline and pamidronate were started, but he developed acute renal failure requiring hemodialysis for 3 weeks. His plasma parathyroid hormonerelated protein (PTHrP)-NH2-terminal (3.9 pmol/l) and serum PTHrP-C-terminal (125.0 pmol / l) levels markedly increased immediately after conditioning. These results suggested that the increased release of PTHrP from myeloma cells, which resulted from destruction of myeloma cells by conditioning, was the primary contributes to the occurrence of hypercalcemia. We should be aware of the occurrence of hypercalcemia when high-dose therapy is to be given to patients with refractory myeloma.

Expression and in vitro modification of parathyroid hormone-related protein (PTHrP) and PTH/PTHrP-receptor in human myeloma cells

To elucidate the role of PTHrP in myeloma, we examined the expression levels of PTHrP and its receptor in human myeloma cell lines and clinical specimens from 13 myeloma cases. In vitro modification of PTHrP expression and production induced by TGF-beta and PMA in PTHrP expressing myeloma cell lines was also investigated. PTHrP expression was detected in six out of seven myeloma cell lines with an inverse correlation with the expression of its receptor, and in 10 out of 13 clinical specimens in varying degrees. The PTHrP expression and secretion into culture medium were enhanced by supplemental TGF-beta and PMA. PMA also seemed to affect PTHrP upregulation via TGF-beta activation. The fundamental role of PTHrP in bone lesions and hypercalcemia in myeloma may be important to consider even during the initial phase of the disease and particularly in the progression of bone complications with hypercalcemia.

Assessment of cellular expression of parathyroid hormone-related protein mRNA and protein in multiple myeloma

The capacity of multiple myeloma cells to generate parathyroid hormone-related protein (PTHrP) has been examined by in situ assessment of PTHrP mRNA and PTHrP protein in myeloma cells of patients in whom the disease was associated with the development of hypercalcaemia. The presence of PTHrP mRNA was evaluated by in situ hybridization using an antisense riboprobe, and PTHrP by immunohistochemistry using a monoclonal antibody, in archival bone marrow trephine specimens from 17 patients. PTHrP mRNA was detected in myeloma cells in 16 of the 17 patients, indicating a high frequency of PTHrP gene expression in myeloma cells in these subjects. PTHrP protein was, on the other hand, detected in the myeloma cells of only five of these patients. The impact of the mercury-based fixation and decalcification procedure used for processing the bone marrow trephine specimens was assessed to determine the influence of this process on the outcome of the immunohistochemical assay for PTHrP. It was shown that this preparative procedure resulted in a marked reduction of immunohistochemically detectable PTHrP, which provides a possible explanation for the lower frequency of positivity for PTHrP in myeloma cells in the bone marrow specimens. The present findings are consistent with the view that PTHrP can be generated in myeloma cells in vivo, and could contribute to osteolysis and hypercalcaemia, as in patients with cancer.

Cell–cell contact between marrow stromal cells and myeloma cells via VCAM-1 and α4β1-integrin enhances production of osteoclast-stimulating activity

Myeloma is a unique hematologic malignancy that exclusively homes in the bone marrow and induces massive osteoclastic bone destruction presumably by producing cytokines that promote the differentiation of the hematopoietic progenitors to osteoclasts (osteoclastogenesis). It is recognized that neighboring bone marrow stromal cells influence the expression of the malignant phenotype in myeloma cells. This study examined the role of the interactions between myeloma cells and neighboring stromal cells in the production of osteoclastogenic factors to elucidate the mechanism underlying extensive osteoclastic bone destruction. A murine myeloma cell line 5TGM1, which causes severe osteolysis, expresses α4β1-integrin and tightly adheres to the mouse marrow stromal cell line ST2, which expresses the vascular cell adhesion molecule-1 (VCAM-1), a ligand for α4β1-integrin. Co-cultures of 5TGM1 with primary bone marrow cells generated tartrate-resistant acid phosphatase-positive multinucleated bone-resorbing osteoclasts. Co-cultures of 5TGM1 with ST2 showed increased production of bone-resorbing activity and neutralizing antibodies against VCAM-1 or α4β1-integrin inhibited this. The 5TGM1 cells contacting recombinant VCAM-1 produced increased osteoclastogenic and bone-resorbing activity. The activity was not blocked by the neutralizing antibody to known osteoclastogenic cytokines including interleukin (IL)-1, IL-6, tumor necrosis factor, or parathyroid hormone-related peptide. These data suggest that myeloma cells are responsible for producing osteoclastogenic activity and that establishment of direct contact with marrow stromal cells via α4β1-integrin/VCAM-1 increases the production of this activity by myeloma cells. They also suggest that the presence of stromal cells may provide a microenvironment that allows exclusive colonization of myeloma cells in the bone marrow.

Cell–cell contact between marrow stromal cells and myeloma cells via VCAM-1 and α4β1-integrin enhances production of osteoclast-stimulating activity

Myeloma is a unique hematologic malignancy that exclusively homes in the bone marrow and induces massive osteoclastic bone destruction presumably by producing cytokines that promote the differentiation of the hematopoietic progenitors to osteoclasts (osteoclastogenesis). It is recognized that neighboring bone marrow stromal cells influence the expression of the malignant phenotype in myeloma cells. This study examined the role of the interactions between myeloma cells and neighboring stromal cells in the production of osteoclastogenic factors to elucidate the mechanism underlying extensive osteoclastic bone destruction. A murine myeloma cell line 5TGM1, which causes severe osteolysis, expresses α4β1-integrin and tightly adheres to the mouse marrow stromal cell line ST2, which expresses the vascular cell adhesion molecule-1 (VCAM-1), a ligand for α4β1-integrin. Co-cultures of 5TGM1 with primary bone marrow cells generated tartrate-resistant acid phosphatase-positive multinucleated bone-resorbing osteoclasts. Co-cultures of 5TGM1 with ST2 showed increased production of bone-resorbing activity and neutralizing antibodies against VCAM-1 or α4β1-integrin inhibited this. The 5TGM1 cells contacting recombinant VCAM-1 produced increased osteoclastogenic and bone-resorbing activity. The activity was not blocked by the neutralizing antibody to known osteoclastogenic cytokines including interleukin (IL)-1, IL-6, tumor necrosis factor, or parathyroid hormone-related peptide. These data suggest that myeloma cells are responsible for producing osteoclastogenic activity and that establishment of direct contact with marrow stromal cells via α4β1-integrin/VCAM-1 increases the production of this activity by myeloma cells. They also suggest that the presence of stromal cells may provide a microenvironment that allows exclusive colonization of myeloma cells in the bone marrow.

Parathyroid hormone-related protein, parathyroid hormone, and vitamin D in hypercalcemia of malignancy

The pathogenesis of cancer-associated hypercalcemia is not yet completely understood. In the majority of cancer patients, hypercalcemia appears to be a consequence of the tumor production of parathyroid hormone (PTH)-related protein (PTHrP). However, patients with humoral hypercalcemia of malignancy, in contrast to those with primary hyperparathyroidism, have an uncoupled bone turnover, and they usually have low circulating levels of 1.25(OH)2D3. We performed a case-control study to assess the relationship of plasma PTHrP, PTH and 1.25(OH)2D3 with hypercalcemia in cancer patients with a variety of tumors. Sixty of these patients had hypercalcemia, and 45 were normocalcemic. We measured PTHrP and PTH by immunoradiometric assay (Nichols), and 1.25(OH)2D3 by radioreceptor assay (Nichols), in plasma in both groups of cancer patients. Using a logistic regression analysis, we found that the higher PTHrP in plasma, the higher association with hypercalcemia occurred in these patients. In addition, the decreased plasma levels of PTH and 1.25(OH)2D3 in the majority of cancer patients were found to be significantly associated with hypercalcemia. Our results indicate that the combined determination of PTH, PTHrP and 1.25(OH)2D3 in plasma represents a more comprehensive approach to the investigation of hypercalcemia in cancer patients. Our data also support the role of PTHrP as a humoral factor responsible for hypercalcemia in these patients.