The cellular basis of metastatic bone disease in patients with lung cancer

Reorganization of the osteocyte lacuno-canalicular network characteristics in tumor sites of an immunocompetent murine model of osteotropic cancers

Mechanosensitive osteocytes are central regulators of bone resorption and formation. However, during the formation of bone metastases, which arise as consequences of breast and prostate cancer and skew homeostatic bone remodeling to favor osteolytic, osteosclerotic or mixed lesions, only a paucity of data exists on tumor-associated osteocyte interaction. Herein, we used a suite of high-resolution imaging and histological techniques to evaluate the effect of osteotropic cancer on cortical bone microarchitecture. Confocal imaging highlighted a direct contact between tumor cells residing in the bone marrow and osteocytes. High-resolution microcomputed tomography revealed a 10-12% larger osteocyte lacuna volume in the presence of tumor cells at day 21 after intratibial injection of EO771-Luc breast and RM1-Luc prostate cancer cells. The 3D representative of the spatial distribution of cortical bone microporosity showed i) a regional accumulation of vascular canals and large lacunae with low connectivity in osteosclerotic regions of interest and ii) an absence of vascular canals and large lacunae in osteolytic regions. These findings pinpoint the relationship between the presence of tumor cells in the bone marrow microenvironment and osteocyte lacunar characteristics and cortical bone blood vessel structure.

Osteocytes remove and replace perilacunar mineral during reproductive cycles

Lactation is associated with an increased demand for calcium and is accompanied by a remarkable cycle of bone loss and recovery that helps to supply calcium and phosphorus for milk production. Bone loss is the result of increased bone resorption that is due, in part, to increased levels of PTHrP and decreased levels of estrogen. However, the regulation of bone turnover during this time is not fully understood. In the 1960s and 1970s many observations were made to suggest that osteocytes could resorb bone and increase the size of their lacunae. This concept became known as osteocytic osteolysis and studies suggested that it occurred in response to parathyroid hormone and/or an increased systemic demand for calcium. However, this concept fell out of favor in the late 1970s when it was established that osteoclasts were the principal bone-resorbing cells. Given that lactation is associated with increased PTHrP levels and negative calcium balance, we recently examined whether osteocytes contribute to bone loss during this time. Our findings suggest that osteocytes can remodel their perilacunar and pericanalicular matrix and that they participate in the liberation of skeletal calcium stores during reproductive cycles. These findings raise new questions about the role of osteocytes in coordinating bone and mineral metabolism during lactation as well as the recovery of bone mass after weaning. It is also interesting to consider whether osteocyte lacunar and canalicular remodeling contribute more broadly to the maintenance of skeletal and mineral homeostasis.

Osteocytic osteolysis: time for a second look?

Over 100 years ago it was suggested that osteocytes could remodel their surrounding environment by removing and replacing bone. In the 1960s and 1970s, many observations were made to suggest that osteocytes could resorb bone and increase the size of their lacunae. This concept became known as osteocytic osteolysis and studies suggested that it occurred in response to diverse stimuli such as parathyroid hormone, calcium restriction, hibernation and reproductive cycles. However, this concept fell out of favor in the late 1970s when it became clear that osteoclasts were the principal bone-resorbing cells in the skeleton. Over the past decade, we have increasingly appreciated that osteocytes are remarkably versatile cells and are involved in all aspects of skeletal biology, including the response to loading, the regulation of bone turnover and the control of mineral metabolism. Recent data have demonstrated that osteocytes remodel their perilacunar and canalicular matrix and participate in the liberation of skeletal calcium stores during lactation. In light of these new findings, it may be time to reassess the concept of osteocytic osteolysis and reconsider whether osteocyte lacunar and canalicular remodeling contributes more broadly to the maintenance of skeletal and mineral homeostasis.

Hypercalcemia in patients of oral squamous cell carcinoma

PURPOSE

This study was performed to measure the total and ionic serum calcium levels and incidence of hypercalcemia in patients with Oral Squamous Cell Carcinoma (OSCC) and its clinical significance and relevance.

MATERIALS AND METHODS

A randomly selected sample of seventy patients of histologically confirmed Oral Squamous Cell Carcinoma (OSCC) at any of the standard clinical stages were included. Fasting blood samples were obtained for measuring serum calcium levels. The elevated values of serum calcium levels were correlated with clinical features of hypercalcemia to draw inference.

RESULTS

Total serum calcium was found to be elevated in 12 patients (17.4%) and serum ionic calcium was elevated in 3 patients (4.29%).

CONCLUSION

The data suggests that hypercalcemia occurred in advanced stages of oral squamous cell carcinoma and its management may be relevant in providing terminal care and prolonging the life span of the patients.

Do osteocytes contribute to bone mineral homeostasis? Osteocytic osteolysis revisited

Osteocytes are cells buried in the bone matrix. They largely contribute to the regulation of bone remodeling in response to mechanical and microenvironmental changes. Much has been recognized in recent years regarding the role of osteocytes in bone homeostasis, nevertheless their ability to directly contribute to mineral equilibrium has been neglected. In the light of the renewed interest in their biology, we revisited the literature and discuss experimental evidence favoring the hypothesis that osteocytes are able to remove and replace the bone matrix according to the systemic needs of the body. We also reviewed reports against this theory, thus providing current views of what is known so far on the ability of osteocytes to mobilize bone mineral. This re-examination of osteocytic osteolysis might stimulate new interest and open new perspectives in osteocyte biology and in the cellular mechanisms that control bone homeostasis.

Pathology of skeletal metastases

Metastatic disease involving the skeleton is an unfortunate and common occurrence in cancer patients. Choosing the best diagnostic approach requires knowledge of the patient's clinical history, the radiologic appearance of the lesion, the differential diagnosis, and the ability of the diagnostic modality to answer the questions that must be addressed. In difficult cases, interaction between the pathologist and clinician before biopsy may make the difference between a rapid procedure serving to definitively diagnose and effectively stage a patient and a costly procedure that provides little or no information.

Autoradiographic evaluation of 99mTc-methylene diphosphonate accumulation in oral cancer invading the mandible

PURPOSE

Skeletal scintigraphy, a sensitive diagnostic tool used to detect changes in bone, is helpful for evaluating bone invasion by oral cancer. However, the exact sites of accumulation of 99mTc-phosphate compounds in the mandible have not yet been fully elucidated. The aim of this study was to determine the localization of 99mTc-methylene diphosphonate (MDP) in the areas of mandible that have been invaded by cancer.

PATIENTS AND METHODS

Seven patients with oral cancer (lower gingiva, 4; tongue, 2; floor of the mouth, 1) who underwent surgical treatment with mandibular bone resection were included in the study. Autoradiography and contact macroradiography were used for evaluation of 99mTc-MDP accumulation.

RESULTS

Radioactivity reflecting accumulation of 99mTc-MDP was documented encircling the portion of the mandible with cancerous invasion, suggesting that 99mTc-MDP accumulated in immature bone. High uptake also was found in the periosteal reactive bone around the cortical bone.

CONCLUSIONS

The amount of increased 99mTc-MDP circumscribing carcinoma invasion varies among cases. Additionally, uptake may not correspond directly with the amount of the carcinoma invasion; that seen in periosteal bone could be attributed mistakenly to bone invasion in planar scintigraphy.

Hypercalcemia in breast cancer

Hypercalcemia is relatively frequent in malignancy with or without osteolytic bone metastases. It is thought that neoplastic cells may secrete substances which not only stimulate osteoclastic activity but are also capable of modifying the absorption, excretion, and resorption of calcium and phosphate ions. Since 1987, we have studied 24 breast cancer patients with hypercalcemia (22 with bone metastases and two without). The group of 22 patients with bone metastases were divided into two subgroups. The first consisted of 10 patients with high serum levels of humoral factors, such as parathyroid hormone-related protein (PTHrP), and/or prostaglandin E2 (PGE2) and/or interleukin 1 (IL-1), and high levels of bone markers, such as alkaline phosphatase, bone Gla protein and urinary hydroxyproline. The second subgroup consisted of 12 patients with high levels of bone markers alone. Bone histologic analysis showed an osteoclastic activation surrounding metastatic tumor tissue in six out of 10 patients of the first subgroup, while an evident osteolysis caused by the tumor cells was noted in seven out of 12 patients of the second subgroup. The two patients without bone metastases showed normal biochemistry and bone histologic examination. The authors, having tried to explain the pathogenesis of hypercalcemia, emphasize the importance of humoral factors secreted by tumor cells as a direct or indirect cause of hypercalcemia. The origin of hypercalcemia remains unclear in two patients without bone metastases.

Radiological detection of bone and bone marrow metastases

Bone scintigraphy is the primary method for the diagnosis of skeletal metastases. This investigation is sensitive, but the interpretation must be performed in the knowledge that it is also nonspecific. Despite this, a correct diagnosis can usually be achieved. The first-hand supplementary investigation, after a doubtful scintigraphic finding, is radiography. In most cases this is sufficient for a diagnosis. When a scintigraphic abnormality cannot be adequately explained, usually because of a negative radiographic examination, a more sensitive modality must be used. Computerized tomography offers increased sensitivity and specificity, and is primarily used for this purpose. In this way contrast resolution is increased and problems caused by obscuring tissue and complicated anatomy are reduced. Since bone metastases migrate via the active bone marrow an alternative supplementary investigation is bone marrow scintigraphy. Its usefulness is restricted by disturbing activity, from the liver and the spleen, which obscures a significant part of the active marrow, and by the fact that a lesion must be of a certain size to become apparent. Magnetic resonance imaging yields excellent images of the extension of a tumor in soft tissue. Owing to high costs and restricted availability it is still mainly used for preoperative location of metastases.

Tumors metastatic to the mandible: analysis of nine cases and review of the literature

Metastases to the mandible are rare. In this article, nine cases of tumors metastatic to the mandible of various origins and locations, including metastasis to the condyle, are reported. The most common primary tumor was breast adenocarcinoma (three cases). The clinical features, diagnosis, and treatment of metastatic lesions, especially emphasizing clinical and radiologic aspects, are described, and a review of the literature is presented.

Tumor-bone interaction induced by transplantable human tumors in nude mice

Tumor-bone interactions were experimentally studied using four transplantable human urogenital tumors in nude mice. The method consisted of subcutaneously (SC) inoculating tumor cells over the calvaria in nude mice after the periosteum has been disrupted. This resulted in a local tumor causing fragmentation of the bone. The degree of tumor-bone interaction also varied with the type of implanted tumors as shown in radiographic and histologic examinations. All tumors were associated with histologic patterns of classical bone remodeling, including bone destruction with osteoclast proliferation and reactive new bone formation. The evidence presented here suggests that the majority of tumor-bone interaction showed a combination of both features, bone destruction and new bone formation, and the mechanisms whereby tumors interact with bone may vary with the biological properties of the tumor. Our new system would be suitable for studying the biology of local interaction between bone and tumor cells and searching out a method to protect the bone from cancer cells.

Bone metastases: pathogenesis, treatment, and rationale for use of resorption inhibitors

Tumors in bone are usually metastatic, with breast, prostate, and lung tumors accounting for more than 80 percent of clinically manifest lesions. Untreated, such metastases can produce the symptoms that most concern cancer patients--pain, pathologic fractures, and paralysis through epidural cord compression. Recent advances in the understanding of the metastatic cascade and the regulation of bone formation and resorption provide unique therapeutic approaches for prevention and treatment of these lesions. This article reviews the prevalence, distribution, diagnosis, and treatment of metastatic cancer in the skeleton, as well as the processes involved in the development of such metastases, the local mediators responsible for some of the destructive changes in bone, and their pathologic results. In addition to considering some of the conventional therapeutic approaches, a rationale for the use of bone resorption inhibitors, such as the diphosphonates (bisphosphonates), is presented for the prevention and amelioration of the pathologic consequences of skeletal metastases.

Histomorphometric analysis of osteoclastic bone resorption in metastatic bone disease from various primary malignomas

The present study deals with qualitative und quantitative analysis of osteoclastic bone resorption in metastatic bone disease. 267 cases were examined histomorphologically and divided into three developmental stages. In the first 'phase of early appearance' no bone resorption takes place. The stimulation of osteoclastic resorption in the surroundings of tumour tissue is typical in the second 'phase of interaction'. Pressure atrophy, aseptic necrosis and osteolysis by the tumour cells themselves are other mechanisms of bone destruction in the last 'phase of carcinomatosis'. Because osteoclasts are exclusively responsible for the loss of bone tissue in the 'phase of interaction', this stage is suited for precise quantitative analysis of osteoclastic resorption. 24 pure osteolytic secondary bone tumours of various primary lesions were examined histomorphometrically. The numerical values were compared with each other and with standard values of healthy individuals. In contrast with normal bone tissue the fractional resorption surfaces und osteoclast indices increase in metastases. Activated osteoclasts are larger and have more nuclei. The numbers of osteoclast index and nuclei per osteoclast are significantly higher in renal than in breast carcinoma. Osteoclasts can be activated in distances of more than 500 micron from tumour tissue. The mean stimulation distance in metastasis from squamous cell carcinoma is markedly higher than in secondary bone tumours of breast carcinoma. Several osteoclast activating substances and divers mechanisms of stimulation might be responsible for different numerical values of morphometric parameters in metastases from various primary malignancies.

The growth characteristics of multilocular ameloblastomas. A histological investigation with some inferences with regard to operative procedures

The growth characteristics of multilocular ameloblastomas and the reaction of the surrounding tissues were studied by means of a histological examination of 31 surgical specimens. Infiltration of spongy bone was observed frequently whereas there was little tendency to invade cortical bone. The periosteum largely prevented extension of the tumour. However, in the region of the mucosa overlying the alveolar process apparent encapsulation was absent. There were indications that the infiltrative growth pattern exhibited by an ameloblastoma within spongy bone was due to secondary enclosure of tumour tissue by remodelled bone.

Patterns and mechanisms of localized bone invasion by tumors: studies with squamous carcinomas of the head and neck

Squamous carcinomas of the head and neck provide a useful model for analyzing patterns and mechanisms of tumor-associated bone destruction. Morphological studies show that a major part of the invasive process is mediated by local osteoclasts which erode bone in front of the advancing tumor. Functional studies indicate that both fresh tumors and tumor cell lines resorb calvarial bone in an in vitro test system, again by stimulating local osteoclasts. Prostaglandins of the E2 type are regularly released by the tumors, together with indomethacin-resistant, nonprostaglandin osteolysins. Control (nonneoplastic) tissues will resorb bone and release osteolytic factors, usually at lower levels of activity--such properties are thus tumor-associated rather than tumor-specific. Xenografts of squamous carcinomas resorb bone in vitro and synthesize osteolysins. They do not invade local bone in their hosts but some grafts regularly produce a systemic hypercalcemia. General implications are discussed, particularly for other human tumors which more frequently metastasize to bone. Possible pointers to the (partial) control of the destructive process are noted.