Transforming growth factor alpha and CD68 immunoreactivity in giant cell tumours of bone: a study on the nature of stromal and giant cells, and their interrelations

miR-181c associates with tumor relapse of high grade osteosarcoma

High-grade osteosarcoma (OS) is characterized by low incidence, high aggressiveness and moderate 5-years survival rate after aggressive poly-chemotherapy and surgery. Here we used miRNA profiling as a tool to possibly predict and monitor OS's development and therapeutic outcome. First, we evaluated the altered expression of selected miRNAs from a case of Giant Cell Tumor (GCT) apparently evolved into an OS. We found that most of modulated miRs were associated with pathways of bone resorption and osteogenesis. miRNA expression also revealed that GCT and OS were distinct tumors. Second, we validated the observed miRNA profile in two independent casuistries of ten GCT (not evolved into malignant tumors) and sixteen OS patients. Interestingly, we found that miR-181c and other three miRNAs identified in the first step of the study were also consistently de-regulated in all OS patients. Ectopic expression of miR-181c reduced cell viability and enhanced chemotherapeutic-induced cell death of U2OS and SAOS2 cells. These findings indicate that: i) miRNAs aberrantly modulated in GCT could be predictive of its development into OS and ii) miRNAs expression could be useful to monitor the OS therapeutic outcome.

Histopathological, immunohistochemical, and image analytic parameters characterizing the stromal component in primary and recurrent giant cell tumor of bone

Giant cell tumor (GCT) of bone is a benign locally aggressive tumor whose biological behavior is unpredictable. Currently, there are no definitive clinical, histological, biochemical, or immunological parameters that can predict its behavior. This study was undertaken to examine whether delineation of reactive and neoplastic stromal component of GCT can help in this regard. 55 cases of GCT (30 primary, 25 recurrent) were subjected to histopathological grading, immunohistochemistry, and image analysis. Spindling of stroma was more frequent in recurrent GCT with 64% cases having more than 50% spindled stroma (p < 0.001). Number of mitosis/10 HPF and higher grade were more in recurrent GCT. Mean percentage positivity for CD68 (38.36%) and α1-ACT (70.86%) was higher in primary than recurrent GCT. PCNA and MiB-1 labeling indices were higher in recurrent (42.62% and 9.18%, respectively) than in primary group (24.75% and 7.7%, respectively). A single numerical parameter encompassing stromal cell population and its proliferation was derived as ratio of PCNA/CD68 and PCNA/α1-ACT. Both ratios were higher in recurrent (0.81 ± 0.38; 1.58 ± 1.50) than in primary GCT (0.58 ± 0.62; 0.34 ± 0.29) (p = 0.002; 0.01). On image analysis, parameters significantly different between the two groups were nuclear area and nuclear integrated optical density. It was thus concluded that recurrent GCT shows higher grade, increased mitosis, more spindling, fewer reactive components, and higher proliferation than primary GCT. Delineation of reactive component (α1-ACT positive) and proliferating component (PCNA positive cells) using immunohistochemistry with calculation of the PCNA/ACT ratio delivers more information than image analysis.

Targeting the giant cell tumor stromal cell: functional characterization and a novel therapeutic strategy

Giant cell tumor of bone (GCTB) is a benign, locally destructive neoplasm, with tumors comprised of mesenchymal fibroblast-like stromal cells; monocytic, mononuclear cells of myeloid lineage; and the characteristic osteoclast-like, multinucleated giant cells. Hampering the study of the complex interaction of its constituent cell types is the propensity of longstanding, repeatedly passaged cell cultures to undergo phenotypic alteration and loss of osteoclast-inducing capacities. In this study, we employed a novel, single-step technique to purify freshly harvested stromal cells using a CD14-negative selection column. Using 9 freshly harvested GCTB specimens and the purified stromal cell component, we performed analyses for markers of osteoblast lineage and analyzed the capacity of the stromal cells to undergo osteoblastic differentiation and induce osteoclastogenesis in co-cultures with monocytic cells. Successful purification of the CD14-negative stromal cells was confirmed via flow cytometric analysis and immunocytochemistry. Osteogenic media upregulated the expression of osteocalcin, suggesting an osteoblastic lineage of the GCTB stromal cells. The effects of the Wnt pathway agonist, SB415286, and recombinant human bone morphogenetic protein (BMP)-2 on osteoblastogenesis varied among samples. Notably, osteogenic media and SB415286 reversed the receptor activator of NF-κB ligand (RANKL)/osteoprotegerin (OPG) expression ratio resulting in diminished osteoclastogenic capacity. Recombinant human BMP2 had the opposite effect, resulting in enhanced and sustained support of osteoclastogenesis. Targeting the giant cell tumor stromal cell may be an effective adjunct to existing anti-resorptive strategies.

Myofibroblastic differentiation of stromal cells in giant cell tumor of bone: an immunohistochemical and ultrastructural study

The nature of the mononuclear stromal cells (MSCs) in giant cell tumor of bone (GCTB) has not been thoroughly investigated. The purpose of this study was to evaluate the degree and significance of myofibroblastic differentiation in 18 cases of GCTB by immunohistochemistry (IH) and/or electron microscopy (EM). All immunostained cases were found positive for smooth muscle actin (SMA) and/or muscle specific actin (MSA), most in 1-33% of the MSCs. Ultrastructurally, most MSCs were fibroblasts, and a significant number of cells displayed myofibroblastic differentiation. Myofibroblasts are an important component of MSCs in GCTB. The myofibroblastic population may be responsible in part for the production of matrix metalloproteinases (MMPs), which probably play a role in bone destruction, tumor aggression, and recurrence.

Giant cell tumor of bone: a basic science perspective

Comprehending the pathogenesis of giant cell tumor of bone (GCT) is of critical importance for developing novel targeted treatments for this locally-aggressive primary bone tumor. GCT is characterized by the presence of large multinucleated osteoclast-like giant cells distributed amongst mononuclear spindle-like stromal cells and other monocytes. The giant cells are principally responsible for the extensive bone resorption by the tumor. However, the spindle-like stromal cells chiefly direct the pathology of the tumor by recruiting monocytes and promoting their fusion into giant cells. The stromal cells also enhance the resorptive ability of the giant cells. This review encompasses many of the attributes of GCT, including the process of giant cell formation and the mechanisms of bone resorption. The significance of the receptor activator of nuclear factor-κB ligand (RANKL) in the development of GCT and the importance of proteases, including numerous matrix metalloproteinases, are highlighted. The mesenchymal lineage of the stromal cells and the origin of the hematopoietic monocytes are also discussed. Several aspects of GCT that require further understanding, including the etiology of the tumor, the mechanisms of metastases, and the development of an appropriate animal model, are also considered. By exploring the current status of GCT research, this review accentuates the significant progress made in understanding the biology of the tumor, and discusses important areas for future investigation.

Expression of CD68 in non-myeloid cell types

CD68, the human homologue of macrosialin, is commonly regarded as a selective marker for human monocytes and macrophages. Its expression is thought to be regulated by a macrophage-specific promoter. However, several immunohistochemical studies have indicated that CD68 antibodies also react with other haematopoietic and non-haematopoietic cell types. We investigated the expression of CD68 in various primary cells and carcinoma cell lines using immunohistochemistry, flow cytometry, Western blot analysis and qRT-PCR. Weak but significant immunoreactivity was detected in lymphocytes and several tumour cell lines whereas staining of primary fibroblasts and endothelial cells was comparable to macrophages. The intensity of CD68 staining in individual cell types depended on the antibody clone and the fixation technique. Anti-CD68 mAb KP1 should be used with great caution for frozen tissue sections due to its reactivity with a wide variety of cell types. Also, care should be taken when distinguishing macrophages from fibroblasts/stromal cells in paraffin sections after formalin fixation since both cell types are stained highly positive for CD68. In accordance, mRNA expression of CD68 was not only detected in macrophages and monocytes but also in fibroblasts as well as endothelial cells and tumour cells, although with a varying intensity. Cloning of full length 5'-sequences and determination of transcription start sites shows that macrophages and fibroblasts initiate transcription within the known promoter region; however, from different start sites, indicating alternative promoter architecture in myeloid versus non-myeloid cells. We suggest that CD68 is not a selective macrophage marker but rather a lysosomal protein that is enriched in macrophages.

Cholesterol granuloma of maxillary sinus

The cholesterol granuloma is a particular form of granulation tissue developing as part of a variety of tissue reactions. It is usually associated with chronic middle ear disease and is common in the mastoid antrum of temporal bone. Cholesterol granuloma is rare in maxillary antrum. A case is reported of cholesterol granuloma in the maxillary sinus of a 42-year-old man, with the unique feature that the soft tissue lesion is enclosed by thick bone, entirely within the sinus.

Osteoclast-rich undifferentiated carcinomas of the urinary tract

Osteoclast-like giant-cell neoplasms of the urinary tract are rare. They are composed of ovoid or spindle-shaped mononuclear cells with evenly spaced osteoclast-like giant cells. Terminology, histogenesis, and biologic behavior of these tumors remain controversial. Six cases of osteoclast-like giant-cell neoplasms of the urinary tract were identified from the consultation files of two of the authors. Patients were all male and elderly (range 65-82), with the exception of one 39-year-old male. In all, 3/6 tumors developed in the bladder and 3/6 in the renal pelvis. Size ranged from 5 to 11 cm. One bladder and three renal pelvis tumors were high stage (pT3) at time of presentation. Adjacent to the osteoclast-like giant-cell neoplasm in the same specimen, all patients had urothelial carcinoma in situ and/or high-grade papillary urothelial carcinoma. Multinucleated cells had identical morphological and immunohistochemical properties of osteoclasts; positive for CD-68, LCA, CD51 and CD54, and negative for cytokeratins and EMA. Varying percentages of mononuclear cells expressed alpha-smooth muscle actin (4/6), desmin (1/6), S-100 (4/6), LCA (2/6) and CD68 (6/6). However, mononuclear cells were also positive for epithelial markers in 4/6 tumors (cytokeratins AE-1/AE-3, Cam 5.2, CK7 and/or EMA). p53 stained mononuclear tumor cells in three cases, paralleling the staining on the accompanying urothelial carcinoma. Ki-67 stained mononuclear tumor cells, but not osteoclast-like giant cells. Follow-up data were available in five cases. One patient developed recurrence of noninvasive urothelial carcinoma and is still alive. Four patients were dead due to disease within 15 months, three with distant metastases. The intimate association of these tumors with urothelial carcinoma along with their immunohistochemical profile supports an epithelial origin for the mononuclear cells and non-neoplastic reactive histiocytic lineage for the osteoclast-like giant cells.

Recruitment of osteoclast precursors by stromal cell derived factor-1 (SDF-1) in giant cell tumor of bone

Giant cell tumor (GCT) of bone is a unique bone lesion that is characterized by an excessive number of multinucleated osteoclasts. GCT consists of neoplastic stromal cells, multinucleated osteoclasts and their precursors, thus serving as a naturally occurring human disease model for the study of osteoclastogenesis. It still remains unclear how stromal cells of GCT recruit osteoclast precursors. In the present study, we characterized the cellular components of GCT and confirmed the presence of CD14(+)-monocytes/CD68(+)-macrophages and CD34(+)-hematopoetic stem cells that express CXCR4, a specific receptor for SDF-1; SDF-1 gene expression and presence of SDF-1 protein were confirmed by real time RT-PCR, in situ hybridization, and immunohistochemistry in the GCT tissue and cultured cells. SDF-1 was present at 25-50 ng/ml in the conditioned media from the GCT cultures, which is in the range of physiological chemotactic concentration. Migration of osteoclast precursors was 2.5-fold higher in response to GCT conditioned media compared to the control media; and migration was inhibited by an average of 36% with anti-SDF-1 neutralizing antibody or competing recombinant SDF-1. These results suggest that SDF-1 is one of the significant chemoattractant factors involved in the recruitment of hematopoietic osteoclast precursor cells during tumor-induced osteoclastogenesis.

A missense mutation in the SH3BP2 gene on chromosome 4p16.3 found in a case of nonfamilial cherubism

OBJECTIVE

Cherubism is a rare hereditary multilocular cystic disease of the jaws, characterized by its typical appearance. Although nonfamilial cases have been reported, it is difficult to distinguish nonfamilial cherubism from central giant cell granuloma. Recent studies have revealed the point mutations in the SH3BP2 gene on chromosome 4p16.3 in cherubism families. In this article, the SH3BP2 gene in nonfamilial cherubism was examined.

PATIENT

A 21-year-old Japanese woman with nonfamilial cherubism.

INTERVENTIONS

Genomic DNA was purified from a blood sample obtained from the patient and used for direct sequencing. In addition, a sample of the lesion, resected during surgery, was used for histologic and immunohistochemical purposes.

RESULTS

Genomic DNA sequencing found a Pro418Arg mutation in the SH3BP2 gene of the patient. In a histochemical analysis, the multinucleated giant cells proved to be strongly positive for PGM-1, KP-1, and tartrate-resistant acid phosphatase and faintly positive for osteopontin.

CONCLUSIONS

The missense mutation Pro418Arg was identified in the SH3BP2 gene from a nonfamilial case of cherubism. DNA diagnosis may play a significant role in the identification of cherubism.

Giant cell reparative granuloma of the temporal bone: neuroradiological and immunohistochemical findings

A 38-year-old man presented with a giant cell reparative granuloma (GCRG) of the left temporal bone. Computed tomography showed a osteolytic middle cranial mass lesion. Magnetic resonance (MR) imaging showed the lesion as low intensity with heterogeneous enhancement by gadolinium on the T1-weighted images, and extremely low intensity on the T2-weighted images. Angiography showed the lesion as highly vascular and fed by branches of the left external carotid artery. After preoperative embolization, gross total removal of the tumor was performed. The postoperative course was uneventful and no evidence of recurrence has been found for more than 4 years. Histological examination revealed GCRG with multinucleated giant cells in the fibrous background, abundant collagen bundles, hemosiderin deposits, and trabeculae of reactive bone. Some of the mononuclear stromal cells and almost all of the giant cells were positive for CD68, suggesting histiocytic differentiation. These histological features reflect the marked decrease in signal intensity on T2-weighted MR images.

Differential expression of transforming growth factor-alpha and macrophage colony-stimulating factor/colony-stimulating factor-1R (c-fins) by multinucleated giant cells involved in pathological bone resorption at the site of orthopaedic implants

The immunologic response to prosthetic biomaterial particles is characterized by macrophage-rich inflammatory infiltrate, formation of multinucleated giant cells, and aseptic loosening at the site of arthroplasty. We investigated the in vivo expression and tissue distribution of transforming growth factor alpha, macrophage colony-stimulating factor, and the receptor for colony-stimulating factor-1 at the site of bone erosion in patients with clinically failed orthopaedic implants (n = 30). The expression was further compared with that detected in the inflamed synovial membranes from patients with rheumatoid arthritis or osteoarthritis (n = 15) and one patient with osteoclastoma (giant cell tumour of bone). Immunostaining of the tissue demonstrated positivity for transforming growth factor alpha within the inflammatory macrophage and multinucleated giant cell infiltrate in the diseased synovial membrane and the bone-implant interface. A comparative analysis between the synovium and retrieval interface membranes (pseudosynovium) revealed a high level of expression of transforming growth factor alpha, with intense membrane staining on multinucleated giant cells in all failed arthroplasties with pseudosynovium. In addition, the frequency, antigenic phenotype, and pattern of transforming growth factor alpha expression on multinucleated giant cells in the interface were markedly similar to those observed for multinucleated giant cells in osteoclastoma. Multinucleated giant cells within the interface lacked the expression of macrophage colony-stimulating factor and colony-stimulating factor-1 receptor, whereas those at the bone surfaces exhibited strong immunoreactivity. The predominant expression of transforming growth factor alpha by multinucleated giant cells in the bone-implant interface and its similarity to osteoclastoma highlight the importance of assessing transforming growth factor alpha as a possible contributor to the development of bone-resorbing giant cells at the site of failed orthopaedic implants.

h-Caldesmon as a specific marker for smooth muscle tumors. Comparison with other smooth muscle markers in bone tumors

Caldesmon is a protein widely distributed in smooth and non-smooth muscle cells and is thought to regulate cellular contraction. Its isoform, high-molecular-weight caldesmon (h-CD), was demonstrated to be specific for smooth muscle cells and smooth muscle tumors of the soft tissue and to never be expressed in myofibroblasts. We performed an immunohistochemical study to examine h-CD expression in the following bone tumors: conventional and non-conventional osteosarcoma, 13; malignant fibrous histiocytoma of bone, 5; giant cell tumors of bone, 5; chondroblastoma, 3; metastatic leiomyosarcoma, 2; and rhabdomyosarcoma, 1. Frequent immunoreactivity for muscle actin (alpha-smooth muscle actin or muscle-specific actin) was seen in 11 of 13 osteosarcomas and all other tumors, whereas h-CD was expressed intensely only in 2 leiomyosarcomas. h-CD is considered a specific and useful marker to distinguish smooth muscle tumor from bone tumors with myoid differentiation.

Primary lung tumors infiltrated by osteoclast-like giant cells

Six primary lung tumors with numerous multinucleated osteoclast-like giant cells (OLGCs) and no osteogenic component were evaluated histologically and immunohistochemically to examine pulmonary lesions inciting an OLGC response. The patients comprised four women and two men ranging in age from 61 to 80 years (average age, 69 years). The tumors consisted of one adenocarcinoma, two sarcomatoid carcinomas, and three giant cell variants of malignant fibrous histiocytoma. One tumor was endobronchial in location, while five were situated peripherally. Tumor diameter spanned from 1 to 6.5 cm (average, 2.7 cm). In addition to the giant cells, common characteristics included the malignant nature of the neoplasms and, in five of six cases, histologically malignant mesenchyme. This array of cases exemplifies the variability of lung lesions which may elicit an OLGC inflammatory response resulting in areas resembling the giant cell variant of malignant fibrous histiocytoma. The results of this study suggest that OLGCs occur preferentially in malignant rather than benign nonosteogenic lung tumors and that sarcomatoid regions of malignant tumors are more likely to be infiltrated by OLGCs than epithelial regions.

Expression of regulatory apoptotic proteins in peripheral giant cell granulomas and lesions containing osteoclast-like giant cells

Peripheral giant cell granuloma consists of mononuclear cells and osteoclast-like giant cells. The proliferative ability of peripheral giant cell granuloma is restricted to the mononuclear cell compartment, whereas multinucleated giant cells lack mitotic activity. Although the proliferative compartment of peripheral giant cell granuloma has been investigated in detail, the expression and distribution of proteins regulating apoptosis is unknown. The present study demonstrates strong expression of bak and bax in the majority of giant cells. In contrast, giant cells show only weak positivity for bcl-2 and moderate positivity for bcl-x. Mononuclear cells were negative to weakly positive for bcl-x. Only scattered mononuclear cells were positive for bak, bax and bcl-2. The frequency of apoptotic nuclei detected by TUNEL-staining compared to regular nuclei was 18 times higher in giant cells than in mononuclear cells. In summary, our findings support the presumption that giant cells of bone and soft tissue tumors are reactive cell forms and not of neoplastic origin.

Giant cell tumor of bone: frequent actin immunoreactivity in stromal tumor cells

Although giant cell tumor (GCT) of bone is a well-recognized neoplasm with distinctive clinical and histopathological features, the origin of tumor cells, particularly of mononuclear cells, has not yet been established. An immunohistochemical study was carried out on 11 cases of GCT of bone to examine the cellular natures of stromal mononuclear cells. In all cases, stromal cells were positive for muscle actin (HHF35) or alpha-smooth muscle actin, and in eight of 11 cases, positivity was intense and extensive. The cell margin of osteoclast-like giant cells (OGC) was stained positively by muscle actin, in addition to intense and diffuse positive staining of the cytoplasm for KP1 (CD68), whereas alpha-smooth muscle actin exhibited a negative reaction on the OGC. In conclusion, the tumor cells with muscle actin and alpha-smooth muscle actin positivities are not rare but frequently numerous in the GCT of bone; whereas further observation is necessary to elucidate whether the stromal cells exhibit myofibroblastic cell differentiation exactly.

Central giant cell granulomas of the jaws: phenotype and proliferation-associated markers

Central giant cell granulomas (CGCGs) are jaw tumors of unknown origin that often exhibit an aggressive, though unpredictable, clinical course. The purpose of this study was to determine the immunoprofile of the mononuclear cells that seem to be responsible for the biologic behavior of these tumors. Numbers of cells in cell cycle were also determined and compared in clinically aggressive and non-aggressive CGCGs. Sixteen aggressive and 12 non-aggressive CGCGs were immunohistochemically stained with antibodies to CD34, CD68, factor XIIIa, alpha-smooth muscle actin, prolyl 4-hydroxylase, Ki-67, and p53 protein. Cell populations and numbers of cells in cell cycle were determined through microscopic quantitative assessment. CD34-positive cells were limited to support vessels. CD68-positive mononuclear cells constituted a small population of cells in all tumors. With two exceptions, factor XIIIa-positive cells were rarely seen. Alpha-smooth muscle actin staining was present in approximately half the tumors, and occasionally large numbers of positive cells were seen. Most mononuclear cells were positive for fibroblast-associated antigen. No phenotypic differences were detected between aggressive and non-aggressive tumors. P53 protein did not appear to be overexpressed in CGCGs. Ki-67 staining showed that only mononuclear cells were in cell cycle, and that there were no differences between aggressive and non-aggressive tumors. We conclude that CGCGs are primarily fibroblastic (and myofibroblastic) tumors in which macrophages appear to play a secondary role. Tumor cells show no differentiation toward endothelial cells or macrophage-related dendrocytes (factor XIIIa). Cellular phenotypes and numbers of cells in cell cycle are similar in both aggressive and non-aggressive tumors.

Giant cell tumor in the skull of a 9-year-old child: immunohistochemistry to confirm a diagnosis rare for age and site

Giant cell tumor of the bone is usually located within the epiphysis of a long bone, the majority of the lesions occurring in the third and fourth decades of life. We report an unusual case of giant cell tumor (GCT) arising in the parietal skull bone of a 9-year-old girl. The tumor exhibited histologic findings typical for GCT, with conspicuous intravascular giant cells. Based on microscopic features, not only conditions like aneurysmal bone cyst or bone changes associated with hyperparathyroidism but also tumors such as chondroblastoma or osteosarcoma had to be considered. Immunohistochemistry revealed strong reactivity of the tumor giant cells and normal bone osteoclasts with CD68 but not Mac-387; tumor stromal cells were uniformly negative for both. The stromal cells exhibited two immunohistochemically distinct phenotypes. One, involving 50-80% of the tumor cells, exhibited negative lysozyme staining with positivity of proliferating cell nuclear antigen (PCNA) in about 30% of the nuclei. The other showed reactivity with lysozyme but negative PCNA staining. Immunohistochemistry thus helped to distinguish chondroblastoma and osteosarcoma, in which lysozyme positivity would reside in macrophages but not within stromal cells. Instead, chondroblastoma would exhibit protein S-100 positivity in the tumor cells. The biological behavior of GCT is difficult to predict based on morphology alone, although the malignant potential seems to rest in the stromal cells rather than the giant cells. Specifically, in reported cases, the intravascular occurrence of giant cells in GCT is not associated with an increased incidence of metastasis.

Peripheral giant cell granuloma. An immunohistochemical and ultrastructural study

OBJECTIVE

To study the nature of multinucleated and mononuclear cells from peripheral giant cell granuloma (PGCG).

MATERIALS AND METHODS

Formalin-fixed, paraffin-embedded sections of 40 cases of PGCG were immunohistochemically stained for vimentin, alpha I-antichymotrypsin, CD68, S-100 protein, lysozyme, leucocyte common antigen (LCA), factor VIII-related antigen and muscle cell actin. Six cases of PGCG were also studied by transmission electron microscopy.

RESULTS

Vimentin, alpha I-antichymotrypsin and CD68 were expressed in both the mononuclear and multinucleated giant cells. Dendritic mononuclear cells, positive for S-100 protein, were noted in 67.5% of the lesions, whereas lysozyme and leucocyte common antigen were detected in occasional mononuclear cells. Ultrastructural examination showed mononuclear cells with signs of phagocytosis and sometimes interdigitations with similar cells. Others presented non-specific characteristics and the third type exhibited cytoplasmic processes and occasional Birbeck granules. Some multinucleated giant cells showed oval nuclei, abundant mitochondria and granular endoplasmic reticulum whereas others presented with irregular nuclei and a great number of cytoplasmic vacuoles.

CONCLUSIONS

Immunohistochemical and ultrastructural results suggest that PGCGs of the jaws are composed mainly of cells of the mononuclear phagocyte system and that Langerhans cells are present in two thirds of the lesions.

Estrogen modulation of osteoclast lysosomal enzyme secretion

Osteoclast-mediated bone resorption is accomplished by secretion of lysosomal proteases into an acidic extracellular compartment. We have previously demonstrated that avian osteoclasts and human osteoclast-like giant cell tumor cells respond in vitro to treatment with 17 beta-estradiol (17 beta-E2) by decreased bone resorption activity. To better understand the mechanism by which this is accomplished, we have investigated the effects of 17 beta-E2 treatment on lysosomal enzyme production and secretion by isolated avian osteoclasts and multinucleated cells from human giant cell tumors in vitro. Isolated cells were cultured with bone particles in the presence of either vehicle or steroid. The conditioned media and cells were harvested, and the levels of cathepsin B, cathepsin L, beta-glucuronidase, lysozyme, and tartrate-resistant acid phosphatase (TRAP) activities were determined. There was a steroid dose-dependent decrease in secreted levels of these enzymes. Cell-associated levels of cathepsin L, beta-glucuronidase, and lysozyme decreased; whereas cell-associated levels of cathepsin B and TRAP increased. These changes were measurable at 10(-10) M and maximal at 10(-8) M 17 beta-E2. The changes were detectable at 4-18 h of treatment and increased through 24 h of treatment. The response was steroid specific, since the inactive estrogen isomer, 17 alpha-E2, failed to alter the activity levels. Moreover, the effects of 17 beta-E2 were blocked when the cells were treated simultaneously with the estrogen antagonist ICI182-780 in conjunction with 17 beta-E2. Human osteoclast-like cells obtained from giant cell tumors of bone responded similarly to estrogen with respect to cathepsin B, cathepsin L, and TRAP activities.(ABSTRACT TRUNCATED AT 250 WORDS)