Mechanisms involved in the metastasis of cancer to bone

Comparison of tumor curettage and resection for treatment of giant cell tumor of the bone around the knee joint

Objective:

To analyze the efficacies of tumor curettage and resection for treatment of giant cell tumor of the bone (GCTB) around the knee joint (KJ).

Methods:

A total of 126 KJ-GCTB cases were treated at our department from August 2011 to February 2015. These cases were divided into two groups (A and B) according to treatment methods. Group A underwent tumor curettage, while group B underwent tumor resection.

Results:

The relapse rates did not differ significantly between the groups (P>0.05), while the complication rate in group A was significantly lower than that in group B (P<0.05). In addition, the Enneking score for group A was significantly higher than that for group B (P<0.05); in addition, postoperative local recurrence, histopathological grading according to Jaffe, and radiographic imaging-based Campanacci’s staging positively correlated (P<0.05).

Conclusion:

Tumor curettage was the preferred surgical approach for patients with KJ-GCTB.

New multidisciplinary prostate bone metastases clinic: first of its kind in Canada

Prostate cancer is the most common non-skin malignancy in men. Almost all men who die from prostate cancer have hormone-refractory prostate cancer with metastasis to bone. Emerging supportive treatments—including chemotherapy, bisphosphonates, and surgery—require integration that is optimized in a multidisciplinary setting. A multidisciplinary clinic for bone metastases has been in place at Toronto–Sunnybrook Regional Cancer Centre since 1999, combining orthopedic surgery, radiation oncology, interventional radiology, and palliative medicine for all patients with bone metastases. The addition of a prostate-focused multidisciplinary clinic integrates these services for patients with advanced prostate cancer.

A multidisciplinary bone metastases clinic at Toronto Sunnybrook Regional Cancer Centre - A review of the experience from 1999 to 2005

Our objective in this study was to review the experience of a one-stop multidisciplinary bone metastases clinic (BMC) that offers a coordinated multidisciplinary approach to the care of cancer patients with bone metastases in a tertiary cancer centre. Patients with symptomatic bone metastases were referred to BMC and assessed by a team of specialists in various disciplines - interventional radiology, orthopedic surgery, palliative medicine, and radiation oncology. At initial consultation, patient demographics, reasons for referral, and case disposition were recorded. From January 1999 to February 2005, a total of 272 patients with bone metastases were referred to the BMC. The median age was 65 years (range 28-95) and median KPS score at consultation was 60 (range 30-90). The majority of patients came from home (74%), while others came from a nursing home or the hospital (9%). Almost a third (28%) of patients had 2 or more reasons of referral, yielding a total of 354 reasons. The most common reason for referral was bone pain (42%), bone metastases (21%), high risk for pathological fracture (12%), and pathological fracture (10%). Of the 272 patients who received consultation, 40% received palliative radiotherapy, 19% received interventional surgery, 7% were referred to other support services such as palliative care, physiotherapy, and 7% had further investigation or imaging. A multidisciplinary clinic is useful for co-coordinating the management of bone metastatic disease in symptomatic patients.

[The role of matrix metalloproteinases and tissue inhibitors of metalloproteinases in invasion of tumours of neuroepithelial tissue]

Tumour invasion requires degradation of extracellular matrix components and migration of cells through degraded structures into surrounding tissues. Matrix metalloproteinases (MMP) constitute a family of zinc and calcium-dependent endopeptidases that play a key role in the breakdown of extracellular matrix, and in processing of cytokines, growth factors, chemokines and cell surface receptors. Their activity is regulated at the levels of transcription, activation and inhibition by tissue inhibitors of metalloproteinases (TIMP). Changes in expression of MMP and TIMP are implicated in tumour invasion, because they may contribute to both migration of tumour cells and angiogenesis. Alterations of MMP expression observed in brain tumours arouse interest in the development and evaluation of synthetic matrix metalloproteinase inhibitors as antitumour agents.

Enhanced metastatic dissemination to multiple organs by melanoma and lymphoma cells in timp-3-/- mice

Identifying versatile inhibitors of metastasis that operate in multiple sites against distinct cancer cell types is important for designing novel therapeutics for metastasis. We show that multiple tissues of timp-3-/- mice are more susceptible to metastatic colonization. Overall, a 5-14-fold increase in liver and kidney colonization occurred by EL-4 lymphoma cells, and a twofold increase upon targeting B16F10 melanoma cells to the bone or lung of timp-3-/- mice. There was a general lack of macrophage or neutrophil localization to metastases in the liver, kidney and lung, and of osteoclasts to bone in both genotypes. Analysis of lung showed that proliferation or angiogenesis were unaltered within the metastatic colonies. Lung-trap assays revealed that initial tumor cell trapping was similar in the lung vasculature of timp-3-/- and wild-type mice. However, more tumor cells were found in timp-3-/- lungs at 48 and 96 h after tumor cell injection indicating more efficient extravasation and initial proliferation. Activation of pro-MMP-2 was greater in timp-3-/- lungs at these time points. These data demonstrate TIMP-3 functions to inhibit metastatic dissemination of diverse cancer cells to multiple organs. TIMP-3 regulates MMP-2 activation to limit tumor cell extravasation and subsequent colonization of the lung, without augmenting inflammatory cell response.

Serum prolidase I activity and some bone metabolic markers in patients with breast cancer: in relation to menopausal status

OBJECTIVES

The purpose of this study was to investigate the diagnostic value of some osteoblastic/osteoclastic biochemical markers and serum prolidase I activity in breast cancer (BC).

DESIGN AND METHODS

Serum bone gla protein (BGP), prolidase I activity, urinary deoxypyridinoline (Dpy) and calcium excretions were measured, in metastatic and nonmetastatic BC patients, and in 52 healthy women.

RESULTS

In patients with metastases, bone turnover markers were found to be significantly higher than those in the control group and in patients without metastases. Serum prolidase activity in patients with and without metastases was also significantly higher than those in the control group, but there was no difference between the two patient groups.

CONCLUSIONS

Bone turnover has been suggested to be accelerated in BC patients with the more pronounced osteolytic activation, especially in metastatic state. Serum prolidase in premenopausal period appears to be valuable in discriminating cancer patients from controls. BGP and to a lesser degree of Dpy, may be useful markers for predicting the metastatic bone involvement, as well as for the more cost effective management of BC patients and monitoring the effects of antiresorptive therapy of malignant osteolysis before any metastasis could be detected by other invasive techniques.

Bone marrow micrometastasis in breast cancer

BACKGROUND

Several studies have demonstrated that bone marrow micrometastasis in patients with breast cancer is an independent prognostic factor for systemic recurrence and poorer survival.

METHODS

This review describes the detection and clinical significance of micrometastatic cells in bone marrow, and examines the correlation between such micrometastasis and established clinicopathological prognostic factors. The relevant English language literature on bone marrow micrometastasis in breast cancer was searched via Medline (1975-2002), cross-referencing with key articles on the subject.

RESULTS AND CONCLUSION

The balance of evidence favours the hypothesis that bone marrow micrometastasis impacts on disease-free and overall survival. Further prospective studies are required to examine this in greater detail, with particular reference to early node-negative breast cancer and the value of adjuvant systemic therapy in patients with bone marrow micrometastasis.

EORTC prostate cancer trials: what have we learnt?

The aims of the European Organization for Research and Treatment of Cancer-GU (EORTC-GU) Group are to improve the treatment of cancer related problems by carrying out multicenter, multinational and intercontinental Phases II and III trials and the dissemination of their results via workshops, congresses and symposia. The first studies in prostate cancer dealt with the use of chemotherapeutic agents in advanced tumours. Mitomycin C was the most active agent identified. We have learnt that the primary tumour should not be used for response assessment in advanced disease but that Quality of life (QoL) assessment consistently applied may be. In later studies QoL and PSA response were considered as the most important endpoints for Phase II trials in this disease. In patients with locally advanced or metastatic disease maximal androgen blockade (MAB), in different forms, has been studied. Conflicting outcomes have been observed, which could be explained by the inclusion of patients with different prognostic factors at entry in the studies. The anti-androgen monotherapy approach in patients with M+ disease with good prognostic factors has been shown to be feasible, side effects using a steroidal agent were higher compared with non-steroidal agents. The hormono-chemotherapy approach in patients with M+ disease and poor prognostic factors at entry showed not to be of any benefit in terms of survival and also QoL was worse in these patients. Patients with locally advanced disease treated with external beam radiation therapy had a significant better survival if this treatment was combined with 3 years of hormonal therapy. The ongoing Phase III study in metastatic prostate cancer is comparing intermittent hormonal therapy and continuous treatment and in locally advanced prostate cancer a Phase III trial is testing the so-called step-up and step-down regimen.

Omega-3 polyunsaturated fatty acids and skeletal health

This minireview on skeletal biology describes the actions of prostaglandins and cytokines involved in the local regulation of bone metabolism, it documents the role of lipids in bone biology, and it presents relationships between fatty acids and other factors that impact skeletal metabolism. The data presented herein show consistent and reproducible beneficial effects of omega-3 (n-3) fatty acids on bone metabolism and bone/joint diseases. Polyunsaturated fatty acids modulate eicosanoid biosynthesis in numerous tissues and cell types, alter signal transduction, and influence gene expression. These effects have not been explored in the skeletal system. Future research on n-3 fatty acids in bone biology should focus on the following two aspects. First, the further elucidation of how n-3 fatty acids alter biochemical and molecular processes involved in bone modeling and bone cell differentiation, and second, the evaluation of the potential pharmaceutical applications of these nutraceutical fatty acids in maintaining bone mineral status and controlling inflammatory bone/joint diseases.

Expression of bone sialoprotein and osteopontin in breast cancer bone metastases

Bone sialoprotein (BSP) and osteopontin (OPN) are prominent, mineral-associated proteins in the extracellular matrix of bone that have been implicated in the metastatic activity of cancer cells. The expression of BSP, which is normally restricted to mineralizing tissues, has been observed in cancers with a high propensity for forming bone metastases. To investigate the relationship between BSP expression and the formation of bone metastases we have conducted an initial study of the expression of BSP in 10 intraductal breast carcinoma bone metastases using immunostaining and in situ hybridization, and compared the expression with OPN. The metastases were characterized by the infiltration of tumour cells into bone with extensive bone resorption evident. Moderate to strong staining for BSP was observed in all (100%) carcinomas, which also expressed BSP mRNA as determined by in situ hybridization. Variable staining for BSP was also observed in the mineralized bone and expression of BSP mRNA could be observed in osteoblastic cells on the bone surface and in some osteocytes at sites of bone remodelling. Contrary to a previous report, BSP expression could be demonstrated by PCR in three breast cancer cell lines, MCF-7, T47-D and MDA-MB-231. Moreover, in sub-cutaneous tumours formed by MDA-MB-231 breast cancer cells injected into athymic mice, higher immunostaining for BSP was seen in large ulcerating tumours in which mineral deposits were formed. In contrast to BSP, staining for OPN in bone metastases was generally restricted to the interface between tumor cells and bone surface of the carcinomas. While OPN staining was also observed in the cytoplasm of osteoclasts, which showed strong hybridization to a digoxygenin-labelled OPN cRNA probe, expression of OPN was not clearly detectable in the tumour cells. These studies provide the first demonstration of BSP expression by tumour cells in bone metastases and support the concept that BSP may have a role in targeting metastatic cells to bone. Expression of OPN in bone metastases appears to be related to increased bone resorptive activity by osteoclasts.

Conjugated linoleic acid and bone biology

Osteoporosis, osteoarthritis and inflammatory joint disease afflict millions of people worldwide. Inflammatory cytokines inhibit chondrocyte proliferation and induce cartilage degradation for which part of the response is mediated by PGE2. Excess production of PGE2 is linked to osteoporosis and arthritis and is associated with bone and proteoglycan loss. PGE2 also influences the IGF-I/IGFBP axis to facilitate bone and cartilage formation. Recent investigations with growing rats given butter fat and supplements of CLA demonstrated an increased rate of bone formation and reduced ex vivo bone PGE2 production, respectively. Furthermore, the supplements of CLA isomers resulted in their enrichment in lipids of various bone compartments of animals. The effects of CLA on bone biology in rats (IGF action and cytokines) appear to be dependent on the level of n-6 and n-3 fatty acids in the diet; however, these studies generally showed that CLA decreased ex vivo bone PGE2 production and in osteoblast-like cultures. Anti-inflammatory diets, including nutraceutical applications of CLA, may be beneficial in moderating cyclooygenase 2 (COX-2) activity or expression (influencing PGE2 biosynthesis) and might help to reduce rheumatoid arthritis (secondary osteoporosis). This review summarizes findings of CLA on bone modeling in rats and effects on cellular functions of osteoblasts and chondrocytes. These experiments indicate that CLA isomers possess anti-inflammatory activity in bone by moderating prostanoid formation.

Low cell motility induced by hsp27 overexpression decreases osteolytic bone metastases of human breast cancer cells in vivo

The mechanisms controlling the formation of osteolytic bone metastases in patients with breast cancer are still poorly understood. To explore the role of motility in the establishment of osteolytic bone metastases, we have used a model of bone metastasis in which MDA-MB-231 breast cancer cells exhibiting low (hsp27-transfectants) and high (control-transfectant) endogenous cell motility were compared. We found that MDA-MB-231 cells exhibiting low cell motility were less capable of establishing osteolytic lesions. The number and the area of the osteolytic lesions in mice inoculated with low motility cells were both significantly smaller. Histomorphometry of bone lesions also demonstrated less tumor area in mice bearing hsp27 transfectants although there was no difference in the osteoclast number per square millimeter of tumor-bone interface. These data suggest that cell motility may be an important mechanism in the metastatic cascade of breast cancer cells to the bone and that controlling cell motility may be a useful target to prevent the establishment of osteolytic bone metastases.

Effects of bisphosphonate on experimental jaw metastasis model in nude mice

The mechanism of osteolysis associated with metastatic cancer of the jaws is essentially osteoclast-mediated. Therefore, it is likely that potent osteoclastic bone resorption inhibitors such as bisphosphonates would be efficacious for the treatment of jaw metastasis. We examined the effects of a third generation bisphosphonate, YM175, in a nude mice jaw metastasis model with intracardiac injection of a human breast cancer cell line, MDA-MB-231. The metastatic lesions in untreated mice were radiographically observed at the body and angle of the mandible. Histology of the mandible of untreated mice revealed that most of the bone marrow cavities had been occupied by the metastatic tumor with active osteoclasts along the trabecular bone. The experimental group showed that YM175 markedly reduced the size of tumor and the number of osteoclasts. These results suggest that YM175 may suppress metastasis formation and tumor growth in jaw through inhibition of osteoclastic bone resorption.

LCC15-MB: a vimentin-positive human breast cancer cell line from a femoral bone metastasis

The LCC15-MB cell line was established from a femoral bone metastasis that arose in a 29-year-old woman initially diagnosed with an infiltrating ductal mammary adenocarcinoma. The tumor had a relatively high (8%) S-phase fraction and 1/23 positive lymph nodes (LN). Both the primary tumor and LN metastasis were positive for estrogen receptor (ER) and progesterone receptor (PgR), but lacked erbB2 expression. Approximately one year later, the patient presented with a 0.8 cm comedo-type intraductal mammary adenocarcinoma in the left breast that was negative for ER and PgR, but positive for erbB2. Thirty-five months after the initial diagnosis she was treated for acute skeletal metastasis, and stabilized with a hip replacement. At this time, tumor cells were removed from surplus involved bone, inoculated into cell culture, and developed into the LCC 15-MB cell line. The bone metastasis was a poorly differentiated adenocarcinoma lacking ER, PgR, and erbB2, characteristics shared by the LCC15-MB cells, although ER can be re-expressed by treatment of the LCC15-MB cells for 5 days with 75 microM 5-aza-2'-deoxycytidine. The LCC15-MB cell line is tumorigenic when implanted subcutaneously in NCr nu/nu mice and produces long-bone metastases after intracardiac injection. Although the bone metastasis from which the LCC15-MB cell line was derived lacked vimentin (VIM) expression, the original primary tumor and lymph node metastasis were strongly VIM positive, as are LCC15-MB cells in vitro and in nude mice. The karyotype and isozyme profiles of LCC15-MB cells are consistent with its origin from a human female, with most chromosome counts in the hypertriploid range. Thirty-two marker chromosomes are present. These cells provide an in vitro/in vivo model in which to study the inter-relationships between ER, VIM, and bone metastasis in human breast cancer.

Bone sialoprotein supports breast cancer cell adhesion proliferation and migration through differential usage of the alpha(v)beta3 and alpha(v)beta5 integrins

Bone sialoprotein (BSP), a secreted glycoprotein found in bone matrix, has been implicated in the formation of mammary microcalcifications and osteotropic metastasis of human breast cancer (HBC). BSP possesses an integrin-binding RGD (Arg-Gly-Asp) domain, which may promote interactions between HBC cells and bone extracellular matrix. Purified BSP, recombinant human BSP fragments and BSP-derived RGD peptides are shown to elicit migratory, adhesive, and proliferative responses in the MDA-MB-231 HBC cell line. Recombinant BSP fragment analysis localized a significant component of these activities to the RGD domain of the protein, and synthetic RGD peptides with BSP flanking sequences (BSP-RGD) also conferred these responses. The fibronectin-derived RGD counterpart, GRGDSP (Gly-Arg-Gly-Asp-Ser-Pro), could not support these cellular responses, emphasizing specificity of the BSP configuration. Although most of the proliferative and adhesive responses could be attributed to RGD interactions, these interactions were only partly responsible for the migrational responses. Experiments with integrin-blocking antibodies demonstrated that BSP-RGD-induced migration utilizes the alpha(v)beta3 vitronectin receptor, whereas adhesion and proliferation responses were alpha(v)beta5-mediated. Using fluorescence activated cell sorting, we selected two separate subpopulations of MDA-MB-231 cells enriched for alpha(v)beta3 or alpha(v)beta5 respectively. Although some expression of the alternate alpha(v) integrin was still retained, the alpha(v)beta5-enriched MDA-MB-231 cells showed enhanced proliferative and adhesive responses, whereas the alpha(v)beta3-enriched subpopulation was suppressed for proliferation and adhesion, but showed enhanced migratory responses to BSP-RGD. In addition, similar analysis of two other HBC cell lines showed less marked, but similar RGD-dependent trends in adhesion and proliferation to the BSP fragments. Collectively, these data demonstrate BSP effects on proliferative, migratory, and adhesive functions in HBC cells and that the RGD-mediated component differentially employs alpha(v)beta3 and alpha(v)beta5 integrin receptors.

Ectopic expression of bone sialoprotein in human thyroid cancer

Bone sialoprotein (BSP) is a small, highly posttranslationally modified integrin binding protein found in the mineral compartment of developing bone. The recent discovery that BSP can be detected in a variety of human cancers, particularly those that metastasize preferentially to the skeleton, shed light on potential new biological functions for this protein. The demonstration of a positive association between BSP expression in primary breast tumors and the development of bone metastases suggests that this glycoprotein could play a role in the selective implantation of breast cancer cells in bone. BSP is also expressed in most lung and prostate cancers as well as in multiple myeloma, three other osteotropic malignancies. Because thyroid carcinoma also metastasizes preferentially to the skeleton, we decided to look at the expression of BSP in a collection of 145 thyroid malignant lesions including 24 follicular thyroid carcinomas (FTCs), 55 papillary thyroid carcinomas (PTCs), 19 medullary thyroid carcinomas (MTCs), 23 anaplastic carcinomas (ACs), and 24 poorly differentiated carcinomas (PDCs). BSP expression was evaluated by immunoperoxidase technique using two specific polyclonal antibodies. Most of the thyroid carcinomas (72%) examined expressed high levels of BSP. Expression of BSP was significantly lower in FTCs and MTCs compared with PDCs, which are more aggressive (p = 0.0009 and 0.0003, respectively). Our study demonstrates for the first time that ectopic BSP expression is a common feature of thyroid cancer. The prognostic value of BSP detection in thyroid adenocarcinoma and the potential role of BSP in the propension of this type of cancer to metastasize to bone are currently under investigation.

The LCC15-MB human breast cancer cell line expresses osteopontin and exhibits an invasive and metastatic phenotype

We have characterized the LCC15-MB cell line which was recently derived from a breast carcinoma metastasis resected from the femur of a 29-year-old woman. LCC15-MB cells are vimentin (VIM) positive, exhibit a stellate morphology in routine cell culture, and form penetrating colonies when embedded in three-dimensional gels of Matrigel or fibrillar collagen. They show high levels of activity in the Boyden chamber chemomigration and chemoinvasion assays, and like other invasive human breast cancer (HBC) cell lines, LCC15-MB cells activate matrix-metalloproteinase-2 in response to treatment with concanavalin A. In addition, these cells are tumorigenic when implanted subcutaneously in nude mice and recolonize bone after arterial injection. Interestingly, both the primary lesion and the bone metastasis from which LCC15-MB were derived, as well as the resultant cell line, abundantly express the bone matrix protein osteopontin (OPN). OPN is also expressed by the highly metastatic MDA-MB-435 cells, but not other invasive or noninvasive HBC cell lines. Expression of OPN is retained in the subcutaneous xenograft and intraosseous metastases of LCC15-MB as detected by immunohistochemistry. Both VIM and OPN expression have been associated with breast cancer invasion and metastasis, and their expression by the LCC15-MB cell line is consistent with its derivation from a highly aggressive breast cancer. These cells provide a useful model for studying molecular mechanisms important for breast cancer metastasis to bone and, in particular, the implication(s) of OPN and VIM expression in this process.

Production and regulation of interleukin-11 by breast cancer cells

We have studied the production of interleukin-11 (Il-11) in 13 breast cancer cell (BCC) lines. Two of these cell lines (MDA-MB-231 and Hs578T) expressed the cytokine at both the protein and mRNA levels. Il-11 did not modulate the growth of five BCC lines examined, including the two cytokine-producing BCC lines. The production of Il-11 was increased by transforming growth factor-beta1 in a dose-dependent manner with a rapid (2 h) and transient (24 h) mRNA induction, but not by epidermal growth factor, insulin-like growth factor-I and -II, basic fibroblast growth factor, platelet-derived growth factor or parathyroid hormone. The cyclic AMP inducer, forskolin, and the activator of protein kinase C, phorbol 12-myristate 13-acetate, also stimulated the production of Il-11. Besides Il-11, MDA-MB-231 and Hs578T were the only BCC lines to produce interleukin-6 (Il-6) protein and mRNA. Since Il-11 and Il-6 are potent stimulators of osteoclast development and bone is a major source of TGF-beta1, our data suggest that Il-11, together with Il-6, contributes to the high bone destructive capacity of MDA-MB-231 cells and could play a role in breast cancer-induced osteolysis.

The mouse mammary tumor cell line, MMT060562, produces prostaglandin E2 and leukemia inhibitory factor and supports osteoclast formation in vitro via a stromal cell-dependent pathway

Osteoclastic bone resorption increases at the site of bone metastasis, but little is known about how tumor cells induce osteoclast (OC) recruitment in the bone marrow microenvironment. To clarify this point, we examined the effects of various mouse tumor cells on OC recruitment using cocultures of tumor cells and mouse marrow cells. The mouse mammary tumor cell lines, MMT060562 (MMT), BALB/c-MC, Jyg-MC(A), or other nonmammary tumor cell lines, LLC and B16, were cocultured with mouse marrow cells, and OC recruitment from marrow cells was determined by counting the number of tartrate-resistant acid phosphatase-positive multinucleated cells (TRAP(+) MNCs) formed. Of the tumor cells examined, MMT and BALB/c-MC stimulated OC formation, but other tumor cells did not. OC formation with MMT was dependent on the number of MMTs inoculated, and only ten cells per well were sufficient to induce OC development. OCs appeared on day 4, and the number reached a maximum on days 5-8 and decreased thereafter. TRAP(+) MNCs induced by MMT satisfied the major criteria of OCs, such as the presence of calcitonin receptors and the ability to resorb calcified tissues. The majority of OCs were formed adjacent to the stromal cells, which were positive for alkaline phosphatase. When spleen cells were cocultured with MMT, no OCs were formed. In contrast, when osteoblastic cells were added to cocultures of spleen cells and MMT, many OCs were formed. The cultured media (CM) of MMT induced OC formation in mouse marrow cultures. Neither parathyroid hormone-like nor interleukin 1-like activity was present in the CM. MMT constitutively produced prostaglandin E2 (PGE2) and OC formation in cocultures was completely inhibited by indomethacin. Fractionation of the CM of MMT by ultrafiltration indicated that the OC-inducing activities were present not only in the fraction with molecular weight below 3 kDa but also in the fraction with molecular weight above 3 kDa. OC-inducing activity with high molecular weight was eluted around 50 kDa by Bio-Gel P-60 column chromatography. The active fractions also possessed leukemia inhibitory factor (LIF) activity, and OC-inducing activity of the peak fraction was inhibited in the presence of anti-LIF neutralizing antibody. The results of this study indicated that MMTs release PGE2 and LIF, which in turn stimulate OC formation via a stromal cell-dependent pathway. These culture systems will help to clarify the mechanisms by which tumor cells induce OC formation in a bone marrow microenvironment.

Role of integrins in the attachment of metastatic follicular thyroid carcinoma cell lines to bone

One of the principle targets for metastasis of follicular thyroid carcinoma (FTC) is the skeleton. Because no data are available on the role of the integrin adhesion molecule family in the attachment of FTC to bone, we studied the attachment characteristics of three FTC cell lines to bone and the role of integrins. Three cell lines were used from the same patient, one (FTC-133) from the primary tumor and two (FTC-236 and FTC-238) from metastases. Attachment of FTC cell lines to bone was assessed on conditioned medium of an osteoblastic cell line, coated onto plastic, as an in vitro model of bone matrix. The synthetic RGD (Arg-Gly-Asp) peptide GRGDS impaired attachment of the FTC cell lines to bone matrix, demonstrating the role of integrins in the attachment of FTC to bone. Attachment of FTC-133 to bone matrix was blocked completely by GRGDS, whereas attachment of FTC-236 and FTC-238 could not be impaired completely. Semiquantitative polymerase chain reaction (PCR) of cDNA from the cell lines indicated stronger expression of alpha5 integrin mRNA in FTC-133 than in the other cell lines. In line with this, attachment of FTC-133 to bone matrix could be inhibited almost completely by anti alpha5 and beta1 integrin antibodies, indicating the importance of the fibronectin receptor in the attachment of FTC-133 to bone. Binding of FTC-236 and FTC-238 to bone matrix could not be inhibited completely by anti-integrin antibodies, suggesting an additional role of nonintegrin adhesion molecules in the attachment of FTC-236 and FTC-238 to bone. The synthetic bone sialoprotein cyclic peptide, CNB, revealed antiadhesive effects in the binding of FTC to bone. In conclusion, integrins play an important role in the attachment of metastatic FTC to bone. Differences in the functional involvement of integrins in the attachment to bone are observed between the three cell lines studied. From the present results, antiadhesive interventions with synthetic RGD peptides in FTC may be designed.

Human breast cancer cell metastasis to long bone and soft organs of nude mice: a quantitative assay

Bone is a common metastatic site in human breast cancer (HBC). Since bone metastasis occurs very rarely from current spontaneous or experimental metastasis models of HBC cells in nude mice, an arterial seeding model involving the direct injection of the cells into the left ventricle has been developed to better understand the mechanisms involved in this process. We present here a sensitive polymerase chain reaction (PCR) method to detect and quantitate bone and soft organ metastasis in nude mice which have been intracardially inoculated with Lac Z transduced HBC cells. Amplification of genomically incorporated Lac Z sequences in MDA-MB-231-BAG HBC cells enables us to specifically detect these cells in mouse organs and bones. We have also created a competitive template to use as an internal standard in the PCR reactions, allowing us to better quantitate levels of HBC metastasis. The results of this PCR detection method correlate well with cell culture detection from alternate long bones from the same mice, and are more sensitive than gross Lac Z staining with X-gal or routine histology. Comparable qualitative results were obtained with PCR and culture in a titration experiment in which mice were inoculated with increasing numbers of cells, but PCR is more quantifiable, less time consuming, and less expensive. This assay can be employed to study the molecular and cellular aspects of bone metastasis, and could easily be used in conjunction with RT-PCR-based analyses of gene products which may be involved with HBC metastasis.

Prognostic relevance of urokinase plasminogen activator detection in micrometastatic cells in the bone marrow of patients with primary breast cancer

Patients with an elevated level of urokinase plasminogen activator (uPA) in breast cancer tissue have an adverse prognosis. This study evaluated the prognostic relevance of uPA detection in disseminated tumour cells in bone marrow. Bone marrow was sampled intraoperatively from both iliac crests in 280 patients with primary breast cancer. Interphase cells were enhanced and stained immunocytologically with two antibodies: 2E11, which detects TAG 12--a tumour-associated glycoprotein typically expressed by almost all breast cancer cells--and the anti-uPA antibody HD-UK9. Thirty-five of the 2E11-positive women (n = 132, 47%) developed metastatic disease (median follow-up time 44 months). Of these, most were uPA positive (n = 23, 65%) and only 12 were uPA negative. Patients with uPA-positive cells in bone marrow (n = 98, 35%) had a significantly shorter metastasis-free interval (36 months) than women who were uPA negative (44.5 months). The worst prognosis was seen in patients positive for both markers (29.5 months), followed by those who were uPA negative and 2E11 positive (37 months). The detection of uPA on disseminated tumour cells characterizes a subgroup of patients with an even worse prognosis, who should undergo more aggressive adjuvant systemic therapy. For the first time, it was possible to evaluate an important qualitative parameter involved in the process of breast cancer metastases.

Bisphosphonates inhibit the adhesion of breast cancer cells to bone matrices in vitro

Bisphosphonates are used with increasing frequency in the management of skeletal complications in patients with breast cancer. In this paper, we have investigated whether bisphosphonates, besides their known beneficial effects on tumor-associated osteoclastic resorption, are capable of inhibiting breast cancer cell adhesion to bone matrix. For that we used two in vitro models for bone matrix (cortical bone slices and cryostat sections of trabecular bone from neonatal mouse tails). Four bone matrix-bound nitrogen-containing bisphosphonates (pamidronate, olpadronate, alendronate, and ibandronate) inhibited adhesion and spreading of breast cancer cells to bone dose-dependently, whereas etidronate and clodronate had little or no effect. Strikingly, the relative order of potency of the bisphosphonates in inhibiting the adhesion of cancer cells to cortical and trabecular bone corresponded to their relative antiresorptive potencies in vivo as well as their ranking in in vitro bone resorption assays with predictive value for their clinical efficacy. It appears that nitrogen-containing bisphosphonates alter selectively the adhesive properties of the extracellular bone matrix preventing the attachment of breast cancer cells to it. Besides the beneficial effects of bisphosphonates on tumor-induced osteoclastic resorption, the previously unrecognized effect presented in this paper makes these agents suitable for earlier pharmacologic intervention in patients with breast cancer at risk of developing bone metastases.

Inhibition of chemomigration of a human prostatic carcinoma cell (TSU-pr1) line by inhibition of epidermal growth factor receptor function

Chemoattractants expressed at bony sites and pelvic lymph nodes are thought to promote the preferential metastasis of human prostate tumor cells to these organs. Epidermal growth factor (EGF) is a potent chemoattractant for several human metastatic prostate tumor cell lines, including the TSU-pr1 cell line, and EGF has been localized to the stroma of both bony sites and pelvic lymph nodes in humans. Hence, we investigated whether the TSU-pr1 cell line expresses a functional EGF receptor (EGFR), which when antagonized reduces EGF-mediated chemomigration of this cell line. In this context, the EGFR immunoprecipitated from cell lysates of TSU-pr1 cells comigrated with the EGFR from A431 cells at a molecular weight of 170 kD. Addition of human EGF (hEGF) to the TSU-pr1 cells for 5 min stimulated the dose-dependent biphasic phosphorylation of the EGFR, with maximal stimulation of EGFR phosphorylation occurring at 2 ng/ml hEGF. In addition, treatment of hEGF-stimulated (2 ng/ml) TSU-pr1 cells with 0.5 microgram/ml anti-hEGF monoclonal antibody or 100 nM staurosporine inhibited EGFR phosphorylation. Conversely, as negative controls, treatment of hEGF-stimulated (2 ng/ml) TSU-pr1 cells with K252a or dimethyl sulfoxide (DMSO) vehicle did not inhibit EGFR phosphorylation. TSU-pr1 cells were stimulated to migration in 4 hr across Boyden chambers in response to 10 ng/ml hEGF. Treatment of the TSU-pr1 cells with anti-hEGFR monoclonal antibody inhibited in a dose-dependent manner the chemomigration of the TSU-pr1 cells across Boyden chambers. Similarly, treatment of the TSU-pr1 cells with staurosporine inhibited in a dose-dependent manner the chemomigration of the TSU-pr1 cells across Boyden chambers. These results demonstrate that antagonists of hEGF-mediated hEGFR phosphorylation also antagonize chemomigration of the TSU-pr1 cells across Boyden chambers, suggesting that antagonists of the EGFR in prostate cancer may be useful in the treatment of metastatic disease.

Epidermal growth factor (EGF) promotes chemomigration of a human prostate tumor cell line, and EGF immunoreactive proteins are present at sites of metastasis in the stroma of lymph nodes and medullary bone

Prostate tumor cells preferentially metastasize to bony sites and lymph nodes at a frequency in excess of that which would be predicted by random tumor cell dissemination. In order to determine whether chemoattractants in these organs promote organ-specific metastasis, we utilized human cell lines derived from and/or related to these organs as sources of potential chemoattractants. Secretory proteins derived from the cell lines MG-63 (osteosarcoma), SK-ES-1 (Ewing's sarcoma), and KG-1 (leukemia) stimulated chemomigration of the TSU-pr1 prostate tumor cells in a dose-dependent manner in Boyden chambers. In addition, secretory proteins from a human prostatic stromal cell line (hPS) and from the TSU-Pr1 prostate tumor cell line were also able to stimulate chemomigration of the TSU-pr1 cells through Boyden chambers. Since lymph nodes and bony sites represent organs of hematopoietic/lymphoid proliferation and activation, we undertook identification of specific cytokines present at these sites which may promote the chemomigration of prostate tumor cells. In this context, the cytokines interleukin-1 alpha, interleukin-2, interleukin-6, tumor necrosis factor-beta, transforming growth factor-beta, interferon alpha 2-a, and granulocyte-macrophage colony-stimulating factor did not stimulate chemomigration of the TSU-pr1 prostate tumor cell line. In contrast, the cytokine epidermal growth factor (EGF) stimulated chemomigration of the TSU-pr1 prostate tumor cells through the Boyden chambers in a dose-dependent manner. Western blot analysis of secretory proteins from the cell lines KG-1, SK-ES-1, MG-63, hPS, and TSU-pr1 identified EGF-immunoreactive proteins in all cases. In addition, EGF immunoreactivity was localized to the stroma of the human prostate, the osteogenic stroma of pelvic medullary bone, and the stroma within the capsule and trabeculae of pelvic lymph nodes. Hence, these results demonstrate that the cytokine EGF promotes the chemomigration of the TSU-pr1 prostate tumor cell line, and that EGF within the stroma of pelvic lymph nodes and medullary bone may act as a chemoattractant for prostate tumor cells, thereby facilitating the preferential formation of metastatic foci within these organs.

Differential effects of 1,25-dihydroxyvitamin D3-analogs on osteoblast-like cells and on in vitro bone resorption

Although numerous studies have shown potent antiproliferative and differentiation-inducing effects of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) and its analogs on cells not directly related to bone metabolism, only few reports focussed on the effects of these analogs on bone. We compared the action of several recently developed analogs with that of 1,25-(OH)2D3 on human (MG-63) and rat (ROS 17/2.8) osteoblast-like cells and on in vitro bone resorption. In MG-63 cells the analogs EB1089 and KH1060 were about 166,000 and 14,000 times more potent than 1,25-(OH)2D3 in stimulating type I procollagen and 100 and 6,000 times more potent in stimulating osteocalcin production, respectively. Also in ROS 17/2.8 cells EB1089 and KH1060 were most potent in inducing osteocalcin synthesis. In vitro bone resorption was 2.3 and 17.5 times more potently stimulated by EB1089 and KH1060, respectively. In MG-63 cells, 1,25-(OH)2D3 and the analogs inhibited cell proliferation, whereas both 1,25-(OH)2D3 and the analogs stimulated the growth of ROS 17/2.8 cells. Differences in potency could neither be explained by affinity for the vitamin D receptor nor by a differential involvement of protein kinase C in the action of the analogs. Together, these data show that also in bone the analogs EB1089 and KH1060 are more potent than 1,25-(OH)2D3 but that the potency of the analogs compared to 1,25-(OH)2D3 is dependent on the biological response. On the basis of these observations it can be concluded that the reported reduced calcemic effect in vivo is not the result of a decreased responsiveness of bone to these analogs. Lastly, in view of eventual clinical application of 1,25-(OH)2D3-analogs, the observed stimulation of in vitro bone resorption and growth of an osteosarcoma cell line warrant in vivo studies to further examine these effects.

Effect of osteoblast supernatants on cancer cell migration and invasion

Malignant tumor cells of different origin seem to have preferential sites for metastasis. Breast cancer, prostate cancer and certain melanomas have bone as one of their preferential targets for metastasis. Bone is continuously being remodelled, a process largely controlled by local growth factors. A possible explanation for malignant cell recruitment to bone is that osteoblast products, directly secreted or released from the matrix by osteoclast resorbing activity, are able to stimulate cancer cell migration. To test this hypothesis we have utilized an in vitro system of differentiating osteoblasts which in culture progress all the way to the formation of mineralized nodules. Conditioned media obtained from these osteoblast cultures at different stages were able to induce chemotactic migration and invasion of both melanoma and breast cancer cells. The migratory and invasive phenotype was accompanied by enhanced gelatinolytic activity of osteoblast stimulated cancer cells. Our data suggest that osteoblasts secrete potent factors able to direct tumor cell migration towards remodelling bone.