Morphological, histomorphometric, and microstructural alterations in human bone metastasis from breast carcinoma

Development of a polarization imaging method to detect paraffin-embedded pathology tissues before applying other techniques

The present article describes the development of a technique, applied to paraffin-embedded tissues, which uses three different wavelengths of monochromatic light (λ1 = 445 nm, λ2 = 540 nm and λ3 = 660 nm) for the measures of the degree of polarization, degree of linear polarization, degree of circular polarization and birefringence, all obtained from measurements of Stokes parameters by using polarized light. The goal of this study was to detect changes in developing embryonic mouse eye when pregnant mice fed diets without folic acid for variable periods compared with a healthy control group. We present a biomedical diagnostic technique based on polarized light detection applied to paraffin-embedded tissues to visualize the structural damage to aid us in the diagnosis before applying other techniques. Through this method, we can visualize and identify which parts of the tissue were altered with respect to the control group.

The effects of metastatic lesion on the structural determinants of bone: Current clinical and experimental approaches

Metastatic bone disease is incurable with an associated increase in skeletal-related events, particularly a 17-50% risk of pathologic fractures. Current surgical and oncological treatments are palliative, do not reduce overall mortality, and therefore optimal management of adults at risk of pathologic fractures presents an unmet medical need. Plain radiography lacks specificity and may result in unnecessary prophylactic fixation. Radionuclide imaging techniques primarily supply information on the metabolic activity of the tumor or the bone itself. Magnetic resonance imaging and computed tomography provide excellent anatomical and structural information but do not quantitatively assess bone matrix. Research has now shifted to developing unbiased data-driven tools that can predict risk of impending fractures and guide individualized treatment decisions. This review discusses the state-of-the-art in clinical and experimental approaches for prediction of pathologic fractures with bone metastases. Alterations in bone matrix quality are associated with an age-related increase in skeletal fragility but the impact of metastases on the intrinsic material properties of bone is unclear. Engineering-based analyses are non-invasive with the capability to evaluate oncological treatments and predict failure due to the progression of metastasis. The combination of these approaches may improve our understanding of the underlying deterioration in mechanical performance.

Histopathological Spectrum of Bone Changes in Skeletal Metastasis

Background: Metastatic carcinoma is the most common secondary malignant tumor affecting the bone. Bone is the third most common site for metastasis after lung and liver. The present study was planned to analyze the histomorphological patterns of bone changes in metastatic tumors and their correlation with the radiological findings. Materials and Methods: The current prospective study was conducted over a span of 2 years, encompassing 150 patients with clinically and radiologically suspected metastatic bone disease. Bone biopsy samples were studied for the pattern of bone changes. Results: Of 150 total cases, 30 cases had metastatic bone tumors. The age of the patients ranged from 37 to 84 years (mean: 57.57 ± 11.9 years). Male-to-female ratio was 2:1. All patients with metastasis presented with a complaint of pain followed by tenderness (20, 66.7%). The lesions were commonly located in the vertebral column (14, 46.7%), followed by femur (6, 20%). The primary site was known in 21 (70%) cases. The tumor histotypes were adenocarcinoma (23, 76.7%), squamous cell carcinoma (5, 16.7%), pleomorphic sarcoma (1, 3.3%), and malignant melanoma (1, 3.3%). Histomorphological patterns of bone changes were osteolytic (16, 53.3%), mixed (8, 26.7%), and osteoblastic (6, 20.0%). Correlation between the radiological findings and histopathological patterns of metastases was found to be statistically significant. Conclusions: Histomorphological assessment of bone changes in metastasis is an important parameter. Besides the histological categorization of metastatic bone disease, it plays a pivotal role in identification of the primary tumor site.

Mechanically robust photodegradable gelatin hydrogels for 3D cell culture and in situ mechanical modification

Highly conjugated, hydrophobically modified gelatin hydrogels were synthesized, polymerized and degraded with orthogonal wavelengths of light.

Osteoclasts in Periprosthetic Osteolysis: The Charnley Arthroplasty Revisited

BACKGROUND

Periprosthetic osteolysis by polyethylene wear debris-triggered osteoclasts is viewed as the main pathophysiological pathway in aseptic loosening in total hip arthroplasty. The present aim was to study osteoclast occurrence in osteolytic lesions in early and late revisions of the Charnley low-friction torque arthroplasty (CLFA).

METHODS

Biopsies of the soft interface membrane and the adjacent bone were taken from osteolytic lesions during revision of 16 loose CLFA, early (2-6 years) or late (>10 years) after primary surgery. By light microscopy (LM), cell-dense regions with signs of osteoclast-mediated bone resorption were selected for transmission electron microscopy. Three additional patients were studied in LM for osteoclast markers (tartrate-resistant acid phosphatase and Cathepsin K).

RESULTS

LM disclosed a low-grade chronic inflammation and birefringent particles in most sections. Multiple conglomerates of tartrate-resistant acid phosphatase positive and Cathepsin K positive mononuclear and multinucleated cells were found deep in the fibrous interface membrane. Transmission electron microscopy showed traces of polyethylene-like particles in 67%-100% of the cells. Osteoclast-like cells exhibiting resorptive activity were few (mean, 0.7%; standard deviation, 0.2%), and multinucleated cells, possibly osteoclast precursor cells, located immediately on the bone were also scarce (mean, 2.7%; standard deviation, 5.3%). Multinucleated (odds ratio, 3.0; 95% confidence interval, 1.7-5.5) and macrophage-like cells (odds ratio, 3.6; 95% confidence interval, 2.2-5.6) were typically located deeper in the inflammatory interface membrane with a pathologic appearance with distension and abundance of phagocytic vacuoles. There were no systematic differences in cell populations between early or late revisions.

CONCLUSION

Despite probable ongoing osteoclastogenesis in the osteolytic lesions, there were few sites of osteoclast-mediated bone resorption. These findings attach a contributing biological explanation to the longevity of the CLFA.

Inhibitors of glutamate release from breast cancer cells; new targets for cancer-induced bone-pain

Glutamate is an important signaling molecule in a wide variety of tissues. Aberrant glutamatergic signaling disrupts normal tissue homeostasis and induces several disruptive pathological conditions including pain. Breast cancer cells secrete high levels of glutamate and often metastasize to bone. Exogenous glutamate can disrupt normal bone turnover and may be responsible for cancer-induced bone pain (CIBP). CIBP is a significant co-morbidity that affects quality of life for many advanced-stage breast cancer patients. Current treatment options are commonly accompanied by serious side-effects that negatively impact patient care. Identifying small molecule inhibitors of glutamate release from aggressive breast cancer cells advances a novel, mechanistic approach to targeting CIBP that could advance treatment for several pathological conditions. Using high-throughput screening, we investigated the ability of approximately 30,000 compounds from the Canadian Compound Collection to reduce glutamate release from MDA-MB-231 breast cancer cells. This line is known to secrete high levels of glutamate and has been demonstrated to induce CIBP by this mechanism. Positive chemical hits were based on the potency of each molecule relative to a known pharmacological inhibitor of glutamate release, sulfasalazine. Efficacy was confirmed and drug-like molecules were identified as potent inhibitors of glutamate secretion from MDA-MB-231, MCF-7 and Mat-Ly-Lu cells.

Bone tissue engineering and regenerative medicine: targeting pathological fractures

Patients with bone diseases have the highest risk of sustaining fractures and of suffering from nonunion bone healing due to tissue degeneration. Current fracture management strategies are limited in design and functionality and do not effectively promote bone healing within a diseased bone environment. Fracture management approaches include pharmaceutical therapy, surgical intervention, and tissue regeneration for fracture prevention, fracture stabilization, and fracture site regeneration, respectively. However, these strategies fail to accommodate the pathological nature of fragility fractures, leading to unwanted side effects, implant failures, and nonunions. To target fragility fractures, fracture management strategies should include bioactive bone substitutes designed for the pathological environment. However, the clinical outcome of these materials must be predictable within various disease environments. Initial development of a targeted treatment strategy should focus on simulating the physiological in vitro bone environment to predict clinical effectiveness of the engineered bone. An in vitro test system can facilitate reduction of implant failures and non-unions in fragility fractures.

Breast cancer cells induce osteolytic bone lesions in vivo through a reduction in osteoblast activity in mice

Bone metastases are severely debilitating and have a significant impact on the quality of life of women with metastatic breast cancer. Treatment options are limited and in order to develop more targeted therapies, improved understanding of the complex mechanisms that lead to bone lesion development are warranted. Interestingly, whilst prostate-derived bone metastases are characterised by mixed or osteoblastic lesions, breast-derived bone metastases are characterised by osteolytic lesions, suggesting unique regulatory patterns. This study aimed to measure the changes in bone formation and bone resorption activity at two time-points (18 and 36 days) during development of the bone lesion following intratibial injection of MDA-MB-231 human breast cancer cells into the left tibiae of Severely Combined Immuno-Deficient (SCID) mice. The contralateral tibia was used as a control. Tibiae were extracted and processed for undecalcified histomorphometric analysis. We provide evidence that the early bone loss observed following exposure to MDA-MB-231 cells was due to a significant reduction in mineral apposition rate, rather than increased levels of bone resorption. This suggests that osteoblast activity was impaired in the presence of breast cancer cells, contrary to previous reports of osteoclast-dependent bone loss. Furthermore mRNA expression of Dickkopf Homolog 1 (DKK-1) and Noggin were confirmed in the MDA-MB-231 cell line, both of which antagonise osteoblast regulatory pathways. The observed bone loss following injection of cancer cells was due to an overall thinning of the trabecular bone struts rather than perforation of the bone tissue matrix (as measured by trabecular width and trabecular separation, respectively), suggesting an opportunity to reverse the cancer-induced bone changes. These novel insights into the mechanisms through which osteolytic bone lesions develop may be important in the development of new treatment strategies for metastatic breast cancer patients.

Interleukin-1β promotes skeletal colonization and progression of metastatic prostate cancer cells with neuroendocrine features

Despite the progress made in the early detection and treatment of prostate adenocarcinoma, the metastatic lesions from this tumor are incurable. We used genome-wide expression analysis of human prostate cancer cells with different metastatic behavior in animal models to reveal that bone-tropic phenotypes upregulate three genes encoding for the cytokine interleukin-1β (IL-1β), the chemokine CXCL6 (GCP-2), and the protease inhibitor elafin (PI3). The Oncomine database revealed that these three genes are significantly upregulated in human prostate cancer versus normal tissue and correlate with Gleason scores ≥7. This correlation was further validated for IL-1β by immunodetection in prostate tissue arrays. Our study also shows that the exogenous overexpression of IL-1β in nonmetastatic cancer cells promotes their growth into large skeletal lesions in mice, whereas its knockdown significantly impairs the bone progression of highly metastatic cells. In addition, IL-1β secreted by metastatic cells induced the overexpression of COX-2 (PTGS2) in human bone mesenchymal cells treated with conditioned media from bone metastatic prostate cancer cells. Finally, we inspected human tissue specimens from skeletal metastases and detected prostate cancer cells positive for both IL-1β and synaptophysin while concurrently lacking prostate-specific antigen (PSA, KLK3) expression. Collectively, these findings indicate that IL-1β supports the skeletal colonization and metastatic progression of prostate cancer cells with an acquired neuroendocrine phenotype.

Location matters: osteoblast and osteoclast distribution is modified by the presence and proximity to breast cancer cells in vivo

Bone metastasis is a common incurable complication of breast cancer affecting around 70% of patients with advanced disease. In order to improve outcomes for these patients, the cellular and molecular mechanisms underlying bone metastasis need to be established. The majority of studies to date have focused on end-stage disease and little is known about the events taking place following initial tumour cell colonisation of bone. Here we report the results of a longitudinal study that provides detailed analysis of the spatial and temporal relationship between bone and cancer cells during progression of bone metastasis. Tumour growth in bone was initiated by intra-cardiac inoculation of MDA-MB-231-GFP breast cancer cells in immunocompromised mice. Differentiating between areas of bone in direct contact with the tumour and areas distal to the cancer cells but within the tumour bearing bone, we performed comprehensive analyses of the number and distribution of osteoclasts and osteoblasts. Tumour colonies were detectable in bone from day 10, while reduced trabecular bone volume was apparent from day 19 onwards. Cancer-induced changes in osteoblast and osteoclast numbers differed substantially depending on whether or not the cells were in direct contact with the tumour. Compared to naïve controls, areas of bone in direct contact with the tumour had significantly reduced osteoblast but increased osteoclast numbers, whereas the reverse was found in distal areas. Our data demonstrate that tumour cells induce substantial changes in the bone microenvironment prior to the appearance of bone lesions, suggesting that early therapeutic intervention may be required to oppose the tumour-induced changes to the microenvironment und thus tumour progression.

Identification of NOG as a specific breast cancer bone metastasis-supporting gene

Metastasis requires numerous biological functions that jointly provide tumor cells from a primary site to seed and colonize a distant organ. Some of these activities are selected for in the primary site, whereas others are acquired at the metastatic niche. We provide molecular evidence showing that the BMP inhibitor, NOG, provides metastatic breast cancer cells with the ability to colonize the bone. NOG expression is acquired during the late events of metastasis, once cells have departed from the primary site, because it is not enriched in primary tumors with high risk of bone relapse. On the contrary, breast cancer bone metastatic lesions do select for high levels of NOG expression when compared with metastasis to the lung, liver, and brain. Pivotal to the bone colonization functions is the contribution of NOG to metastatic autonomous and nonautonomous cell functions. Using genetic approaches, we show that when NOG is expressed in human breast cancer cells, it facilitates bone colonization by fostering osteoclast differentiation and bone degradation and also contributes to metastatic lesions reinitiation. These findings reveal how aggressive cancer cell autonomous and nonautonomous functions can be mechanistically coupled to greater bone metastatic potential.

A by-product of glutathione production in cancer cells may cause disruption in bone metabolic processes

Bone is a frequent site for metastasis of breast and prostate cancers, often resulting in pathologic changes in bone metabolism and severe pain. The mechanisms involved are not well understood, but tumour cells may release factors that interfere with bone homeostasis. Several observations have led us to hypothesize that the functional disruptions in bone metastasis are the result of a biological process common to many cell types. The high metabolic activity characteristic of cancer cells often upregulates oxidative stress protection mechanisms such as the antioxidant molecule glutathione. In maintaining redox balance, this normal metabolic response may result in unintended pathologic effects in certain sensitive organ sites. Malignant glioma cells kill surrounding neurons in the brain specifically by secreting the amino acid glutamate, an obligatory waste product of glutathione synthesis. We suggest that glutamate release is a plausible mechanism that may account for the pathologic changes in bone metastasis, since bone, like brain, is also highly sensitive to glutamatergic disruption. This report reviews the available evidence to draw a mechanistic connection between tumour cell oxidative stress and the pathology seen in patients with bone metastasis.

The role of the BMP signaling antagonist noggin in the development of prostate cancer osteolytic bone metastasis

Members of the BMP and Wnt protein families play a relevant role in physiologic and pathologic bone turnover. Extracellular antagonists are crucial for the modulation of their activity. Lack of expression of the BMP antagonist noggin by osteoinductive, carcinoma-derived cell lines is a determinant of the osteoblast response induced by their bone metastases. In contrast, osteolytic, carcinoma-derived cell lines express noggin constitutively. We hypothesized that cancer cell-derived noggin may contribute to the pathogenesis of osteolytic bone metastasis of solid cancers by repressing bone formation. Intra-osseous xenografts of PC-3 prostate cancer cells induced osteolytic lesions characterized not only by enhanced osteoclast-mediated bone resorption, but also by decreased osteoblast-mediated bone formation. Therefore, in this model, uncoupling of the bone remodeling process contributes to osteolysis. Bone formation was preserved in the osteolytic lesions induced by noggin-silenced PC-3 cells, suggesting that cancer cell-derived noggin interferes with physiologic bone coupling. Furthermore, intra-osseous tumor growth of noggin-silenced PC-3 cells was limited, most probably as a result of the persisting osteoblast activity. This investigation provides new evidence for a model of osteolytic bone metastasis where constitutive secretion of noggin by cancer cells mediates inhibition of bone formation, thereby preventing repair of osteolytic lesions generated by an excess of osteoclast-mediated bone resorption. Therefore, noggin suppression may be a novel strategy for the treatment of osteolytic bone metastases.

Cancer cell lines release glutamate into the extracellular environment

Bone is one of the most frequent sites for metastasis of breast and prostate cancers. Bone metastases are associated with pathologic changes in bone turnover and severe pain. The mechanisms that trigger these effects are not well understood, but it is postulated that tumour cells release factors which interfere with signalling processes critical to bone homeostasis. We have identified that several cancer cell lines known to cause bone disruption in animal models of bone metastasis appear to secrete glutamate into their extracellular environment in vitro. Although these cells also express specific glutamate receptors, the implications of this potentially disruptive chemical signal are discussed in relation to normal glutamate-dependent communication processes in bone and a possible mechanistic connection is made between tumour cell glutamate release and the development of pathological changes in bone turnover.

Comparison of quantitative cancellous bone connectivity analyses at two- and three-dimensional levels in dialysis patients

Assessment of cancellous bone connectivity has the potential to aid in predicting fracture risk. Today, cancellous bone connectivity is generally assessed using bone sections obtained from biopsy. However, how reliably such two-dimensional (2-D) analyses visualize the 3-D properties has not been evaluated. Biopsied iliac bone samples were obtained from 47 chronic hemodialysis patients. Bone samples were observed using a microfocus X-ray computed tomography (microCT) system en bloc, and the cancellous bone microstructure was quantitatively assessed at both the 2- and 3-D levels. Cancellous bone microarchitecture was successfully reconstructed from the data obtained by the microCT system. Most of the results from node-strut analysis (NSA) revealed no statistically significant correlations between the 2- and 3-D analyses, with the exception that the number of nodes (N.Nd/TV) showed a mild but significant correlation. In contrast, the marrow space star volumes (V*m) of the 2- and 3-D analyses were highly correlated. NSA parameters including N.Nd/TV showed significant correlations with V*m at the 3-D level. In conclusion, V*m values were similar in the 2- and 3-D analyses, while most of the 2-D NSA parameters did not reflect the 3-D ones. Since V*m and most of the NSA parameters were correlated in the 3-D analyses, 2-D NSA would seem to have serious limitations for the assessment of cancellous bone microstructural properties. Further studies will thus be needed to establish appropriate methods for assessing cancellous bone connectivity in clinical practice.

Bisphosphonate treatment and radiotherapy in metastatic breast cancer

Patients with advanced breast cancer frequently develop metastasis to bone. Bone metastasis results in intractable pain and high risk of pathologic fractures due to osteolysis. The treatment of breast cancer patients with bone metastases requires a multidisciplinary approach. Radiotherapy is an established treatment for metastatic bone pain. It may be delivered either as a localized low dose treatment for localized bone pain or systemically for more widespread symptoms. Bisphosphonates have been shown to reduce morbidity and bone pain from bone metastases when given to patients with metastatic bone disease. In vivo studies indicate that early bisphosphonates administration in combination with radiotherapy improves remineralization and restabilization of osteolytic bone metastases in animal tumor models. This review focused on a brief discussion about biology of bone metastases, the effects of radiotherapy and bisphosphonate therapy, and possible mechanisms of combination therapy in metastatic breast cancer patients.

Bosentan® inhibits tumor vascularization and bone metastasis in an immunocompetent skin-fold chamber model of breast carcinoma cell metastasis

Angiogenic factors including endothelin-1 (ET-1) play a key role in the progression of breast metastases to bone. We investigated the impact of ET-1 on the development of bone metastases in an immunocompetent murine skin-fold chamber model. Murine mammary carcinoma 4T1 was injected in a skin-fold chamber implanted on CB6 mice along with bone explants. Furthermore, mice were treated with or without a dual selective antagonist of both ET-1 receptors. The progression of the vascularization within the chamber was monitored over time by intravital microscopy (IVM). The tumor growth and the development of bone metastases were assessed by cytokeratin-19 gene expression and histological studies. Results indicate that this new model associated with IVM allows for the continuous monitoring of the change in vascularization associated with the development of bone metastases. Additionally, treatment with an antagonist of both ET-1 receptors was associated with the presence of significantly less vessels near the tumor mass compared to control mice. These changes were correlated with smaller tumor masses and reduced bone invasion (P < 0.05). Thus, in an immunocompetent murine model of breast carcinoma metastases to bone, our data support the hypothesis that vascularization plays a role in tumor development and progression and that ET-1 specifically modulates the angiogenesis associated with breast metastases to the bone.

Combination of early bisphosphonate administration and irradiation leads to improved remineralization and restabilization of osteolytic bone metastases in an animal tumor model

BACKGROUND

The goal of the current study was to analyze the combined effect of bisphosphonates (BPs) and irradiation on remineralization and restabilization of osteolytic bone metastases in an animal tumor model.

METHODS

Bone metastases were induced in male Wistar rats via intraosseous injection of the Walker carcinosarcoma 256B cell line into both proximal tibia metaphyses on Day 1 of the study. Three treatment groups were analyzed. All animals received a single radiation dose of 17 grays (in the form of 6-megaelectron-volt electrons) on Day 7 and were sacrificed on Day 49. Group 1 (the control group) was treated with irradiation only. Groups 2 and 3 received additional BPs (clodronate; daily intraperitoneal injection dose, 20 mg/kg per day). In Group 2, BPs were given before irradiation, on Days 3-6; this schedule later was referred to as early BP treatment. In Group 3, BPs were administered simultaneously with irradiation, on Days 7-10; this schedule later was referred to as simultaneous BP treatment. The endpoints of the study were bone density and microstructural parameters of bone on Day 49. Bone density was measured using X-ray absorption. Microstructural parameters of bone were assessed using histomorphometry. A total of thirty tibiae were analyzed in each group.

RESULTS

After irradiation, bone density was significantly higher among animals in the early BP treatment group compared with those in the control group and those in the simultaneous BP treatment group (P = 0.001). Histomorphometric analysis of bone showed significantly better-preserved (P < 0.001) microstructural parameters (bone area, trabecular number, and trabecular separation) in the early BP treatment group compared with the control and simultaneous BP treatment groups.

CONCLUSIONS

Early BP administration in combination with irradiation led to improved remineralization and restabilization of osteolytic bone metastases in an animal tumor model.