Advances in the biology of bone metastasis: How the skeleton affects tumor behavior (original) (raw)
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Tumor-bone cellular interactions in skeletal metastases
Journal of musculoskeletal & neuronal interactions, 2004
Human tumor cells inoculated into the arterial circulation of immunocompromised mice can reliably cause bone metastases, reproducing many of the clinical features seen in patients. Animal models permit the identification of tumor-produced factors, which act on bone cells, and of bone-derived factors. Local interactions stimulated by these factors drive a vicious cycle between tumor and bone that perpetuates skeletal metastases. Bone metastases can be osteolytic, osteoblastic, or mixed. Parathyroid hormone-related protein, PTHrP, is a common osteolytic factor, while vascular endothelial growth factor and interleukins 8 and 11 also contribute. Osteoblastic metastases can be caused by tumor-secreted endothelin-1, ET-1. Other potential osteoblastic factors include bone morphogenetic proteins, platelet-derived growth factor, connective tissue growth factor, stanniocalcin, N-terminal fragments of PTHrP, and adrenomedullin. Osteoblasts are the main regulators of osteoclasts, and stimulatio...
Therapeutic targets for bone metastases in breast cancer
Breast Cancer Research, 2011
Once metastatic breast cancer cells are in the bone marrow, they do not, on their own, destroy bone. Instead, they alter the functions of bone-resorbing (osteoclasts) and bone-forming cells (osteoblasts) and hijack signals coming from the bone matrix, thereby disrupting physiological bone remodeling [2,3]. Indeed, there is a 'vicious cycle' whereby metastatic cells residing in the bone marrow secrete factors that stimulate osteoclastmediated bone resorption and growth factors released from resorbed bone stimulate tumor growth [2]. Breast cancer cells may also interact with preosteoclasts, resulting in direct stimulation of osteoclast diff erentiation and maturation [4]. Furthermore, breast cancer cells secrete factors that inhibit osteoblast diff erentiation and activity [2,3]. Th eir interaction with osteoblasts also induces the release of cytokines that promote tumor growth [4]. Taken together, this leads to an imbalance between bone resorption and bone formation, resulting in enhanced skeletal destruction and, as a consequence of osteolysis, occurrence of pathological fractures (Figure 1). Several molecules that are produced by breast cancer cells-for example, parathyroid hormone-related protein, interleukins (IL-6, IL-8, and IL-11), cytokines (macrophage colony stimulating factor (M-CSF)) and prostaglandins-stimulate osteoclast activity through the activa tion of the receptor activator of nuclear factor-kB ligand (RANKL)/RANK pathway, which is the primary mediator of osteoclast-mediated bone resorption [3,5]. Breast cancer cells may also directly stimulate
The role of the bone microenvironment in skeletal metastasis
Journal of Bone Oncology, 2013
The bone microenvironment provides a fertile soil for cancer cells. It is therefore not surprising that the skeleton is a frequent site of cancer metastasis. It is believed that reciprocal interactions between tumour and bone cells, known as the ''vicious cycle of bone metastasis'' support the establishment and orchestrate the expansion of malignant cancers in bone. While the full range of molecular mechanisms of cancer metastasis to bone remain to be elucidated, recent research has deepened our understanding of the cell-mediated processes that may be involved in cancer cell survival and growth in bone. This review aims to address the importance of the bone microenvironment in skeletal cancer metastasis and discusses potential therapeutic implications of novel insights.
Changes in Cytokines of the Bone Microenvironment during Breast Cancer Metastasis
International Journal of Breast Cancer, 2012
It is commonly accepted that cancer cells interact with host cells to create a microenvironment favoring malignant colonization. The complex bone microenvironment produces an ever changing array of cytokines and growth factors. In this study, we examined levels of MCP-1, IL-6, KC, MIP-2, VEGF, MIG, and eotaxin in femurs of athymic nude mice inoculated via intracardiac injection with MDA-MB-231 GFP human metastatic breast cancer cells, MDA-MB-231BRMS1 GFP , a metastasis suppressed variant, or PBS. Animals were euthanized (day 3, 11, 19, 27 after injection) to examine femoral cytokine levels at various stages of cancer cell colonization. The epiphysis contained significantly more cytokines than the diaphysis except for MIG which was similar throughout the bone. Variation among femurs was evident within all groups. By day 27, MCP-1, MIG, VEGF and eotaxin levels were significantly greater in femurs of cancer cell-inoculated mice. These pro-osteoclastic and angiogenic cytokines may manipulate the bone microenvironment to enhance cancer cell colonization.
Clinical & Experimental Metastasis, 2010
Bone likely provides a hospitable environment for cancer cells as suggested by their preferential localization to the skeleton. Previous work has shown that osteoblast-derived cytokines increased in the presence of metastatic breast cancer cells. Thus, we hypothesized that osteoblast-derived cytokines, in particular IL-6, MCP-1, and VEGF, would be localized to the bone metaphyses, an area to which breast cancer cells preferentially traffic. Human metastatic MDA-MB-231 breast cancer cells were inoculated into the left ventricle of the heart of athymic mice. Three to four weeks later, tumor localization within isolated femurs was examined using lCT and MRI. In addition, IL-6, MCP-1, and VEGF localization were assayed via immunohistochemistry. We found that MDA-MB-231 cells colonized trabecular bone, the area in which murine MCP-1 and VEGF were visualized in the bone matrix. In contrast, IL-6 was expressed by murine cells throughout the bone marrow. MDA-MB-231 cells produced VEGF, whose expression was not only associated with the breast cancer cells, but also increased with tumor growth. This is the first study to localize MCP-1, VEGF, and IL-6 in bone compartments via immunohistochemistry. These data suggest that metastatic cancer cells may co-opt bone cells into creating a niche facilitating cancer cell colonization.
Contribution of Bone Tissue Modulus to Breast Cancer Metastasis to Bone
Cancer Microenvironment, 2011
Certain tumors, such as breast, frequently metastasize to bone where they can induce bone destruction. Currently, it is well-accepted that the tumor cells are influenced by other cells and growth factors present in the bone microenvironment that lead to tumor-induced bone disease. Over the past 20 years, many groups have studied this process and determined the major contributing factors; however, these results do not fully explain the changes in gene expression and cell behavior that occur when tumor cells metastasize to bone. More recently, groups studying metastasis from soft tissue sites have determined that the rigidity of the microenvironment, which increases during tumor progression in soft tissue, can regulate tumor cell behavior and gene expression. Therefore, we began to investigate the role of the rigid bone extracellular matrix in the regulation of genes that stimulate tumor-induced bone disease. We found that the rigidity of bone specifically regulates parathyroid hormone-related protein (PTHrP) and Gli2 expression in a transforming growth factor β (TGF-β) and mechanotransduction-dependent mechanism. In this review, we summarize the mechanotransduction signaling pathway and how this influences TGF-β signaling and osteolytic gene expression.
Mechanisms of bone metastases of breast cancer
Endocrine Related Cancer, 2009
Cancer development is a multi-step process driven by genetic alterations that elicit the progressive transformation of normal human cells into highly malignant derivatives. The altered cell proliferation phenotype of cancer involves a poorly characterized sequence of molecular events, which often result in the development of distant metastasis. In the case of breast cancer, the skeleton is among the most common of metastatic sites. In spite of its clinical importance, the underlying cellular and molecular mechanisms driving bone metastasis remain elusive. Despite advances in our understanding of the phenotype of cancer cells, the increased focus on the contribution of the tumor microenvironment and the recent revival of interest in the role of tumorpropagating cells (so called cancer stem cells) that may originate or be related to normal stem cells produced in the bone marrow, many important questions remain unanswered. As such, a more complete understanding of the influences of both the microenvironment and the tumor phenotype, which impact the entire multi-step metastatic cascade, is required. In this review, the importance of tumor heterogeneity, tumor-propagating cells, the microenvironment of breast cancer metastasis to bone as well as many current endocrine therapies for the prevention and treatment of metastatic breast cancer is discussed.
Skeletal metastases: Decreasing tumor burden by targeting the bone microenvironment
Journal of Cellular Biochemistry, 2007
Several common cancers often metastasize to the skeleton in advanced disease. Bone metastases are incurable and cause protracted, severe symptoms. Growth of tumor in bone is driven by a vicious cycle: tumor-secreted factors stimulate bone cells, which in turn release growth factors and cytokines. The bone-derived factors fuel the vicious cycle by acting back on the tumor cells. The vicious cycle offers novel targets for the treatment of advanced cancers. Treatments can inhibit bone cells (osteoclasts and osteoblasts) that are stimulated by tumor-secreted factors. Drugs can also inhibit tumor responses to factors enriched in the bone microenvironment, such as transforming growth factor-b. Animal models show that these approaches, especially combination treatments, can reduce tumor burden. The results suggest a novel paradigm in which tumor growth can be effectively inhibited by drugs that target cells in the bone microenvironment and not the tumor cells themselves.
Cellular Players in Breast Cancer Bone Metastases
Clinical Reviews in Bone and Mineral Metabolism, 2013
The current paradigm for bone metastasis is that there is a mutual interaction between osteoclasts and cancer cells, known as the tumor/bone vicious cycle. This model is based largely on findings in immune compromised animals showing amelioration of bone metastases by targeting the osteoclasts. Thus, osteoclast inhibitors are the standard of care in breast cancer bone metastasis. However, clinical studies demonstrate only a 28 % reduction in skeletal-related events in patients with bone metastases treated with bisphosphonates, and currently, there is limited evidence supporting anti-resorptive therapies in reducing the overall incidence of bone metastasis or extending survival. These data indicate that other cells, in addition to the osteoclasts, control tumor growth in bone. This review will discuss the role of the osteoclast, and then focus on additional cellular players, thus expanding the model of bone metastasis pathophysiology to include immune and stromal components.
The Bone Microenvironment: a Fertile Soil for Tumor Growth
Current Osteoporosis Reports, 2016
Bone metastatic disease remains a significant and frequent problem for cancer patients that can lead to increased morbidity and mortality. Unfortunately, despite decades of research, bone metastases remain incurable. Current studies have demonstrated that many properties and cell types within the bone and bone marrow microenvironment contribute to tumor induced bone disease. Furthermore, they have pointed to the importance of understanding how tumor cells interact with their microenvironment in order to help improve both the development of new therapeutics and the prediction of response to therapy.