The Microenvironmental Effect in the Progression, Metastasis, and Dormancy of Breast Cancer: A Model System within Bone Marrow

Increased expression of musashi 1 on breast cancer cells has implication to understand dormancy and survival in bone marrow

Breast cancer (BC) stem cells (CSCs) resist treatment and can exist as dormant cells in tissues such as the bone marrow (BM). Years before clinical diagnosis, BC cells (BCCs) could migrate from the primary site where the BM niche cells facilitate dedifferentiation into CSCs. Additionally, dedifferentiation could occur by cell autonomous methods. Here we studied the role of Msi 1, a RNA-binding protein, Musashi I (Msi 1). We also analyzed its relationship with the T-cell inhibitory molecule programmed death-ligand 1 (PD-L1) in CSCs. PD-L1 is an immune checkpoint that is a target in immune therapy for cancers. Msi 1 can support BCC growth through stabilization of oncogenic transcripts and modulation of stem cell-related gene expression. We reported on a role for Msi 1 to maintain CSCs. This seemed to occur by the differentiation of CSCs to more matured BCCs. This correlated with increased transition from cycling quiescence and reduced expression of stem cell-linked genes. CSCs co-expressed Msi 1 and PD-L1. Msi 1 knockdown led to a significant decrease in CSCs with undetectable PD-L1. This study has implications for Msi 1 as a therapeutic target, in combination with immune checkpoint inhibitor. Such treatment could also prevent dedifferentiation of breast cancer to CSCs, and to reverse tumor dormancy. The proposed combined treatment might be appropriate for other solid tumors.

Quantitative cell imaging approaches to metastatic state profiling

Genetic heterogeneity of metastatic dissemination has proven challenging to identify exploitable markers of metastasis; this bottom-up approach has caused a stalemate between advances in metastasis and the late stage of the disease. Advancements in quantitative cellular imaging have allowed the detection of morphological phenotype changes specific to metastasis, the morphological changes connected to the underlying complex signaling pathways, and a robust readout of metastatic cell state. This review focuses on the recent machine and deep learning developments to gain detailed information about the metastatic cell state using light microscopy. We describe the latest studies using quantitative cell imaging approaches to identify cell appearance-based metastatic patterns. We discuss how quantitative cancer biologists can use these frameworks to work backward toward exploitable hidden drivers in the metastatic cascade and pioneering new Frontier drug discoveries specific for metastasis.

Combined Interaction of Cellular and Extracellular Components Causes Genetic Cascade Activation in Breast Cancer Metastasis

Breast cancer (BC) consists of malignant cells as well as surrounding non-malignant cells-Fibroblasts, macrophages, endothelial cells, lymphocytes, neutrophils, mesenchymal stem cells, and extracellular matrix (ECM). This surrounding stroma is referred to as the Breast Tumor Microenvironment (BTME). The components of BTME interact with cancerous breast cells for the promotion of BC. The reciprocal cross-talk between BTME and neoplastic breast cells, through the secretion of chemicals, growth factors and chemokines, may lead to cell proliferation, migration, metastasis as well as immune response suppression. Multiple genetic loci, in association with stromal components, are linked to immunological stimuli to induce BC in ductal cells. These genes participate in tumor activation pathways and promote carcinogenesis via Fibroblast, Leukocyte, and Endothelial Cells-mediated responses. The collaborative effect of the cellular components and BTME-associated genes plays vital role in tumor initiation and metastasis of breast cells. This process involves genes which cause degenerative changes in ECM leading to Epithelial-Mesenchymal Transitions (EMT), which finally causes metastatic BC. This shows that metastatic breast cancer results from combined activation of different cellular and extracellular components and their activity is primarily controlled by activation of genetic cascade. These components work simultaneously to cause metastatic BC.

The Relationship Between Mesenchymal Stem Cells and Tumor Dormancy

Tumor dormancy, a state of tumor, is clinically undetectable and the outgrowth of dormant tumor cells into overt metastases is responsible for cancer-associated deaths. However, the dormancy-related molecular mechanism has not been clearly described. Some researchers have proposed that cancer stem cells (CSCs) and disseminated tumor cells (DTCs) can be seen as progenitor cells of tumor dormancy, both of which can remain dormant in a non-permissive soil/niche. Nowadays, research interest in the cancer biology field is skyrocketing as mesenchymal stem cells (MSCs) are capable of regulating tumor dormancy, which will provide a unique therapeutic window to cure cancer. Although the influence of MSCs on tumor dormancy has been investigated in previous studies, there is no thorough review on the relationship between MSCs and tumor dormancy. In this paper, the root of tumor dormancy is analyzed and dormancy-related molecular mechanisms are summarized. With an emphasis on the role of the MSCs during tumor dormancy, new therapeutic strategies to prevent metastatic disease are proposed, whose clinical application potentials are discussed, and some challenges and prospects of the studies of tumor dormancy are also described.

Stromal-Derived Extracellular Vesicles Suppress Proliferation of Bone Metastatic Cancer Cells Mediated By ERK2

Bone is a common site of cancer metastasis, including cancers such as breast, prostate, and multiple myeloma. Disseminated tumor cells (DTC) shed from a primary tumor may travel to bone and can survive undetected for years before proliferating to form overt metastatic lesions. This period of time can be defined as metastatic latency. Once in the metastatic microenvironment, DTCs engage in intercellular communication with surrounding stromal cells, which can influence cancer cell survival, proliferation, and ultimately disease progression. The role of the surrounding tumor microenvironment in regulating DTC fate is becoming increasingly recognized. We have previously shown that in the bone microenvironment, osteoblasts are "educated" by interactions with breast cancer cells, and these "educated" osteoblasts (EO) produce soluble factors that regulate cancer cell proliferation. In this study, we provide evidence indicating that EOs produce small extracellular vesicles (sEV) that suppress breast cancer proliferation, in part through regulation of ERK1/2 signaling. In addition, using EdU-incorporation assays and propidium iodide staining we demonstrate that exposure to EO-derived sEVs decreases breast cancer cell entry to S-phase of cell cycle. We also have evidence that particular microRNAs, including miR-148a-3p, are enriched in EO-derived sEVs, and that miR-148a-3p is capable of regulating breast cancer proliferation. IMPLICATIONS: These findings underscore the importance of sEV-mediated communication in the earlier stages of cancer progression, and suggest that EO-derived sEVs may be one mechanism by which the bone microenvironment suppresses breast cancer cell proliferation.

Primary non-Hodgkin lymphoma of the right femur and subsequent metastasis to the left femur: A case report and literature review

Non-Hodgkin lymphoma of the bone is rare and typically causes an extensive bone lesion. The present study describes a case of diffuse large B-cell primary non-Hodgkin lymphoma of the bone, which occurred in the right femur, and was initially treated with surgery and chemotherapy. Following a 7-year period of complete remission, a new, similar lesion was identified in the left femur. With both lesions, there was no accompanying destruction of any other bones or organ involvement. Metastasis of PLB to the contralateral side is extremely rare and, to the best of our knowledge, this is the first report of this particular presentation in China or worldwide. We hypothesized that the present situation arose due to mechanisms involving the tumor microenvironment, circulating tumor cells, lymphocyte homing and self-seeding. The present report describes the case in detail, and discusses the possible underlying mechanisms and their potential contribution to the treatment of non-Hodgkin lymphoma, as well as the prevention of metastasis and recurrence, which may be of considerable clinical significance.

Osteoprotegerin rich tumor microenvironment: implications in breast cancer

Osteoprotegerin (OPG) is a soluble decoy receptor for tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL). It belongs to the tumor necrosis factor receptor superfamily (TNFRSF). OPG was initially discovered to contribute to homeostasis of bone turnover due to its capability of binding to receptor activator of nuclear factor-kappaB (NF-kB). However, apart from bone turnover, OPG plays important and diverse role(s) in many biological functions. Besides having anti-osteoclastic activity, OPG is thought to exert a protective anti-apoptotic action in OPG-expressing tumors by overcoming the physiologic mechanism of tumor surveillance exerted by TRAIL. Along with inhibiting TRAIL induced apoptosis, it can induce proliferation by binding to various cell surface receptors and thus turning on the canonical cell survival and proliferative pathways. OPG also induces angiogenesis, one of the hallmarks of cancer, thus facilitating tumor growth. Recently, the understanding of OPG and its different roles has been augmented substantially. This review is aimed at providing a very informative overview as to how OPG affects cancer progression especially breast cancer.

Ear Sponge Assay: A Method to Investigate Angiogenesis and Lymphangiogenesis in Mice

Angiogenesis and lymphangiogenesis have become important research areas in the biomedical field. The outgrowth of new blood (angiogenesis) and lymphatic (lymphangiogenesis) vessels from preexisting ones is involved in many pathologies including cancer. In-depth investigations of molecular determinants such as proteases in these complex processes require reliable in vivo models. Here we present the ear sponge assay as an easy, rapid, quantitative and reproducible model of angiogenesis and lymphangiogenesis. In this system, a gelatin sponge soaked with tumor cells, cell-conditioned medium, or a compound to be tested is implanted, for 2-4 weeks, between the two mouse ear skin layers. The two vascular networks are next examined through histological procedures.

Hypoxia-induced reactive oxygen species mediate N-cadherin and SERPINE1 expression, EGFR signalling and motility in MDA-MB-468 breast cancer cells

One of the hallmarks of the tumour microenvironment is hypoxia resulting from increased oxygen consumption by proliferative cancer cells and altered vasculature. Hypoxic tension initiates various cellular signals and can drive epithelial to mesenchymal transition (EMT), a process important in cancer progression. In this study, using the antioxidant N-acetylcysteine (NAC), we show that hypoxia-induced reactive oxygen species (ROS) in MDA-MB-468 breast cancer cells, selectively regulate hypoxia-induced increases in N-cadherin and SERPINE1, two proteins involved in cell adhesion. Treatment of cells with NAC also attenuated hypoxia-mediated activation of EGFR, but did not have any effect on hypoxia-mediated induction of HIF1α. Exogenous hydrogen peroxide phenocopied the effects of hypoxia on N-cadherin and SERPINE1 expression and EGFR activation, suggesting its possible involvement in these hypoxia-mediated events. Reflective of their effect on cell adhesion proteins and EGFR (associated with migratory phenotypes), NAC also reduced cell migration under hypoxic conditions, a crucial event in metastasis. Our findings suggest a selective role for redox signalling in the regulation of specific components of the responses to hypoxia and induction of EMT in breast cancer cells. This study provides new evidence supporting the potential of targeting ROS as a therapeutic strategy for the control of breast cancer metastasis.

Immune modulation by a cellular network of mesenchymal stem cells and breast cancer cell subsets: Implication for cancer therapy

The immune modulatory properties of mesenchymal stem cells (MSCs) are mostly controlled by the particular microenvironment. Cancer stem cells (CSCs), which can initiate a clinical tumor, have been the subject of intense research. This review article discusses investigative studies of the roles of MSCs on cancer biology including on CSCs, and the potential as drug delivery to tumors. An understanding of how MSCs behave in the tumor microenvironment to facilitate the survival of tumor cells would be crucial to identify drug targets. More importantly, since CSCs survive for decades in dormancy for later resurgence, studies are presented to show how MSCs could be involved in maintaining dormancy. Although the mechanism by which CSCs survive is complex, this article focus on the cellular involvement of MSCs with regard to immune responses. We discuss the immunomodulatory mechanisms of MSC-CSC interaction in the context of therapeutic outcomes in oncology. We also discuss immunotherapy as a potential to circumventing this immune modulation.

Leptin signals via TGFB1 to promote metastatic potential and stemness in breast cancer

Epidemiological studies have shown obesity to be linked with poorer outcomes in breast cancer patients. The molecular mechanisms responsible for the increased risk of invasive/metastatic disease with obesity are complex, but may include elevated levels of adipokines such as leptin. Using physiological levels of leptin found in obesity in a novel chronic in vitro treatment model (≤200 ng/ml for 14 days), we confirmed the occurrence of leptin-mediated changes in growth, apoptosis and metastatic behavior, and gene expression changes representing epithelial-to-mesenchymal transition (EMT) and a cancer stem cell (CSC) like phenotype in breast epithelial and cancer cell lines (MCF10A, MCF10AT1, MCF7 and MDA-MB-231). Further, we have discovered that these effects were accompanied by increased expression of TGFB1, and could be significantly reduced by co-treatment with neutralizing antibody against TGFB1, indicating that the induction of these characteristics was mediated via TGFB1. Occurring in both MCF7 and MCF10AT1 cells, it suggests these actions of leptin to be independent of estrogen receptor status. By linking leptin signalling to the established TGFB1 pathway of metastasis / EMT, this study gives a direct mechanism by which leptin can contribute to the poorer outcomes of obese cancer patients. Inhibitors of TGFB1 are in currently in phase III clinical trials in other malignancies, thus identifying the connection between leptin and TGFB1 will open new therapeutic opportunities for improving outcomes for obese breast cancer patients.

Prognostic significance of TRAIL-R3 and CCR-2 expression in tumor epithelial cells of patients with early breast cancer

Background

Tumor epithelial cells (TEpCs) and spindle-shaped stromal cells, not associated with the vasculature, of patients with early breast cancer express osteoprotegerin (OPG), tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), receptor activator of nuclear factor kappa B ligand, stromal cell derived factor-1, interleukin-6, macrophage colony stimulating factor, chemokine (C-C motif) ligand-2 (CCL-2) and their receptors at significantly higher levels compared with non-neoplastic breast tissues. We evaluated the clinicopathological significance of these ligands and receptors in TEpC and spindle-shaped stromal cells, not associated with the vasculature, to determine their impact on prognosis of patients with early-stage breast cancer.

Methods

We conducted immunohistochemical analyses of protein expression in primary tumors of patients with early breast cancer and analyzed their association with standard prognostic parameters and clinical outcomes, including local relapse, metastatic recurrence, disease-free survival (DFS), metastasis-free survival (MFS), and overall survival (OS).

Results

Elevated levels of TRAIL-R3 and chemokine (C-C motif) receptor 2 (CCR-2) in TEpCs and OPG and CCL-2 in stromal cells were significantly associated with a higher risk of metastasis (p = 0.032, p = 0.003, p = 0.038, and p = 0.049; respectively). Moreover, high expression of TRAIL-R3 and CCR-2 in TEpCs was associated with shorter DFS, MFS, and OS. High TRAIL-R3 expression in TEpCs was an independent prognostic factor for DFS and OS, and high CCR-2 expression in these cells was an independent prognostic factor for MFS.

Conclusions

High levels of TRAIL-R3 and CCR-2 expression in TEpCs identified patients with early breast cancer with poor outcomes.

Aluminium and the human breast

The human population is exposed to aluminium (Al) from diet, antacids and vaccine adjuvants, but frequent application of Al-based salts to the underarm as antiperspirant adds a high additional exposure directly to the local area of the human breast. Coincidentally the upper outer quadrant of the breast is where there is also a disproportionately high incidence of breast cysts and breast cancer. Al has been measured in human breast tissues/fluids at higher levels than in blood, and experimental evidence suggests that at physiologically relevant concentrations, Al can adversely impact on human breast epithelial cell biology. Gross cystic breast disease is the most common benign disorder of the breast and evidence is presented that Al may be a causative factor in formation of breast cysts. Evidence is also reviewed that Al can enable the development of multiple hallmarks associated with cancer in breast cells, in particular that it can cause genomic instability and inappropriate proliferation in human breast epithelial cells, and can increase migration and invasion of human breast cancer cells. In addition, Al is a metalloestrogen and oestrogen is a risk factor for breast cancer known to influence multiple hallmarks. The microenvironment is established as another determinant of breast cancer development and Al has been shown to cause adverse alterations to the breast microenvironment. If current usage patterns of Al-based antiperspirant salts contribute to causation of breast cysts and breast cancer, then reduction in exposure would offer a strategy for prevention, and regulatory review is now justified.

Fulvic Acid Attenuates Resistin-Induced Adhesion of HCT-116 Colorectal Cancer Cells to Endothelial Cells

A high level of serum resistin has recently been found in patients with a number of cancers, including colorectal cancer (CRC). Hence, resistin may play a role in CRC development. Fulvic acid (FA), a class of humic substances, possesses pharmacological properties. However, the effect of FA on cancer pathophysiology remains unclear. The aim of this study was to investigate the effect of resistin on the endothelial adhesion of CRC and to determine whether FA elicits an antagonistic mechanism to neutralize this resistin effect. Human HCT-116 (p53-negative) and SW-48 (p53-positive) CRC cells and human umbilical vein endothelial cells (HUVECs) were used in the experiments. Treatment of both HCT-116 and SW-48 cells with resistin increases the adhesion of both cells to HUVECs. This result indicated that p53 may not regulate this resistin effect. A mechanistic study in HCT-116 cells further showed that this resistin effect occurs via the activation of NF-κB and the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Co-treating cells with both FA and resistin revealed that FA significantly attenuated the resistin-increased NF-κB activation and ICAM-1/VCAM-1 expression and the consequent adhesion of HCT-116 cells to HUVECs. These results demonstrate the role of resistin in promoting HCT-116 cell adhesion to HUVECs and indicate that FA might be a potential candidate for the inhibition of the endothelial adhesion of CRC in response to resistin.

The bone marrow niche in support of breast cancer dormancy

Despite the success in detecting breast cancer (BC) early and, with aggressive therapeutic intervention, BC remains a clinical problem. The bone marrow (BM) is a favorable metastatic site for breast cancer cells (BCCs). In BM, the survival of BCCs is partly achieved by the supporting microenvironment, including the presence of immune suppressive cells such as mesenchymal stem cells (MSCs). The heterogeneity of BCCs brings up the question of how each subset interacts with the BM microenvironment. The cancer stem cells (CSCs) survive in the BM as cycling quiescence cells and, forming gap junctional intercellular communication (GJIC) with the hematopoietic supporting stromal cells and MSCs. This type of communication has been identified close to the endosteum. Additionally, dormancy can occur by soluble mediators such as cytokines and also by the exchange of exosomes. These latter mechanisms are reviewed in the context of metastasis of BC to the BM for transition as dormant cells. The article also discusses how immune cells such as macrophages and regulatory T-cells facilitate BC dormancy. The challenges of studying BC dormancy in 2-dimensional (2-D) system are also incorporated by proposing 3-D system by engineering methods to recapitulate the BM microenvironment.

Biological roles of human bone morphogenetic protein 9 in the bone microenvironment of human breast cancer MDA-MB-231 cells

Bone marrow stroma plays a critical role in the bone metastasis of breast cancer. Bone marrow-derived mesenchymal stem cells (BMSC) are critical to facilitate cancer progression. Human bone morphogenetic protein 9 (BMP9) is the most potent osteogenic factor and one of bone-stored growth factors involved in both promotion and inhibition of different cancers. However, it is unclear whether BMP9 correlates with the bone metastasis of breast cancer. This study was to evaluate the role of BMP9 in the interaction between BMSC and breast cancer cells (BCC). To determine whether BMP9 is able to block the tumor promoting effect of BMSC, an in vitro model was developed using breast cancer MDA-MB-231 cells co-cultured with bone marrow-derived mesenchymal stem cells HS-5 with-BMP9 overexpression. The expressions of metastasis-related genes were detected to identify important factors mediating the role of BMP9 in breast cancer cells. Results showed BMP9 could inhibit invasion and promote apoptosis of MDA-MB-231 cells. The expressions of interleukin-6 (IL-6), matrix metalloproteinase-2 (MMP-2) and monocyte chemoattratctant protein-1 (MCP-1) decreased in the MDA-MB-231 cells of BMP9 over-expression group, and the expressions of epithelial-mesenchymal transition (EMT)-related molecules was also reduced. On the other hand, the expression of stromal cell derived factor-1 (SDF-1) decreased in HS-5 cells of BMP9 over-expression group. Taken together, BMP9 is able to inhibit the migration and promote the apoptosis of breast cancer by regulating the interaction between MDA-MB-231 cells and HS-5 cells in which SDF-1/CXCR4-PI3K pathway and EMT are involved.

CD105 expression on CD34-negative spindle-shaped stromal cells of primary tumor is an unfavorable prognostic marker in early breast cancer patients

Several studies have confirmed that the breast tumor microenvironment drives cancer progression and metastatic development. The aim of our research was to investigate the prognostic significance of the breast tumor microenvironment in untreated early breast cancer patients. Therefore, we analyzed the association of the expression of α-SMA, FSP, CD105 and CD146 in CD34-negative spindle-shaped stromal cells, not associated with the vasculature, in primary breast tumors with classical prognostic marker levels, metastatic recurrence, local relapse, disease-free survival, metastasis-free survival and the overall survival of patients. In the same way, we evaluated the association of the amount of intra-tumor stroma, fibroblasts, collagen deposition, lymphocytic infiltration and myxoid changes in these samples with the clinical-pathological data previously described. This study is the first to demonstrate the high CD105 expression in this stromal cell type as a possible independent marker of unfavorable prognosis in early breast cancer patients. Our study suggests that this new finding can be useful prognostic marker in the clinical-pathological routine.

Extracellular vesicles as carriers of microRNA, proteins and lipids in tumor microenvironment

In recent years, the knowledge about the control of tumor microenvironment has increased and emerged as an important player in tumorigenesis. The role of normal stromal cells in the tumor initiation and progression has brought our vision in to the forefront of cell-to-cell communication. In this review, we focus on the mechanism of communication between stromal and tumor cells, which is based on the exchange of extracellular vesicles (EVs). We describe several, evergrowing, pieces of evidence that EVs transfer messages through their miRNA, lipid, protein and nucleic acid contents. A better understanding of this sophisticated method of communication between normal cancer cells may lead to developing novel approaches for personalized diagnostics and therapeutics.

A low-molecular-weight heparin-coated doxorubicin-liposome for the prevention of melanoma metastasis

Tumor metastasis is the biggest challenge in cancer therapy. During the metastasis process, metastatic cells could acquire stealth ability toward immune system through the formation of a protection cloak by hijacking platelets (PTs). Heparins, a heterogeneous mixture of glycosaminoglycans, can inhibit metastatic cascades by blocking P-selectin-mediated intercellular adhesion between tumor cells and PTs. In this study, low-molecular-weight heparin-coated doxorubicin-loaded liposome (LMWH-DOX-Lip) was developed for metastasis preventative therapy. The formation of LMWH-DOX-Lip was based on electrostatic interactions between the negatively charged heparins and cationic lipids. LMWH-DOX-Lip prepared at the optimum prescription possessed high entrapment efficiency, ideal particle size and zeta potential. Morphology of LMWH-DOX-Lip was characterized by atomic force microscopy and transmission electron microscopy. The results of confocal microscopic observations and flow cytometry analysis indicated that LMWH-DOX-Lip mediated an efficient cellular uptake in B16F10 melanoma cell line. Besides, LMWH-DOX-Lip displayed an increased cytotoxic over their unmodified counterparts. Furthermore, the inhibition effect of LMWH-DOX-Lip on adhesion between tumor cells and PTs/P-selectin was observed. In vivo study performed on a pulmonary melanoma mouse model revealed a substantially tumor metastasis prevention by LMWH-DOX-Lip. All these results suggested that LMWH-DOX-Lip could significantly inhibit metastasis through preventing the tumor cell-platelet interactions and in the meantime suppressed tumor growth.

Cancer cells remodel themselves and vasculature to overcome the endothelial barrier

Metastasis refers to the spread of cancer cells from a primary tumor to distant organs mostly via the bloodstream. During the metastatic process, cancer cells invade blood vessels to enter circulation, and later exit the vasculature at a distant site. Endothelial cells that line blood vessels normally serve as a barrier to the movement of cells into or out of the blood. It is thus critical to understand how metastatic cancer cells overcome the endothelial barrier. Epithelial cancer cells acquire increased motility and invasiveness through epithelial-to-mesenchymal transition (EMT), which enables them to move toward vasculature. Cancer cells also express a variety of adhesion molecules that allow them to attach to vascular endothelium. Finally, cancer cells secrete or induce growth factors and cytokines to actively prompt vascular hyperpermeability that compromises endothelial barrier function and facilitates transmigration of cancer cells through the vascular wall. Elucidation of the mechanisms underlying metastatic dissemination may help develop new anti-metastasis therapeutics.

Tumor necrosis factor-alpha-converting enzyme activities and tumor-associated macrophages in breast cancer

The role of the tumor microenvironment especially of tumor-associated macrophages (TAMs) in the progression and metastatic spread of breast cancer is well established. TAMs have primarily a M2 (wound-healing) phenotype with minimal cytotoxic activities. The mechanisms by which tumor cells influence TAMs to display a pro-tumor phenotype are still debated although the key roles of immunomodulatory cytokines released by tumor cells, including colony-stimulating factor 1, tumor necrosis factor (TNF) and soluble TNF receptors 1/2, soluble vascular cell adhesion molecule 1, soluble interleukin 6 receptor and amphiregulin, have been demonstrated. Importantly, these factors are released through ectodomain shedding by the activities of the tumor necrosis factor-alpha-converting enzyme (TACE/ADAM17). The role of TACE activation leading to autocrine effects on tumor progression has been extensively studied. In contrast, limited information is available on the role of tumor cell TACE activities on TAMs in breast cancer. TACE inhibitors, currently in clinical trials, will certainly affect TAMs and subsequently treatment outcomes based on the substrates it releases. Furthermore, whether targeting a subset of the molecules shed by TACE, specifically those leading to TAMs with altered functions and phenotype, holds greater therapeutic promises than past clinical trials of TACE antagonists' remains to be determined. Here, the potential roles of TACE ectodomain shedding in the breast tumor microenvironment are reviewed with a focus on the release of tumor-derived immunomodulatory factors shed by TACE that directs TAM phenotypes and functions.

Association between ligands and receptors related to the progression of early breast cancer in tumor epithelial and stromal cells

BACKGROUND

Despite advances in the study of breast cancer (BC), it remains the second leading cause of mortality among women. BC is a heterogeneous system, mainly composed of tumor epithelial cells (TEpCs) and stromal cells (SCs); the interaction through the ligands and their receptors (Rs) plays a major role in BC progression. The aim of the present study was to evaluate the association between ligands, such as osteoprotegerin, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), receptor activator of nuclear factor kappa B ligand (RANKL), stromal cell-derived factor (SDF)-1, interleukin (IL)-6, macrophage colony stimulating factor, chemokine (C-C motif) ligand-2 (CCL-2), and their Rs in TEpC and spindle-shaped SCs not closely associated with the vasculature.

PATIENTS AND METHODS

We studied the expression of all those factors in 63 primary tumors of untreated patients with BC with infiltrative ductal carcinoma (I/II stage) and 10 non-neoplastic tissues. The percentage of positive cells and the staining intensity were analyzed by immunohistochemistry. Mann-Whitney test and Spearman's rank correlation coefficient were used (P ≤ .05).

RESULTS

We found a significant association between the expression of RANKL, IL-6, SDF-1, and CCL-2 in TEpC and the receptor activator of nuclear factor kappa B (RANK), IL-6R, C-X-C chemokine R type 4, and chemokine (C-C motif) R-2 (CCR-2) in spindle-shaped SC. The expression of TRAIL, RANKL, and CCL-2 in spindle-shaped SC also was associated with the expression of TRAIL-receptor 1, TRAIL-receptor 4, RANK, and CCR-2 in TEpC.

CONCLUSIONS

Because the described ligands and Rs are implicated in BC progression, our results suggest that these factors could be involved in the crosstalk between TEpC and SC in the early stages of BC.

Tumor self-seeding by circulating tumor cells in nude mouse models of human osteosarcoma and a preliminary study of its mechanisms

PURPOSE

The purpose of this study is to determine whether and how tumor self-seeding by circulating tumor cells (CTCs) plays a role in the initiation and progression of osteosarcoma.

METHODS

Two different nude mouse models of human osteosarcoma were established for detecting tumor self-seeding by fluorescently labeled CTCs. Various tumor growth indicators were quantitated for seeded and unseeded groups. Growth mechanisms were characterized using cell proliferation assays and immunohistochemical staining. Conditioned media of primary osteosarcoma cells was characterized in a Transwell migration assay and enzyme-linked immunosorbent assay. The effect of cytokines secreted by primary tumor cells was verified by small interfering RNA and recombinant human cytokine experiments.

RESULTS

Red fluorescent protein-labeled CTCs seeded primary tumors in both models. Seeded primary tumors groups grew faster than control groups (P < 0.05), which was partially attributed to the CTCs having a higher proliferation rate and higher vascular endothelial growth factor expression after self-seeding. Conditioned media of primary osteosarcoma cells attracted CTCs, through an IL-6-dependent mechanism.

CONCLUSIONS

CTC tumor self-seeding occurs in osteosarcoma and promotes the growth of primary osteosarcoma. CTCs appear to be recruited by cytokines secreted by primary osteosarcoma cells, particularly IL-6.

A review of stem cell translation and potential confounds by cancer stem cells

Mesenchymal stem cells (MSCs) are multipotent cells found in both fetal and adult tissues. MSCs show promise for cellular therapy for several disorders such as those associated with inflammation. In adults, MSCs primarily reside in the bone marrow (BM) and adipose tissues. In BM, MSCs are found at low frequency around blood vessels and trabecula. MSCs are attractive candidates for regenerative medicine given their ease in harvesting and expansion and their unique ability to bypass the immune system in an allogeneic host. Additionally, MSCs exert pathotropism by their ability to migrate to diseased regions. Despite the "attractive" properties of MSCs, their translation to patients requires indepth research. "Off-the-shelf" MSCs are proposed for use in an allogeneic host. Thus, the transplanted MSCs, when placed in a foreign host, could receive cue from the microenvironment for cellular transformation. An important problem with the use of MSCs involves their ability to facilitate the support of breast and other cancers as carcinoma-associated fibroblasts. MSCs could show distinct effect on each subset of cancer cells. This could lead to untoward effect during MSC therapy since the MSCs would be able to interact with undiagnosed cancer cells, which might be in a dormant state. Based on these arguments, further preclinical research is needed to ensure patient safety with MSC therapy. Here, we discuss the basic biology of MSCs, discuss current applications, and provide evidence why it is important to understand MSC biology in the context of diseased microenvironment for safe application.

Crossing the endothelial barrier during metastasis

During metastasis, cancer cells disseminate to other parts of the body by entering the bloodstream in a process that is called intravasation. They then extravasate at metastatic sites by attaching to endothelial cells that line blood vessels and crossing the vessel walls of tissues or organs. This Review describes how cancer cells cross the endothelial barrier during extravasation and how different receptors, signalling pathways and circulating cells such as leukocytes and platelets contribute to this process. Identification of the mechanisms that underlie cancer cell extravasation could lead to the development of new therapies to reduce metastasis.