Chemokine receptors in advanced breast cancer: differential expression in metastatic disease sites with diagnostic and therapeutic implications

New Emerging Chemokine Receptors: CCR5 or CXCR5 on Tumor Is Associated with Poor Response to Chemotherapy and Poor Prognosis in Locally Advanced Triple-Negative Breast Cancer

BACKGROUND

We aim to investigate any possible associations between chemokine receptor expression and responses to neoadjuvant chemotherapy (NAC) along with outcomes in patients with triple-negative breast cancer (TNBC) with locally advanced disease.

METHOD

Expressions of chemokine receptors were examined immunohistochemically after staining archival tissue of surgical specimens (n = 63) using specific antibodies for CCR5, CCR7, CXCR4, and CXCR5.

RESULTS

Patients with high CCR5, CCR7, CXCR4, and CXCR5 expression on tumors and high CXCR4 expression on tumor-infiltrating lymphocytes (TILs) were less likely to have a pathological complete response (pCR) or Class 0-I RCB-Index compared to others. Patients with residual lymph node metastases (ypN-positive), high CCR5TM(tumor), and high CXCR4TM expressions had an increased hazard ratio (HR) compared to others (DFS: HR = 2.655 [1.029-6.852]; DSS: HR = 2.763 [1.008-7.574]), (DFS: HR = 2.036 [0.805-5.148]; DSS: HR = 2.689 [1.020-7.090]), and (DFS: HR = 2.908 [1.080-7.829]; DSS: HR = 2.132 (0.778-5.846)), respectively. However, patients without CXCR5TIL expression had an increased HR compared to those with CXCR5TIL (DFS: 2.838 [1.266-6.362]; DSS: 4.211 [1.770-10.016]).

CONCLUSIONS

High expression of CXCR4TM and CCR5TM was found to be associated with poor prognosis, and CXCR5TM was associated with poor chemotherapy response in the present cohort with locally advanced TNBC. Our results suggest that patients with TNBC could benefit from a chemokine receptor inhibitor therapy containing neoadjuvant chemotherapy protocols.

Evaluation of immune density, PD-L1, and CXCR4 expressions in metaplastic breast carcinoma to predict potential immunotherapy benefit

Metaplastic breast carcinoma (MBC) -rare but fatal subtype of invasive breast carcinomas- provides limited benefit from conventional triple-negative breast carcinoma chemotherapy. We aimed to determine the immune density of this tumor and to evaluate of programmed death-ligand 1 (PD-L1) and chemokine receptor type 4 (CXCR4) expressions to determine whether it would benefit from immunotherapy. Clinicopathological characteristics of 85 patients diagnosed as MBC between 1997 and 2017 were retrospectively assessed. We evaluated the immunohistochemical expression of PD-L1 and CXCR4, and the extent of tumour infiltrating lymphocytes (TILs), with survival data. TILs groups were statistically significantly associated with lymph node status, histological subtype, squamous component, local recurrence and/or systemic metastasis, and disease-related deaths (p < 0.05). PD-L1 positivity in immune cells (ICs) has a statistically significant relationship with the presence of squamous component (p = 0.011) and HER2 positivity (p = 0.031). PD-L1 positivity in tumor cells (TCs) was found to be significantly more frequent in high-TILs density (p = 0.003). PD-L1 combined positive score was significantly associated with the tumors containing high-TILs density (p = 0.012) and squamous component (p = 0.035). Disease-free and disease-specific survival rates were found to be longer for the cases displaying PD-L1 positivity in ICs; and also PD-L1 positivity in ICs was found to be an independent prognostic factor. When the expression of CXCR4 was compared with clinicopathological and survival parameters, no statistically significant association was found (p > 0.05). Based on the results of this retrospective study, PD-L1 and TILs appear to be prognostic. This study provides rationale for further studies to determine whether a subset of patients with metaplastic breast cancer could derive a meaningful benefit from immune-targeting therapies.

Potential therapeutic role for pigment epithelium-derived factor in post-menopausal breast cancer bone metastasis

OBJECTIVES

This review discusses key oestrogens associated with the circulating pre- and post-menopausal milieu and how they may impact intratumoral oestrogen levels and breast cancer (BC) metastasis. It also identifies critical steps in BC metastasis to bone from the viewpoint of pigment epithelium-derived factor (PEDF) function, and discusses the role of several associated pro-metastatic biomarkers in BC bone metastasis.

KEY FINDINGS

PEDF is regulated by oestrogen in a number of oestrogen-sensitive tissues. Changes in circulating oestrogen levels associated with menopause may enhance the growth of BC bone metastases, leading to the establishment of a pre-metastatic niche. The establishment of such a pre-metastatic niche is driven by several key mediators, with pro-osteoclastic and pro-metastatic function which are upregulated by BC cells. These mediators appear to be regulated by oestrogen, as well as differentially affected by menopausal status. PEDF interacts with several pro-metastatic, pro-osteoclastic biomarkers, including C-X-C motif chemokine receptor 4 (CXCR4) and nuclear factor kappa B (NFκB) in BC bone metastasis.

CONCLUSION

Mediators such as CXCR4 and MT1-MMP underpin the ability of PEDF to function as an antimetastatic in other cancers such as osteosarcoma, highlighting the possibility that this serpin could be used as a therapeutic against BC metastasis in future.

Association of chemokine (CXC motif) receptor 4 expression with lymphovascular invasion and lymph node metastasis of invasive breast cancer

BACKGROUND

The histological tumor grade influences the prognosis of breast cancer. In metastatic breast cancer, stromal cells produce chemokine (CXC motif) ligand 12 or stromal cell-derived factor-1 as a chemoattractant, which binds to chemokine (CXC motif) receptor 4 (CXCR4) expressed by breast cancer cells.

OBJECTIVE

This study aimed to determine the expression of CXCR4 in invasive breast cancer in relation to lymphovascular invasion (LVI) and lymph node metastasis.

METHODS

This observational study retrospectively investigated a paraffin block archived sample diagnosed with invasive breast cancer. The results of immunohistochemical staining with CXCR4 antibody and expression analysis were evaluated using light microscopy. The data were statistically analyzed using the chi-square test and presented in a table using SPSS version 18. P-values of <0.05 were considered statistically significant.

RESULTS

The expression of CXCR4 was significantly associated with the incidence of LVI and lymph node metastasis in invasive breast cancer (both p = 0.001).

CONCLUSIONS

The results show that the expression of CXCR4 varies and support its decisive role in the incidence of LVI and lymph node metastasis in invasive breast cancer.

In Early Breast Cancer, the Ratios of Neutrophils, Platelets and Monocytes to Lymphocytes Significantly Correlate with the Presence of Subsets of Circulating Tumor Cells but Not with Disseminated Tumor Cells

Simple Summary

Circulating tumor cells (CTCs) are potential precursors of metastasis and while travelling through the peripheral blood, they crosstalk with different blood cells before a few of them manage to settle down as disseminated tumor cells (DTCs). Little is known about the correlation of blood cells with CTCs/DTCs in early breast cancer (BC). We retrospectively recorded clinical data, results for CTCs, DTCs and blood cell counts from 171 early staged diagnosed BC patients and demonstrated that the presence of epithelial CTCs was related to reduced lymphocyte and monocyte counts, to elevated neutrophil to lymphocyte and platelet to lymphocyte ratios while CTCs in epithelial mesenchymal transition associated with a reduced monocyte to lymphocyte ratio. No significant correlations were found for DTCs, however, DTC-positive patients, harboring a lower platelet to lymphocyte ratio, had a significant shorter overall survival. We confirm that pro-inflammatory markers in blood are closely related to the presence of CTC subtypes, the precursors of metastasis.

Abstract

Circulating tumor cells (CTCs) crosstalk with different blood cells before a few of them settle down as disseminated tumor cells (DTCs). We evaluated the correlation between CTC subtypes, DTCs and the neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR) and monocyte to lymphocyte ratio (MLR) for better prognostication of 171 early staged diagnosed breast cancer (BC) patients. —Clinical data and blood values before treatment were retrospectively recorded, representing the 75% percentile, resulting in 3.13 for NLR, 222.3 for PLR and 0.39 for MLR, respectively. DTCs were analyzed by immunocytochemistry using the pan-cytokeratin antibodyA45-B/B3. CTCs were determined applying the AdnaTests BreastCancerDetect and EMT (Epithelial Mesenchymal Transition) Detect. —Reduced lymphocyte (p = 0.007) and monocyte counts (p = 0.012), an elevated NLR (p = 0.003) and PLR (p = 0.001) significantly correlated with the presence of epithelial CTCs while a reduced MLR was related to EMT-CTCs (p = 0.045). PLR (p = 0.029) and MLR (p = 0.041) significantly related to lymph node involvement and monocyte counts significantly correlated with OS (p = 0.034). No correlations were found for NLR, PLR and MLR with DTCs, however, DTC-positive patients, harboring a lower PLR, had a significant shorter OS (p = 0.043). —Pro-inflammatory markers are closely related to different CTC subsets. This knowledge might improve risk prognostication of these patients.

Breast Cancer Genomics: Primary and Most Common Metastases

Specific genomic alterations have been found in primary breast cancer involving driver mutations that result in tumorigenesis. Metastatic breast cancer, which is uncommon at the time of disease onset, variably impacts patients throughout the course of their disease. Both the molecular profiles and diverse genomic pathways vary in the development and progression of metastatic breast cancer. From the most common metastatic site (bone), to the rare sites such as orbital, gynecologic, or pancreatic metastases, different levels of gene expression indicate the potential involvement of numerous genes in the development and spread of breast cancer. Knowledge of these alterations can, not only help predict future disease, but also lead to advancement in breast cancer treatments. This review discusses the somatic landscape of breast primary and metastatic tumors.

C-C Chemokine Receptor 7 in Cancer

C-C chemokine receptor 7 (CCR7) was one of the first two chemokine receptors that were found to be upregulated in breast cancers. Chemokine receptors promote chemotaxis of cells and tissue organization. Since under homeostatic conditions, CCR7 promotes migration of immune cells to lymph nodes, questions immediately arose regarding the ability of CCR7 to direct migration of cancer cells to lymph nodes. The literature since 2000 was examined to determine to what extent the expression of CCR7 in malignant tumors promoted migration to the lymph nodes. The data indicated that in different cancers, CCR7 plays distinct roles in directing cells to lymph nodes, the skin or to the central nervous system. In certain tumors, it may even serve a protective role. Future studies should focus on defining mechanisms that differentially regulate the unfavorable or beneficial role that CCR7 plays in cancer pathophysiology, to be able to improve outcomes in patients who harbor CCR7-positive cancers.

Investigating CXCR4 expression of tumor cells and the vascular compartment: A multimodal approach

The C-X-C chemokine receptor 4 (CXCR4) is G protein-coupled receptor that upon binding to its cognate ligand, can lead to tumor progression. Several CXCR4-targeted therapies are currently under investigation, and with it comes the need for imaging agents capable of accurate depiction of CXCR4 for therapeutic stratification and monitoring. PET agents enjoy the most success, but more cost-effective and radiation-free approaches such as ultrasound (US) imaging could represent an attractive alternative. In this work, we developed a targeted microbubble (MB) for imaging of vascular CXCR4 expression in cancer. A CXCR4-targeted MB was developed through incorporation of the T140 peptide into the MB shell. Binding properties of the T140-MB and control, non-targeted MB (NT-MB) were evaluated in MDA-MB-231 cells where CXCR4 expression was knocked-down (via shRNA) through optical imaging, and in the lymphoma tumor models U2932 and SuDHL8 (high and low CXCR4 expression, respectively) by US imaging. PET imaging of [18F]MCFB, a tumor-penetrating CXCR4-targeted small molecule, was used to provide whole-tumor CXCR4 readouts. CXCR4 expression and microvessel density were performed by immunohistochemistry analysis and western blot. T140-MB were formed with similar properties to NT-MB and accumulated sensitively and specifically in cells according to their CXCR4 expression. In NOD SCID mice, T140-MB persisted longer in tumors than NT-MB, indicative of target interaction, but showed no difference between U2932 and SuDHL8. In contrast, PET imaging with [18F]MCFB showed a marked difference in tumor uptake at 40-60 min post-injection between the two tumor models (p<0.05). Ex vivo analysis revealed that the large differences in CXCR4 expression between the two models are not reflected in the vascular compartment, where the MB are restricted; in fact, microvessel density and CXCR4 expression in the vasculature was comparable between U2932 and SuDHL8 tumors. In conclusion, we successfully developed a T140-MB that can be used for imaging CXCR4 expression in the tumor vasculature.

Contribution of Heparan Sulphate Binding in CCL21-Mediated Migration of Breast Cancer Cells

Simple Summary

Breast cancer is a leading cause of cancer-related deaths worldwide, predominantly caused by metastasis. Chemokine receptor CCR7 and its ligand CCL21 are implicated in the metastasis of breast cancer to the lymph nodes. Chemokine function is dependent upon binding to their specific chemokine receptors and negatively charged molecules on the cell surface (heparan sulphate). The role of heparan sulphate in CCR7-mediated lymph node metastasis was investigated by creating a non-heparan sulphate binding mutant chemokine CCL21. Mutant-CCL21 was tested in vitro in a range of assays, including cell migration, calcium flux and surface plasmon resonance spectroscopy. Mutant-CCL21 induced leukocyte chemotaxis in diffusion gradients but did not stimulate trans-endothelial migration of breast cancer cells. A murine model was used to assess the potential of mutant-CCL21 to prevent lymph node metastasis in vivo. Lymph node metastasis was significantly reduced by the administration of mutant-CCL21 compared to the control. Targeting chemokine–heparan sulphate interactions may be a promising approach to inhibit chemokine activity and metastasis.

Abstract

Chemokine receptor CCR7 is implicated in the metastasis of breast cancer to the lymph nodes. Chemokine function is dependent upon their binding to both cell-surface heparan sulphate (HS) and to their specific receptors; thus, the role of HS in CCR7-mediated lymph node metastasis was investigated by creating a non-HS binding chemokine CCL21 (mut-CCL21). Mut-CCL21 (Δ103–134) induced leukocyte chemotaxis in diffusion gradients but did not stimulate trans-endothelial migration of PBMCs (p < 0.001) and 4T1-Luc cells (p < 0.01). Furthermore, the effect of heparin and HS on the chemotactic properties of wild-type (WT) and mut-CCL21 was examined. Interestingly, heparin and HS completely inhibit the chemotaxis mediated by WT-CCL21 at 250 and 500 µg/mL, whereas minimal effect was seen with mut-CCL21. This difference could potentially be attributed to reduced HS binding, as surface plasmon resonance spectroscopy showed that mut-CCL21 did not significantly bind HS compared to WT-CCL21. A murine model was used to assess the potential of mut-CCL21 to prevent lymph node metastasis in vivo. Mice were injected with 4T1-Luc cells in the mammary fat pad and treated daily for a week with 20 µg mut-CCL21. Mice were imaged weekly with IVIS and sacrificed on day 18. Luciferase expression was significantly reduced in lymph nodes from mice that had been treated with mut-CCL21 compared to the control (p = 0.0148), suggesting the potential to target chemokine binding to HS as a therapeutic option.

At the Bench: Pre-clinical evidence for multiple functions of CXCR4 in cancer

Signaling through chemokine receptor, C-X-C chemokine receptor type 4 (CXCR4) regulates essential processes in normal physiology, including embryogenesis, tissue repair, angiogenesis, and trafficking of immune cells. Tumors co-opt many of these fundamental processes to directly stimulate proliferation, invasion, and metastasis of cancer cells. CXCR4 signaling contributes to critical functions of stromal cells in cancer, including angiogenesis and multiple cell types in the tumor immune environment. Studies in animal models of several different types of cancers consistently demonstrate essential functions of CXCR4 in tumor initiation, local invasion, and metastasis to lymph nodes and distant organs. Data from animal models support clinical observations showing that integrated effects of CXCR4 on cancer and stromal cells correlate with metastasis and overall poor prognosis in >20 different human malignancies. Small molecules, Abs, and peptidic agents have shown anticancer efficacy in animal models, sparking ongoing efforts at clinical translation for cancer therapy. Investigators also are developing companion CXCR4-targeted imaging agents with potential to stratify patients for CXCR4-targeted therapy and monitor treatment efficacy. Here, pre-clinical studies demonstrating functions of CXCR4 in cancer are reviewed.

Stromal Cell-Derived Factor 1α (SDF-1α) in Invasive Breast Cancer: Associations with Vasculo-Angiogenic Factors and Prognostic Significance

(1) Background: Tumour angiogenesis is critical for the progression of neoplasms. A prospective study was designed to examine the utility of stromal cell-derived factor 1α (SDF-1α) and selected vasculo-angiogenic parameters for estimating the probability of disease relapse in 84 primary, operable invasive breast cancer (IBrC) patients (40 (48%) with stage IA and 44 (52%) with stage IIA and IIB). (2) Methods: We explored the prognostic value of the plasma levels of SDF-1α, vascular endothelial growth factor A (VEGF-A), the soluble forms of VEGF receptors type 1 and 2, and the number of circulating endothelial progenitor cells (circulating EPCs) in breast cancer patients. The median follow-up duration was 58 months, with complete follow-up for the first event. (3) Results: According to ROC curve analysis, the optimal cut-off point for SDF-1α (for discriminating between patients at high and low risk of relapse) was 42 pg/mL, providing 57% sensitivity and 75% specificity. Kaplan-Meier curves for disease-free survival (DFS) showed that concentrations of SDF-1α lower than 42 pg/dL together with a VEGFR1 lower than 29.86 pg/mL were significantly associated with shorter DFS in IBrC patients (p = 0.0381). Patients with both SDF-1α lower than 42 pg/dL and a number of circulating EPCs lower than 9.68 cells/µL had significantly shorter DFS (p = 0.0138). (4) Conclusions: Our results imply the clinical usefulness of SDF-1α, sVEGFR1 and the number of circulating EPCs as prognostic markers for breast cancer in clinical settings.

Cytoplasmic CCR7 (CCR7c) immunoexpression is associated with local tumor recurrence in triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is a subtype of cancer, which tests negative for estrogen receptors, progesterone receptors, and lacks overexpression of the human epidermal growth factor 2 (C-erbB2, HER2/neu) gene. The expression of chemokines and their receptors, including CCR7, has been described in several types of cancer, contributing to tumor progression.

AIM OF THE STUDY

This study investigated the association between the membrane and cytoplasmic CCR7 expression and the prognosis of TNBC.

MATERIALS AND METHODS

Surgical paraffin histopathology blocks and clinico-pathological data were assessed from 133 patients. Samples were analyzed by immunohistochemistry and immunofluorescence using the Tissue Microarray technique for scoring the intensity of CCR7 expression.

RESULTS

TNBC patients in which the CCR7 labeling was predominantly in the cytoplasm of tumor cells presented increased local tumor recurrence (P = 0.033). Conversely, there was no statistical difference in five-year overall survival between the patients with low (77%) versus high (80%) cytoplasmic CCR7 expression (P = 0.7104). Additionally, the risk of death between these groups was 1.19 (95% CI = 0.48-2.91).

CONCLUSION

The cytoplasmic CCR7 expression associates with an increased incidence of tumor relapse in TNBC, not affecting patients survival. Consequently, the cell compartment in which the CCR7 localizes could serve as a prognostic marker in this cancer subtype.

Molecular insights and novel approaches for targeting tumor metastasis

In recent years, due to the effective drug delivery and preciseness of tumor sites or microenvironment, the targeted drug delivery approaches have gained ample attention for tumor metastasis therapy. The conventional treatment approaches for metastasis therapy have reported with immense adverse effects because they exhibited maximum probability of killing the carcinogenic cells along with healthy cells. The tumor vasculature, comprising of vasculogenic impressions and angiogenesis, greatly depends upon the growth and metastasis in the tumors. Therefore, various nanocarriers-based delivery approaches for targeting to tumor vasculature have been attempted as efficient and potential approaches for the treatment of tumor metastasis and the associated lesions. Furthermore, the targeted drug delivery approaches have found to be most apt way to overcome from all the limitations and adverse effects associated with the conventional therapies. In this review, various approaches for efficient targeting of pharmacologically active chemotherapeutics against tumor metastasis with the cohesive objectives of prognosis, tracking and therapy are summarized.

64Cu-Labeled Ubiquitin for PET Imaging of CXCR4 Expression in Mouse Breast Tumor

Ubiquitin has been recently identified as a chemokine receptor 4 (CXCR4) natural ligand, offering great potential for positron emission computed tomography (PET) imaging of CXCR4 expression. This study reports the preparation and evaluation of (64Cu)-radiolabeled ubiquitin for CXCR4 imaging. The ubiquitin was first fused with a C-terminal GGCGG sequence, and the resulting recombinant ubiquitin derivative UbCG4 was then functionalized with the trans-cyclooctene (TCO) moiety via thiol-maleimide click reaction, followed by 64Cu-radiolabeling through the TCO/Tz (tetrazine)-based Diels-Alder click reaction. In the prepared in vitro studies, the prepared (64Cu)-UbCG4 showed significantly higher specific uptakes in the 4T1 breast cancer cells compared with the uptakes in the CXCR4-knockdown 4T1 cells. In the in vivo evaluation in the 4T1-xenograft mouse model, (64Cu)-UbCG4 demonstrated a similar tumor uptake but much lower backgrounds compared with 64Cu-labeled AMD3465. These results suggested that (64Cu)-UbCG4 could serve as a potent PET tracer for the noninvasive imaging of CXCR4 expression in tumors.

Receptor Conversion in Distant Breast Cancer Metastases: A Systematic Review and Meta-analysis

Background

In metastatic breast cancer, hormone and/or human epidermal growth factor receptor 2 (HER2)-targeted therapy decision-making is still largely based on tissue characteristics of the primary tumor. However, a change of estrogen receptor alpha (ERα), progesterone receptor (PR), and HER2 status in distant metastases has frequently been reported. The actual incidence of this phenomenon has been debated.

Methods

We performed a meta-analysis including 39 studies assessing receptor conversion from primary breast tumors to paired distant breast cancer metastases. We noted the direction of change (positive to negative or vice versa) and performed subgroup analyses for different thresholds for positivity, the type of test used to assess HER2 receptor status, and metastasis location-specific differences (two-sided tests).

Results

Overall, the incidence of receptor conversion varied largely between studies. For ERα, PR, and HER2, we found that random effects pooled positive to negative conversion percentages of 22.5% (95% confidence interval [CI] = 16.4% to 30.0%), 49.4% (95% CI = 40.5% to 58.2%), and 21.3% (95% CI = 14.3% to 30.5%), respectively. Negative to positive conversion percentages were 21.5% (95% CI = 18.1% to 25.5%), 15.9% (95% CI = 11.3% to 22.0%), and 9.5% (95% CI = 7.4% to 12.1%). Furthermore, ERα discordance was statistically significantly higher in the central nervous system and bone compared with liver metastases (20.8%, 95% CI = 15.0% to 28.0%, and 29.3%, 95% CI = 13.0% to 53.5%, vs 14.3%, 95% CI = 11.3% to 18.1, P = .008 and P < .001, respectively), and PR discordance was higher in bone (42.7%, 95% CI = 35.1% to 50.6%, P < .001) and liver metastases (47.0%, 95% CI = 41.0% to 53.0%, P < .001) compared with central nervous system metastases (23.3%, 95% CI = 16.0% to 32.6%).

Conclusions

Receptor conversion for ERα, PR, and HER2 occurs frequently in the course of disease progression in breast cancer. Large prospective studies assessing the impact of receptor conversion on treatment efficacy and survival are needed. Meanwhile, reassessing receptor status in metastases is strongly encouraged.

Bone Metastasis of Breast Cancer

Bone is the most common site of metastasis for breast cancer. Bone metastasis significantly affects both quality of life and survival of the breast cancer patient. Clinically, complications secondary to bone metastasis include pain, pathologic fractures, spinal cord compression, and hypercalcemia of malignancy. Because bone metastasis is extremely common in patients with metastatic breast cancer, clinical management of bone metastases is an important and challenging aspect of treatment in the metastatic setting.The skeleton is a metabolically active organ system that undergoes continuous remodeling throughout life. A delicate balance of the bone-forming osteoblasts and bone-resorbing osteoclasts in the dynamic microenvironment of the skeleton maintains normal bone remodeling and integrity. The presence of metastatic lesions in bone disrupts the normal bone microenvironment and upsets the fine balance between the key components. The changes in the bone microenvironment then create a vicious cycle that further promotes bone destruction and tumor progression.Various therapeutic options are available for bone metastases of breast cancer. Treatment can be tailored for each patient and, often requires multiple therapeutic interventions. Commonly used modalities include local therapies such as surgery, radiation therapy and radiofrequency ablation (RFA) together with systemic therapies such as endocrine therapy, chemotherapy, monoclonal antibody-based therapy, bone-enhancing therapy and radioisotope therapy. Despite the use of various therapeutic modalities, bone metastases eventually become resistant to therapy, and disease progresses.In this chapter, we describe the clinical picture and biological mechanism of bone metastases in breast cancer. We also discuss known risk factors as well as detection and assessment of bone metastases. We present therapeutic options for bone metastasis using a multidisciplinary approach. Further, we describe future directions for bone metastasis management, focusing on novel bone-specific targeted therapies.

The Interplay between Circulating Tumor Cells and the Immune System: From Immune Escape to Cancer Immunotherapy

Circulating tumor cells (CTCs) have aroused increasing interest not only in mechanistic studies of metastasis, but also for translational applications, such as patient monitoring, treatment choice, and treatment change due to tumor resistance. In this review, we will assess the state of the art about the study of the interactions between CTCs and the immune system. We intend to analyze the impact that the cells of the immune system have in limiting or promoting the metastatic capability of CTCs. To this purpose, we will examine studies that correlate CTCs, immune cells, and patient prognosis, and we will also discuss relevant animal models that have contributed to the understanding of the mechanisms of immune-mediated metastasis. We will then consider some studies in which CTCs seem to play a promising role in monitoring cancer patients during immunotherapy regimens. We believe that, from an accurate and profound knowledge of the interactions between CTCs and the immune system, new immunotherapeutic strategies against cancer might emerge in the future.

A fully human CXCR4 antibody demonstrates diagnostic utility and therapeutic efficacy in solid tumor xenografts

For physiologically important cancer therapeutic targets, use of non-invasive imaging for therapeutic guidance and monitoring may improve outcomes for treated patients. The CXC chemokine receptor 4 (CXCR4) is overexpressed in many cancers including non-small cell lung cancer (NSCLC) and triple negative breast cancer (TNBC). CXCR4 overexpression contributes to tumor growth, progression and metastasis. There are several CXCR4-targeted therapeutic agents currently in clinical trials. Since CXCR4 is also crucial for normal biological functions, its prolonged inhibition could lead to unwanted toxicities. While CXCR4-targeted imaging agents and inhibitors have been reported and evaluated independently, there are currently no studies demonstrating CXCR4-targeted imaging for therapeutic guidance.

Monoclonal antibodies (mAbs) are commonly used for cancer therapy and imaging. Here, an ⁸⁹Zr-labeled human CXCR4-mAb (⁸⁹Zr-CXCR4-mAb) was evaluated for detection of CXCR4 expression with positron emission tomography (PET) while its native unmodified analogue was evaluated for therapy in relevant models of NSCLC and TNBC. In vitro and in vivo evaluation of ⁸⁹Zr-CXCR4-mAb showed enhanced uptake in NSCLC xenografts with a high expression of CXCR4. It also had the ability to detect lymph node metastases in an experimental model of metastatic TNBC. Treatment of high and low CXCR4 expressing NSCLC and TNBC xenografts with CXCR4-mAb demonstrated a therapeutic response correlating with the expression of CXCR4. Considering the key role of CXCR4 in normal biological functions, our results suggest that combination of ⁸⁹Zr-CXCR4-mAb-PET with non-radiolabeled mAb therapy may provide a precision medicine approach for selecting patients with tumors that are likely to be responsive to this treatment.

Emerging roles of the CXCL12/CXCR4 axis in pancreatic cancer progression and therapy

Chemokine networks regulate a variety of cellular, physiological, and immune processes. These normal functions can become appropriated by cancer cells to facilitate a more hospitable niche for aberrant cells by enhancing growth, proliferation, and metastasis. This is especially true in pancreatic cancer, where chemokine signaling is a vital component in the development of the supportive tumor microenvironment and the signaling between the cancer cells and surrounding stromal cells. Although expression patterns vary among cancer types, the chemokine receptor CXCR4 has been implicated in nearly every major malignancy and plays a prominent role in pancreatic cancer development and progression. This receptor, in conjunction with its primary chemokine ligand CXCL12, promotes pancreatic cancer development, invasion, and metastasis through the management of the tumor microenvironment via complex crosstalk with other pathways. Thus, CXCR4 likely contributes to the poor prognoses observed in patients afflicted with this malignancy. Recent exploration of combination therapies with CXCR4 antagonists have demonstrated improved outcomes, and abolishing the contribution of this pathway may prove crucial to effectively treat pancreatic cancer at both the primary tumor and metastases.

Bone metastasis-related signaling pathways in breast cancers stratified by estrogen receptor status

Background: Breast cancer bone metastasis (BCBM)-specific genes have been reported without considering biological differences based on estrogen receptor (ER) status. The aims of this study were to identify BCBM-specific genes using our patient dataset and validate previously reported BCBM-specific genes, and to determine whether ER-status-related biological differences matter in identification of BCBM-specific genes.

Methods: We used Affymetrix GeneChips to analyze 365 primary human epidermal growth factor receptor 2 (HER2)-negative invasive breast cancer specimens. Genes that were differentially expressed between patients who developed bone metastasis and those who developed non-bone metastasis were identified using Cox proportional hazards model, and differential expression of gene sets was assessed using gene set analysis. We performed gene set analysis to determine whether biological function associated with bone metastasis were different by ER status using 2,246 functionally annotated gene sets assembled from Gene Ontology data base.

Results: Among 16,712 probe sets, 592 were overexpressed in the bone metastasis cohort compared to the non-bone-metastasis cohort (false discovery rate ≤ 0.05). However, no BCBM-specific genes met our significance tests when the cancers were stratified by ER status. In ER-positive and ER-negative breast cancers, 151 and 125 gene sets, respectively, were overexpressed for BCBM and the majority of BCBM-related pathways were different. Of significant gene sets, only 13 gene sets were overlapped between ER-positive and -negative cohorts.

Conclusion: ER-positive and ER-negative breast cancers have different biological pathways in BCBM development. We have yet to explore BCBM-related biomarkers and targets considering the biological features associated with BCBM depending on the ER status.

Chemokine (C-C motif) receptor 7 (CCR7) associates with the tumour immune microenvironment but not progression in invasive breast carcinoma

Some previous studies have reported that the chemokine (C‐C motif) receptor 7 (CCR7) plays a role in breast cancer, is associated with lymph node metastasis and drives the site of distant metastasis. However, the impact of its expression on patient outcome and its association with tumour infiltrating inflammatory cells remain to be validated. We evaluated CCR7 protein expression by immunohistochemistry in a large well characterized cohort (n = 866) of early invasive primary breast cancers. CCR7 was expressed in the cytoplasm and membrane of tumour cells. We observed a weak positive association of high CCR7 expression when in either cellular component, but not both together, with axillary lymph node stage 3 tumours (p = 0.043). Logistic regression analysis of lymph node stage revealed no independent predictive value for CCR7 expression. CCR7 expression was higher in HER2 positive tumours (p = 0.03) and associated with positive CD68+ FOXP3+ tumour infiltrating cells. CCR7 staining was negatively associated with CD3+ cells. There was no significant association of CCR7 expression with breast cancer recurrence or survival. We conclude that while CCR7 is not a useful biomarker for predicting lymph node metastasis, it may reflect altered intra‐ and inter‐cellular signalling related to the immune microenvironment. The subcellular localization of CCR7 appears to affect the nature of these interactions.

CCL18 from tumor-cells promotes epithelial ovarian cancer metastasis via mTOR signaling pathway

CCL18 is a chemotactic cytokine involved in the pathogenesis and progression of various disorders, including cancer. Previously, our results showed high levels of CCL18 in the serum of epithelial ovarian carcinoma patients suggesting its potential as a circulating biomarker. In this study, we determined that CCL18 expression was up-regulated in ovarian carcinoma compared with adjacent tissue and was expressed in carcinoma cells in the tumor and not in normal ovarian epithelial cells by laser capture microdissection coupled with real-time RT-PCR. Moreover, correlation analysis showed that the CCL18 level was positively correlated with the metastasis of patients with ovarian cancer. Survival analysis also revealed that an increased level of CCL18 was associated with worse survival time in ovarian cancer patients. Over-expression of CCL18 led to enhanced migration and invasion of the Skov3 ovarian cancer cell line in vitro and in vivo. Finally, proteomics analysis demonstrated that CCL18-mediated ovarian cancer invasiveness was strongly correlated with the mTORC2 pathway. These findings suggest that the CCL18 chemokine has an important role in chemokine-mediated tumor metastasis, and may serve as a potential predictor for poor survival outcomes for ovarian cancer. © 2015 The Authors. Molecular Carcinogenesis published by Wiley Periodicals, Inc.

Chemokine axes in breast cancer: factors of the tumor microenvironment reshape the CCR7-driven metastatic spread of luminal-A breast tumors

Chemokine axes have been shown to mediate site-specific metastasis in breast cancer, but their relevance to different subtypes has been hardly addressed. Here, with the focus on the CCR7-CCL21 axis, patient datasets demonstrated that luminal-A tumors express relatively low CCR7 levels compared with more aggressive disease subtypes. Furthermore, lymph node metastasis was not associated with high CCR7 levels in luminal-A patients. The metastatic pattern of luminal-A breast tumors may be influenced by the way luminal-A tumor cells interpret signals provided by factors of the primary tumor microenvironment. Thus, CCR7-expressing human luminal-A cells were stimulated simultaneously by factors representing 3 tumor microenvironment arms typical of luminal-A tumors, hormonal, inflammatory, and growth stimulating: estrogen + TNF-α + epidermal growth factor. Such tumor microenvironment stimulation down-regulated the migration of CCR7-expressing tumor cells toward CCL21 and inhibited the formation of directional protrusions toward CCL21 in a novel 3-dimensional hydrogel system. CCL21-induced migration of CCR7-expressing tumor cells depended on PI3K and MAPK activation; however, when CCR7-expressing cancer cells were prestimulated by tumor microenvironment factors, CCL21 could not effectively activate these signaling pathways. In vivo, pre-exposure of the tumor cells to tumor microenvironment factors has put restraints on CCL21-mediated lymph node-homing cues and shifted the metastatic pattern of CCR7-expressing cells to the aggressive phenotype of dissemination to bones. Several of the aspects were also studied in the CXCR4-CXCL12 system, demonstrating similar patient and in vitro findings. Thus, we provide novel evidence to subtype-specific regulation of the CCR7-CCL21 axis, with more general implications to chemokine-dependent patterns of metastatic spread, revealing differential regulation in the luminal-A subtype.

CXCR4-SDF-1 interaction potentially mediates trafficking of circulating tumor cells in primary breast cancer

Background

Cytokines are involved in cancer invasion and metastasis. Circulating tumor cells (CTCs) play key role in tumor dissemination and are an independent survival predictor in breast cancer patients. The aim of this study was to assess correlation between CTCs and plasma cytokines in primary breast cancer (PBC) patients.

Methods

This study included 147 chemotherapy naïve PBC patients. Peripheral blood mononuclear cells (PBMC) were depleted of hematopoetic cells using RossetteSep™ negative selection kit. RNA extracted from CD45-depleted PBMC was interrogated for expression of EMT (Twist1, Snail1, Slug, Zeb1) and epithelial (Ck19) gene transcripts by qRT-PCR. The concentrations of 51 plasma cytokines were measured using multiplex bead arrays.

Results

CTCs were detected in 25.2 % patients. CTCs exhibiting only epithelial markers (CTC_EP) and only EMT markers (CTC_EMT) were present evenly in 11.6 % patients, while CTCs co-expressing both markers were detected in 2.0 % patients. Patients with presence of CTC_EP in peripheral blood had significantly elevated levels of plasma IFN-α2, IL-3, MCP-3, β-NGF, SCF, SCGF-β, TNF-β and SDF-1 compared to patients without CTC_EP. CTC_EP exhibited overexpression of SDF-1 receptor and CXCR4, but not other corresponding cytokine receptor, and in multivariate analysis SDF-1 was independently associated with CTC_EP. There was an inverse correlation between CTC_EMT and plasma cytokines CTACK, β-NGF and TRAIL, while presence of either subtype of CTCs was associated with increased level of TGF-β2.

Conclusion

Using cytokine profiling, we identified cytokines associated with CTCs subpopulations in peripheral blood of PBC. Our data suggest that CXCR4-SDF-1 axis is involved in mobilization and trafficking of epithelial CTCs.

Emerging nanomedicine approaches fighting tumor metastasis: animal models, metastasis-targeted drug delivery, phototherapy, and immunotherapy

Nanomedicine approaches may bring new opportunities for tumor metastasis treatment.

MSN anti-cancer nanomedicines: chemotherapy enhancement, overcoming of drug resistance, and metastasis inhibition

In the anti-cancer war, there are three main obstacles resulting in high mortality and recurrence rate of cancers: the severe toxic side effect of anti-cancer drugs to normal tissues due to the lack of tumor-selectivity, the multi-drug resistance (MDR) to free chemotherapeutic drugs and the deadly metastases of cancer cells. The development of state-of-art nanomedicines based on mesoporous silica nanoparticles (MSNs) is expected to overcome the above three main obstacles. In the view of the fast development of anti-cancer strategy, this review highlights the most recent advances of MSN anti-cancer nanomedicines in enhancing chemotherapeutic efficacy, overcoming the MDR and inhibiting metastasis. Furthermore, we give an outlook of the future development of MSNs-based anti-cancer nanomedicines, and propose several innovative and forward-looking anti-cancer strategies, including tumor tissue-cell-nuclear successionally targeted drug delivery strategy, tumor cell-selective nuclear-targeted drug delivery strategy, multi-targeting and multi-drug strategy, chemo-/radio-/photodynamic-/ultrasound-/thermo-combined multi-modal therapy by virtue of functionalized hollow/rattle-structured MSNs.

A radiogallium-DOTA-based bivalent peptidic ligand targeting a chemokine receptor, CXCR4, for tumor imaging

We have developed a novel radiogallium (Ga)-DOTA-based bivalent peptidic ligand targeting a chemokine receptor, CXCR4, for tumor imaging. A CXCR4 imaging probe with two CXCR4 antagonists (Ac-TZ14011) on Ga-DOTA core, Ga-DOTA-TZ2, was synthesized, and the affinity and binding to CXCR4 was evaluated in CXCR4 expressing cells in vitro. The affinity of Ga-DOTA-TZ2 for CXCR4 was 20-fold greater than the corresponding monovalent probe, Ga-DOTA-TZ1. (67)Ga-DOTA-TZ2 showed the significantly higher accumulation in CXCR4-expressing tumor cells compared with (67)Ga-DOTA-TZ1, suggesting the bivalent effect enhances its binding to CXCR4. The incorporation of two CXCR4 antagonists to Ga-DOTA could be effective in detecting CXCR4-expressing tumors.

Liver resections of isolated liver metastasis in breast cancer: results and possible prognostic factors

Background. Breast cancer liver metastasis is a hematogenous spread of the primary tumour. It can, however, be the expression of an isolated recurrence. Surgical resection is often possible but controversial. Methods. We report on 29 female patients treated operatively due to isolated breast cancer liver metastasis over a period of six years. Prior to surgery all metastases appeared resectable. Liver metastasis had been diagnosed 55 (median, range 1–177) months after primary surgery. Results. Complete resection of the metastases was performed in 21 cases. The intraoperative staging did not confirm the preoperative radiological findings in 14 cases, which did not generally lead to inoperability. One-year survival rate was 86% in resected patients and 37.5% in nonresected patients. Significant prognostic factors were R0 resection, low T- and N-stages as well as a low-grade histopathology of the primary tumour, lower number of liver metastases, and a longer time interval between primary surgery and the occurrence of liver metastasis. Conclusions. Complete resection of metastases was possible in three-quarters of the patients. Some of the studied factors showed a prognostic value and therefore might influence indication for resection in the future.

Bioinformatics analysis of breast cancer bone metastasis related gene-CXCR4

OBJECTIVE

To analyze breast cancer bone metastasis related gene-CXCR4.

METHODS

This research screened breast cancer bone metastasis related genes by high-flux gene chip.

RESULTS

It was found that the expressions of 396 genes were different including 165 up-regulations and 231 down-regulations. The expression of chemokine receptor CXCR4 was obviously up-regulated in the tissue with breast cancer bone metastasis. Compared with the tissue without bone metastasis, there was significant difference, which indicated that CXCR4 played a vital role in breast cancer bone metastasis.

CONCLUSIONS

The bioinformatics analysis of CXCR4 can provide a certain basis for the occurrence and diagnosis of breast cancer bone metastasis, target gene therapy and evaluation of prognosis.

The potential of hypoxia markers as target for breast molecular imaging--a systematic review and meta-analysis of human marker expression

Background

Molecular imaging of breast cancer is a promising emerging technology, potentially able to improve clinical care. Valid imaging targets for molecular imaging tracer development are membrane-bound hypoxia-related proteins, expressed when tumor growth outpaces neo-angiogenesis. We performed a systematic literature review and meta-analysis of such hypoxia marker expression rates in human breast cancer to evaluate their potential as clinically relevant molecular imaging targets.

Methods

We searched MEDLINE and EMBASE for articles describing membrane-bound proteins that are related to hypoxia inducible factor 1α (HIF-1α), the key regulator of the hypoxia response. We extracted expression rates of carbonic anhydrase-IX (CAIX), glucose transporter-1 (GLUT1), C-X-C chemokine receptor type-4 (CXCR4), or insulin-like growth factor-1 receptor (IGF1R) in human breast disease, evaluated by immunohistochemistry. We pooled study results using random-effects models and applied meta-regression to identify associations with clinicopathological variables.

Results

Of 1,705 identified articles, 117 matched our selection criteria, totaling 30,216 immunohistochemistry results. We found substantial between-study variability in expression rates. Invasive cancer showed pooled expression rates of 35% for CAIX (95% confidence interval (CI): 26-46%), 51% for GLUT1 (CI: 40-61%), 46% for CXCR4 (CI: 33-59%), and 46% for IGF1R (CI: 35-70%). Expression rates increased with tumor grade for GLUT1, CAIX, and CXCR4 (all p < 0.001), but decreased for IGF1R (p < 0.001). GLUT1 showed the highest expression rate in grade III cancers with 58% (45-69%). CXCR4 showed the highest expression rate in small T1 tumors with 48% (CI: 28-69%), but associations with size were only significant for CAIX (p < 0.001; positive association) and IGF1R (p = 0.047; negative association). Although based on few studies, CAIX, GLUT1, and CXCR4 showed profound lower expression rates in normal breast tissue and benign breast disease (p < 0.001), and high rates in carcinoma in situ. Invasive lobular carcinoma consistently showed lower expression rates (p < 0.001).

Conclusions

Our results support the potential of hypoxia-related markers as breast cancer molecular imaging targets. Although specificity is promising, combining targets would be necessary for optimal sensitivity. These data could help guide the choice of imaging targets for tracer development depending on the envisioned clinical application.

Bone Targeted Therapies for Bone Metastasis in Breast Cancer

Cancer metastasis to the bone develops commonly in patients with various malignancies, and is a major cause of morbidity and diminished quality of life in many affected patients. Emerging treatments for metastatic bone disease have arisen from advances in our understanding of the unique cellular and molecular mechanisms that contribute to the bone metastasis. The tendency of cancer cells to metastasize to bone is probably the end result of many factors including vascular pathways, the highly vascular nature of the bone marrow (which increases the probability that cancer cells will be deposited in bone marrow capillaries), and molecular characteristics of the cancer cells that allow them to adapt to the bone marrow microenvironment. The goals of treating osseous metastases are manifold. Proper treatment can lead to significant improvements in pain control and function, and maintain skeletal integrity. The treatment plan requires a multidisciplinary approach. Widespread metastatic disease necessitates systemic therapy, while a localized problem is best managed with surgery, external beam radiotherapy, or both. Patients with bone metastasis can have prolonged survival, and proper management can have a significant impact on their quality of life. We will review the factors in this article that are promising molecular bone-targeted therapies or will be likely targets for future therapeutic intervention to restore bone remodeling and suppress tumor growth.

The HER2 amplicon in breast cancer: Topoisomerase IIA and beyond

HER2 gene amplification is observed in about 15% of breast cancers. The subgroup of HER2-positive breast cancers appears to be heterogeneous and presents complex patterns of gene amplification at the locus on chromosome 17q12-21. The molecular variations within the chromosome 17q amplicon and their clinical implications remain largely unknown. Besides the well-known TOP2A gene encoding Topoisomerase IIA, other genes might also be amplified and could play functional roles in breast cancer development and progression. This review will focus on the current knowledge concerning the HER2 amplicon heterogeneity, its clinical and biological impact and the pitfalls associated with the evaluation of gene amplifications at this locus, with particular attention to TOP2A and the link between TOP2A and anthracycline benefit. In addition it will discuss the clinical and biological implications of the amplification of ten other genes at this locus (MED1, STARD3, GRB7, THRA, RARA, IGFPB4, CCR7, KRT20, KRT19 and GAST) in breast cancer.

Halting metastasis through CXCR4 inhibition

Metastasis occurs when cancer cells leave the primary tumor site and migrate to distant parts of the body. The CXCR4-SDF-1 pathway facilitates this migration, and its expression has become the hallmark of several metastatic cancers. Targeted approaches are currently being developed to inhibit this pathway, and several candidates are now in clinical trials. Continued exploration of CXCR4 inhibitors will generate compounds that have improved activity over current candidates.

Assessing HER2 amplification in breast cancer: findings from the Australian In Situ Hybridization Program

In August 2006, the Australian government approved subsidized trastuzumab therapy for human epidermal growth factor receptor 2 (HER2)-positive early breast cancer, and it was mandated that HER2 testing should be performed using in situ hybridization (ISH) rather than immunohistochemistry (IHC). Here we review results of the first regulated, nationwide program to provide HER2 ISH testing for all newly diagnosed breast cancer patients, with a particular emphasis on cases where IHC and ISH results were discordant. Data from all laboratories participating in the program were collated. Cases with an equivocal ISH test result [by chromogenic ISH (CISH) or silver ISH (SISH)] were tested centrally by fluorescence ISH. Most laboratories also performed HER2 IHC, and 200 cases with discordant IHC and ISH results were selected for further analysis in a central laboratory. A total of 26 laboratories were involved and 53,402 tests were reported. Over a 4-year period the HER2 positivity rate decreased for primary cancers from 23.8 to 14.6 %, but remained relatively constant for samples from metastases. Average ISH reporting times were <5 days for all yearly reporting periods. Test-repeat rates decreased for CISH (8.9-3.6 %) and SISH (13.7-8.4 %). Only 12 of 196 cases remained discordant after retesting in a central laboratory. These findings demonstrate the successful implementation of a regulated, national program that continues to collect data on HER2 status. The results also highlight the differences in IHC interpretation between local laboratories and a central, more experienced, laboratory. This model could be used to establish future biomarker-testing programs in other countries.

Imaging agents for the chemokine receptor 4 (CXCR4)

The interaction between the chemokine receptor 4 (CXCR4) and stromal cell-derived factor-1 (SDF-1, also known as CXCL12) is a natural regulatory process in the human body. However, CXCR4 over-expression is also found in diseases such as cancer, where it plays a role in, among others, the metastatic spread. For this reason it is an interesting biomarker for the field of diagnostic oncology, and therefore, it is gaining increasing interest for applications in molecular imaging. Especially "small-molecule" imaging agents based on T140, FC131 and AMD3100 have been extensively studied. SDF-1, antibodies, pepducins and bioluminescence have also been used to visualize CXCR4. In this critical review reported CXCR4 targeting imaging agents are described based on their affinity, specificity and biodistribution. The level wherein CXCR4 is up-regulated in cancer patients and its relation to the different cell lines and animal models used to evaluate the efficacy of the imaging agents is also discussed (221 references).

Strategies for the discovery and development of therapies for metastatic breast cancer

Nearly all deaths caused by solid cancers occur as a result of metastasis--the formation of secondary tumours in distant organs such as the lungs, liver, brain and bone. A major obstruction to the development of drugs with anti-metastatic efficacy is our fragmented understanding of how tumours 'evolve' and metastasize, at both the biological and genetic levels. Furthermore, although there is significant overlap in the metastatic process among different types of cancer, there are also marked differences in the propensity to metastasize, the extent of metastasis, the sites to which the tumour metastasizes, the kinetics of the process and the mechanisms involved. Here, we consider the case of breast cancer, which has some marked distinguishing features compared with other types of cancer. Considerable progress has been made in the development of preclinical models and in the identification of relevant signalling pathways and genetic regulators of metastatic breast cancer, and we discuss how these might facilitate the development of novel targeted anti-metastatic drugs.

Differential Expression of Chemokine Receptors and their Roles in Cancer Imaging

Chemokine/chemokine receptor interactions play diverse roles in cell migration and homeostasis. Emerging evidence suggests that cancer cells co-opt chemokine networks for survival, proliferation, immune evasion, and metastasis. Most of the chemokine receptors are reported to be involved in tumor progression. Given their extensive implication in cancer progression, several chemokine receptor/ligand axes are considered as potential therapeutic targets. This review provides a survey of chemokine receptor expression in cancer and evaluates the potential of chemokine receptor imaging as a tool for molecular characterization of cancer.

Cellular host responses to gliomas

Background

Glioblastoma multiforme (GBM) is the most aggressive type of malignant primary brain tumors in adults. Molecular and genetic analysis has advanced our understanding of glioma biology, however mapping the cellular composition of the tumor microenvironment is crucial for understanding the pathology of this dreaded brain cancer. In this study we identified major cell populations attracted by glioma using orthotopic rodent models of human glioma xenografts. Marker-specific, anatomical and morphological analyses revealed a robust influx of host cells into the main tumor bed and tumor satellites.

Methodology/Principal Findings

Human glioma cell lines and glioma spheroid orthotopic implants were used in rodents. In both models, the xenografts recruited large numbers of host nestin-expressing cells, which formed a ‘network’ with glioma. The host nestin-expressing cells appeared to originate in the subventricular zone ipsilateral to the tumor, and were clearly distinguishable from pericytes that expressed smooth muscle actin. These distinct cell populations established close physical contact in a ‘pair-wise’ manner and migrated together to the deeper layers of tumor satellites and gave rise to tumor vasculature. The GBM biopsy xenografts displayed two different phenotypes: (a) low-generation tumors (first in vivo passage in rats) were highly invasive and non-angiogenic, and host nestin-positive cells that infiltrated into these tumors displayed astrocytic or elongated bipolar morphology; (b) high-generation xenografts (fifth passage) had pronounced cellularity, were angiogenic with ‘glomerulus-like’ microvascular proliferations that contained host nestin-positive cells. Stromal cell-derived factor-1 and its receptor CXCR4 were highly expressed in and around glioma xenografts, suggesting their role in glioma progression and invasion.

Conclusions/Significance

Our data demonstrate a robust migration of nestin-expressing host cells to glioma, which together with pericytes give rise to tumor vasculature. Mapping the cellular composition of glioma microenvironment and deciphering the complex ‘crosstalk’ between tumor and host may ultimately aid the development of novel anti-glioma therapies.

Expression of chemokine receptors on circulating tumor cells in patients with solid tumors

Background

The study was performed to investigate the expression of chemokine receptors (CR) on circulating tumor cells (CTC), which may be of importance for organ-specific metastases and cancer treatment since CR are potential drug-targets.

Methods

Blood samples from patients with metastatic carcinoma (MC) or melanoma (MM) were enriched for CTC and expression of CR (CXCR4, CCR6, CCR7 and CCR9) was evaluated by flow cytometry.

Results

CTC were detected in 49 of 68 patients (72%) [28 MC; 21 MM] with a median number of 3 CTC (range: 1-94)/10 mL of blood. CXCR4 was expressed on CTC in 82% (40/49) of patients [median number 1 CTC/10 mL blood; range 1-14] and CCR6 in 29 patients (59%; median 1, range: 1-14). In MM patients, CCR7 was expressed on CTC in 6 (29%) samples and CCR9 in 12 (57%). A positive correlation between surface expression of CR and organ-specific metastatic pattern was not observed.

Conclusions

CR were expressed on CTC of patients with solid tumors. Along with our findings, the observation that CR could be involved in CTC proliferation and migration of tumor cells appoints CTC as potential CR-antagonist therapeutic target.

SLUG promotes prostate cancer cell migration and invasion via CXCR4/CXCL12 axis

Background

SLUG is a zinc-finger transcription factor of the Snail/Slug zinc-finger family that plays a role in migration and invasion of tumor cells. Mechanisms by which SLUG promotes migration and invasion in prostate cancers remain elusive.

Methods

Expression level of CXCR4 and CXCL12 was examined by Western blot, RT-PCR, and qPCR analyses. Forced expression of SLUG was mediated by retroviruses, and SLUG and CXCL12 was downregulated by shRNAs-expressing lentiviruses. Migration and invasion of prostate cancer were measured by scratch-wound assay and invasion assay, respectively.

Research

We demonstrated that forced expression of SLUG elevated CXCR4 and CXCL12 expression in human prostate cancer cell lines PC3, DU145, 22RV1, and LNCaP; conversely, reduced expression of SLUG by shRNA downregulated CXCR4 and CXCL12 expression at RNA and protein levels in prostate cancer cells. Furthermore, ectopic expression of SLUG increased MMP9 expression and activity in PC3, 22RV1, and DU-145 cells, and SLUG knockdown by shRNA downregulated MMP9 expression. We showed that CXCL12 is required for SLUG-mediated MMP9 expression in prostate cancer cells. Moreover, we found that migration and invasion of prostate cancer cells was increased by ectopic expression of SLUG and decreased by SLUG knockdown. Notably, knockdown of CXCL12 by shRNA impaired SLUG-mediated migration and invasion in prostate cancer cells. Lastly, our data suggest that CXCL12 and SLUG regulate migration and invasion of prostate cancer cells independent of cell growth.

Conclusion

We provide the first compelling evidence that upregulation of autocrine CXCL12 is a major mechanism underlying SLUG-mediated migration and invasion of prostate cancer cells. Our findings suggest that CXCL12 is a therapeutic target for prostate cancer metastasis.

Crosstalk between chemokine receptor CXCR4 and cannabinoid receptor CB2 in modulating breast cancer growth and invasion

Background

Cannabinoids bind to cannabinoid receptors CB₁ and CB₂ and have been reported to possess anti-tumorigenic activity in various cancers. However, the mechanisms through which cannabinoids modulate tumor growth are not well known. In this study, we report that a synthetic non-psychoactive cannabinoid that specifically binds to cannabinoid receptor CB₂ may modulate breast tumor growth and metastasis by inhibiting signaling of the chemokine receptor CXCR4 and its ligand CXCL12. This signaling pathway has been shown to play an important role in regulating breast cancer progression and metastasis.

Methodology/Principal Findings

We observed high expression of both CB₂ and CXCR4 receptors in breast cancer patient tissues by immunohistochemical analysis. We further found that CB₂-specific agonist JWH-015 inhibits the CXCL12-induced chemotaxis and wound healing of MCF7 overexpressing CXCR4 (MCF7/CXCR4), highly metastatic clone of MDA-MB-231 (SCP2) and NT 2.5 cells (derived from MMTV-neu) by using chemotactic and wound healing assays. Elucidation of the molecular mechanisms using various biochemical techniques and confocal microscopy revealed that JWH-015 treatment inhibited CXCL12-induced P44/P42 ERK activation, cytoskeletal focal adhesion and stress fiber formation, which play a critical role in breast cancer invasion and metastasis. In addition, we have shown that JWH-015 significantly inhibits orthotopic tumor growth in syngenic mice in vivo using NT 2.5 cells. Furthermore, our studies have revealed that JWH-015 significantly inhibits phosphorylation of CXCR4 and its downstream signaling in vivo in orthotopic and spontaneous breast cancer MMTV-PyMT mouse model systems.

Conclusions/Significance

This study provides novel insights into the crosstalk between CB₂ and CXCR4/CXCL12-signaling pathways in the modulation of breast tumor growth and metastasis. Furthermore, these studies indicate that CB₂ receptors could be used for developing innovative therapeutic strategies against breast cancer.

Role of RANK, RANKL, OPG, and CXCR4 tissue markers in predicting bone metastases in breast cancer patients

This is a retrospective study on 40 breast cancer patients, of which 20 have bone metastases, 10 have visceral metastases, and 10 have no evidence of disease, aimed at evaluating the role of CXCR4 and the RANK/RANKL/OPG system to predict bone metastases. CXCR4 expression, alone or in combination with RANK, identified patients destined to relapse to bone.

BACKGROUND

The RANK/RANKL/OPG system is active in primary cancers such as breast, prostate, and also in their bone metastases. CXCR4 chemokine receptor is highly expressed in human breast cancer cells and is believed to facilitate the homing of tumor cells to organs such as bone that express high levels of its ligand SDF1. Our study aimed to investigate whether the analysis of these markers with an inexpensive and simple test can help to predict bone metastases in breast cancer patients.

PATIENTS AND METHODS

Marker expression was evaluated by immunohistochemical staining in paraffin-embedded tissue sections of primary breast cancers from 40 individuals: 20 patients with bone metastases (BM), 10 with visceral metastases (VM; considered together as the relapsed group), and 10 with no evidence of disease (NED).

RESULTS

RANKL was not detected in tumor cells. OPG- and RANK-positive tumors are found with similar frequency in NED (20%) and in relapsed patients (23% and 17%, respectively). However, in the latter subgroup, only RANK positivity was always associated with bone relapse. The frequency of CXCR4-positive tumors was three-fold higher in relapsed (30%) than in NED (10%) patients and positivity was always linked to bone metastases. Considering NED and VM patients together versus BM patients, we observed that CXCR4 expression, alone (P = .008) or in combination with RANK (P < .001), identified patients destined to relapse to bone.

CONCLUSION

Our results provide the first clinical evidence to support a pivotal role of combined CXCR4 and RANK expression in predicting bone relapse.

Comparative role of acetylation along c-SRC/ETS1 signaling pathway in bone metastatic and invasive mammary cell phenotypes

Metastatic cells switch between different modes of migration through supramolecular plasticity mechanism(s) still largely unknown. The aim of the present paper was to clarify some molecular aspects of the epigenetic control of migration of 1833-bone metastatic cells compared to MDA-MB231-parental mammary carcinoma cells. Active c-Src overexpression enhanced 1833-cell spontaneous migration and CXCR4-mediated chemoinvasion toward CXCL12 ligand. Only in metastatic cells, in fact, c-Src seemed to stabilize nuclear CXCR4-protein receptor possibly due to tyrosine phosphorylation, by impairing protein-degradative smear and causing instead an electrophoretic-mobility shift; the cytosolic steady-state level of CXCR4 was enhanced, and the protein appeared also phosphorylated. These findings suggested the triggering of unique signaling pathways in metastasis for homing of breast-cancer cells to congenial environment of specific organs. Microenvironmental stimuli activating c-Src might influence Ets1 binding to CXCR4 promoter and consequent transactivation, as well as CXCR4 post-translational regulatory mechanisms such as phosphorylation. Enhancement of Ets1 activity and CXCR4 induction by c-Src overexpression were prevented by histone deacetylase (HDAC) blockade. In contrast, HDAC inhibition with trichostatin A increased cytosolic phosphorylated CXCR4 expression in MDA-MB231 cells, but Ets1 involvement was practically unneeded. c-Src might be suggested as a bio-marker predicting metastasis sensitivity patterns to HDAC inhibitors. Rationally designed and individualized therapy may become possible as more is learned about the target molecules of HDAC's inhibitory agents and their roles, as undertaken for CXCR4 that is likely to be crucial for homing, angiogenesis and survival in a c-Src-dependent manner in bone-metastatic mammary cells.

Optimal management of bone metastases in breast cancer patients

Bone metastasis in breast cancer is a significant clinical problem. It not only indicates incurable disease with a guarded prognosis, but is also associated with skeletal-related morbidities including bone pain, pathological fractures, spinal cord compression, and hypercalcemia. In recent years, the mechanism of bone metastasis has been further elucidated. Bone metastasis involves a vicious cycle of close interaction between the tumor and the bone microenvironment. In patients with bone metastases, the goal of management is to prevent further skeletal-related events, manage complications, reduce bone pain, and improve quality of life. Bisphosphonates are a proven therapy for the above indications. Recently, a drug of a different class, the RANK ligand antibody, denosumab, has been shown to reduce skeletal-related events more than the bisphosphonate, zoledronic acid. Other strategies of clinical value may include surgery, radiotherapy, radiopharmaceuticals, and, of course, effective systemic therapy. In early breast cancer, bisphosphonates may have an antitumor effect and prevent both bone and non-bone metastases. Whilst two important Phase III trials with conflicting results have led to controversy in this topic, final results from these and other key Phase III trials must still be awaited before a firm conclusion can be drawn about the use of bisphosphonates in this setting. Advances in bone markers, predictive biomarkers, multi-imaging modalities, and the introduction of novel agents have ushered in a new era of proactive management for bone metastases in breast cancer.

CXCR4 suppression attenuates EGFRvIII-mediated invasion and induces p38 MAPK-dependent protein trafficking and degradation of EGFRvIII in breast cancer cells

Our previous report has shown that the constitutively activated EGFR variant, EGFRvIII, up-regulates the pro-metastatic chemokine receptor CXCR4 in breast cancer cells. Here we evaluated the biological effect and cell signaling effects of silencing CXCR4 expression in EGFRvIII-expressing breast cancer cells. Short hairpin RNA (shRNA)-mediated suppression of CXCR4 expression significantly reduced the invasive potential and proliferation of EGFRvIII-expressing breast cancer cells. These cells exhibited a reduction of EGFRvIII activity and protein expression due to increased protein degradation and altered protein trafficking. In conclusion, suppression of CXCR4 inhibits EGFRvIII-mediated breast cancer cell invasion and proliferation.

Breast cancer at bone metastatic sites: recent discoveries and treatment targets

Breast carcinoma is the most common cancer of women. Bones are often involved with breast carcinoma metastases with the resulting morbidity and reduced quality of life. Breast cancer cells arriving at bone tissues mount supportive microenvironment by recruiting and modulating the activity of several host tissue cell types including the specialized bone cells osteoblasts and osteoclasts. Pathologically activated osteoclasts produce osteolytic lesions associated with bone pain, pathological fractures, cord compression and other complications of metastatic breast carcinoma at bone. Over the last decade there has been enormous growth of knowledge in the field of osteoclasts biology both in the physiological state and in the tumor microenvironment. This knowledge allowed the development and implementation of several targeted therapeutics that expanded the armamentarium of the oncologists dealing with the metastases-associated osteolytic disease. While the interactions of cancer cells with resident bone cells at the established metastatic gross lesions are well-studied, the preclinical events that underlie the progression of disseminated tumor cells into micrometastases and then into clinically-overt macrometastases are just starting to be uncovered. In this review, we discuss the established information and the most recent discoveries in the pathogenesis of osteolytic metastases of breast cancer, as well as the corresponding investigational drugs that have been introduced into clinical development.