CXCR4 knockdown by small interfering RNA abrogates breast tumor growth in vivo

Opposing roles of CXCR4 and CXCR7 in breast cancer metastasis

INTRODUCTION

CXCL12-CXCR4 signaling has been shown to play a role in breast cancer progression by enhancing tumor growth, angiogenesis, triggering cancer cell invasion in vitro, and guiding cancer cells to their sites of metastasis. However, CXCR7 also binds to CXCL12 and has been recently found to enhance lung and breast primary tumor growth, as well as metastasis formation. Our goal was to dissect the contributions of CXCR4 and CXCR7 to the different steps of metastasis - in vivo invasion, intravasation and metastasis formation.

METHODS

We overexpressed CXCR4, CXCR7 or both in the rat mammary adenocarcinoma cell line MTLn3. Stable expressors were used to form tumors in severe combined immunodeficiency (SCID) mice, and in vivo invasiveness, intravital motility, intravasation, and metastasis were measured.

RESULTS

We found that CXCR4 overexpression increased the chemotactic and invasive behavior of MTLn3 cells to CXCL12, both in vitro and in vivo, as well as in vivo motility and intravasation. CXCR7 overexpression enhanced primary tumor growth and angiogenesis (as indicated by microvessel density and VEGFA expression), but decreased in vivo invasion, intravasation, and metastasis formation. In vitro, expression of CXCR7 alone had no effect in chemotaxis or invasion to CXCL12. However, in the context of increased CXCR4 expression, CXCR7 enhanced chemotaxis to CXCL12 but decreased invasion in response to CXCL12 in vitro and in vivo and impaired CXCL12 stimulated matrix degradation. The changes in matrix degradation correlated with expression of matrix metalloproteinase 12 (MMP12).

CONCLUSIONS

We find that CXCR4 and CXCR7 play different roles in metastasis, with CXCR4 mediating breast cancer invasion and CXCR7 impairing invasion but enhancing primary tumor growth through angiogenesis.

HER2 interacts with CD44 to up-regulate CXCR4 via epigenetic silencing of microRNA-139 in gastric cancer cells

BACKGROUND & AIMS

Human epidermal growth factor receptor 2 (HER2) (neu/ERBB2) is overexpressed on many types of cancer cells, including gastric cancer cells; HER2 overexpression has been associated with metastasis and poor prognosis. We investigated the mechanisms by which HER2 regulates cell migration and invasion.

METHODS

HER2 expression or activity was reduced in gastric cancer cell lines using small interfering RNAs or the monoclonal antibody, trastuzumab. We identified proteins that interact with HER2 or microRNAs (miRNAs) involved in HER2 signaling. We used various software programs to identify miRNAs that regulate factors in the HER2 signaling pathway. We analyzed expression patterns of these miRNAs in gastric cancer cell lines and tumor samples from patients.

RESULTS

We found that CD44 binds directly to HER2, which up-regulates the expression of metastasis-associated protein-1, induces deacetylation of histone H3 lysine 9, and suppresses transcription of microRNA139 (miR-139) to inhibit expression of its target gene, C-X-C chemokine receptor type 4 (CXCR4). Knockdown of HER2 and CD44 reduced invasive activity of cultured gastric cancer cells and suppressed tumor growth in nude mice. Lymph node metastasis was associated with high levels of HER2, CD44, and CXCR4, and reduced levels of miR-139 in human metastatic gastric tumors. Cultures of different types of metastatic cancer cells with histone deacetylase inhibitors and/or DNA methyltransferase resulted in up-regulation of miR-139.

CONCLUSIONS

HER2 interaction with CD44 up-regulates CXCR4 by inhibiting expression of miR-139, at the epigenetic level, in gastric cancer cells. These findings indicate how HER2 signaling might promote gastric tumor progression and metastasis.

CXCR4 in Cancer and Its Regulation by PPARgamma

Chemokines are peptide mediators involved in normal development, hematopoietic and immune regulation, wound healing, and inflammation. Among the chemokines is CXCL12, which binds principally to its receptor CXCR4 and regulates leukocyte precursor homing to bone marrow and other sites. This role of CXCL12/CXCR4 is “commandeered” by cancer cells to facilitate the spread of CXCR4-bearing tumor cells to tissues with high CXCL12 concentrations. High CXCR4 expression by cancer cells predisposes to aggressive spread and metastasis and ultimately to poor patient outcomes. As well as being useful as a marker for disease progression, CXCR4 is a potential target for anticancer therapies. It is possible to interfere directly with the CXCL12:CXCR4 axis using peptide or small-molecular-weight antagonists. A further opportunity is offered by promoting strategies that downregulate CXCR4 pathways: CXCR4 expression in the tumor microenvironment is modulated by factors such as hypoxia, nucleosides, and eicosanoids. Another promising approach is through targeting PPAR to suppress CXCR4 expression. Endogenous PPARγ such as 15-deoxy-Δ^12,14-PGJ₂ and synthetic agonists such as the thiazolidinediones both cause downregulation of CXCR4 mRNA and receptor. Adjuvant therapy using PPARγ agonists may, by stimulating PPARγ-dependent downregulation of CXCR4 on cancer cells, slow the rate of metastasis and impact beneficially on disease progression.

MicroRNA-146a and AMD3100, two ways to control CXCR4 expression in acute myeloid leukemias

CXCR4 is a negative prognostic marker in acute myeloid leukemias (AMLs). Therefore, it is necessary to develop novel ways to inhibit CXCR4 expression in leukemia. AMD3100 is an inhibitor of CXCR4 currently used to mobilize cancer cells. CXCR4 is a target of microRNA (miR)-146a that may represent a new tool to inhibit CXCR4 expression. We then investigated CXCR4 regulation by miR-146a in primary AMLs and found an inverse correlation between miR-146a and CXCR4 protein expression levels in all AML subtypes. As the lowest miR-146a expression levels were observed in M5 AML, we analyzed the control of CXCR4 expression by miR-146a in normal and leukemic monocytic cells and showed that the regulatory miR-146a/CXCR4 pathway operates during monocytopoiesis, but is deregulated in AMLs. AMD3100 treatment and miR-146a overexpression were used to inhibit CXCR4 in leukemic cells. AMD3100 treatment induces the decrease of CXCR4 protein expression, associated with miR-146a increase, and increases sensitivity of leukemic blast cells to cytotoxic drugs, this effect being further enhanced by miR-146a overexpression. Altogether our data indicate that miR-146a and AMD3100, acting through different mechanism, downmodulate CXCR4 protein levels, impair leukemic cell proliferation and then may be used in combination with anti-leukemia drugs, for development of new therapeutic strategies.

Cancer to bone: a fatal attraction

When cancer metastasizes to bone, considerable pain and deregulated bone remodelling occurs, greatly diminishing the possibility of cure. Metastasizing tumour cells mobilize and sculpt the bone microenvironment to enhance tumour growth and to promote bone invasion. Understanding the crucial components of the bone microenvironment that influence tumour localization, along with the tumour-derived factors that modulate cellular and protein matrix components of bone to favour tumour expansion and invasion, is central to the pathophysiology of bone metastases. Basic findings of tumour-bone interactions have uncovered numerous therapeutic opportunities that focus on the bone microenvironment to prevent and treat bone metastases.

Cancer to bone: a fatal attraction

When cancer metastasizes to bone, considerable pain and deregulated bone remodelling occurs, greatly diminishing the possibility of cure. Metastasizing tumour cells mobilize and sculpt the bone microenvironment to enhance tumour growth and to promote bone invasion. Understanding the crucial components of the bone microenvironment that influence tumour localization, along with the tumour-derived factors that modulate cellular and protein matrix components of bone to favour tumour expansion and invasion, is central to the pathophysiology of bone metastases. Basic findings of tumour-bone interactions have uncovered numerous therapeutic opportunities that focus on the bone microenvironment to prevent and treat bone metastases.

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.

Significance of CXCR4, phosphorylated STAT3 and VEGF-A expression in resected non-small cell lung cancer

C-X-C chemokine receptor type 4 (CXCR4) plays an important role in determining the metastatic potential of non-small cell lung cancer. In order to elucidate the effect and mechanism of CXCR4 in tumor angiogenesis we evaluated the clinical significance of CXCR4, phosphorylated signal transducer and activator of transcription 3 (P-STAT3), and vascular endothelial growth factor (VEGF) expression in patients with completely resected non-small cell lung cancer (NSCLC). A total of 208 cases of resected NSCLC were collected, and expression of CXCR4, P-STAT3 and VEGF-A in tumor tissue was investigated using immunohistochemistry (IHC). We reviewed the patient clinical records to determine the association of the expression of these proteins with the clinical course of the disease. Expression of CXCR4, P-STAT3 and VEGF-A was detected in 56.3, 46.2 and 51.9% of the samples, respectively. We observed co-expression between CXCR4, P-STAT3 and VEGF-A. Using multivariate analysis, the expression levels of CXCR4 and VEGF-A were identified as independent prognostic factors that affected overall survival. In conclusion, the results of this study suggest that CXCR4, P-STAT3 and VEGF-A expression may play a role in tumor progression and angiogenesis of NSCLC. However, further studies are needed to uncover the detailed mechanism that underlies the role of these proteins in NSCLC.

CXCL12 (SDF1alpha)-CXCR4/CXCR7 pathway inhibition: an emerging sensitizer for anticancer therapies?

Addition of multiple molecularly targeted agents to the existing armamentarium of chemotherapeutics and radiotherapies represents a significant advance in the management of several advanced cancers. In certain tumor types with no efficacious therapy options, these agents have become the first line of therapy, for example, sorafenib in advanced hepatocellular carcinoma or bevacizumab in recurrent glioblastoma. Unfortunately, in many cases, the survival benefits are modest, lasting only weeks to a few months. Moreover, they may not show benefit in patients with localized disease (i.e., in the adjuvant setting). Recent studies have provided increasing evidence that activation of the chemokine CXCL12 (SDF1α) pathway is a potential mechanism of tumor resistance to both conventional therapies and biological agents via multiple complementary actions: (i) by directly promoting cancer cell survival, invasion, and the cancer stem and/or tumor-initiating cell phenotype; (ii) by recruiting "distal stroma" (i.e., myeloid bone marrow-derived cells) to indirectly facilitate tumor recurrence and metastasis; and (iii) by promoting angiogenesis directly or in a paracrine manner. Here, we discuss recent preclinical and clinical data that support the potential use of anti-CXCL12 agents (e.g., AMD3100, NOX-A12, or CCX2066) as sensitizers to currently available therapies by targeting the CXCL12/CXCR4 and CXCL12/CXCR7 pathways.

CXCR4 antagonist 4F-benzoyl-TN14003 inhibits leukemia and multiple myeloma tumor growth

OBJECTIVE

The chemokine receptor CXCR4 and its ligand CXCL12 are involved in the progression and dissemination of a diverse number of solid and hematological malignancies. Binding CXCL12 to CXCR4 activates a variety of intracellular signal transduction pathways that regulate cell chemotaxis, adhesion, survival, proliferation, and apoptosis.

MATERIALS AND METHODS

Here, we demonstrate that the CXCR4 antagonist, 4F-benzoyl-TN14003 (BKT140), but not AMD3100, exhibits a CXCR4-dependent preferential cytotoxicity toward malignant cells of hematopoietic origin. BKT140 significantly and preferentially stimulated multiple myeloma apoptotic cell death. BKT140 treatment induced morphological changes, phosphatidylserine externalization, decreased mitochondrial membrane potential, caspase-3 activation, sub-G1 arrest, and DNA double-stranded breaks.

RESULTS

In vivo, subcutaneous injections of BKT140 significantly reduced, in a dose-dependent manner, the growth of human acute myeloid leukemia and multiple myeloma xenografts. Tumors from animals treated with BKT140 were smaller in size and weights, had larger necrotic areas and high apoptotic scores.

CONCLUSIONS

Taken together, these results suggest a potential therapeutic use for BKT140 in multiple myeloma and leukemia patients.

Second AKT: the rise of SGK in cancer signalling

The serum and glucocorticoid kinase (SGK) family of serine/threonine kinases consists of three isoforms, SGK-1, SGK-2 and SGK-3. This family of kinases is highly homologous to the AKT kinase family, sharing similar upstream activators and downstream targets. SGKs have been implicated in the regulation of cell growth, proliferation, survival and migration: cellular processes that are dysregulated in cancer. Furthermore, SGKs lie downstream of phosphoinositide-3-kinase (PI3Kinase) signalling and interact at various levels with RAS/RAF/ERK signalling, two pathways that are involved in promoting tumorigenesis. Recent evidence suggests that mutant PI3Kinase can induce tumorigenesis through an AKT-independent but SGK3-dependent mechanism, thus implicating SGKs as potential players in malignant transformation. Here, we will review the current state of knowledge on the regulation of the SGKs and their role in normal cell physiology and transformation with a particular focus on SGK3.

Effects of human mesenchymal stem cells on ER-positive human breast carcinoma cells mediated through ER-SDF-1/CXCR4 crosstalk

BACKGROUND

Adult human mesenchymal stem cells (hMSC) have been shown to home to sites of carcinoma and affect biological processes, including tumour growth and metastasis. Previous findings have been conflicting and a clear understanding of the effects of hMSCs on cancer remains to be established. Therefore, we set out to investigate the impact of hMSCs on the oestrogen receptor positive, hormone-dependent breast carcinoma cell line MCF-7.

RESULTS

In this study, we show the effects of hMSCs on cancer cells are mediated through a secreted factor(s) which are enhanced by cancer cell-hMSC contact/communication. In addition to enhanced proliferation when in co-culture with hMSCs, MCF-7 cells were found to have increased migration potential in vitro. Inhibition of ER signalling by the pure anti-oestrogen ICI 182,780 decreased the effect of hMSCs on MCF-7 cell proliferation and migration supporting a role for ER signalling in the hMSC/MCF-7 cell interaction. Additionally, hMSCs have been shown to secrete a wide variety of growth factors and chemokines including stromal cell-derived factor-1 (SDF-1). This coupled with the knowledge that SDF-1 is an ER-mediated gene linked with hormone-independence and metastasis led to the investigation of the SDF-1/CXCR4 signalling axis in hMSC-MCF-7 cell interaction. Experiments revealed an increase in SDF-1 gene expression both in vivo and in vitro when MCF-7 cells were cultured with hMSCs. SDF-1 treatment of MCF-7 cells alone increased proliferation to just below that seen with hMSC co-culture. Additionally, blocking SDF-1 signalling using a CXCR4-specific inhibitor decreased hMSC induced proliferation and migration of MCF-7. However, the combined treatment of ICI and AMD3100 reduced MCF-7 cell proliferation and migration below control levels, indicating targeting both the ER and CXCR4 pathways is effective in decreasing the hMSCs induction of MCF-7 cell proliferation and migration.

CONCLUSIONS

The sum of these data reveals the relationship between tumour microenvironment and tumour growth and progression. Better understanding of the mechanisms involved in this tumour stroma cell interaction may provide novel targets for the development of treatment strategies for oestrogen receptor positive, hormone-independent, and endocrine-resistant breast carcinoma.

CXCR4 and cancer

The chemokine receptor CXCR4 belongs to the large superfamily of G protein-coupled receptors and has been identified to play a crucial role in a number of biological processes, including the trafficking and homeostasis of immune cells such as T lymphocytes. CXCR4 has also been found to be a prognostic marker in various types of cancer, including leukemia and breast cancer, and recent evidence has highlighted the role of CXCR4 in prostate cancer. Furthermore, CXCR4 expression is upregulated in cancer metastasis, leading to enhanced signaling. These observations suggest that CXCR4 is important for the progression of cancer. The CXCR4-CXCL12 (stromal cell-derived factor 1 (SDF-1)) axis has additionally been identified to have a role in normal stem cell homing. Interestingly, cancer stem cells also express CXCR4, indicating that the CXCR4-SDF-1 axis may direct the trafficking and metastasis of these cells to organs that express high levels of SDF-1, such as the lymph nodes, lungs, liver, and bone. This review focuses on the current knowledge of CXCR4 regulation and how deregulation of this protein may contribute to the progression of cancer.

Basal and steroid hormone-regulated expression of CXCR4 in human endometrium and endometriosis

Endometriosis is associated with activation of local and systemic inflammatory mechanisms, including increased levels of chemokines and other proinflammatory cytokines. We have previously reported increased gene expression of chemokine receptor 4 (CXCR4), the receptor for CXCL12, in lesions of the rat model of endometriosis. The CXCR4-CXCL12 axis has been shown to have both immune (HIV infection, lymphocyte chemotaxis) and nonimmune functions, including roles in tissue repair, angiogenesis, invasion, and migration. There is evidence indicating that these mechanisms are also at play in endometriosis; therefore, we hypothesized that activation of the CXCR4-CXCL12 axis could be responsible, at least in part, for the survival and establishment of endometrial cells ectopically. Immunohistochemistry (IHC) showed that CXCR4 protein levels were significantly higher in endometriotic lesions compared to the endometrium of controls. Next, we determined basal gene and protein expression of CXCR4 and CXCL12 and regulation by estradiol (E2) and/or progesterone (P4) in endometrial cell lines using quantitative polymerase chain reaction (qPCR), and Western blots. Basal CXCR4 gene expression levels were higher in epithelial versus stromal cells; conversely, CXCL12 was expressed at higher levels in stromal vs epithelial cells. CXCR4 gene expression was significantly downregulated by ovarian steroid hormones in endometrial epithelial. These data suggest that steroid modulation of CXCR4 is defective in endometriosis, although the specific mechanism involved remains to be elucidated. These findings have implications for future therapeutic strategies specifically targeting the inflammatory component in endometriosis.

Nuclear expression of CXCR4 is associated with advanced colorectal cancer

BACKGROUND AND OBJECTIVES

CXCR4 and its ligand, SDF-1alpha, play an important role in the targeted metastasis of colon cancer. In this study, we analyzed an expression of CXCR4 in clinical samples and showed that SDF-1alpha affected the expression of CXCR4 in colon cancer cells.

MATERIALS AND METHODS

A total of 388 patients with colorectal cancer (CRC) who underwent surgery in Taipei Veterans General Hospital from 2000 to 2004 were included. The expression of CXCR4 in CRC was visualized by immunohistochemistry (anti-CXCR4 mAb, R&D 12G5). HCT116, SW480, and SW620 cells were treated with SDF-1alpha in vitro and the CXCR4 proteins located in the cytoplasmic and nuclear compartments were separated and analyzed with western blotting.

RESULTS

The frequency of cytoplasmic and nuclear expression of CXCR4 in colorectal cancers was 35.6% and 36.9%, respectively. Nuclear but not cytoplasmic expression of CXCR4 was associated with advanced CRC (p < 0.001) and lymphovascular invasion. However, in multivariate analysis, nuclear expression of CXCR4 did not correlate with patients' outcome. In the in vitro study, SDF-1alpha, stimulation of three colorectal carcinoma lines enhanced the CXCR4 nuclear expression.

CONCLUSION

Expression of the CXCR4 plays a role in CRC progression and may be associated with SDF-1alpha stimulation.

Multiple functions of CXCL12 in a syngeneic model of breast cancer

Background

A growing body of work implicates chemokines, in particular CXCL12 and its receptors, in the progression and site-specific metastasis of various cancers, including breast cancer. Various agents have been used to block the CXCL12-CXCR4 interaction as a means of inhibiting cancer metastasis. However, as a potent chemotactic factor for leukocytes, CXCL12 also has the potential to enhance anti-cancer immunity. To further elucidate its role in breast cancer progression, CXCL12 and its antagonist CXCL12_(P2G) were overexpressed in the syngeneic 4T1.2 mouse model of breast carcinoma.

Results

While expression of CXCL12_(P2G) significantly inhibited metastasis, expression of wild-type CXCL12 potently inhibited both metastasis and primary tumor growth. The effects of wild-type CXCL12 were attributed to an immune response characterized by the induction of CD8⁺ T cell activity, enhanced cell-mediated cytotoxicity, increased numbers of CD11c⁺ cells in the tumor-draining lymph nodes and reduced accumulation of myeloid-derived suppressor cells in the spleen.

Conclusions

This study highlights the need to consider carefully therapeutic strategies that block CXCL12 signaling. Therapies that boost CXCL12 levels at the primary tumor site may prove more effective in the treatment of metastatic breast cancer.

Suppression of CDK2 expression by siRNA induces cell cycle arrest and cell proliferation inhibition in human cancer cells

Cyclin-dependent kinase 2 (CDK2) is a member of serine/ threonine protein kinases, which initiates the principal transitions of the eukaryotic cell cycle and is a promising target for cancer therapy. The present study was designed to inhibit cdk2 gene expression to induce cell cycle arrest and cell proliferation suppression. Here, we constructed a series of RNA interference (RNAi) plasmids which can successfully express small interference RNA (siRNA) in the transfected human cells. The results showed that the RNAi plasmids containing the coding sequences for siRNAs down-regulated the cdk2 gene expression in human cancer cells at the mRNA and the protein levels. Furthermore, we found that the cell cycle was arrested at G0G1 phases and the cell proliferation was inhibited by different siRNAs. These results demonstrate that suppression of CDK2 activity by RNAi may be an effective strategy for gene therapy in human cancers.

Breast cancer stromal fibroblasts promote the generation of CD44+CD24- cells through SDF-1/CXCR4 interaction

Background

Breast cancer stem cells (BCSCs) have been recently identified in breast carcinoma as CD44⁺CD24^- cells, which exclusively retain tumorigenic activity and display stem cell-like properties. Using a mammosphere culture technique, MCF7 mammosphere cells are found to enrich breast cancer stem-like cells expressing CD44⁺CD24^-. The stromal cells are mainly constituted by fibroblasts within a breast carcinoma, yet little is known of the contributions of the stromal cells to BCSCs.

Methods

Carcinoma-associated fibroblasts (CAFs) and normal fibroblasts (NFs) were isolated and identified by immunohistochemistry. MCF7 mammosphere cells were co-cultured with different stromal fibroblasts by a transwell cocultured system. Flow cytometry was used to measure CD44 and CD24 expression status on MCF7. ELISA (enzyme-linked immunosorbent assay) was performed to investigate the production of stromal cell-derived factor 1 (SDF-1) in mammosphere cultures subject to various treatments. Mammosphere cells were injected with CAFs and NFs to examine the efficiency of tumorigenity in NOD/SCID mice.

Results

CAFs derived from breast cancer patients were found to be positive for α-smooth muscle actin (α-SMA), exhibiting the traits of myofibroblasts. In addition, CAFs played a central role in promoting the proliferation of CD44⁺CD24^- cells through their ability to secrete SDF-1, which may be mediated to SDF-1/CXCR4 signaling. Moreover, the tumorigenicity of mammosphere cells with CAFs significantly increased as compared to that of mammosphere cells alone or with NFs.

Conclusion

We for the first time investigated the effects of stromal fibroblasts on CD44⁺CD24^- cells and our findings indicated that breast CAFs contribute to CD44⁺CD24^- cell proliferation through the secretion of SDF-1, and which may be important target for therapeutic approaches.

Essential role of cell cycle regulatory genes p21 and p27 expression in inhibition of breast cancer cells by arsenic trioxide

Arsenic trioxide (As2O3), a component of traditional Chinese medicine, has been used successfully for the treatment of acute promyelocytic leukemia (APL), and As2O3 is of potential therapeutic value for the treatment of other promyelocytic malignancies and some solid tumors including breast cancer. However, the precise molecular mechanisms through which As2O3 induces cell cycle arrest and apoptosis in solid tumors have not been clearly understood. The goal of our study is to gain insight into the general biological processes and molecular functions that are altered by As2O3 treatment in MCF-7 breast cancer cells and to identify the key signaling processes that are involved in the regulation of these physiological effects. In the present study, MCF-7 cells were treated with 5 μM As2O3, and the differential gene expression was then analyzed by DNA microarray. The results showed that As2O3 treatment changed the expression level of several genes that involved in cell cycle regulation, signal transduction, and apoptosis. Notably, As2O3 treatment increased the mRNA and protein levels of the cell cycle inhibitory proteins, p21 and p27. Interestingly, knocking down p21 or p27 individually did not alter As2O3-induced apoptosis and cell cycle arrest; however, the simultaneous down-regulation of both p21 and p27 resulted in attenuating of G1, G2/M arrest and reduction in apoptosis, thus indicating that p21 and p27 as the primary molecular targets of As2O3 against breast cancer. Overall, our results provide new insights into As2O3-related signaling activities, which may facilitate the development of As2O3-based anticancer strategies and/or combination therapies against solid tumors.

The role of HER2 in cancer therapy and targeted drug delivery

HER2 is highly expressed in a significant proportion of breast cancer, ovarian cancer, and gastric cancer. Since the discovery of its role in tumorigenesis, HER2 has received great attention in cancer research during the past two decades. Successful development of the humanized monoclonal anti-HER2 antibody (Trastuzumab) for the treatment of breast cancer further spurred scientists to develop various HER2 specific antibodies, dimerization inhibitors and kinase inhibitors for cancer therapy. On the other hand, the high expression of HER2 and the accessibility of its extracellular domain make HER2 an ideal target for the targeted delivery of anti-tumor drugs as well as imaging agents. Although there is no natural ligand for HER2, artificial ligands targeting HER2 have been developed and applied in various targeted drug delivery systems. The emphasis of this review is to elucidate the roles of HER2 in cancer therapy and targeted drug delivery. The structure and signal pathway of HER2 will be briefly described. The role of HER2 in tumorigenesis and its relationship with other tumor markers will be discussed. For the HER2 targeted cancer therapy, numerous strategies including the blockage of receptor dimerization, inhibition of the tyrosine kinase activity, and interruption of the downstream signal pathway will be summarized. For the targeted drug delivery to HER2 positive tumor cells, various targeting ligands and their delivery systems will be described in details.

Tachykinins and Neurokinin Receptors in Bone Marrow Functions: Neural-Hematopoietic Link

After many decades of neuropeptide research, advances in the field of tachykinins have considerably increased and shown their implications in several physiological processes. In this review we focus on the role of the tachykinins in the regulation of hematopoietic functions. Evidence has shown that neural control of this process is emerging as a significant category in hematopoietic modulation. In the context of this regulation, we discuss the existence of a complex network involving the neurokinin receptors, tachykinins and cytokines. This network is tightly regulated by each of its components.

Evaluation of a CXCR4 antagonist in a xenograft mouse model of inflammatory breast cancer

CXCL12/CXCR4 signaling, being important in the homing of cancer cells to lungs, bone and other organs, is a promising therapeutic target. Our purpose was to determine whether a peptide-based antagonist of CXCR4 would reduce primary tumor growth and/or metastasis in a preclinical mouse model of inflammatory breast cancer. We improved an existing model of inflammatory breast cancer for this study by luciferase transfection of SUM149 cells and the monitoring of such cells in mice by imaging and the luciferase assay. We implanted 2 x 10(6) SUM49-Luc cells along with matrigel into the left thoracic mammary fat pad of nude mice to produce tumors. Our mouse model exhibited important features of inflammatory breast cancer, namely, aggressive local disease, local metastases and distant metastases. To evaluate the efficacy of a CXCR4 antagonist CTCE-9908, by itself or in combination with paclitaxel, we treated groups of ten mice each with CTCE-9908 (25 mg/kg, injected subcutaneously 5 days/week), control peptide SC-9908, paclitaxel (10 mg/kg, injected subcutaneously twice a week), and CTCE-9908 plus paclitaxel concurrently. We assessed all mice weekly by whole-body luciferase imaging to quantify relative primary tumor burden and distant metastases. At the end of the experiment, we quantified primary tumors by weight and lung metastases by luciferase activity assay on tissue lysates. Paclitaxel, a known chemotherapeutic, inhibited primary tumor growth in our model (P < 0.05). CTCE-9908 did not significantly inhibit primary tumor growth or lung metastases as compared to control groups, without or with paclitaxel (P > 0.05). However, CTCE-9908 as a single therapy inhibited organ-specific metastasis to leg (P < 0.05 by chi-squared test and by two-sample t-test).

Nuclear localization of CXCR4 determines prognosis for colorectal cancer patients

Chemokines and their receptors are implicated in formation of colorectal cancer metastases. Especially CXCR4 is an important factor, determining migration, invasiveness, metastasis and proliferation of colorectal cancer cells. Object of this study was to determine expression of CXCR4 in tumor tissue of colorectal cancer patients and associate CXCR4 expression levels to clinicopathological parameters. Levels of CXCR4 expression of a random cohort of patients, who underwent primary curative resection of a colorectal carcinoma, were retrospectively determined by quantitative real-time RT-PCR and semi-quantitative analyses of immunohistochemical stained paraffin sections. Expression levels were associated to clinicopathological parameters. Using RT-PCR we found that a high expression of CXCR4 in the primary tumor was an independent prognostic factor for a poor disease free survival (p = 0.03, HR: 2.0, CI = 1.1-3.7). Immunohistochemical staining showed that nuclear distribution of CXCR4 in the tumor cells was inversely associated with disease free and overall survival (p = 0.04, HR: 2.6, CI = 1.0-6.2), while expression in the cytoplasm was not associated with prognosis. In conclusion, our study showed that a high expression of nuclear localized CXCR4 in tumor cells is an independent predictor for poor survival for colorectal cancer patients.

Prognostic significance of CXCR-4 expression in oral squamous cell carcinoma

OBJECTIVE

We investigated the prognostic significance of CXC chemokine receptor CXCR-4 expression in patients with oral squamous cell carcinoma (OSCC) and its relationship with matrix metalloproteinase 2 (MMP-2), MMP-9, and Ki-67 expression.

STUDY DESIGN

The CXCR-4, MMP-2, MMP-9, and Ki-67 expression was assessed immunohistochemically in 74 OSCC patients. The results were analyzed in connection with clinicopathologic factors.

RESULTS

The CXCR-4 expression was positive in 45 cases and significantly correlated with lymph node metastasis (P = .037), MMP-9 expression (P = .025), and Ki-67 expression (P = .001). Univariate analysis showed that CXCR-4 expression, MMP-9 expression, Ki-67 expression, tumor size, lymph node metastasis, clinical stage, and recurrence positively correlated with prognosis. Multivariate analysis indicated that CXCR-4 expression was an independent prognostic factor for poor survival in patients with OSCC.

CONCLUSION

Expression of CXCR-4 is a significant prognostic indicator for poor survival in patients with OSCC and correlates with expression of MMP-9 and Ki-67. The inhibition of CXCR-4 represents a possible molecular approach to the treatment of OSCC.

Chemokine–chemokine receptors in cancer immunotherapy

A surge in interest in the chemokine–chemokine receptor network is probably related to the expanding roles that chemokines have now been identified to play in human biology, particularly immunity. Specific tissue microenvironments express distinct chemokines and both hematopoietic and nonhematopoietic cells have receptor expression profiles that permit the coordinated trafficking and organization of cells within these specific tissues. Since the chemokine network plays critical roles in both the function of the immune system and the progression of cancer, it is an attractive target for therapeutic manipulation. This review will focus on chemokine and chemokine receptor network-related therapeutic interventions that utilize host–tumor interactions particularly involving the immune system.

High chemokine receptor CXCR4 level in triple negative breast cancer specimens predicts poor clinical outcome

INTRODUCTION

Basal-like tumors or triple negative breast cancers are those that lack hormone-receptor and HER-2 expressions. They are considered to be aggressive tumors, and molecular mechanism to account for this is poorly understood. CXCR4 is a chemokine receptor that has been linked to breast cancer invasion and metastasis. We postulate that high CXCR4 overexpression level in cancer specimens predicts a poor outcome in patients with triple negative breast cancers.

METHODS

One hundred fifty-one patients with triple negative breast cancers were prospectively accrued and analyzed. All had undergone standardized treatment and surveillance protocols. From each specimen, CXCR4 levels were detected using Western blots. Results were quantified against 1 microg of HeLa cells (positive controls). CXCR4 expression was defined as high (>or=6-fold) or low (<6-fold). Primary endpoints were cancer recurrence and death. Statistical analysis performed included Kaplan-Meier survival analysis, log-rank test, and Cox proportional hazard model.

RESULTS

At a median follow-up of 37 mo, patients whose tumors had high CXCR4 overexpression (>or=6-fold) had a significantly higher incidence of cancer recurrence (P=0.014) and cancer-related death (P=0.026) than those in the low CXCR4 group (<6-fold). After adjusting for tumor size and nodal status, the relative risk for cancer recurrence and death in the high CXCR4 group was 2.1-fold (P=0.007; 95% CI: 1.22 to 3.8) and 2-fold (P=0.047; 95% CI: 1.01 to 4.06) higher than those in the low CXCR4 group, respectively.

CONCLUSION

High CXCR4 overexpression in cancer specimens predicts a worse outcome in patients who have triple negative breast cancer.

SLITs suppress tumor growth in vivo by silencing Sdf1/Cxcr4 within breast epithelium

The genes encoding Slits and their Robo receptors are silenced in many types of cancer, including breast, suggesting a role for this signaling pathway in suppressing tumorigenesis. The molecular mechanism underlying these tumor-suppressive effects has not been delineated. Here, we show that loss of Slits, or their Robo1 receptor, in murine mammary gland or human breast carcinoma cells results in coordinate up-regulation of the Sdf1 and Cxcr4 signaling axis, specifically within mammary epithelium. This is accompanied by hyperplastic changes in cells and desmoplastic alterations in the surrounding stroma. A similar inverse correlation between Slit and Cxcr4 expression is identified in human breast tumor tissues. Furthermore, we show in a xenograft model that Slit overexpression down-regulates CXCR4 and dominantly suppresses tumor growth. These studies classify Slits as negative regulators of Sdf1 and Cxcr4 and identify a molecular signature in hyperplastic breast lesions that signifies inappropriate up-regulation of key prometastatic genes.

Post-transcriptional regulation of chemokine receptor CXCR4 by estrogen in HER2 overexpressing, estrogen receptor-positive breast cancer cells

Expression of the chemokine receptor CXCR4, a G protein-coupled receptor, and HER2, a receptor tyrosine kinase, strongly correlates with the aggressive and metastatic potential of breast cancer cells. We studied estrogen regulation of CXCR4 in estrogen receptor (ER)-positive MCF-7 breast cancer cells overexpressing HER2 (MCF7-HER2). Although estrogen evoked no change in CXCR4 mRNA levels, CXCR4 protein was significantly up-regulated after estrogen treatment of these cells, whereas estrogen had no effect on CXCR4 protein level in parental MCF7 cells that are low in HER2. Use of the CXCR4 specific inhibitor, AMD 3100, indicated that this increase in CXCR4 protein was partially responsible for the increase in estrogen-induced migration of these cells. The estrogen-induced increase in CXCR4 protein in MCF-7-HER2 cells was abrogated by the antiestrogen ICI 182780 and by gefitinib (Iressa; a phospho-tyrosine kinase inhibitor), indicating an ER-mediated effect and confirming involvement of receptor tyrosine kinases, respectively. Using specific pathway inhibitors, we show that the estrogen-induced increase in CXCR4 involves PI3K/AKT, MAPK and mTOR pathways. PI3K/AKT and MAPK pathways are known to result in the phosphorylation and functional inactivation of tuberin (TSC2) of tuberous sclerosis complex thereby negating its inhibitory effects on mTOR, which in turn stimulates the translational machinery. Small interfering RNA (siRNA) mediated knockdown of tuberin elevated the level of CXCR4 protein in MCF7-HER2 cells and also nullified further estrogen up-regulation of CXCR4. This study suggests a pivotal role of PI3 K, MAPK and mTOR pathways, via tuberin, in post-transcriptional control of CXCR4, initiated through estrogen-stimulated crosstalk between ER and HER2. Thus, post-transcriptional regulation of CXCR4 by estrogens acting through ER via kinase pathways may play a critical role in determining the metastatic potential of breast cancer cells.

A CXCR4 antagonist CTCE-9908 inhibits primary tumor growth and metastasis of breast cancer

BACKGROUND

CXCL12/CXCR4 signaling may be involved in tumor growth and angiogenesis, and homing of cancer cells to bone and other organs. Our purpose was to determine whether inhibition of CXCR4 with a peptide-based antagonist would reduce tumor growth and metastasis of breast cancer.

METHODS

We used two mouse models of breast cancer. In the first model, 1 x 10(6) MDA-MB-231 breast cancer cells transfected with luciferase were implanted into the inguinal mammary fat pad to produce primary tumors. In the second model, 1 x 10(5) MDA-231-BSC12 cells were injected into the left cardiac ventricle to produce bone metastases. CTCE-9908, a peptide analog of CXCL12 that competitively binds to CXCR4, was used to test the effect of inhibiting CXCR4. Five mice from each mouse model were treated with CTCE-9908 (25 mg/kg, injected subcutaneously 5 d/wk). All mice were assessed weekly using bioluminescent imaging to quantify relative volumes of tumor burden.

RESULTS

Bioluminescencent imaging showed that the mice treated with CTCE-9908 had significantly less primary tumor burden than the control mice. At 5 and 6 wk, the mice treated with CTCE-9908 had a 7-fold reduction and 5-fold reduction in primary tumor burden, respectively. Treatment with CTCE-9908 also significantly inhibited the rate of metastases compared with the control group. At 5 and 6 wk, the mice treated with CTCE-9908 demonstrated a 9-fold reduction and 20-fold reduction in metastatic tumor burden, respectively.

CONCLUSION

Treatment with the CXCR4 antagonist CTCE-9908 significantly reduced metastasis as well as primary tumor growth in mouse models of breast cancer.

Mesenchymal stem cells in early entry of breast cancer into bone marrow

Background

An understanding of BC cell (BCC) entry into bone marrow (BM) at low tumor burden is limited when compared to highly metastatic events during heavy tumor burden. BCCs can achieve quiescence, without interfering with hematopoiesis. This occurs partly through the generation of gap junctions with BM stroma, located close to the endosteum. These events are partly mediated by the evolutionary conserved gene, Tac1.

Methodogy/Principal Findings

This study focuses on the role of mesenchymal stem cells (MSCs), Tac1, SDF-1 and CXCR4 in BCC entry into BM. The model is established in studies with low numbers of tumor cells, and focuses on cancer cells with low metastatic and invasion potential. This allowed us to recapitulate early event, and to study cancer cells with low invasive potential, even when they are part of larger numbers of highly metastatic cells. A novel migration assay showed a facilitating role of MSCs in BCC migration across BM endothelial cells. siRNA and ectopic expression studies showed a central role for Tac1 and secondary roles for SDF-1α and CXCR4. We also observed differences in the mechanisms between low invasive and highly metastatic cells. The in vitro studies were verified in xenogeneic mouse models that showed a preference for low invasive BCCs to BM, but comparable movement to lung and BM by highly metastatic BCCs. The expressions of Tac1 and production of SDF-1α were verified in primary BCCs from paired samples of BM aspirates and peripheral blood.

Conclusions/Significance

MSC facilitate BCC entry into BM, partly through Tac1-mediated regulation of SDF-1α and CXCR4. We propose a particular population of BCC with preference for BM could be isolated for characterization. This population might be the subset that enter BM at an early time period, and could be responsible for cancer resurgence and resistance to current therapies.

CXCR-4 knockdown by small interfering RNA inhibits cell proliferation and invasion of oral squamous cell carcinoma cells

BACKGROUND

Oral squamous cell carcinomas (OSCCs) are characterized by a high degree of local invasion and a high rate of metastases to cervical lymph nodes. Downregulation of CXCR-4 by siRNA inhibits invasion and growth of breast and colon cancer cells. However, there have been no reports on the downregulation of CXCR-4 by small interfering RNA (siRNA) in oral cancer cells.

METHODS

We generated two stable CXCR-4-knockdown clones (KBsi and KOSCC-25Bsi) from the KB and KOSCC-25B OSCC cell lines by lentiviral delivery. In vitro invasion and cell proliferation assays were used to investigate the effect of CXCR-4 downregulation on cell proliferation and invasiveness in KBsi and KOSCC-25Bsi. Immunohistochemistry was performed to evaluate the correlation between CXCR-4 expression and proliferation in 26 OSCC tissue samples.

RESULTS

CXCR4-knockdown OSCC cells showed reduced invasiveness. The invasiveness of KBsi decreased to 29.5% of the vector-infected controls, and KOSCC-25Bsi decreased to 38.1% of the control vector-infected cells (P < 0.05). The CXCR4-knockdown OSCC cells grew significantly slower than the vector-infected control cells. KBsi and KOSCC-25Bsi cells proliferated at 69.5% and 71.7%, respectively, of the rate of control vector-infected cells (P < 0.05). CXCR-4-positive group had significantly higher PCNA labeling index than CXCR-4-negative group in OSCC tissue samples.

CONCLUSION

These results suggest that the downregulation of CXCR-4 induces anti-proliferative and anti-invasive effects in OSCC and that CXCR-4 might be a useful target molecule for the treatment of OSCC.

CXCL12/CXCR4 transactivates HER2 in lipid rafts of prostate cancer cells and promotes growth of metastatic deposits in bone

Chemokines and their receptors function in migration and homing of cells to target tissues. Recent evidence suggests that cancer cells use a chemokine receptor axis for metastasis formation at secondary sites. Previously, we showed that binding of the chemokine CXCL12 to its receptor CXCR4 mediated signaling events resulting in matrix metalloproteinase-9 expression in prostate cancer bone metastasis. A variety of methods, including lipid raft isolation, stable overexpression of CXCR4, cellular adhesion, invasion assays, and the severe combined immunodeficient-human bone tumor growth model were used. We found that (a) CXCR4 and HER2 coexist in lipid rafts of prostate cancer cells; (b) the CXCL12/CXCR4 axis results in transactivation of the HER2 receptor in lipid rafts of prostate cancer cells; (c) Src kinase mediates CXCL12/CXCR4 transactivation of HER2 in prostate cancer cells; (d) a pan-HER inhibitor desensitizes CXCR4-induced transactivation and subsequent matrix metalloproteinase-9 secretion and invasion; (e) lipid raft-disrupting agents inhibited raft-associated CXCL12/CXCR4 transactivation of the HER2 and cellular invasion; (f) overexpression of CXCR4 in prostate cancer cells leads to increased HER2 phosphorylation and migratory properties of prostate cancer cells; and (g) CXCR4 overexpression enhances bone tumor growth and osteolysis. These data suggest that lipid rafts on the cell membrane are the key site for CXCL12/CXCR4-induced HER2 receptor transactivation. This transactivation contributes to enhanced invasive signals and metastatic growth in the bone microenvironment.

Procollagen I COOH-terminal fragment induces VEGF-A and CXCR4 expression in breast carcinoma cells

The COOH-terminal fragment of procollagen type I (C3) is produced in tissues with high synthesis of collagen I, such as in breast cancer stroma and in bone. We previously demonstrated that C3 is chemoattractant for breast carcinoma and endothelial cells, and that in tumor cells it induces expression and activation of metalloproteinases (MMP) -2 and -9. Here we demonstrate that C3 induces expression of vascular-endothelial growth factor (VEGF) and of CXCR4, the receptor of the CXCL12/SDF-1 chemokine, in MDA MB 231 breast cancer cells. We show that the changes in gene expression and motility induced by C3 occur in a timely succession and are mediated by multiple and different signaling pathways. C3 induces early phosphorylation of p38/MAPK. Induction of VEGF expression requires continual activity of p38/MAPK and of Protein Kinase C (PKC). Pro-MMP-2 and -9 are induced through a signaling pathway involving G0alpha.i protein, and cell migration requires the activity of a combination of these signaling pathways. Our results suggest that C3 acts as a stromal-derived, cancer-promoting agent active in inducing the migratory phenotype and the survival of cancer cells and determining timely changes in their gene expression that establish conditions promoting tumor angiogenesis and invasion.

Inhibition of CXCR4 activity with AMD3100 decreases invasion of human colorectal cancer cells in vitro

AIM: To investigate the effect and mechanism of blockade of the CXC chemokine receptor-4 (CXCR4) signaling pathway by AMD3100, a small non-peptide CXCR4 inhibitor, on invasion and metastasis of colorectal cancer cells in vitro.

METHODS: Human colorectal cancer cell line SW480 was treated with AMD3100 at different final concentrations. 3-(4,5-dimethylthiazol-2-yl)-2.5-dipheny-tetrazolium bromide (MTT) assay was used to detect the effect of AMD3100 on cell proliferation. The invasion ability of SW480 cells was determined by cell invasion assay kit. In the presence of AMD3100, the CXCL12-mediated migratory response of SW480 cells was tested by classical chemotaxis assays. RT-PCR analysis and Western blotting were used to detect the expression of vascular endothelial growth factor (VEGF), matrix metalloproteinase-2 (MMP-2) and -9 (MMP-9) in SW480 cells.

RESULTS: Cell viability was significantly suppressed by AMD3100 in a dose-dependent manner. AMD3100 (100 and 1000 ng/mL) significantly inhibited the invasion ability of SW480 cells. Treatment with AMD3100 markedly reduced the expression of VEGF and MMP-9 but not MMP-2 in SW480 cells.

CONCLUSION: The CXCL12/CXCR4 system is an important mediator of proliferation and invasion of CXCR4-expressing colorectal cancer cells. AMD3100 inhibited invasion and metastasis activity of the colorectal cancer cell line SW480 through down-regulation of VEGF and MMP-9 expression.

CXCR4 membrane expression in node-negative breast cancer

CXC chemokine receptor 4 (CXCR4) has been reported to be involved in organ-specific homing of breast cancer-derived metastasis. We investigated CXCR4 expression by immunohistochemistry as a possible new prognostic factor for primary breast cancer. Two groups of women treated for breast cancer in 1991 at the Centre for the fight against cancer of Upper Normandy-France (Centre de Lutte contre le Cancer de Haute Normandie) were assessed retrospectively. CXCR4 expression was evaluated using standard immunohistochemistry. Usual prognostic factors were recorded in the computer database. Final date of follow-up was December 31, 2001. Tissues were available for 110 node-positive and 84 node-negative breast cancer patients treated in 1991. CXCR4 membrane staining was considered a strong prognostic factor for both 10-year metastasis-free- (p < 0.0001) and overall survival (p < 0.0001) in node-negative but not in node-positive breast cancer patients. CXCR4 cytoplasmic staining was not considered a significant prognostic factor. Our results suggest that CXCR4 membrane staining could be considered a new prognostic factor. Moreover, targeting CXCR4 in primary breast cancer patients may be a new therapeutic concept. However, these results warrant further investigation.

Pilot and feasibility study of serum chemokines as markers to distinguish prostatic disease in men with low total serum PSA

BACKGROUND

The incidence and prevalence of both benign prostatic hypertrophy (BPH) and prostate cancer (PCa) increase with the aging process. Our laboratory recently showed that the chemokines CXCL5 and CXCL12, which normally function as inflammatory mediators, are secreted at higher levels by aging prostate stromal fibroblasts and elicit proliferative responses from both prostate stromal fibroblast and epithelial cells. Because both CXCL5 and CXCL12 are secreted molecules, we hypothesized that their levels in patient serum might serve as biomarkers to distinguish between BPH and PCa.

METHODS

Serum CXCL5 and CXCL12 levels were determined using sandwich ELISAs for 51 men demonstrating low serum PSA values of < or =10 ng/ml who underwent diagnostic needle biopsy for the detection of PCa. The bivariate relationship of circulating chemokine levels, age, and disease status in the prostate was tested using the Wilcoxon rank-sum test.

RESULTS

Total serum CXCL12 levels were significantly higher for men who were biopsy positive compared to those who were biopsy negative for cancer and histological prostatitis (P = 0.050). Among men who were biopsy negative for PCa, total serum CXCL5 levels were inversely associated with prostate volume and were significantly higher in men with concomitant BPH and histological prostatitis compared to those without evidence of prostatic disease (P < 0.003).

CONCLUSIONS

The results of this pilot and feasibility study suggest that serum or plasma CXCL5 and CXCL12 levels may potentially distinguish between BPH and PCa among patients presenting with low serum PSA, and may be useful toward facilitating decisions to perform diagnostic needle biopsy in this patient population.

Calcium carbonate nanoparticle delivering vascular endothelial growth factor-C siRNA effectively inhibits lymphangiogenesis and growth of gastric cancer in vivo

A nonviral gene carrier, calcium carbonate (CaCO3) nanoparticle, was evaluated for efficient in vitro and in vivo delivery of small interfering RNA (siRNA) targeting vascular endothelial growth factor-C (VEGF-C). The chemically synthesized CaCO3 nanoparticle has a 58 nm diameter and +28.6 mV positive surface charge. It is capable of forming a CaCO3 nanoparticle-DNA complex and transferring DNA into targeted cells with high transfection efficiency while effectively protecting the encapsulated DNA from degradation. Furthermore, the CaCO3 nanoparticle-DNA complex has no obvious cytotoxicity for SGC-7901 cells, while a liposome-DNA complex exhibited measurable cytotoxicity. SGC-7901 cells transfected with a VEGF-C-targeted siRNA via CaCO3 nanoparticle exhibit significantly reduced VEGF-C expression as measured by real-time PCR and enzyme-linked immunosorbent assay; whereas no decrease in VEGF-C expression is observed in cells treated by control transfection. Transfection of SGC-7901 cells with VEGF-C siRNA via CaCO3 nanoparticle also dramatically suppresses tumor lymphangiogenesis, tumor growth and regional lymph-node metastasis in subcutaneous xenografts. Significant downregulation of VEGF-C messenger RNA expression in a subcutaneous xenograft derived from VEGF-C siRNA-treated SGC-7901 cells was confirmed by real-time PCR as compared to controls. We conclude that CaCO3 nanoparticle is a novel and nonviral system for effective delivery of siRNA for cancer gene therapy.

Chemokines: novel targets for breast cancer metastasis

Recent studies have highlighted the possible involvement of chemokines and their receptors in breast cancer progression and metastasis. Chemokines and their receptors constitute a superfamily of signalling factors whose prognosis value in breast cancer progression remains unclear. We will examine here the expression pattern of chemokines and their receptors in mammary gland physiology and carcinogenesis. The nature of the cells producing chemokines or harboring chemokine receptors appears to be crucial in certain conditions for example, the infiltration of the primary tumor by leukocytes and angiogenesis. In addition, chemokines, their receptors and the interaction with glycosaminoglycan (GAGs) are key players in the homing of cancer cells to distant metastasis sites. Several lines of evidence, including in vitro and in vivo models, suggest that the mechanism of action of chemokines in cancer development involves the modulation of proliferation, apoptosis, invasion, leukocyte recruitment or angiogenesis. Furthermore, we will discuss the regulation of chemokine network in tumor neovascularity by decoy receptors. The reasons accounting for the deregulation of chemokines and chemokine receptors expression in breast cancer are certainly crucial for the comprehension of chemokine role in breast cancer and are in several cases linked to estrogen receptor status. The targeting of chemokines and chemokine receptors by antibodies, small molecule antagonists, viral chemokine binding proteins and heparins appears as promising tracks to develop therapeutic strategies. Thus there is significant interest in developing strategies to antagonize the chemokine function, and an opportunity to interfere with metastasis, the leading cause of death in most patients.

Role of WISP-2/CCN5 in the maintenance of a differentiated and noninvasive phenotype in human breast cancer cells

WISP-2/CCN5 is an estrogen-regulated member of the "connective tissue growth factor/cysteine-rich 61/nephroblastoma overexpressed" (CCN) family of the cell growth and differentiation regulators. The WISP-2/CCN5 mRNA transcript is undetectable in normal human mammary cells, as well as in highly aggressive breast cancer cell lines, in contrast with its higher level in the breast cancer cell lines characterized by a more differentiated phenotype. We report here that knockdown of WISP-2/CCN5 by RNA interference in estrogen receptor alpha (ERalpha)-positive MCF-7 breast cancer cells induced an estradiol-independent growth linked to a loss of ERalpha expression and promoted epithelial-to-mesenchymal transdifferentiation. In contrast, forced expression of WISP-2/CCN5 directed MCF-7 cells toward a more differentiated phenotype. When introduced into the poorly differentiated, estrogen-independent, and invasive MDA-MB-231 breast cancer cells, WISP-2/CCN5 was able to reduce their proliferative and invasive phenotypes. In a series of ERalpha-positive tumor biopsies, we found a positive correlation between the expression of WISP-2/CCN5 and ID2, a transcriptional regulator of differentiation in normal and transformed breast cells. We propose that WISP-2/CCN5 is an important regulator involved in the maintenance of a differentiated phenotype in breast tumor epithelial cells and may play a role in tumor cell invasion and metastasis.

Genomic signatures of breast cancer metastasis

Despite significant advances in the treatment of primary cancer, the ability to predict the metastatic behavior of a patient's cancer, as well as to detect and eradicate such recurrences, remain major clinical challenges in oncology. While many potential molecular biomarkers have been identified and tested previously, none have greatly improved the accuracy of specimen evaluation over routine histopathological criteria and they predict individual outcomes poorly. However, the recent introduction of high-throughput microarray technology has opened new avenues in genomic investigation of cancer, and through application in tissue-based studies and appropriate animal models, has facilitated the identification of gene expression signatures that are associated with the lethal progression of breast cancer. The use of these approaches has the potential to greatly impact our knowledge of tumor biology, to provide efficient biomarkers, and enable development towards customized prognostication and therapies for the individual.