CXCR4 peptide antagonist inhibits primary breast tumor growth, metastasis and enhances the efficacy of anti-VEGF treatment or docetaxel in a transgenic mouse model

Cancer cell metabolism as new targets for novel designed therapies

Metabolic processes are altered in cancer cells, which obtain advantages from this metabolic reprogramming in terms of energy production and synthesis of biomolecules that sustain their uncontrolled proliferation. Due to the conceptual progresses in the last decade, metabolic reprogramming was recently included as one of the new hallmarks of cancer. The advent of high-throughput technologies to amass an abundance of omic data, together with the development of new computational methods that allow the integration and analysis of omic data by using genome-scale reconstructions of human metabolism, have increased and accelerated the discovery and development of anticancer drugs and tumor-specific metabolic biomarkers. Here we review and discuss the latest advances in the context of metabolic reprogramming and the future in cancer research.

Process of hepatic metastasis from pancreatic cancer: biology with clinical significance

PURPOSE

Pancreatic cancer shows a remarkable preference for the liver to establish secondary tumors. Selective metastasis to the liver is attributed to the development of potential microenvironment for the survival of pancreatic cancer cells. This review aims to provide a full understanding of the hepatic metastatic process from circulating pancreatic cancer cells to their settlement in the liver, serving as a basic theory for efficient prediction and treatment of metastatic diseases.

METHODS

A systematic search of relevant original articles and reviews was performed on PubMed, EMBASE and Cochrane Library for the purpose of this review.

RESULTS

Three interrelated phases are delineated as the contributions of the interaction between pancreatic cancer cells and the liver to hepatic metastasis process. Chemotaxis of disseminated pancreatic cancer cells and simultaneous defensive formation of platelets or neutrophils facilitate specific metastasis toward the liver. Remodeling of extracellular matrix and stromal cells in hepatic lobules and angiogenesis induced by proangiogenic factors support the survival and growth of clinical micrometastasis colonizing the liver. The bimodal role of the immune system or prevalence of cancer cells over the immune system makes metastatic progression successfully proceed from micrometastasis to macrometastasis.

CONCLUSIONS

Pancreatic cancer is an appropriate research object of cancer metastasis representing more than a straight cascade. If any of the successive or simultaneous phases, especially tumor-induced immunosuppression, is totally disrupted, hepatic metastasis will be temporarily under control or even cancelled forever. To shrink cancers on multiple fronts and prolong survival for patients, novel oral or intravenous anti-cancer agents covering one or different phases of metastatic pancreatic cancer are expected to be integrated into innovative strategies on the premise of safety and efficacious biostability.

SDF-1alpha concentration dependent modulation of RhoA and Rac1 modifies breast cancer and stromal cells interaction

Background

The interaction of SDF-1alpha with its receptor CXCR4 plays a role in the occurrence of distant metastasis in many solid tumors. This interaction increases migration from primary sites as well as homing at distant sites.

Methods

Here we investigated how SDF-1α could modulate both migration and adhesion of cancer cells through the modulation of RhoGTPases.

Results

We show that different concentrations of SDF-1α modulate the balance of adhesion and migration in cancer cells. Increased migration was obtained at 50 and 100 ng/ml of SDF-1α; however migration was reduced at 200 ng/ml. The adhesion between breast cancer cells and BMHC was significantly increased by SDF-1α treatment at 200 ng/ml and reduced using a blocking monoclonal antibody against CXCR4. We showed that at low SDF-1α concentration, RhoA was activated and overexpressed, while at high concentration Rac1 was promoting SDF-1α mediating-cell adhesion.

Conclusion

We conclude that SDF-1α concentration modulates migration and adhesion of breast cancer cells, by controlling expression and activation of RhoGTPases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1556-7) contains supplementary material, which is available to authorized users.

The therapeutic potential of a C-X-C chemokine receptor type 4 (CXCR-4) antagonist on hypertrophic scarring in vivo

Effective prevention and treatment of hypertrophic scars (HTSs), a dermal form of fibrosis that frequently occurs following thermal injury to deep dermis, are unsolved significant clinical problems. Previously, we have found that stromal cell-derived factor 1/CXCR4 signaling is up-regulated during wound healing in burn patients and HTS tissue after thermal injury. We hypothesize that blood-borne mononuclear cells are recruited into wound sites after burn injury through the chemokine pathway of stromal cell-derived factor 1 and its receptor CXCR4. Deep dermal injuries to the skin are often accompanied by prolonged inflammation, which leads to chemotaxis of mononuclear cells into the wounds by chemokine signaling where fibroblast activation occurs and ultimately HTS are formed. Blocking mononuclear cell recruitment and fibroblast activation, CXCR4 antagonism is expected to reduce or minimize scar formation. In this study, the inhibitory effect of CXCR4 antagonist CTCE-9908 on dermal fibrosis was determined in vivo using a human HTS-like nude mouse model, in which split-thickness human skin is transplanted into full-thickness dorsal excisional wounds in athymic mice, where these wounds subsequently develop fibrotic scars that resemble human HTS as previously described. CTCE-9908 significantly attenuated scar formation and contraction, reduced the accumulation of macrophages and myofibroblasts, enhanced the remodeling of collagen fibers, and down-regulated the gene and protein expression of fibrotic growth factors in the human skin tissues. These findings support the potential therapeutic value of CXCR4 antagonist in dermal fibrosis and possibly other fibroproliferative disorders.

Downregulation of CXCR4 in Metastasized Breast Cancer Cells and Implication in Their Dormancy

Our understanding of the mechanism of cancer dormancy is emerging, but the underlying mechanisms are not fully understood. Here we analyzed mouse xenograft tumors derived from human breast cancer tissue and the human breast cancer cell line MDA-MB-231 to identify the molecules associated with cancer dormancy. In immunohistological examination using the proliferation marker Ki-67, the tumors included both proliferating and dormant cancer cells, but the number of dormant cells was remarkably increased when they metastasized to the lung. In the gene expression analysis of the orthotopic cancer cells by a single-cell multiplex real-time quantitative reverse transcription PCR followed by flow cytometric analysis, restrained cellular proliferation was associated with downregulation of the chemokine receptor CXCR4. In the immunohistological and flow cytometric analyses, the expression level of CXCR4 in the metastasized cancer cells was decreased compared with that in the cancer cells in orthotopic tumors, although the expression level of the CXCR4 ligand CXCL12 was not reduced in the lung. In addition, the proliferation of the metastasized cancer cells was further decreased by the CXCR4 antagonist administration. In the ex vivo culture of the metastasized cancer cells, the expression level of CXCR4 was increased, and in the xenotransplantation of ex vivo cultured cancer cells, the expression level of CXCR4 was again decreased in the metastasized cancer cells in the lung. These findings indicate that CXCR4 is downregulated in metastasized breast cancer cells and implicated in their dormancy.

Antileukemia activity of the novel peptidic CXCR4 antagonist LY2510924 as monotherapy and in combination with chemotherapy

Targeting the stromal cell-derived factor 1α (SDF-1α)/C-X-C chemokine receptor type 4 (CXCR4) axis has been shown to be a promising therapeutic approach to overcome chemoresistance in acute myeloid leukemia (AML). We investigated the antileukemia efficacy of a novel peptidic CXCR4 antagonist, LY2510924, in preclinical models of AML. LY2510924 rapidly and durably blocked surface CXCR4 and inhibited stromal cell-derived factor 1 (SDF-1)α-induced chemotaxis and prosurvival signals of AML cells at nanomolar concentrations more effectively than the small-molecule CXCR4 antagonist AMD3100. In vitro, LY2510924 chiefly inhibited the proliferation of AML cells with little induction of cell death and reduced protection against chemotherapy by stromal cells. In mice with established AML, LY2510924 caused initial mobilization of leukemic cells into the circulation followed by reduction in total tumor burden. LY2510924 had antileukemia effects as monotherapy as well as in combination with chemotherapy. Gene expression profiling of AML cells isolated from LY2510924-treated mice demonstrated changes consistent with loss of SDF-1α/CXCR4 signaling and suggested reduced proliferation and induction of differentiation, which was proved by showing the attenuation of multiple prosurvival pathways such as PI3K/AKT, MAPK, and β-catenin and myeloid differentiation in vivo. Effective disruption of the SDF-1α/CXCR4 axis by LY2510924 may translate into effective antileukemia therapy in future clinical applications.

Discovery of novel N-aryl piperazine CXCR4 antagonists

A novel series of CXCR4 antagonists with substituted piperazines as benzimidazole replacements is described. These compounds showed micromolar to nanomolar potency in CXCR4-mediated functional and HIV assays, namely inhibition of X4 HIV-1(IIIB) virus in MAGI-CCR5/CXCR4 cells and inhibition of SDF-1 induced calcium release in Chem-1 cells. Preliminary SAR investigations led to the identification of a series of N-aryl piperazines as the most potent compounds. Results show SAR that indicates type and position of the aromatic ring, as well as type of linker and stereochemistry are significant for activity. Profiling of several lead compounds showed that one (49b) reduced susceptibility towards CYP450 and hERG, and the best overall profile when considering both SDF-1 and HIV potencies (6-20 nM).

Investigational therapies targeting signal transducer and activator of transcription 3 for the treatment of cancer

INTRODUCTION

Signal transducer and activator of transcription 3 (STAT3) mediates the expression of a variety of genes in response to cell stimuli and thus plays a key role in several cellular processes such as cell growth and apoptosis. Deregulation of the STAT3 activity has been shown in many malignancies, including breast, head and neck, prostate, pancreas, ovarian and brain cancers and melanoma. Thus, STAT3 may represent an ideal target for cancer therapy.

AREAS COVERED

The authors review recent data on the role of STAT3 in tumor initiation and progression, as well as the ongoing clinical trials in cancer patients. The content includes information derived from trial databases, regulatory authorities and scientific literature.

EXPERT OPINION

Targeting STAT3 activation leads to the inhibition of tumor growth and metastasis both in vitro and in vivo without affecting normal cells; this suggests that STAT3 could be a valid molecular target for cancer therapy. Extensive clinical research is trying to find anti-STAT3 agents with high single-agent activity. The identification and development of novel drugs that can target deregulated STAT3 activation effectively is both a scientific and clinical challenge that needs to be addressed in the near future.

Crucial microRNAs and genes of human primary breast cancer explored by microRNA-mRNA integrated analysis

This study aimed to screen potential microRNAs (miRNAs) and genes related to human primary breast cancer. The gene and miRNA expression profile data of GSE19783 was obtained from Gene Expression Omnibus. The matched messenger RNA (mRNA) and miRNA expression profiles of 100 human primary breast cancer samples were chosen for further analysis. The miRNA-gene regulatory modules were screened via iterative multiplicative updating algorithm. The potential functions of genes in modules were predicted by functional and pathway enrichment analysis; meanwhile, the potential functions of miRNAs were predicted by functional enrichment analysis. Furthermore, miRNA-miRNA functional synergistic network and miRNA-miRNA co-regulatory network were constructed. Totally, 16 miRNA-gene modules were screened, containing 222 miRNA-gene interactions. The genes in these modules were mainly related to breast cancer. Genes in module 6 (e.g., SFRP1) were enriched in cell junction assembly; genes in module 8 and 12 (e.g., ESR1 and ERBB4) were significantly implicated in mammary gland alveolus and lobule development. Meanwhile, genes in module 12 (e.g., ERBB4) were enriched in the pathway of endocytosis. Besides, several miRNAs (e.g., miR-375) were enriched in inflammatory cell apoptotic process; some other miRNAs (e.g., miR-139-5p and miR-9) were enriched in response to vitamin D. Additionally, miR-139-5p with several other miRNAs (e.g., miR-9) co-regulated SFRP1; miR-375, miR-592, and miR-135a co-regulated ESR1 and ERBB4. Some miRNAs (e.g., miR-139-5p and miR-9) and their target gene SFRP1, as well as several other miRNAs (e.g., miR-375, miR-592, and miR-135a) and their target genes (e.g., ESR1 and ERBB4), might be crucial in the pathogenesis of primary breast cancer.

Blockade of CXCL12/CXCR4 signaling inhibits intrahepatic cholangiocarcinoma progression and metastasis via inactivation of canonical Wnt pathway

Background

Intrahepatic cholangiocarcinoma (IHCC) is the second most frequent primary malignant liver tumor following hepatocellular carcinoma. It is a highly fatal disease and has few therapeutics. The CXC chemokine ligand-12 (CXCL12)/CXC chemokine receptor type 4 (CXCR4) axis has been shown to be involved in tumorgenesis, proliferation, and angiogenesis in a variety of cancers including IHCC. However, its prognostic significance in IHCC is unclear. The purpose of this study was to examine the functional role of CXCR4 in the progression and metastasis of IHCC and explore the underlying mechanism.

Methods

The CXCR4 expression, overall survival, and the clinical characteristics including age, sex, differentiation degree, tumor size, vascular invasion, lymph node metastasis, TNM stage, and T stage were analyzed for 122 IHCC patients. Short hairpin RNA (shRNA) against CXCR4 was used to disrupt the CXCL12/CXCR4 signal transduction pathways in IHCC cell lines. In vitro assays, including CCK-8 assay, flow cytometry, and colony formation assay, and in vivo tumor formation assay were utilized to detect the cell phenotype of CXCR4 knockdown cells. Transwell and wound healing assays were used to examine the IHCC cell invasion and migration ability. The Wnt pathway was assessed by Western blot and β-Catenin/Tcf transcription reporter assay.

Results

We demonstrated that CXCR4 expression was closely correlated with IHCC progression and metastasis characteristics. The overall survival of patients with high CXCR4 expression was significantly lower than that of patients with low CXCR4 expression. Furthermore, we showed that the abrogation of CXCR4 had significantly negative influence on the IHCC cell phenotype, including in vitro cell proliferation, cell cycle, colony formation, cell invasion, and in vivo tumorigenicity. In addition, CXCR4 knockdown downregulated Wnt target genes and mesenchymal markers such as Vimentin and Slug.

Conclusions

In conclusion, our result shows that high CXCR4 expression is associated with IHCC progression and metastasis via the canonical Wnt pathway, suggesting that CXCR4 may serve as a promising therapeutic target for IHCC.

CXCL12/CXCR4 blockade by oncolytic virotherapy inhibits ovarian cancer growth by decreasing immunosuppression and targeting cancer-initiating cells

Signals mediated by the chemokine CXCL12 and its receptor CXCR4 are involved in the progression of ovarian cancer through enhancement of tumor angiogenesis and immunosuppressive networks that regulate dissemination of peritoneal metastasis and development of cancer-initiating cells (CICs). In this study, we investigated the antitumor efficacy of a CXCR4 antagonist expressed by oncolytic vaccinia virus (OVV) against an invasive variant of the murine epithelial ovarian cancer cell line ID8-T. This variant harbors a high frequency of CICs that form multilayered spheroid cells and express the hyaluronan receptor CD44, as well as stem cell factor receptor CD117 (c-kit). Using an orthotopic ID8-T tumor model, we observed that i.p. delivery of a CXCR4 antagonist-expressing OVV led to reduced metastatic spread of tumors and improved overall survival compared with oncolysis alone. Inhibition of tumor growth with the armed virus was associated with efficient killing of CICs, reduced expression of ascitic CXCL12 and vascular endothelial growth factor, and decreases in i.p. numbers of endothelial and myeloid cells, as well as plasmacytoid dendritic cells. These changes, together with reduced recruitment of T regulatory cells, were associated with higher ratios of IFN-γ(+)/IL-10(+) tumor-infiltrating T lymphocytes, as well as induction of spontaneous humoral and cellular antitumor responses. Similarly, the CXCR4 antagonist released from virally infected human CAOV2 ovarian carcinoma cells inhibited peritoneal dissemination of tumors in SCID mice, leading to improved tumor-free survival in a xenograft model. Our findings demonstrate that OVV armed with a CXCR4 antagonist represents a potent therapy for ovarian CICs with a broad antitumor repertoire.

Prognostic value of stromal cell-derived factor 1 expression in patients with gastric cancer after surgical resection

Aberrant chemokine stromal cell-derived factor 1 (SDF-1) expression has been shown to be involved in the development and progression of various malignancies. Our present study aims to investigate the clinical and prognostic value of SDF-1 expression and improve risk stratification in patients with gastric cancer. Peritumoral and intratumoral SDF-1 levels were assessed in 220 retrospectively enrolled gastric cancer patients, and their relations with clinicopathological features and clinical outcomes were evaluated. A predictive nomogram was created to refine risk stratification for overall survival of gastric cancer patients. Compared with peritumor tissues, tumor tissues showed decreased SDF-1 expression levels according to TNM stage progression in gastric cancer specimens. Peritumoral SDF-1 expression correlated positively with tumor invasion depth and lymph node metastasis, whereas intratumoral SDF-1 expression associated negatively with tumor size, tumor differentiation, tumor invasion depth, lymph node metastasis, and clinical TNM stage. Moreover, both low peritumoral SDF-1 expression and high intratumoral SDF-1 expression indicated favorable overall survival, and SDF-1 risk derived from the peritumoral/intratumoral SDF-1 expression signature could stratify prognosis of patients with gastric cancer. After backward elimination, SDF-1 risk was identified as an independent prognostic factor for survival. Finally, a predictive nomogram was generated with identified independent prognosticators to assess patient survival at 3 and 5 years following surgery. Conclusively, SDF-1 risk, an identified independent prognostic factor, could be developed into a nomogram with tumor invasion depth, lymph node involvement, and distant metastasis to refine predictive accuracy for survival in patients with gastric cancer after surgical resection.

CXCR4 inhibition enhances radiosensitivity, while inducing cancer cell mobilization in a prostate cancer mouse model

Preclinical studies show that stroma affects sensitivity of prostate cancer cells via activation of the CXCR4/CXCL12 pathway. Here we studied the effect of CXCR4 inhibition combined with irradiation in prostate cancer cells. In an in vitro co-culture with stromal cells, the CXCR4 inhibitor AMD3100 sensitized prostate cancer cell lines PC3-Luc and LNCaP to irradiation (P = 0.04). Tumor growth and metastasis were evaluated in mice xenografted with luciferase-expressing PC3 cells that received 5 Gy irradiation weekly ± 3.5 mg/kg AMD3100 daily intraperitoneally. The irradiated xenografts showed higher CXCR4 (P = 0.006) and CXCL12 (P = 0.01) expression, compared to controls. AMD3100 sensitized the xenografts to irradiation at the fourth week of treatment (P = 0.02). However AMD3100 also mobilized tumor cells at days 14 and 21 (P < 0.0001), as shown by bioluminescent imaging. In conclusion, AMD3100 transiently enhances prostate cancer radiosensitivity, but induces cancer cell mobilization.

Use of rodents as models of human diseases

Advances in molecular biology have significantly increased the understanding of the biology of different diseases. However, these discoveries have not yet been fully translated into improved treatments for patients with diseases such as cancers. One of the factors limiting the translation of knowledge from preclinical studies to the clinic has been the limitations of in vivo diseases models. In this brief review, we will discuss the advantages and disadvantages of rodent models that have been developed to simulate human pathologies, focusing in models that employ xenografts and genetic modification. Within the framework of genetically engineered mouse (GEM) models, we will review some of the current genetic strategies for modeling diseases in the mouse and the preclinical studies that have already been undertaken. We will also discuss how recent improvements in imaging technologies may increase the information derived from using these GEMs during early assessments of potential therapeutic pathways. Furthermore, it is interesting to note that one of the values of using a mouse model is the very rapid turnover rate of the animal, going through the process of birth to death in a very short timeframe relative to that of larger mammalian species.

Specific protein markers for stem cell cross-talk with neighboring cells in the environment

A stem cell interacts with the neighboring cells in its environment. To maintain a living organism's metabolism, either cell-cell or cell-environment interactions may be significant. Usually, these cells communicate with each other through biological signaling by interactive behaviors of primary proteins or complementary chemicals. The signaling intermediates offer the stem cell's functionality on its metabolism. With the rapid advent of omics technologies, various specific markers by which stem cells cooperate with their surroundings have been discovered and established. In this article, we review several stem cell markers used to communicate with either cancer or immune cells in the human body.

Irradiation enhances expression of cxcr4 in murine glioma cells via HIF-1α-independent pathway

OBJECTIVE

To investigate levels of chemokine (C-X-C motif) receptor 4 (cxcr4) mRNA and protein in X-irradiated glioma cells.

METHODS

Murine malignant glioma GL261 cells transfected with hypoxia-inducible factor (HIF)-1α miRNA or control miRNA were irradiated with X-radiation. Cxcr4 mRNA and protein were analysed using real-time reverse transcription-polymerase chain reaction and Western blot, respectively.

RESULTS

Levels of cxcr4 protein in GL261 cells increased in a radiation dose-dependent manner 48 h after 0, 5, 10 and 15 Gy X-irradiation. Irradiation of both HIF-1α knockdown cells and control cells resulted in a significant increase in cxcr4 mRNA levels, compared with nonirradiated cells, at 24 h after 5 Gy X-irradiation.

CONCLUSION

Irradiation enhances expression of cxcr4 in glioma cells via a HIF-1α-independent pathway.

CXC and CC chemokines as angiogenic modulators in nonhaematological tumors

Chemokines are a superfamily of structurally homologous heparin-binding proteins that includes potent inducers and inhibitors of angiogenesis. The imbalance between angiogenic and angiostatic chemokine activities can lead to abnormalities, such as chronic inflammation, dysplastic transformation, and even tumor development and spreading. In this review, we summarize the current literature regarding the role of chemokines as modulators of tumor angiogenesis and their potential role as therapeutic targets in patients with nonhaematological tumors.

CXCL12 modulation of CXCR4 and CXCR7 activity in human glioblastoma stem-like cells and regulation of the tumor microenvironment

Chemokines are crucial autocrine and paracrine players in tumor development. In particular, CXCL12, through its receptors CXCR4 and CXCR7, affects tumor progression by controlling cancer cell survival, proliferation and migration, and, indirectly, via angiogenesis or recruiting immune cells. Glioblastoma (GBM) is the most prevalent primary malignant brain tumor in adults and despite current multimodal therapies it remains almost incurable. The aggressive and recurrent phenotype of GBM is ascribed to high growth rate, invasiveness to normal brain, marked angiogenesis, ability to escape the immune system and resistance to standard of care therapies. Tumor molecular and cellular heterogeneity severely hinders GBM therapeutic improvement. In particular, a subpopulation of chemo- and radio-therapy resistant tumorigenic cancer stem-like cells (CSCs) is believed to be the main responsible for tumor cell dissemination to the brain. GBM cells display heterogeneous expression levels of CXCR4 and CXCR7 that are overexpressed in CSCs, representing a molecular correlate for the invasive potential of GBM. The microenvironment contribution in GBM development is increasingly emphasized. An interplay exists between CSCs, differentiated GBM cells, and the microenvironment, mainly through secreted chemokines (e.g., CXCL12) causing recruitment of fibroblasts, endothelial, mesenchymal and inflammatory cells to the tumor, via specific receptors such as CXCR4. This review covers recent developments on the role of CXCL12/CXCR4-CXCR7 networks in GBM progression and the potential translational impact of their targeting. The biological and molecular understanding of the heterogeneous GBM cell behavior, phenotype and signaling is still limited. Progress in the identification of chemokine-dependent mechanisms that affect GBM cell survival, trafficking and chemo-attractive functions, opens new perspectives for development of more specific therapeutic approaches that include chemokine-based drugs.

A phase I trial of LY2510924, a CXCR4 peptide antagonist, in patients with advanced cancer

PURPOSE

Overexpression of C-X-C motif receptor 4 (CXCR4) is implicated in tumor progression. LY2510924 is a peptide antagonist, which blocks stromal cell-derived factor-1 (SDF1) from CXCR4 binding.

EXPERIMENTAL DESIGN

This phase I study included two parts: a 3+3 dose escalation (part A) and dose confirmation (part B). LY2510924 was administered as a daily subcutaneous injection on a 28-day cycle. The primary objective was to determine the recommended phase II dose. Secondary objectives included safety, pharmacokinetics, efficacy, and pharmacodynamic response, including mobilization of CD34(+) hematopoietic stem cells into the peripheral blood.

RESULTS

Forty-five patients were enrolled, 25 in part A and 20 in part B. Patients were administered increasing doses of LY2510924: 1.0, 2.5, 5.0, 10, 20, and 30 mg/day for part A and 2.5 or 20 mg/day for part B. Two patients (30-mg/day cohort) experienced dose-limiting toxicities of grade 3 increased neutrophil count. The maximum tolerated dose (MTD) was 20 mg/day. The most common drug-related treatment-emergent adverse events were fatigue (9%), injection-site reaction (9%), injection site pruritus (7%), and nausea (7%). The best response was stable disease for nine patients (20%). At the end of cycle 1, mean peak LY2510924 plasma concentration and the 24-hour area under the plasma concentration versus time curve increased slightly more than dose proportionally. LY2510924 dose dependently increased CD34(+) cell counts in peripheral blood up to 18-fold.

CONCLUSIONS

LY2510924 demonstrated CD34(+) cell mobilization at doses ≥2.5 mg/day with a tolerable safety profile up to an MTD of 20 mg/day.

Posttranscriptional control of the chemokine receptor CXCR4 expression in cancer cells

We demonstrate that CXCR4 mRNA contains ARE in its 3′-UTR and regulated by the RNA-binding proteins, TTP and HuR. Normalization of the aberrant TTP-HuR axis resulted in reduced invasion and migration of breast cancer cells toward CXCL12.

CXCR4 is a chemokine receptor that is overexpressed in certain cancer types and involved in migration toward distant organs. The molecular mechanisms underlying CXCR4 expression in invasive cancer, particularly posttranscriptional regulation, are poorly understood. Here, we find that CXCR4 harbors AU-rich elements (AREs) in the 3′-untranslated region (3′-UTR) that bind and respond to the RNA-binding proteins, tristetraprolin (TTP/ZFP36) and HuR (ELAVL1). Different experimental approaches, including RNA immunoprecipitation, 3′-UTR reporter, RNA shift and messenger RNA (mRNA) half-life studies confirmed functionality of the CXCR4 ARE. Wild-type TTP, but not the zinc finger mutant, C124R, was able to bind CXCR4 mRNA and ARE. In the invasive breast cancer phenotype, aberrant expression of CXCR4 is linked to both TTP deficiency and HuR overexpression. HuR silencing led to decreased CXCR4 mRNA stability and expression, and significant reduction in migration of the cells toward the CXCR4 ligand, CXCL12. Derepression of TTP using miR-29a inhibitor led to significant reduction in CXCR4 mRNA stability, expression and migration capability of the cells. The study shows that CXCR4 is regulated by ARE-dependent posttranscriptional mechanisms that involve TTP and HuR, and that aberration in this pathway helps cancer cells migrate toward the CXCR4 ligand. Targeting posttranscriptional control of CXCR4 expression may constitute an alternative approach in cancer therapy.

The prognostic value of CXCR4 in ovarian cancer: a meta-analysis

OBJECTIVE

Recent reports have shown that C-X-C chemokine receptor 4 (CXCR4) is expressed in ovarian cancer and plays an important role in metastasis. However, the prognostic value of CXCR4 in ovarian cancer remains controversial and has not been emphasized. The aim of this study is to evaluate the prognostic significance of CXCR4 in ovarian cancer by performing a meta-analysis.

METHODS

We systematically searched for studies evaluating the relationship between CXCR4 expression and the outcome of ovarian cancer patients. Only articles in which CXCR4 expression was detected by immunohistochemical staining were included. Hazard ratios (HRs) and relative risk (RR) with 95% confidence intervals (CIs) were pooled as effect size (ES) across studies for overall survival (OS) and progression-free survival (PFS).

RESULTS

A total of 729 patients from 7 studies (6 articles) were included in this meta-analysis. Our results showed that high CXCR4 expression was significantly associated with poor prognosis in terms of OS (ES, 2.81; 95% CI, 1.16-6.80; p = 0.022) and PFS (ES, 8.48; 95% CI, 2.13-33.70; p = 0.002) in ovarian cancer patients. The association between high CXCR4 expression and poor ovarian cancer prognosis in OS was also statistically significant in subgroups of Asian and III-IV patients constituting 70%.

CONCLUSIONS

The present meta-analysis indicated that high CXCR4 expression was associated with poor prognosis in ovarian cancer. More studies, especially larger scale and well-matched researches, are warranted to clarify the prognostic effect of CXCR4 on the outcome of ovarian cancer.

Expression of CXCR4 is associated with progression and invasion in patients with nasal-surface basal cell carcinoma

BACKGROUND

Basal cell carcinoma (BCC) is the most common type of skin cancer with an increasing incidence worldwide that imposes a considerable burden on public health. C-X-C chemokine receptor (CXCR4) plays a vital role in initiation, progression and metastasis of several types of cancers. The aim of the present study was to investigate the expression and clinical significance of CXCR4 in BCC.

METHODS

In this study, 80 samples of primary BCC were assessed for CXCR4 expression using immunohistochemistry. The mRNA and protein expression levels of CXCR4 were evaluated by real-time reverse transcription polymerase chain reaction and Western blot analysis, respectively.

RESULTS

CXCR4-positive staining was detected in 70% of BCC samples. Overexpression of CXCR4 was significantly associated with tumor size (>2 vs. 2 cm, p = 0.002) and pathological type (invasive vs. noninvasive, p = 0.007). CXCR4 was also upregulated at transcriptional and translational levels.

CONCLUSION

Our study revealed that the expression of CXCR4 was associated with progression and invasion in patients with BCC. It may be a considerable biomarker to assess invasiveness of nasal-surface BCC and to guide clinical management of such tumors.

Discovery and computer aided potency optimization of a novel class of small molecule CXCR4 antagonists

Amongst the chemokine signalling axes involved in cancer, chemokine CXCL12 acting on chemokine receptor CXCR4 is particularly significant since it orchestrates migration of cancer cells in a tissue-specific metastatic process. High CXCR4 tumour expression is associated with poor prognosis of lung, brain, CNS, blood and breast cancers. We have identified a new class of small molecule CXCR4 antagonists based on the use of computational modelling studies in concert with experimental determination of in vitro activity against CXCL12-induced intracellular calcium mobilisation, proliferation and chemotaxis. Molecular modelling proved to be a useful tool in rationalising our observed potencies, as well as informing the direction of the synthetic efforts aimed at producing more potent compounds.

Targeting CXCL12/CXCR4 signaling with oncolytic virotherapy disrupts tumor vasculature and inhibits breast cancer metastases

Oncolytic viruses hold promise for the treatment of cancer, but their interaction with the tumor microenvironment needs to be elucidated for optimal tumor cell killing. Because the CXCR4 receptor for the stromal cell-derived factor-1 (SDF-1/CXCL12) chemokine is one of the key stimuli involved in signaling interactions between tumor cells and their stromal microenvironment, we used oncolytic virotherapy with a CXCR4 antagonist to target the CXCL12/CXCR4 signaling axis in a triple-negative 4T1 breast carcinoma in syngeneic mice. We show here that CXCR4 antagonist expression from an oncolytic vaccinia virus delivered intravenously to mice with orthotopic tumors attains higher intratumoral concentration than its soluble counterpart and exhibits increased efficacy over that mediated by oncolysis alone. A systemic delivery of the armed virus after resection of the primary tumor was efficacious in inhibiting the development of spontaneous metastasis and increased overall tumor-free survival. Inhibition of tumor growth with the armed virus was associated with destruction of tumor vasculature, reductions in expression of CXCL12 and VEGF, and decrease in intratumoral numbers of bone marrow-derived endothelial and myeloid cells. These changes led to induction of antitumor antibody responses and resistance to tumor rechallenge. Engineering an oncolytic virus armed with a CXCR4 antagonist represents an innovative strategy that targets multiple elements within the tumor microenvironment. As such, this approach could have a significant therapeutic impact against primary and metastatic breast cancer.

Emerging targeted agents in metastatic breast cancer

Extensive preclinical experimentation has conceptually changed the way we perceive breast cancer, with the wide spectrum of genomic alterations governing its malignant progression now being recognized. Functional genomics has helped us identify important genetic defects that can be pharmaceutically targeted in the setting of metastatic disease. Rationally chosen combination regimens are now under clinical investigation. Recent data underline the functional importance of the tumour-associated stroma, with several candidate molecular targets now emerging. Data elucidating a cellular hierarchy within the breast cancer cellular compartment support the existence of a therapy-resistant subpopulation of breast cancer stem cells. Identification of the developmental pathways that dictate their malignant phenotype and use of high-throughput screening techniques are leading to new therapeutic avenues. In this Review, we present the biological rationale for the clinical development of more than 15 different classes of targeted agents in breast cancer, along with evidence supporting rational combinations. However, metastatic breast cancer resembles a Darwinian evolutionary system, with 'driver' mutations and epigenetic changes determining clonal selection according to branching trajectories. This evolution is reflected in the molecular heterogeneity of the disease and poses severe impediments to the successful clinical development of emerging targeted agents.

CXCR4 inhibition with AMD3100 sensitizes prostate cancer to docetaxel chemotherapy

Several in vitro and in vivo models have revealed the key role of CXCR4/CXCL12 axis in tumor-stroma interactions. Stromal cells present in the tumor microenvironment express high levels of CXCL12 protein, directly stimulating proliferation and migration of CXCR4-expressing cancer cells. This specific prosurvival influence of stromal cells on tumor cells is thought to protect them from cytotoxic chemotherapy and is postulated as a possible explanation for the minimal residual disease in hematological and solid cancers. Therefore, CXCR4/CXCL12 signaling is an attractive therapeutic target in cancer, as proven in preclinical leukemia mouse models, where CXCR4 inhibition sensitized cancer cells to conventional chemotherapy. This study investigates whether inhibition of CXCR4 with the specific inhibitor AMD3100 sensitizes human prostate cancer cells to docetaxel. We showed that both mouse and human stromal cell lines have a protective effect on PC3-luc cells by promoting their survival after chemotherapy. Furthermore, we demonstrated that AMD3100 sensitizes PC3-luc cells to docetaxel. In a subcutaneous xenograft mouse model of human prostate carcinoma, we showed that a combination of docetaxel and AMD3100 exerts increased antitumor effect compared with docetaxel alone. We concluded that CXCR4 inhibition chemosensitizes prostate cancer cells, both in vitro and in vivo. To explore the relevance of these findings, we analyzed CXCR4 expression levels in human prostate cancer samples. We found that cancer cells present in bone metastatic lesions express higher CXCR4 levels relative to the cells present in primary tumors and lymph node metastatic lesions. These findings underscore the potential of CXCR4 inhibitors as chemosensitizing agents.

CXCR4/CXCL12 in non-small-cell lung cancer metastasis to the brain

Lung cancer represents the leading cause of cancer-related mortality throughout the world. Patients die of local progression, disseminated disease, or both. At least one third of the people with lung cancer develop brain metastases at some point during their disease, even often before the diagnosis of lung cancer is made. The high rate of brain metastasis makes lung cancer the most common type of tumor to spread to the brain. It is critical to understand the biologic basis of brain metastases to develop novel diagnostic and therapeutic approaches. This review will focus on the emerging data supporting the involvement of the chemokine CXCL12 and its receptor CXCR4 in the brain metastatic evolution of non-small-cell lung cancer (NSCLC) and the pharmacological tools that may be used to interfere with this signaling axis.

Small molecule inhibitors of CXCR4

CXCR4 is a G-protein-coupled receptor involved in a number of physiological processes in the hematopoietic and immune systems. The SDF-1/CXCR4 axis is significantly associated with several diseases, such as HIV, cancer, WHIM syndrome, rheumatoid arthritis, pulmonary fibrosis and lupus. For example, CXCR4 is one of the major co-receptors for HIV entry into target cells, while in cancer it plays an important role in tumor cell metastasis. Several promising CXCR4 antagonists have been developed to block SDF-1/CXCR4 interactions that are currently under different stages of development. The first in class CXCR4 antagonist, plerixafor, was approved by the FDA in 2008 for the mobilization of hematopoietic stem cells and several other drugs are currently in clinical trials for cancer, HIV, and WHIM syndrome. While the long-term safety data for the first generation CXCR4 antagonists are not yet available, several new compounds are under preclinical development in an attempt to provide safer and more efficient treatment options for HIV and cancer patients.

Effective inhibition of metastases and primary tumor growth with CTCE-9908 in esophageal cancer

BACKGROUND

In spite of multimodular treatment, the therapeutic options for esophageal carcinoma are limited, and metastases remain the leading cause of tumor-related mortality. Expression of the chemokine receptor CXCR4 significantly correlates with poor survival rates in patients with esophageal carcinoma and is associated with lymph node and bone marrow metastases. The aim of this study was to evaluate the effect of the CXCR4 antagonist CTCE-9908 on metastatic homing and primary tumor growth in vitro and in vivo in an orthotopic xenograft model of esophageal cancer.

MATERIALS AND METHODS

OE19 cells were examined for stromal cell-derived factor 1 alpha-mediated migration under CTCE-9908 treatment. The CTCE-9908 treatment was further evaluated in an in vitro proliferation assay and orthotopic esophageal model, accompanied by magnetic resonance imaging. Tumor and metastases were immunohistochemically examined for CXCR4 expression.

RESULTS

CTCE-9908 has an inhibitory effect on stromal cell-derived factor 1 alpha-mediated migration and proliferation of OE19 cells. Treatment with CTCE-9908 in the orthotopic esophageal model leads to a reduction of metastatic spread and primary tumor growth. This was confirmed by magnetic resonsance imaging. Treatment with CTCE-9908 results in altered CXCR4 expression pattern exhibiting a high degree of variability.

CONCLUSION

CTCE-9908 effectively inhibits OE19 cell migration and proliferation in vitro, reduces metastases to lung, liver, and lymph nodes in vivo, and moreover leads to tumor growth reduction in an orthotopic model of esophageal carcinoma.

The emerging role of CXC chemokines and their receptors in cancer

Chemokines and their receptors have a multifaceted role in tumor biology and are implicated in nearly all aspects of cancer growth, survival and dissemination. Modulation of the interaction between chemokines and their cell surface receptor is, therefore, a promising area for the development of new cancer medicines. In this review, we look at the compelling evidence that is emerging to support targeting CXC chemokines, also known as family α chemokines, as novel therapeutic strategies in the treatment of cancer.

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).

The mesenchymal tumor microenvironment: a drug-resistant niche

Drug and radiation resistance represent a challenge for most anticancer therapies. Diverse experimental approaches have provided evidence that the tumor-associated microenvironment constitutes both a protective shell that impedes drug or radiation access and a permissive or promotive microenvironment that encourages a nurturing cancer (i.e., cancer stem cell) niche where tumor cells overcome treatment- and cancer-induced stresses. Better understanding of the effects of the tumor microenvironment on cancer cells before, during and immediately after chemo- or radiotherapy is imperative to design new therapies aimed at targeting this tumor-protective niche. This review summarizes some of the known mesenchymal stromal effects that account for drug resistance, the main signal transduction pathways associated with this resistance and the therapeutic efforts directed to increase the success of current therapies. Special emphasis is given to environment-mediated drug resistance in general and to cell adhesion-mediated drug resistance in particular.

The synthetic triterpenoid CDDO-methyl ester delays estrogen receptor-negative mammary carcinogenesis in polyoma middle T mice

Novel drugs are needed for the prevention and treatment of breast cancer. Synthetic triterpenoids are a promising new class of compounds with activity in a variety of preclinical cancer models. We tested activity of the methyl ester derivative of the synthetic triterpenoid, 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO-Me), in a relevant model of estrogen receptor-negative breast cancer, the polyoma-middle T (PyMT), in which the oncoprotein drives carcinogenesis. The developing tumors recapitulate key features of the human disease. Mice were fed CDDO-Me (50 mg/kg diet), starting at 4 weeks of age. CDDO-Me significantly increased the age of mice at onset of first tumor (P < 0.001) by an average of 4.3 weeks and overall survival (P < 0.001) by 5.2 weeks. The drug also inhibited the infiltration of tumor-associated macrophages into mammary glands of PyMT mice at 12 weeks of age and reduced levels of the chemokines CXCL12 and CCL2 in primary PyMT mammary tumor cells. Treatment with this multifunctional drug also inhibited secretion of matrix metalloproteinase-9 in primary tumor cells from PyMT mice and decreased proliferation of these cells by inhibiting cyclin D1 and decreasing phosphorylation of epidermal growth factor receptor and STAT3.

Hybrid peptide dendrimers for imaging of chemokine receptor 4 (CXCR4) expression

The chemokine receptor 4 (CXCR4), which is overexpressed in many types of cancer, is an emerging target in the field of molecular imaging and therapeutics. The CXCR4 binding of several peptides, including the cyclic Ac-TZ14011, has already been validated. In this study mono-, di- and tetrameric Ac-TZ14011-containing dendrimers were prepared and functionalized with a multimodal (hybrid) label, consisting of a Cy5.5-like fluorophore and a DTPA chelate. Confocal microscopy revealed that all three dendrimers were membrane bound at 4 °C, consistent with CXCR4 binding in vitro. The unlabeled dimer and tetramer had a somewhat lower affinity for CXCR4 than the unlabeled monomer. However, when labeled with the multimodal label the CXCR4 affinity of the dimer and tetramer was considerably higher compared to that of the labeled monomer. On top of that, biodistribution studies revealed that the additional peptides in the dimer and tetramer reduced nonspecific muscle uptake. Thus, multimerization of the cyclic Ac-TZ14011 peptide reduces the negative influence of the multimodal label on the receptor affinity and the biodistribution.

Targeting of the innate immunity/inflammation as complementary anti-tumor therapies

Different types of cancer take advantage of inflammatory components to improve their life-span in the organs. A sustenance of growth factors and cytokines (e.g. interleukin (IL)-1, tumor necrosis factor, IL-6, vascular endothelial growth factor) supports malignant cell progression and contributes to suppress the body immune defense. Strategies to modulate the host micro-environment offer new approaches for anti-cancer therapies. For these reasons new molecules with anti-tumor and anti-inflammatory features (e.g. trabectedin) are looked at with new eyes in the light of the crucial link between inflammation and cancer.

Targeting tumor cell motility to prevent metastasis

Mortality and morbidity in patients with solid tumors invariably result from the disruption of normal biological function caused by disseminating tumor cells. Tumor cell migration is under intense investigation as the underlying cause of cancer metastasis. The need for tumor cell motility in the progression of metastasis has been established experimentally and is supported empirically by basic and clinical research implicating a large collection of migration-related genes. However, there are few clinical interventions designed to specifically target the motility of tumor cells and adjuvant therapy to specifically prevent cancer cell dissemination is severely limited. In an attempt to define motility targets suitable for treating metastasis, we have parsed the molecular determinants of tumor cell motility into five underlying principles including cell autonomous ability, soluble communication, cell-cell adhesion, cell-matrix adhesion, and integrating these determinants of migration on molecular scaffolds. The current challenge is to implement meaningful and sustainable inhibition of metastasis by developing clinically viable disruption of molecular targets that control these fundamental capabilities.

Antiangiogenic therapy, hypoxia, and metastasis: risky liaisons, or not?

All human cells, including cancer cells, need oxygen and nutrients to survive. A widely used strategy to combat cancer is therefore the starvation of tumor cells by cutting off the blood supply of tumors. Clinical experience indeed shows that tumor progression can be delayed by anti-angiogenic agents. However, emerging evidence indicates that in certain experimental conditions, hypoxia as a result of pruning of the tumor microvasculature can promote tumor invasion and metastasis, although these findings are contextual and debated. Genetic studies in mice unveiled that vascular-targeting strategies that avoid aggravation of tumor hypoxia or even promote tumor oxygenation might prevent such an invasive metastatic switch. In this article, we will discuss the emerging link between hypoxia signaling and the various steps of metastasis.

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.