The influence of tumor-host interactions in the stromal cell-derived factor-1/CXCR4 ligand/receptor axis in determining metastatic risk in breast cancer

Evaluation of the influence of the C-X-C motif chemokine ligand 12 / C-X-C chemokine receptor 4 axis on canine mammary gland tumor cell migration

C-X-C motif chemokine ligand 12 (CXCL12) is one of the chemokines that binds to C-X-C chemokine receptor 4 (CXCR4) on tumor cell membranes and induces chemotaxis and/or migration. Mammary gland tumors (MGT) are the most common neoplasms in intact female dogs, with local invasion and distant metastasis regarded as problems. However, the influence of the CXCL12/CXCR4 axis on canine MGT cell migration has not been elucidated. This study aimed to evaluate the expression of CXCL12 and CXCR4 in canine MGT cells and tissues and investigate the influence of CXCL12 protein on the migratory ability of MGT cells. CXCL12 expression was evaluated in 10 canine malignant MGT tissues. CXCL12 expression in tumor cells was identified in all examined tissues; however, the staining pattern and intensity differed between the tumors. Immunocytochemistry revealed three canine MGT cell lines as CXCR4-positive. Migratory ability was evaluated using a wound healing assay, and the migration of CXCR4-positive MGT cells was significantly activated by the addition of CXCL12 protein. This influence was canceled by pre-treatment with a CXCR4 antagonist. The results of our study suggest that the CXCL12/CXCR4 axis may be associated with the migration of canine MGT.

Demystifying the CXCR4 conundrum in cancer biology: Beyond the surface signaling paradigm

The oncogenic chemokine duo CXCR4-CXCL12/SDF-1 (C-X-C Receptor 4-C-X-C Ligand 12/ Stromal-derived factor 1) has been the topic of intense scientific disquisitions since Muller et al., in her ground-breaking research, described this axis as a critical determinant of organ-specific metastasis in breast cancer. Elevated CXCR4 levels correlate with distant metastases, poor prognosis, and unfavourable outcomes in most solid tumors. Therapeutic impediment of the axis in clinics with Food and Drug Administration (FDA) approved inhibitors like AMD3100 or Plerixafor yield dubious results, contrary to pre-clinical developments. Clinical trials entailing inhibition of CXCR7 (C-X-C Receptor 7), another convicted chemokine receptor that exhibits affinity for CXCL12, reveal outcomes analogous to that of CXCR4-CXCL12 axis blockade. Of note, the cellular CXCR4 knockout phenotype varies largely from that of inhibitor treatments. These shaky findings pique great curiosity to delve further into the realm of this infamous chemokine receptor to provide a probable explanation. A multitude of recent reports suggests the presence of an increased intracellular CXCR4 pool in various cancers, both cytoplasmic and nuclear. This intracellular CXCR4 protein reserve seems active as it correlates with vital tumor attributes, viz. prognosis, aggressiveness, metastasis, and disease-free survival. Diminishing this entire intracellular CXCR4 load apart from the surface signals looks encouraging from a therapeutic point of view. Transcending beyond the classically accepted concept of ligand-mediated surface signaling, this review sheds new light on plausible associations of intracellularly compartmentalised CXCR4 with various aspects of tumorigenesis. Besides, this review also puts forward a comprehensive account of CXCR4 regulation in different cancers.

High ratio of pCXCR4/CXCR4 tumor infiltrating immune cells in primary high grade ovarian cancer is indicative for response to chemotherapy

Background

Ovarian cancer (OC) is the fifth most common malignant female cancer with a high mortality, mainly because of aggressive high-grade serous carcinomas (HGSOC), but also due to absence of specific early symptoms and effective detection strategies. The CXCL12-CXCR4 axis is considered to have a prognostic impact and to serve as potential therapeutic target. Therefore we investigated the role of pCXCR4 and CXCR4 expression of the tumor cells and of tumor infiltrating immune cells (TIC) in high-grade serous OC and their association with the recurrence-free (RFS) and overall survival (OS).

Methods

A tissue microarray of 47 primary high grade ovarian serous carcinomas and their recurrences was stained with primary antibodies directed against CXCR4 and pCXCR4. Beside the evaluation of the absolute tumor as well as TIC expression in primary and recurrent cancer biopsies the corresponding ratios for pCXCR4 and CXCR4 were generated and analyzed. The clinical endpoints were response to chemotherapy, OS as well as RFS.

Results

Patients with a high pCXCR4/CXCR4 TIC ratio in primary cancer biopsies showed a significant longer RFS during the first two years (p = 0.025). However, this effect was lost in the long-term analysis including a follow-up period of 5 years (p = 0.128). Interestingly, the Multivariate Cox regression analysis showed that a high pCXCR4/CXCR4 TIC ratio in primary cancer independently predicts longer RFS (HR 0.33; 95CI 0.13 - 0.81; p = 0.015). Furthermore a high dichotomized distribution of CXCR4 positive tumor expression in recurrent cancer biopsies showed a significantly longer 6-month RFS rate (p = 0.018) in comparison to patients with low CXCR4 positive tumor expression. However, this effect was not independent of known risk factors in a Multivariate Cox regression (HR 0.57; 95CI 0.24 - 1.33; p = 0.193).

Conclusions

To the best of our knowledge we show for the first time that a high pCXCR4/CXCR4 TIC ratio in primary HGSOC biopsies is indicative for better RFS and response to chemotherapy.

Highlights

• We observed a significant association between high pCXCR4/CXCR4 TIC ratio and better RFS in primary cancer biopsies, especially during the early postoperative follow-up and independent of known risk factors for recurrence.

• High CXCR4 tumor expression in recurrent HGSOC biopsies might be indicative for sensitivity to chemotherapy. We found evidence that at the beginning of the disease (early follow-up) the role of the immune response seems to be the most crucial factor for progression. On the other hand in recurrent/progressive disease the biology of the tumor itself becomes more important for prognosis.

• We explored for the first time the predictive and prognostic role of pCXCR4/CXCR4 TIC ratio in high-grade serous ovarian cancer.

Overexpression of chemokine receptor CXCR4 predicts lymph node metastatic risk in patients with melanoma: A systematic review and meta-analysis

CXCR4 is a member of CXC-type and G protein-coupled receptors that can conduce many biological processes, including hemostasis, migration, and adhesion of different types of immune cells. Also, the contribution of CXCR4 in metastasis cascade and development of various malignancies has been addressed in previous reports. This meta-analysis was performed to explore whether the CXCR4 expression affects prognosis and clinicopathologic features in melanoma cancer. Our study involved 656 melanoma patients from 13 reports by detailed literature search from PubMed, Embase, Web of Science, and Google Scholar up to April 2021. To evaluate the association between CXCR4 expression and clinicopathological features of melanoma, we calculated odds ratios (ORs) with its 95% confidence intervals (CIs). We indicated that the CXCR4 overexpression was obviously correlated with ulceration (OR = 0.56, 95% CI: 0.38 to 0.74; I2 = 0.0%, P = 0.999), tumor thickness (OR = 0.56, 95% CI: 0.38 to 0.74; I2 = 0.0%, P = 0.999) and lymph node metastasis (OR = 8.54, 95% CI: 1.04 to 16.04; I2 = 98.9, P < 0.0001). In conclusion, our results reveal that CXCR4 is involved in enhancing the progression and metastasis of melanoma, and further clinical studies are necessary to investigate the role of CXCR4 as a diagnostic and therapeutic biomarker through the progress of melanoma cancer.

Application of a small molecule inhibitor screen approach to identify CXCR4 downstream signaling pathways that promote a mesenchymal and fulvestrant-resistant phenotype in breast cancer cells

Chemokine receptor 4 (CXCR4) and its ligand stromal-derived factor 1 (SDF-1) have well-characterized functions in cancer metastasis; however, the specific mechanisms through which CXCR4 promotes a metastatic and drug-resistant phenotype remain widely unknown. The aim of the present study was to demonstrate the application of a phenotypic screening approach using a small molecule inhibitor library to identify potential CXCR4-mediated signaling pathways. The present study demonstrated a new application of the Published Kinase Inhibitor Set (PKIS), a library of small molecule inhibitors from diverse chemotype series with varying levels of selectivity, in a phenotypic medium-throughput screen to identify potential mechanisms to pursue. Crystal violet staining and brightfield microscopy were employed to evaluate relative cell survival and changes to cell morphology in the screens. ‘Hits’ or lead active compounds in the first screen were PKIS inhibitors that reversed mesenchymal morphologies in CXCR4-activated breast cancer cells without the COOH-terminal domain (MCF-7-CXCR4-ΔCTD) and in the phenotypically mesenchymal triple-negative breast cancer cells (MDA-MB-231, BT-549 and MDA-MB-157), used as positive controls. In a following screen, the phenotypic and cell viability screen was used with a positive control that was both morphologically mesenchymal and had acquired fulvestrant resistance. Compounds within the same chemotype series were identified that exhibited biological activity in the screens, the ‘active’ inhibitors, were compared with inactive compounds. Relative kinase activity was obtained using published datasets to discover candidate kinase targets responsible for CXCR4 activity. MAP4K4 and MINK reversed both the mesenchymal and drug-resistant phenotypes, NEK9 and DYRK2 only reversed the mesenchymal morphology, and kinases, including ROS, LCK, HCK and LTK, altered the fulvestrant-resistant phenotype. Oligoarray experiments revealed pathways affected in CXCR4-activated cells, and these pathways were compared with the present screening approach to validate our screening tool. The oligoarray approach identified the integrin-mediated, ephrin B-related, RhoA, RAC1 and ErbB signaling pathways to be upregulated in MCF-7-CXCR4-ΔCTD cells, with ephrin B signaling also identified in the PKIS phenotypic screen. The present screening tool may be used to discover potential mechanisms of targeted signaling pathways in solid cancers.

The diverse and complex roles of atypical chemokine receptors in cancer: From molecular biology to clinical relevance and therapy

Chemokines regulate directed cell migration, proliferation and survival and are key components in cancer biology. They exert their functions by interacting with seven-transmembrane domain receptors that signal through G proteins (GPCRs). A subgroup of four chemokine receptors known as the atypical chemokine receptors (ACKRs) has emerged as essential regulators of the chemokine functions. ACKRs play diverse and complex roles in tumor biology from tumor initiation to metastasis, including cancer cell proliferation, adherence to endothelium, epithelial-mesenchymal transition (EMT), extravasation from blood vessels, tumor-associated angiogenesis or protection from immunological responses. This chapter gives an overview on the established and emerging roles that the atypical chemokine receptors ACKR1, ACKR2, ACKR3 and ACKR4 play in the different phases of cancer development and dissemination, their clinical relevance, as well as on the hurdles to overcome in ACKRs targeting as cancer therapy.

The Role of ACKR3 in Breast, Lung, and Brain Cancer

Recent reports regarding the significance of chemokine receptors in disease have put a spotlight on atypical chemokine receptor 3 (ACKR3). This atypical chemokine receptor is overexpressed in numerous cancer types and has been involved in the modulation of tumor cell proliferation and migration, tumor angiogenesis, or resistance to drugs, thus contributing to cancer progression and metastasis occurrence. Here, we focus on the clinical significance and potential mechanisms underlying the pathologic role of ACKR3 in breast, lung, and brain cancer and discuss its possible relevance as a prognostic factor and potential therapeutic target in these contexts.

Gestational Tissue-Derived Human Mesenchymal Stem Cells Use Distinct Combinations of Bioactive Molecules to Suppress the Proliferation of Human Hepatoblastoma and Colorectal Cancer Cells

Background

Cancer has been considered a serious global health problem and a leading cause of morbidity and mortality worldwide. Despite recent advances in cancer therapy, treatments of advance stage cancers are mostly ineffective resulting in poor survival of patients. Recent evidences suggest that multipotent human mesenchymal stem cells (hMSCs) play important roles in growth and metastasis of several cancers by enhancing their engraftment and inducing tumor neovascularization. However, the effect of hMSCs on cancer cells is still controversial because there are also evidences demonstrating that hMSCs inhibited growth and metastasis of some cancers.

Methods

In this study, we investigated the effects of bioactive molecules released from bone marrow and gestational tissue-derived hMSCs on the proliferation of various human cancer cells, including C3A, HT29, A549, Saos-2, and U251. We also characterized the hMSC-derived factors that inhibit cancer cell proliferation by protein fractionation and mass spectrometry analysis.

Results

We herein make a direct comparison and show that the effects of hMSCs on cancer cell proliferation and migration depend on both hMSC sources and cancer cell types and cancer-derived bioactive molecules did not affect the cancer suppressive capacity of hMSCs. Moreover, hMSCs use distinct combination of bioactive molecules to suppress the proliferation of human hepatoblastoma and colorectal cancer cells. Using protein fractionation and mass spectrometry analysis, we have identified several novel hMSC-derived factors that might be able to suppress cancer cell proliferation.

Conclusion

We believe that the procedure developed in this study could be used to discover other therapeutically useful molecules released by various hMSC sources for a future in vivo study.

Examination of methylation changes of VIM, CXCR4, DOK7, and SPDEF genes in peripheral blood DNA in breast cancer patients

BACKGROUND

Studying whole blood DNA methylation as a risk marker has valuable applications in either diagnosis or staging of breast cancer. We investigated whole blood DNA methylation status of VIM, CXCR4, DOK7, and SPDEF genes in breast cancer patients in comparison to healthy control subjects.

MATERIALS AND METHODS

60 patients with breast cancer and 40 healthy controls were examined. Genomic DNA isolated from peripheral blood and restriction enzyme polymerase chain reaction (REP) method was applied for analysis. Real-time PCR was used to confirm methylation status of the aforementioned genes and therefore to find out the methylation differences between normal and breast cancer subjects.

RESULTS

Level of DOK7 promoter hypomethylation in normal and breast cancer samples was significant (P-value = 0.001). The study, also, showed that hypomethylation of VIM and CXCR4 genes are significant in patients compared with normal cases (P-value < 0.05). Furthermore, SPDEF promoter hypomethylation was not significantly differed between normal and breast cancer samples (P-value = 0.2).

CONCLUSIONS

Hypermethylation of DOK7 gene in DNA from patients affected with breast cancer offers a biomarker for diagnosis of the breast cancer. This study indicates that methylation status of VIM and CXCR4 genes changes in breast cancer; so, they can be used as molecular biomarkers in breast cancer prognosis.

High Cytoplasmic CXCR4 Expression Predicts Prolonged Survival in Triple-Negative Breast Cancer Patients Treated with Adjuvant Chemotherapy

BACKGROUND

Chemokine receptor CXC chemokine receptor type 4 (CXCR4) and its ligand CXC motif chemokine 12 (CXCL12; stromal cell-derived factor-1) are implicated in tumor growth, metastasis, and tumor cell-microenvironment interaction. A number of studies have reported that increased CXCR4 expression is associated with worse prognosis in triple-negative breast cancer (TNBC), but its prognostic significance has not been studied in TNBC patients treated with adjuvant chemotherapy.

METHODS

Two hundred eighty-three TNBC patients who received adjuvant chemotherapy were retrospectively analyzed. Tissue microarray was constructed from formalinfixed, paraffin-embedded tumor tissue and immunohistochemistry for CXCR4 and CXCL12 was performed. Expression of each marker was compared with clinicopathologic characteristics and outcome.

RESULTS

High cytoplasmic CXCR4 expression was associated with younger age (p = .008), higher histologic grade (p = .007) and lower pathologic stage (p = .045), while high CXCL12 expression was related to larger tumor size (p = .045), positive lymph node metastasis (p = .005), and higher pathologic stage (p = .017). The patients with high cytoplasmic CXCR4 experienced lower distant recurrence (p = .006) and better recurrence-free survival (RFS) (log-rank p = .020) after adjuvant chemotherapy. Cytoplasmic CXCR4 expression remained an independent factor of distant recurrence (p = .019) and RFS (p = .038) after multivariate analysis.

CONCLUSIONS

High cytoplasmic CXCR4 expression was associated with lower distant recurrence and better RFS in TNBC patients treated with adjuvant chemotherapy. This is the first study to correlate high CXCR4 expression to better TNBC prognosis, and the underlying mechanism needs to be elucidated in further studies.

CXCR4 and its ligand CXCL12 display opposite expression profiles in feline mammary metastatic disease, with the exception of HER2-overexpressing tumors

BACKGROUND

The receptor CXCR4 and its ligand CXCL12 play crucial roles in breast cancer. Despite the fact that the spontaneous feline mammary carcinoma (FMC) is considered a suitable model for breast cancer studies, the importance of the CXCR4/CXCL12 axis in FMC is completely unknown. Therefore, this work aims to elucidate the role of CXCR4 and its ligand in the progression of FMC and metastatic disease.

METHODS

CXCR4 and CXCL12 expression was analyzed by immunohistochemistry and immunofluorescence on primary tumors (PT), regional and distant metastases of female cats with mammary carcinoma and correlated with serum CXCL12 levels, tumor molecular subtypes and clinicopathological features.

RESULTS

CXCR4 was more expressed in PT than in metastases (p = 0.0067), whereas CXCL12 was highly expressed in metastatic lesions located in liver and lung (p < 0.0001), as reported for human breast cancer. Moreover, cats with CXCR4 positive PT exhibited significantly lower serum CXCL12 levels than cats with CXCR4 negative mammary carcinomas (p = 0.0324). At metastatic lesions, HER2-overexpressing tumors presented higher CXCR4 expression than the other molecular tumor subtypes (p = 0.012) and significant differences in overall (p = 0.0147) and disease-free survival (p = 0.0279) curves between the cats with CXCL12 positive and CXCL12 negative tumors were found. Indeed, CXCL12 negative PT were associated with unfavorable prognosis in cats with HER2-overexpressing tumors.

CONCLUSIONS

This work exposes part of the complex interaction between CXCR4 and CXCL12 in PT, but also in metastases of a breast cancer model. These findings could uncover novel therapeutic tools to be used in cats and humans.

Ligand-activated PPARγ downregulates CXCR4 gene expression through a novel identified PPAR response element and inhibits breast cancer progression

Stromal Derived Factor-1α (SDF-1α) and its cognate receptor CXCR4 play a key role in mediating breast cancer cell invasion and metastasis. Therefore, drugs able to inhibit CXCR4 activation may add critical tools to reduce tumor progression, especially in the most aggressive form of the breast cancer disease. Peroxisome Proliferator-Activated Receptor (PPAR) γ, a member of the nuclear receptor superfamily, has been found to downregulate CXCR4 gene expression in different cancer cells, however the molecular mechanism underlying this effect is not fully understood. Here, we identified a novel PPARγ-mediated mechanism that negatively regulates CXCR4 expression in both epithelial and stromal breast cancer cells. We found that ligand-activated PPARγ downregulated CXCR4 transcriptional activity through the recruitment of the silencing mediator of retinoid and thyroid hormone receptor (SMRT) corepressor onto a newly identified PPAR response element (PPRE) within the CXCR4 promoter in breast cancer cell lines. As a consequence, the PPARγ agonist rosiglitazone (BRL) significantly inhibited cell migration and invasion and this effect was PPARγ-mediated, since it was reversed in the presence of the PPARγ antagonist GW9662. According to the ability of cancer-associated fibroblasts (CAFs), the most abundant component of breast cancer stroma, to secrete high levels of SDF-1α, BRL reduced migratory promoting activities induced by conditioned media (CM) derived from CAFs and affected CXCR4 downstream signaling pathways activated by CAF-CM. In addition, CAFs exposed to BRL showed a decreased expression of CXCR4, a reduced motility and invasion along with a phenotype characterized by an altered morphology. Collectively, our findings provide novel insights into the role of PPARγ in inhibiting breast cancer progression and further highlight the utility of PPARγ ligands for future therapies aimed at targeting both cancer and surrounding stromal cells in breast cancer patients.

Peroxisome Proliferator-Activated Receptor γ and PGC-1α in Cancer: Dual Actions as Tumor Promoter and Suppressor

Peroxisome proliferator-activated receptor γ (PPARγ) is part of a nuclear receptor superfamily that regulates gene expression involved in cell differentiation, proliferation, immune/inflammation response, and lipid metabolism. PPARγ coactivator-1α (PGC-1α), initially identified as a PPARγ-interacting protein, is an important regulator of diverse metabolic pathways, such as oxidative metabolism and energy homeostasis. The role of PGC-1α in diabetes, neurodegeneration, and cardiovascular disease is particularly well known. PGC-1α is also now known to play important roles in cancer, independent of the role of PPARγ in cancer. Though many researchers have studied the expression and clinical implications of PPARγ and PGC-1α in cancer, there are still many controversies about the role of PPARγ and PGC-1α in cancer. This review examines and summarizes some recent data on the role and action mechanisms of PPARγ and PGC-1α in cancer, respectively, particularly the recent progress in understanding the role of PPARγ in several cancers since our review was published in 2012.

The good and bad faces of the CXCR4 chemokine receptor

Chemokines are chemotactic cytokines that promote cell migration and activation under homeostatic and inflammatory conditions. Chemokines bind to seven transmembrane-spanning receptors that are coupled to heterotrimeric guanine nucleotide-binding (G) proteins, which are the responsible for intracellularly transmitting the activating signals for cell migration. Hematopoiesis, vascular development, lymphoid organ morphogenesis, cardiogenesis and neural differentiation are amongst the processes involving chemokine function. In addition, immune cell trafficking from bone marrow to blood circulation, and from blood and lymph to lymphoid and inflamed tissues, is tightly regulated by chemokines both under physiological conditions and also in autoimmune diseases. Furthermore, chemokine binding to their receptors stimulate trafficking to and positioning of cancer cells into target tissues and organs during tumour dissemination. The CXCL12 chemokine (also known as stromal-cell derived factor-1α, SDF-1α) plays key roles in hematopoiesis and lymphoid tissue architecture, in cardiogenesis, vascular formation and neurogenesis, as well as in the trafficking of solid and hematological cancer cell types. CXCL12 binds to the CXCR4 receptor, a multi-facetted molecule which tightly mirrors CXCL12 functions in homeostasis and disease. This review addresses the important roles of the CXCR4-CXCL12 axis in homeostasis, specially focusing in hematopoiesis, as well as it provides a picture of CXCR4 as mediator of cancer cell spreading, and a view of the available CXCR4 antagonists in different cancer types.

Serum SDF-1 levels are a reliable diagnostic marker of feline mammary carcinoma, discriminating HER2-overexpressing tumors from other subtypes

The feline mammary carcinoma (FMC) is the third most common tumor in cat, sharing many clinicopathological features with human breast cancer and thus, considered a suitable model for comparative oncology. Due to its poor prognosis, further studies are required to improve the diagnostic accuracy and treatment of cats with spontaneous mammary carcinoma. Recently, it was reported that the overexpression of stromal cell-derived factor-1 (SDF-1) has great value in human breast cancer diagnosis, suggesting that diagnostic tools and therapies targeting the SDF-1 ligand can improve the clinical outcome. In this study, we aimed to evaluate if serum SDF-1 levels can also be used as a biomarker of mammary carcinoma in cats and to analyze if serum SDF-1 levels are associated with clinicopathological features, linked to a specific FMC subtype or correlated with the tumor expression of SDF-1 receptor, the chemokine C-X-C motif receptor 4 (CXCR4). Results showed that cats with mammary carcinoma had significantly higher serum SDF-1 levels than healthy controls (p=0.035) and ROC analysis revealed that the best cut-off value to differentiate sick from healthy animals was 2 ng/ml (specificity: 80%; sensitivity: 57%; AUC=0.715). Significant associations were also found between cats with elevated serum SDF-1 concentrations (≥ 2 ng/ml) and HER2-overexpressing mammary carcinomas (Luminal B-like and HER2-positive subtypes, p<0.0001), CXCR4-negative mammary carcinomas (p=0.027), mammary carcinomas with small size (<3 cm, p=0.027) and tumors with low Ki-67 expression (p=0.012). No statistical associations were found between serum SDF-1 levels and overall or disease-free survival. In summary, our results show that serum SDF-1 levels can be used as a biomarker of feline mammary carcinoma, especially in cats with HER2-overexpressing mammary tumors. Data suggest that targeted therapies against the SDF-1 ligand and/or its CXC4 receptor may be effective for the treatment of FMC, as described for human breast cancer, strengthening the concept that spontaneous feline mammary carcinoma is a suitable model for comparative oncology.

Phosphorylated CXCR4 expression has a positive prognostic impact in colorectal cancer

BACKGROUND

The CXCL12-CXCR4 chemokine axis plays an important role in cell trafficking as well as in tumor progression. In colorectal cancer (CRC), the chemokine receptor CXCR4 has been shown to be an unfavorable prognostic factor in some studies, however, the role of its activated (phosphorylated) form, pCXCR4, has not yet been evaluated. Here, we aimed to investigate the prognostic value of CXCR4 and pCXCR4 in a large cohort of CRC patients.

PATIENTS AND METHODS

A tissue microarray (TMA) of 684 patient specimens of primary CRCs was analyzed by immunohistochemistry (IHC) for the expression of CXCR4 and pCXCR4 by tumor cells and tumor-infiltrating immune cells (TICs).

RESULTS

The combined high expression of CXCR4 and pCXCR4 showed a favorable 5-year overall survival rate (68%; 95%CI = 59-76%) compared to tumors showing a high expression of CXCR4 only (48%; 95%CI = 41-54%). High expression of pCXCR4 was significantly associated with a favorable prognosis in a test and validation group (p = 0.015 and p = 0.0001). Moreover, we found that CRCs with a high density of pCXCR4+ tumor-infiltrating immune cells (TICs) also showed a favorable prognosis in a test and validation group (p = 0.054 and p = 0.004). Univariate Cox regression analysis for TICs revealed that a high density of pCXCR4+ TICs was a favorable prognostic marker for overall survival (HR = 0.97,95%CI = 0.96-1.00; p = 0.01). In multivariate Cox regression survival analyses a high expression of pCXCR4 in tumor cells lost its association with a better overall survival (HR = 0.99; 95%CI = 0.99-1.00, p = 0.098).

CONCLUSION

Our results show that high densities of CXCR4 and pCXCR4 positive TICs are favorable prognostic factors in CRC.

A meta-analysis of CXCL12 expression for cancer prognosis

Background:

CXCL12 (SDF1) is reported to promote cancer progression in several preclinical models and this is corroborated by the analysis of human tissue specimens. However, the relationship between CXCL12 expression and cancer survival has not been systematically assessed.

Methods:

We conducted a systematic review and meta-analysis of studies that evaluated the association between CXCL12 expression and cancer survival.

Results:

Thirty-eight studies inclusive of 5807 patients were included in the analysis of overall, recurrence-free or cancer-specific survival, the majority of which were retrospective. The pooled hazard ratios (HRs) for overall and recurrence-free survival in patients with high CXCL12 expression were 1.39 (95% CI: 1.17–1.65, P=0.0002) and 1.12 (95% CI: 0.82–1.53, P=0.48) respectively, but with significant heterogeneity between studies. On subgroup analysis by cancer type, high CXCL12 expression was associated with reduced overall survival in patients with oesophagogastric (HR 2.08; 95% CI: 1.31–3.33, P=0.002), pancreatic (HR 1.54; 95% CI: 1.21–1.97, P=0.0005) and lung cancer (HR 1.37; 95% CI: 1.08–1.75, P=0.01), whereas in breast cancer patients high CXCL12 expression conferred an overall survival advantage (HR 0.5; 95% CI: 0.38–0.66, P<0.00001).

Conclusions:

Determination of CXCL12 expression has the potential to be of use as a cancer biomarker and adds prognostic information in various cancer types. Prospective or prospective–retrospective analyses of CXCL12 expression in clearly defined cancer cohorts are now required to advance our understanding of the relationship between CXCL12 expression and cancer outcome.

Downregulation of CXCR7 inhibits proliferative capacity and stem cell-like properties in breast cancer stem cells

Breast cancer stem cells (bCSCs) are considered an obstacle in breast cancer therapy because they exhibit long-term proliferative potential, phenotypic plasticity and high resistance to the current therapeutics. CXC chemokine receptor type 7 (CXCR7), which provides a growth advantage to breast cancer cells, has recently been demonstrated to play an important role in the maintenance of stem cell-like properties in the CSCs of glioblastoma and lung cancer, yet its role in bCSCs remains elusive. In this study, CD44⁺/CD24^low bCSC-enriched cells (bCSCs for short) were isolated from MCF-7 cells, and CXCR7 was stably knocked down in bCSCs via lentivirus-mediated transduction with CXCR7 short hairpin RNA (shRNA). Knockdown of CXCR7 in bCSCs decreased the proportion of CD44⁺/CD24^low cells, and markedly reduced the clonogenicity of the cells. Moreover, silencing of CXCR7 downregulated the expression of stem cell markers, such as aldehyde dehydrogenase 1 (ALDH1), Oct4, and Nanog. In addition, CXCR7 silencing in bCSCs suppressed cell proliferation and G1/S transition in vitro, and delayed tumor growth in vivo in a xenograft mouse model. In situ immunohistochemical analysis revealed a reduction in Ki-67 expression and enhanced apoptosis in the xenograft tumors as a result of CXCR7 silencing. Furthermore, combined treatment with CXCR7 silencing and epirubicin displayed an outstanding anti-tumor effect compared with either single treatment. Our study demonstrates that CXCR7 plays a critical role in the maintenance of stem cell-like properties and promotion of growth in bCSCs, and suggests that CXCR7 may be a candidate target for bCSCs in breast cancer therapy.

CXCR4 over-expression and survival in cancer: a system review and meta-analysis

C-X-C chemokine receptor 4 (CXCR4) is frequently over-expressed in various types of cancer; many agents against CXCR4 are in clinical development currently despite variable data for the prognostic impact of CXCR4 expression. Here eighty-five studies with a total of 11,032 subjects were included to explore the association between CXCR4 and progression-free survival (PFS) or overall survival (OS) in subjects with cancer. Pooled analysis shows that CXCR4 over-expression is significantly associated with poorer PFS (HR 2.04; 95% CI, 1.72-2.42) and OS (HR=1.94; 95% CI, 1.71-2.20) irrespective of cancer types. Subgroup analysis indicates significant association between CXCR4 and shorter PFS in hematological malignancy, breast cancer, colorectal cancer, esophageal cancer, renal cancer, gynecologic cancer, pancreatic cancer and liver cancer; the prognostic effects remained consistent across age, risk of bias, levels of adjustment, median follow-up period, geographical area, detection methods, publication year and size of studies. CXCR4 over-expression predicts unfavorable OS in hematological malignancy, breast cancer, colorectal cancer, esophageal cancer, head and neck cancer, renal cancer, lung cancer, gynecologic cancer, liver cancer, prostate cancer and gallbladder cancer; these effects were independence of age, levels of adjustment, publication year, detection methods and follow-up period. In conclusion, CXCR4 over-expression is associated with poor prognosis in cancer.

Significance and therapeutic implications of endothelial progenitor cells in angiogenic-mediated tumour metastasis

Cancer conveys profound social and economic consequences throughout the world. Metastasis is responsible for approximately 90% of cancer-associated mortality and, when it occurs, cancer becomes almost incurable. During metastatic dissemination, cancer cells pass through a series of complex steps including the establishment of tumour-associated angiogenesis. The human endothelial progenitor cells (hEPCs) are a cell population derived from the bone marrow which are required for endothelial tubulogenesis and neovascularization. They also express abundant inflammatory cytokines and paracrine angiogenic factors. Clinically hEPCs are highly correlated with relapse, disease progression, metastasis and treatment response in malignancies such as breast cancer, ovarian cancer and non-small-cell lung carcinoma. It has become evident that the hEPCs are involved in the angiogenesis-required progression and metastasis of tumours. However, it is not clear in what way the signalling pathways, controlling the normal cellular function of human BM-derived EPCs, are hijacked by aggressive tumour cells to facilitate tumour metastasis. In addition, the actual roles of hEPCs in tumour angiogenesis-mediated metastasis are not well characterised. In this paper we reviewed the clinical relevance of the hEPCs with cancer diagnosis, progression and prognosis. We further summarised the effects of tumour microenvironment on the hEPCs and underlying mechanisms. We also hypothesized the roles of altered hEPCs in tumour angiogenesis and metastasis. We hope this review may enhance our understanding of the interaction between hEPCs and tumour cells thus aiding the development of cellular-targeted anti-tumour therapies.

Prognostic significance of CXCL12, CXCR4, and CXCR7 in patients with breast cancer

BACKGROUND

The chemokine CXCL12 and its receptors CXCR4 and CXCR7 play important roles in cancer invasion and metastasis. This study investigated the mRNA expressions of CXCL12, CXCR4, and CXCR7 to illustrate the role of these biomarkers in breast cancer metastasis and prognosis.

METHODS

The mRNA expressions of CXCL12, CXCR4, and CXCR7 in 115 primary breast cancer and regional lymph node specimens were detected by quantitative reverse-transcription polymerase chain reaction. Survival time was analyzed by Kaplan-Meier survival curves using log-rank test. Univariable and multivariable Cox regression analyses were performed to assess independent prognostic factors for survival.

RESULTS

The expression levels of CXCR4 and CXCR7 in breast cancer tissues were significantly higher than that in adjacent normal tissues (P=0.022 and P<0.001, respectively), while the expression level of CXCL12 in breast cancer tissues did not differ from that in adjacent normal tissues (P=0.156). Furthermore, CXCL12 exhibited significant differences in expression between primary tumor and lymph node metastasis tumor (P=0.039). CXCR4 and CXCR7 expressions in metastasis tumor were also higher, although no significant difference was observed (P=0.067 and P=0.054, respectively). Kaplan-Meier survival analysis revealed that patients exhibiting high CXCR4 and CXCR7 expression experienced a shorter survival period compared with those with low expression. When analyzed with a Cox regression model, the expressions of CXCL12, CXCR4 and CXCR7 were independent prognostic factors for overall survival.

CONCLUSIONS

The mRNA expressions of CXCL12, CXCR4, and CXCR7 play important roles in the progression and metastasis of breast cancer and may act as predictive factors significantly affecting the prognosis.

Immunohistochemical expression of CXCR4 on breast cancer and its clinical significance

Many tumor cells express chemokines and chemokine receptors, and, for this reason, these molecules can affect the tumor progression. It is known that breast cancer is a complex and heterogeneous neoplasia comprising distinct diseases, histological characteristics, and clinical outcomes. The most studied role for CXCL12 chemokine and its receptor CXCR4 in breast cancer pathogenesis is the metastasis event, although several reports have demonstrated its involvement in other processes, such as angiogenesis and tumor growth. It has been found that CXCR4 is required for breast cancer cell migration to other sites such as lung, bone, and lymph nodes, which express high levels of CXCL12 chemokine. Therefore, CXCR4 is being considered a prognostic marker in breast cancer. Within this context, this review summarizes established studies involving expression of CXCR4 on breast cancer, focusing on its clinical significance.

The intricate role of CXCR4 in cancer

Chemokines mediate numerous physiological and pathological processes related primarily to cell homing and migration. The chemokine CXCL12, also known as stromal cell-derived factor-1, binds the G-protein-coupled receptor CXCR4, which, through multiple divergent pathways, leads to chemotaxis, enhanced intracellular calcium, cell adhesion, survival, proliferation, and gene transcription. CXCR4, initially discovered for its involvement in HIV entry and leukocytes trafficking, is overexpressed in more than 23 human cancers. Cancer cell CXCR4 overexpression contributes to tumor growth, invasion, angiogenesis, metastasis, relapse, and therapeutic resistance. CXCR4 antagonism has been shown to disrupt tumor-stromal interactions, sensitize cancer cells to cytotoxic drugs, and reduce tumor growth and metastatic burden. As such, CXCR4 is a target not only for therapeutic intervention but also for noninvasive monitoring of disease progression and therapeutic guidance. This review provides a comprehensive overview of the biological involvement of CXCR4 in human cancers, the current status of CXCR4-based therapeutic approaches, as well as recent advances in noninvasive imaging of CXCR4 expression.

Cell migration on planar and three-dimensional matrices: a hydrogel-based perspective

The migration of cells is a complex process that is dependent on the properties of the surrounding environment. In vivo, the extracellular environment is complex with a wide range of physical features, topographies, and protein compositions. There have been a number of approaches to design substrates that can recapitulate the complex architecture in vivo. Two-dimensional (2D) substrates have been widely used to study the effect of material properties on cell migration. However, such substrates do not capture the intricate structure of the extracellular environment. Recent advances in hydrogel assembly and patterning techniques have enabled the design of new three-dimensional (3D) scaffolds and microenvironments. Investigations conducted on these matrices provide growing evidence that several established migratory trends obtained from studies on 2D substrates could be significantly different when conducted in a 3D environment. Since cell migration is closely linked to a wide range of physiological functions, there is a critical need to examine migratory trends on 3D matrices. In this review, our goal is to highlight recent experimental studies on cell migration within engineered 3D hydrogel environments and how they differ from planar substrates. We provide a detailed examination of the changes in cellular characteristics such as morphology, speed, directionality, and protein expression in 3D hydrogel environments. This growing field of research will have a significant impact on tissue engineering, regenerative medicine, and in the design of biomaterials.

CXCL12 chemokine expression suppresses human pancreatic cancer growth and metastasis

Pancreatic ductal adenocarcinoma is an unsolved health problem with nearly 75% of patients diagnosed with advanced disease and an overall 5-year survival rate near 5%. Despite the strong link between mortality and malignancy, the mechanisms behind pancreatic cancer dissemination and metastasis are poorly understood. Correlative pathological and cell culture analyses suggest the chemokine receptor CXCR4 plays a biological role in pancreatic cancer progression. In vivo roles for the CXCR4 ligand CXCL12 in pancreatic cancer malignancy were investigated. CXCR4 and CXCR7 were consistently expressed in normal and cancerous pancreatic ductal epithelium, established cell lines, and patient-derived primary cancer cells. Relative to healthy exocrine ducts, CXCL12 expression was pathologically repressed in pancreatic cancer tissue specimens and patient-derived cell lines. To test the functional consequences of CXCL12 silencing, pancreatic cancer cell lines stably expressingthe chemokine were engineered. Consistent with a role for CXCL12 as a tumor suppressor, cells producing the chemokine wereincreasingly adherent and migration deficient in vitro and poorly metastatic in vivo, compared to control cells. Further, CXCL12 reintroduction significantly reduced tumor growth in vitro, with significantly smaller tumors in vivo, leading to a pronounced survival advantage in a preclinical model. Together, these data demonstrate a functional tumor suppressive role for the normal expression of CXCL12 in pancreatic ducts, regulating both tumor growth andcellulardissemination to metastatic sites.

Immune regulation by atypical chemokine receptors

Chemokines have fundamental roles in regulating immune and inflammatory responses, primarily through their control of leukocyte migration and localization. The biological functions of chemokines are typically mediated by signalling through G protein-coupled chemokine receptors, but chemokines are also bound by a small family of atypical chemokine receptors (ACKRs), the members of which are unified by their inability to initiate classical signalling pathways after ligand binding. These ACKRs are emerging as crucial regulatory components of chemokine networks in a wide range of developmental, physiological and pathological contexts. In this Review, we discuss the biochemical and immunological properties of ACKRs and the potential unifying themes in this family, and we highlight recent studies that identify novel roles for these molecules in development , homeostasis, inflammatory disease, infection and cancer.

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

Background

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

Methods

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

Results

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

Conclusions

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

Effects of stromal cell derived factor-1 and CXCR4 on the promotion of neovascularization by hyperbaric oxygen treatment in skin flaps

Hyperbaric oxygen (HBO) is known to increase the survival of skin flaps by promoting neovascularization; however, the detailed mechanisms involved are not fully understood. In the present study, we aimed to characterize the effects of HBO treatment on neovascularization and skin flap survival. We also analyzed the mechanisms associated with the expression of angiogenic molecules, such as stromal cell derived factor-1 (SDF‑1) and its specific receptor CXCR4, to assess the effects of SDF-1 and CXCR4 on the promotion of neovascularization by HBO treatment in skin flaps. The epigastric pedicle skin flap model was established in rats that were randomly divided into the following groups: i) sham‑operated (SH group); ii) ischemia followed by reperfusion and analysis on the third and fifth day (IR3d and IR5d groups, respectively) postoperatively; iii) ischemia followed by reperfusion, HBO treatment and analysis on the third and fifth day (HBO3d and HBO5d groups, respectively) postoperatively. In the two HBO groups, animals received 1 h of HBO treatment in a 2.0 ATA chamber with 100% O2 twice per day for 3 days and then daily for 2 consecutive days following surgery. On the postoperative third and fifth day, skin flap survival measurement, histological analysis, immunohistochemical staining and western blotting for SDF‑1 and CXCR4 expression, were performed. Compared with those of the IR groups, skin flap survival, microvessel density (MVD) and expression of SDF‑1 and CXCR4 proteins were significantly increased in the HBO groups. Pearson's correlation analysis demonstrated a positive correlation between MVD and the high expression of SDF‑1 and CXCR4 following HBO treatment. Results of this study suggested that the effects of HBO treatment in promoting neovascularization may be explained by the upregulation of SDF‑1 and CXCR4 expression in the skin flaps of rats.

The impact of chemokine receptor CXCR4 on breast cancer prognosis: a meta-analysis

BACKGROUND

C-X-C chemokine receptor type 4 (CXCR4) has been implicated in the invasiveness and metastasis of diverse cancers. However, the published data remain controversial on the correlation between CXCR4 expression level, as well as its subcellular distribution in tumor cells, and the clinical outcome of patients with breast cancer.

METHODS

To identify the precise role of CXCR4 in the clinical outcome of breast cancer, we performed a meta-analysis including 15 published studies. Original data included the hazard ratios (HRs) of overall survival (OS) and disease-free survival (DFS) in breast cancer with high CXCR4 expression versus low expression. We pooled hazard ratios (HRs) with 95% confidence intervals (CIs) to estimate the hazard.

RESULTS

A total of 15 published studies (including 3104 patients) were eligible. Overall survival (OS) and disease-free survival (DFS) of breast cancer were found to be significantly related to CXCR4 expression level, with the HR being 1.65 (95%CI: 1.34-2.03; P<0.00001) and 1.94 (95%CI: 1.42-2.65; P<0.00001) respectively. Stratified analysis according to subcellular distribution of CXCR4 showed that high expression in whole cells, cytoplasm and nucleus could predict unfavorable OS, with the HR of 2.02 (95%CI: 1.43-2.85; P<0.0001), 1.57 (95%CI: 1.13-2.18; P=0.007), and 1.47 (95%CI: 1.19-1.81; P=0.0004) respectively. As for DFS, elevated expression level of CXCR4 both in whole cells and cytoplasm predicted a poor outcome, with the HR being 2.23 (95%CI: 1.48-3.37; P=0.0001) and 1.76 (95%CI: 1.11-2.80; P=0.02), while high expression in the nucleus had no statistical significance, with HR 1.15 (95%CI: 0.52-2.55; P=0.73).

CONCLUSIONS

Increased CXCR4 expression, especially in whole cells and cytoplasm, may serve as a poor prognostic indicator in patients with breast cancer. Future studies are warranted to investigate the relationship between CXCR4 expression and survival of patients with breast carcinoma, which could help predict the clinical outcome and guide clinical decision-making for therapy.

Use of a single hybrid imaging agent for integration of target validation with in vivo and ex vivo imaging of mouse tumor lesions resembling human DCIS

Screening of biomarker expression levels in tumor biopsy samples not only provides an assessment of prognostic and predictive factors, but may also be used for selection of biomarker-specific imaging strategies. To assess the feasibility of using a biopsy specimen for a personalized selection of an imaging agent, the chemokine receptor 4 (CXCR4) was used as a reference biomarker.

The emerging role of CXC chemokines in epithelial ovarian cancer

In recent years, chemokines have generated intense investigations due to their involvement in both physiological and pathological processes of inflammation, particularly in ovarian biology. The physiological process of ovulation in the normal ovary involves various chemokines that mediate the healing of the ruptured endometrium. It is now being reported that many of these chemokines are also associated with the cancer of the ovary. Chronic inflammation underlies the progression of ovarian cancer; therefore, it raises the possibility that chemokines are involved in the inflammatory process and mediate immune responses that may favour or inhibit tumour progression. Ovarian cancer is a gynaecological cancer responsible for highest rate of mortality in women. Although there have been several investigations and advances in surgery and chemotherapy, the survival rate for this disease remains low. This is mainly because of a lack of specific symptoms and biomarkers for detection. In this review, we have discussed the emerging role of the CXC chemokines in epithelial ovarian cancer (EOC). The CXC group of chemokines is gaining importance in the field of ovarian cancer for being angiostatic and angiogenic in function. While there have been several studies on the angiogenesis function, emerging research shows that ELR(-) CXC chemokines, CXCL9 and CXCL10, are angiostatic. Importantly, the angiostatic chemokines can inhibit the progression of EOC. Given that there are currently no biomarkers or specific therapeutic targets for the disease, these chemokines are emerging as promising targets for therapy.

CXCL12/CXCR4 axis plays pivotal roles in the organ-specific metastasis of pancreatic adenocarcinoma: A clinical study

Pancreatic cancer is one of the most lethal types of cancer, and curative resection is only applicable to potentially limited cases due to early metastasis and local invasion. This study reports the influence of CXCL12 and its receptor CXCR4 on the progression of pancreatic cancer and highlights the correlation between the CXCL12/CXCR4 axis and the organ-specific metastasis of pancreatic adenocarcinoma (PAC). A total of 34 patients with pancreatic cancer participated in the current study. The expression of CXCL12 and CXCR4 in cancerous tissues, paracancerous tissues, normal pancreas and lymph nodes surrounding the pancreas were investigated using immunohistochemistry and RT-PCR; furthermore, their relationship with clinicopathological factors was explored (PV9000 method). The positive rate of CXCL12 protein was 13.3% (4/30), the positive rate of CXCR4 protein was 80% (24/30) in tumor tissues. Additionally, a significant correlation between the expression pattern of the CXCL12/CXCR4 axis with lymph node metastasis was identified (P<0.05), excluding gender, age, tumor node metastasis (TNM) stage and differentiation (all P>0.05). Also, the positive rate of CXCL12 protein was 50% (15/30), the positive rate of CXCR4 protein was 73.3% (22/30) in the lymphocytes in lymph nodes surrounding the pancreas. Furthermore, we found that CXCL12 and CXCR4 expression in paratumorous vessels and neural tissue were significantly strongly positive. The paratumorous vessels and neural tissue with positive CXCL12 and CXCR4 expression were invaded by CXCL12-positive pancreatic cancer cells. The chemotactic interaction between CXCR4 and its ligand CXCL12 may be a critical event during the progression of pancreatic cancer. The CXCL12/CXCR4 axis plays an important role in the progression and organ-specific metastasis of pancreatic adenocarcinoma.

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).

Survival outcomes in endometrial cancer patients are associated with CXCL12 and estrogen receptor expression

CXCL12 is a chemotactic cytokine that has pro-metastatic functions in several malignancies through interactions with its receptor, CXCR4. CXCL12 is an estrogen-regulated gene, and notably, estrogen is a major risk factor for endometrial cancer (EC) development. As few studies examine concurrent CXCL12, CXCR4, and estrogen receptor (ER) expression in EC patients, we examined this pathway in 199 EC patients with data from the University of Pittsburgh Medical Center Cancer Registry. Immunohistochemistry (IHC) was used to detect CXCR4, CXCL12 and ER protein expression. As CXCR4 expression was positive in all cases, this investigation focused on associations between CXCL12 and ER expression, clinicopathologic factors and survival outcomes using chi-square tests, Kaplan-Meier graphs, and log-rank tests. CXCL12 expression was negative in 63 cases (32%) and positive in 136 cases (68%). Negative CXCL12 expression was borderline significantly associated with metastasis (χ(2) p = 0.07). ER expression was negative in 75 cases (38%) and positive in 124 cases (62%). Positive ER expression was significantly associated with low grade and early stage tumors (χ(2) p < 0.001). CXCL12 and ER were not significantly associated (χ(2) p = 0.11). Positive CXCL12 expression was associated with longer overall survival (OS) (log-rank p = 0.006) and longer recurrence-free survival (RFS) (log-rank p = 0.01) in ER negative patients, but not in ER positive patients. We identified a unique molecular signature associated with better OS and RFS in EC patients. In addition to pathological characteristics of the tumor, expression of CXCL12 and ER may be clinically useful for assigning adjuvant treatment to EC cases.

Bone morphogenetic protein 4 (BMP4) is required for migration and invasion of breast cancer

Bone-morphogenetic proteins (BMPs) play an important role in development and many cellular processes. However, their functional role in the development and progression of breast cancer is not clearly understood. In the present study, we performed a systematic expression analysis of the 14 types of BMPs in 10 human breast cancer cell lines. We found that bone morphogenetic protein 4 (BMP4) was one of the most frequently expressed BMPs. Furthermore, the expression level of BMP4 was maybe correlated with the metastatic potential of the cancer lines. Accordingly, overexpression of BMP4 in the breast cancer cell lines MCF-7 and MBA-MD-231 promoted the migration and invasion phenotypes of the cancer cells, whereas RNAi-mediated knockdown of BMP4 expression inhibited the migration and invasion activities of the cancer cells. To identify the important factors that may mediate the BMP4 functions in breast cancer cells, we analyzed a panel of cancer-related genes, and found that the expression of matrix metalloproteinase-1 (MMP-1) and C-X-C chemokine receptor type 4 (CXCR4) sharply increased at both the mRNA and protein levels in the breast cancer cells overexpressing BMP4. Interestingly, when breast cancer cells MDA-MB-231 or MCF-7 were co-cultured with the osteoblast-like cells MG63 to mimic a bone metastasis microenvironment, BMP4 did not exhibit any significant effect on the expression of OPG or RANKL, two important factors in bone remodeling. BMPs antagonists, Noggin, parallel inhibited breast cancer cell migration and invasion and induced bone remodeling. Taken together, our results strongly suggest that BMP4 may promote the migration and invasion of breast cancer cells, at least in part by up-regulating the expressions of MMP-1 and CXCR4. It is conceivable that novel therapeutics for breast cancer may be developed by targeting BMP4 signaling pathway and/or its important downstream mediators in breast cancer cells.

An integrated genomic approach identifies ARID1A as a candidate tumor-suppressor gene in breast cancer

Tumor-suppressor genes (TSGs) have been classically defined as genes whose loss of function in tumor cells contributes to the formation and/or maintenance of the tumor phenotype. TSGs containing nonsense mutations may not be expressed because of nonsense-mediated RNA decay (NMD). We combined inhibition of the NMD process, which clears transcripts that contain nonsense mutations, with the application of high-density single-nucleotide polymorphism arrays analysis to discriminate allelic content in order to identify candidate TSGs in five breast cancer cell lines. We identified ARID1A as a target of NMD in the T47D breast cancer cell line, likely as a consequence of a mutation in exon-9, which introduces a premature stop codon at position Q944. ARID1A encodes a human homolog of yeast SWI1, which is an integral member of the hSWI/SNF complex, an ATP-dependent, chromatin-remodeling, multiple-subunit enzyme. Although we did not find any somatic mutations in 11 breast tumors, which show DNA copy-number loss at the 1p36 locus adjacent to ARID1A, we show that low ARID1A RNA or nuclear protein expression is associated with more aggressive breast cancer phenotypes, such as high tumor grade, in two independent cohorts of over 200 human breast cancer cases each. We also found that low ARID1A nuclear expression becomes more prevalent during the later stages of breast tumor progression. Finally, we found that ARID1A re-expression in the T47D cell line results in significant inhibition of colony formation in soft agar. These results suggest that ARID1A may be a candidate TSG in breast cancer.

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

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

BACKGROUND

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSION

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

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

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

CXCL12 expression by healthy and malignant ovarian epithelial cells

Background

CXCL12 has been widely reported to play a biologically relevant role in tumor growth and spread. In epithelial ovarian cancer (EOC), CXCL12 enhances tumor angiogenesis and contributes to the immunosuppressive network. However, its prognostic significance remains unclear. We thus compared CXCL12 status in healthy and malignant ovaries, to assess its prognostic value.

Methods

Immunohistochemistry was used to analyze CXCL12 expression in the reproductive tracts, including the ovaries and fallopian tubes, of healthy women, in benign and borderline epithelial tumors, and in a series of 183 tumor specimens from patients with advanced primary EOC enrolled in a multicenter prospective clinical trial of paclitaxel/carboplatin/gemcitabine-based chemotherapy (GINECO study). Univariate COX model analysis was performed to assess the prognostic value of clinical and biological variables. Kaplan-Meier methods were used to generate progression-free and overall survival curves.

Results

Epithelial cells from the surface of the ovary and the fallopian tubes stained positive for CXCL12, whereas the follicles within the ovary did not. Epithelial cells in benign, borderline and malignant tumors also expressed CXCL12. In EOC specimens, CXCL12 immunoreactivity was observed mostly in epithelial tumor cells. The intensity of the signal obtained ranged from strong in 86 cases (47%) to absent in 18 cases (<10%). This uneven distribution of CXCL12 did not reflect the morphological heterogeneity of EOC. CXCL12 expression levels were not correlated with any of the clinical parameters currently used to determine EOC prognosis or with HER2 status. They also had no impact on progression-free or overall survival.

Conclusion

Our findings highlight the previously unappreciated constitutive expression of CXCL12 on healthy epithelia of the ovary surface and fallopian tubes, indicating that EOC may originate from either of these epithelia. We reveal that CXCL12 production by malignant epithelial cells precedes tumorigenesis and we confirm in a large cohort of patients with advanced EOC that CXCL12 expression level in EOC is not a valuable prognostic factor in itself.

Trial Registration

ClinicalTrials.gov: NCT00052468

Association of genetic polymorphisms of CXCL12/SDF1 gene and its receptor, CXCR4, to the susceptibility and prognosis of non-small cell lung cancer

BACKGROUND

The aim of this study was to evaluate the relations of chemokine CXCL12, previously known as stromal cell-derived factor-1 (SDF1), and its receptor, CXCR4, gene variants on non-small cell lung cancer (NSCLC) risk and disease severity.

METHODS

Through a case-control study design, genomic DNA samples of 247 NSCLC patients and 328 age and sex-matched controls were subjected to polymerase chain reaction-restriction fragment length polymorphism analysis. The validity of this technique was proven by direct sequencing of amplified products. Statistical analyses were conducted to explore the contribution of polymorphism of the CXCL12/SDF1 gene and CXCR4, in the susceptibility to and prognosis of NSCLC.

RESULTS

Overall, the genotype frequencies of CXCL12/SDF1 gene and CXCR4, were significantly different between lung cancer patients and controls (p<0.0001), and also different between patients with lung cancers of various stages (p<0.0001). Logistic regression analysis revealed that higher odds ratios (ORs) for lung cancer were seen for individuals with CXCL12/SDF1 AA (an OR of 1.95, 95% CI 1.08-3.50, p=0.018), or CXCR4 TT (an OR of 4.71, 95% CI 1.99-11.2, p<0.0001), and for individuals with both CXCL12/SDF1 AA and CXCR4 TT genotypes (an OR of 12.4, 95% CI 1.56-98.3, p=0.002). The patients carrying a homologous AA genotype at CXCL12/SDF1, or a homologous TT genotype at CXCR4, had a tendency to advanced disease and toward poorer prognoses compared with other patients.

CONCLUSION

A significant association between the polymorphisms of CXCL12/SDF1 and CXCR4, and the susceptibility to and prognosis of NSCLC was demonstrated.

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.

Loss of runt-related transcription factor 3 expression leads hepatocellular carcinoma cells to escape apoptosis

BACKGROUND

Runt-related transcription factor 3 (RUNX3) is known as a tumor suppressor gene for gastric cancer and other cancers, this gene may be involved in the development of hepatocellular carcinoma (HCC).

METHODS

RUNX3 expression was analyzed by immunoblot and immunohistochemistry in HCC cells and tissues, respectively. Hep3B cells, lacking endogenous RUNX3, were introduced with RUNX3 constructs. Cell proliferation was measured using the MTT assay and apoptosis was evaluated using DAPI staining. Apoptosis signaling was assessed by immunoblot analysis.

RESULTS

RUNX3 protein expression was frequently inactivated in the HCC cell lines (91%) and tissues (90%). RUNX3 expression inhibited 90±8% of cell growth at 72 h in serum starved Hep3B cells. Forty-eight hour serum starvation-induced apoptosis and the percentage of apoptotic cells reached 31±4% and 4±1% in RUNX3-expressing Hep3B and control cells, respectively. Apoptotic activity was increased by Bim expression and caspase-3 and caspase-9 activation.

CONCLUSION

RUNX3 expression enhanced serum starvation-induced apoptosis in HCC cell lines. RUNX3 is deleted or weakly expressed in HCC, which leads to tumorigenesis by escaping apoptosis.

Immunity to Trop-1, a newly identified breast cancer antigen, inhibits the growth of breast cancer in mice

This study describes the immunotherapeutic properties of vaccines that encode tumor-associated calcium signal transducer-1 (Trop-1), a newly identified breast cancer antigen, in mice with breast cancer. Previously we found that Trop-1 was over-expressed in cellular breast cancer vaccines that were highly enriched for cells that induced therapeutic CTL-mediated immune responses in mice with breast cancer, as compared with non-enriched vaccines. In this study, to determine if the expression of Trop-1 by cells in the enriched vaccine was responsible for its therapeutic benefits, an expression plasmid that specified the Trop-1 gene was transfected into the LM fibroblast cells, which was then used as a vaccine. To augment their immunogenic properties, the fibroblasts were genetically modified before Trop-1 DNA-transfer to secrete IL-2 and to express allogeneic MHC class I H-2K(b)-determinants. Mice with established breast cancer treated solely by immunization with fibroblasts modified to express Trop-1 developed CD8(+) cell-mediated immunity to the breast cancer cells. The immunity was sufficient to prolong the survival of mice with established breast cancer. In some instances, the immunity was sufficient to result in rejection of the tumor; the mice remained tumor free more than 60 days.

The CXCR4-CXCL12 pathway facilitates the progression of pancreatic cancer via induction of angiogenesis and lymphangiogenesis

BACKGROUND

This study reports the influence of CXCL12 and its receptor CXCR4 on the progression of pancreatic cancer and illuminates the correlation between the CXCL12/CXCR4 axis and the angiogenesis and lymphangiogenesis of pancreatic adenocarcinoma (PAC).

METHODS

A total of 30 patients with pancreatic cancer participated in the current study. The expression of CXCL12 and CXCR4 in cancerous tissues, paracancerous tissues, normal pancreas, and lymph nodes surrounding the pancreas were investigated using real-time PCR and immunohistochemistry, respectively. In addition, we assessed microvessel density (MVD) and microlymphatic vessel density (MLVD) in tumor tissues using immunohistochemistry.

RESULTS

CXCL12 expression in tumor tissues was significantly lower than that of paracancerous tissues, normal pancreas, and lymph nodes. In contrast, CXCR4 expression in cancerous tissues was considerably higher than that of normal pancreas. Additionally, a significant correlation between the expression pattern of the CXCL12/CXCR4 axis and clinicopathologic features, such as lymph node metastasis, was identified. Furthermore, we found that CXCL12 expression was significantly associated with MVD but not significantly associated with MLVD, while CXCR4 expression was significantly associated with MLVD but not significantly associated with MVD.

CONCLUSIONS

The chemotactic interaction between CXCR4 and its ligand CXCL12 may be a critical event during the progression of pancreatic cancer. The underlying mechanism may be the induction of angiogenesis and lymphangiogenesis regulated by the interaction of CXCL12 and CXCR4.

Correlation effect of EGFR and CXCR4 and CCR7 chemokine receptors in predicting breast cancer metastasis and prognosis

BACKGROUND

The chemokine receptors CXCR4 and CCR7 play an important role in cancer invasion and metastasis. This study investigated the expression of CXCR4, CCR7, CXCL12, CCL21, and EGFR to illustrate the role of these biomarkers in breast cancer metastasis and prognosis.

METHODS

The CXCR4, CCR7, CXCL12, CCL21, and EGFR biomarkers were analyzed along with ER, PR, and HER-2/neu in breast cancer tissue microarray (TMA) specimens, including 200 primary breast cancer specimens by immunohistochemistry. Corresponding lymph nodes from the same patients were also examined using the same method.

RESULTS

Together with their CXCL12 and CCL21 ligands, CXCR4 and CCR7 were significantly highly expressed in tumor cells with lymph node (LN) metastasis. Similarly, EGFR was expressed highly in tumors with LN metastasis. The ligands were especially expressed in metastatic tumors than in primary tumors from the same patients. Moreover, the expression of both CXCR4 accompanied by CCR7 and CXCL12 accompanied by CCL21 were up-regulated. Kaplan-Meier survival analysis revealed that patients exhibiting high CXCR4, CCR7, and EGFR expression experienced a shorter survival period compared with those with low expression.

CONCLUSIONS

The expression of CXCR4, CCR7, and EGFR may be associated with LN metastasis. Moreover, the expression of these receptors can serve as an indicator of undesirable prognosis in patients with breast cancer.

Emerging therapeutic targets in breast cancer bone metastasis

In the past decade, our understanding of the molecular mechanisms that underlie breast cancer pathology and progression has dramatically improved. Using this knowledge, we have identified additional targets and developed novel therapeutic interventions in breast cancer. Together, these translational research efforts are helping to usher us into an age of personalized cancer therapy. Metastasis to bone is a common and devastating consequence of breast cancer. Bisphosphonates, which represent the current gold standard in bone metastasis therapies, are being improved with newer and more efficacious generations of these compounds being developed. Breast cancer growth in the bone requires activation of various signaling pathways in both cancer cells and stromal cells, including those that are stimulated by TGF-β and RANKL, and mediated through the Src tyrosine kinase. Bone cells and cancer cells alike express promising targets for therapeutic intervention, including Cathepsin K, CXCR4 and GPNMB. In this article we discuss the molecular mechanisms behind these pro-metastatic molecules and review the most recent findings in the clinical development of their associated targeted therapies.

Role of endothelial progenitor cells in breast cancer angiogenesis: from fundamental research to clinical ramifications

Blood vessel formation (neovascularization) in tumors can occur through two mechanisms: angiogenesis and vasculogenesis. Angiogenesis results from proliferation and sprouting of existing blood vessels close to the tumor, while vasculogenesis is believed to arise from recruitment of circulating cells, largely derived from the bone marrow, and de novo clonal formation of blood vessels from these cells. Increasing evidence in animal models indicate that bone marrow-derived endothelial precursor cells (EPC) can contribute to tumor angiogenesis. This review aims to collate existing literature and provide an overview on the current knowledge of EPC involvement in breast cancer angiogenesis. We also discuss recent attempts to use EPC as biomarker and therapeutic target in clinical trials.