CXCR3 expression is associated with poor survival in breast cancer and promotes metastasis in a murine model

Unlocking the potential of Escherichia coli K-12: A novel approach for malignancy reduction in colorectal cancer through gene expression modulation

Studies have noted the association between Escherichia coli K-12 (E. coli K-12) and the reduction of malignancy in colorectal cancer (CRC). However, the molecular mechanisms underlying this relationship have not been thoroughly explored. The aim of this study was to identify the genes influenced by E. coli K-12 and their connection to CRC. We identified the genes affected by E. coli K-12 using the GSE50040 dataset. Additionally, we investigated the relationship between the expression of genes affected by E. coli K-12 and CRC using the cancer genome atlas data. The association between the expression of E. coli K-12-affected genes and patient prognosis was investigated using clinical data. Pathways related to CRC and E. coli K-12-related genes were analyzed using the Enrichr tool. Furthermore, we employed a protein-protein interaction (PPI) network to identify hub genes associated with both E. coli K-12 and CRC. To validate our findings, we conducted RT-qPCR analysis on CRC samples and adjacent normal tissue. The results of GSE50040 showed that E. coli K-12 could change the expression of many genes related to CRC in colorectal cell lines. The results showed that E. coli K-12 reduces the expression of several genes linked to the main pathways used by cancer cells, such as the metastasis, WNT, cell proliferation pathway, and mTORC1. It was demonstrated that elevated BGN, FJX1, and LZTS1 expression is linked to a bad prognosis in patients and that E. coli K-12 may be able to lower this expression. Also, based on the PPI network, genes such as KLF4 and CXCL3 were identified as hub genes related to genes affected by E. coli K-12. When KLF4 and CXCL3 expression levels in cancer samples were compared to nearby normal tissue, a significant change in these genes' expression levels was found in CRC. Our findings demonstrated the potential relationship between oncogene genes and genes impacted by E. coli K-12. Also, our findings demonstrated that E. coli K-12 may regulate the expression of genes linked to a high death rate. In summary, the results of this study suggest that E. coli K-12 can be regarded as a significant probiotic with the potential to mitigate the risk of CRC development.

Sulfated CXCR3 Peptide Trap Use as a Promising Therapeutic Approach for Age-Related Macular Degeneration

BACKGROUND AND OBJECTIVES

Chemokines have various biological functions and potential roles in the development or progression of neuroinflammatory diseases. However, the specific pathogenic roles of chemokines in the major cause for vision loss among the elderly, the leading cause of blindness in older individuals, remain elusive. Chemokines interact with their receptors expressed in the endothelium and on leukocytes. The sulfation of tyrosine residues in chemokine receptors increases the strength of ligand-receptor interaction and modulates signaling. Therefore, in the present study, we aimed to construct a human recombinant sulfated CXCR3 peptide trap (hCXCR3-S2) and mouse recombinant sulfated CXCR3 peptide trap (mCXCR3-S2) to demonstrate in vivo effects in preventing choroidal neovascularization (CNV) and chemotaxis.

MATERIALS AND METHODS

We generated expression vectors for mCXCR3-S2 and hCXCR3-S2 with GST domains and their respective cDNA sequences. Following overexpression in E. coli BL21 (DE3), we purified the fusion proteins from cell lysates using affinity chromatography. First, the impact of hCXCR3-S2 was validated in vitro. Subsequently, the in vivo efficacy of mCXCR3-S2 was investigated using a laser-induced CNV mouse model, a mouse model of neovascular age-related macular degeneration (AMD).

RESULTS

hCXCR3-S2 inhibited the migration and invasion of two human cancer cell lines. Intravitreal injection of mCXCR3-S2 attenuated CNV and macrophage recruitment in neovascular lesions of mouse models. These in vitro and in vivo effects were significantly stronger with CXCR3-S2 than with wild-type CXCR3 peptides.

CONCLUSION

These findings demonstrate that the sulfated form of the CXCR3 peptide trap is a valuable tool that could be supplemented with antivascular endothelial growth factors in AMD treatment.

Research progress of CXCR3 inhibitors

The human CXCR3 receptor was initially identified and cloned in the mid-1990s. In the process of understanding CXCR3, it gradually found that it plays an important role in the process of a variety of diseases, including inflammation, immune diseases, cancer, cardiovascular diseases, central nervous system diseases, etc., which attracted the attention of many researchers. Subsequently, some small molecule inhibitors targeting CXCR3 receptors were also developed. Unfortunately, no CXCR3 inhibitors have been approved for marketing by FDA. Up to now, only one CXCR3 small molecule inhibitor has entered the clinical trial stage, but it has not achieved ideal results in the end. Therefore, there is still much to think about and explore for the development of CXCR3 inhibitors. This article reviews the important role of CXCR3 in various physiological and pathological processes and some small molecule inhibitors of CXCR3.

The role of CXCR3 and its ligands in cancer

Chemokines are a class of small cytokines or signaling proteins that are secreted by cells. Owing to their ability to induce directional chemotaxis of nearby responding cells, they are called chemotactic cytokines. Chemokines and chemokine receptors have now been shown to influence many cellular functions, including survival, adhesion, invasion, and proliferation, and regulate chemokine levels. Most malignant tumors express one or more chemokine receptors. The CXC subgroup of chemokine receptors, CXCR3, is mainly expressed on the surface of activated T cells, B cells, and natural killer cells, and plays an essential role in infection, autoimmune diseases, and tumor immunity by binding to specific receptors on target cell membranes to induce targeted migration and immune responses. It is vital to treat infections, autoimmune diseases, and tumors. CXCR3 and its ligands, CXCL9, CXCL10, and CXCL11, are closely associated with the development and progression of many tumors. With the elucidation of its mechanism of action, CXCR3 is expected to become a new indicator for evaluating the prognosis of patients with tumors and a new target for clinical tumor immunotherapy. This article reviews the significance and mechanism of action of the chemokine receptor CXCR3 and its specific ligands in tumor development.

Rethinking the chemokine cascade in brain metastasis: Preventive and therapeutic implications

Brain metastasis (BrM) is one of the major causes of death in cancer patients and is associated with an estimated 10-40 % of total cancer cases. The survival rate of brain metastatic patients has not improved due to intratumor heterogeneity, the survival adaptations of brain homing metastatic cells, and the lack of understanding of underlying molecular mechanisms that limit the availability of effective therapies. The heterogeneous population of immune cells and tumor-initiating cells or cancer stem cells in the tumor microenvironment (TME) release various factors, such as chemokines that upon binding to their cognate receptors enhance tumor growth at primary sites and help tumor cells metastasize to the brain. Furthermore, brain metastatic sites have unique heterogeneous microenvironment that fuels cancer cells in establishing BrM. This review explores the crosstalk of chemokines with the heterogeneous TME during the progression of BrM and recognizes potential therapeutic approaches. We also discuss and summarize different targeted, immunotherapeutic, chemotherapeutic, and combinatorial strategies (with chemo-/immune- or targeted-therapies) to attenuate chemokines mediated BrM.

Cxcl10 chemokine induces migration of ING4-deficient breast cancer cells via a novel crosstalk mechanism between the Cxcr3 and Egfr receptors

The chemokine Cxcl10 has been associated with poor prognosis in breast cancer, but the mechanism is not well understood. Our previous study have shown that CXCL10 was repressed by the ING4 tumor suppressor, suggesting a potential inverse functional relationship. We thus investigated a role for Cxcl10 in the context of ING4 deficiencies in breast cancer. We first analyzed public gene expression datasets and found that patients with CXCL10-high/ING4-low expressing tumors had significantly reduced disease-free survival in breast cancer. In vitro, Cxcl10 induced migration of ING4-deleted breast cancer cells, but not of ING4-intact cells. Using inhibitors, we found that Cxcl10-induced migration of ING4-deleted cells required Cxcr3, Egfr, and the Gβγ subunits downstream of Cxcr3, but not Gαi. Immunofluorescent imaging showed that Cxcl10 induced early transient colocalization between Cxcr3 and Egfr in both ING4-intact and ING4-deleted cells, which recurred only in ING4-deleted cells. A peptide agent that binds to the internal juxtamembrane domain of Egfr inhibited Cxcr3/Egfr colocalization and cell migration. Taken together, these results presented a novel mechanism of Cxcl10 that elicits migration of ING4-deleted cells, in part by inducing a physical or proximal association between Cxcr3 and Egfr and signaling downstream via Gβγ. These results further indicated that ING4 plays a critical role in the regulation of Cxcl10 signaling that enables breast cancer progression.

Contribution of CXCR3-mediated signaling in the metastatic cascade of solid malignancies

Metastasis is a significant cause of the mortality resulting from solid malignancies. The process of metastasis is complex and is regulated by numerous cancer cell-intrinsic and -extrinsic factors. CXCR3 is a chemokine receptor that is frequently expressed by cancer cells, endothelial cells and immune cells. CXCR3A signaling in cancer cells tends to promote the invasive and migratory phenotype of cancer cells. Indirectly, CXCR3 modulates the anti-tumor immune response resulting in variable effects that can permit or inhibit metastatic progression. Finally, the activity of CXCR3B in endothelial cells is generally angiostatic, which limits the access of cancer cells to key conduits to secondary sites. However, the interaction of these activities within a tumor and the presence of opposing CXCR3 splice variants clouds the picture of the role of CXCR3 in metastasis. Consequently, thorough analysis of the contributions of CXCR3 to cancer metastasis is necessary. This review is an in-depth examination of the involvement of CXCR3 in the metastatic process of solid malignancies.

Role of CXCL10 in the progression of in situ to invasive carcinoma of the breast

Tumor immune microenvironment plays a crucial role in tumor progression. We performed immune profiling to compare immune-related gene expression between ductal carcinoma in situ (DCIS) and invasive carcinoma of the breast using nCounter PanCancer immune Profiling Panel and found that CXCL10 was the most significant gene that had the highest difference in expression between them. Effect of CXCL10 on breast cancer cell proliferation and invasion was examined in vitro, and expression of CXCL10 and its relationship with immune cell infiltration was assessed in breast cancer samples. CXCL10 induced cell proliferation, migration and epithelial-mesenchymal transition in MCF-7 and MDA-MB-231 breast cancer cell lines. We confirmed that CXCL10 mRNA expression was significantly higher in invasive carcinoma than in DCIS, especially in hormone receptor (HR)-negative tumors using a validation set. CXCL10 mRNA expression showed a positive correlation with tumor infiltrating lymphocyte (TIL) density in both DCIS and invasive carcinoma; CXCL10-positive tumors generally showed higher infiltration of CD8+ and FOXP3+TILs as well as PD-L1+ immune cells compared to CXCL10-negative tumors, albeit with different patterns according to HR status. In conclusion, our study showed that CXCL10 promotes tumor cell proliferation, invasion, and immune cell infiltration, implying its contribution in the progression of DCIS to invasive carcinoma of the breast.

Interferon-γ-Inducible Chemokines as Prognostic Markers for Lung Cancer

Interferon (IFN)-γ-inducible chemokines in the CXCR3/ligand axis are involved in cell-mediated immunity and play a significant role in the progression of cancer. We enrolled patients with lung cancer (n = 144) and healthy volunteers as the controls (n = 140). Initial blood samples were collected and concentrations of IFN-γ and IFN-γ-inducible chemokines CXCL9, CXCL10, and CXCL11 were measured using enzyme-linked immunosorbent assay. Of patients with lung cancer, 125 had non-small cell lung cancer (NSCLC) and 19 had small cell lung cancer. The area under the curve (AUC) (95% CI) of CXCL9 was 0.83 (0.80-0.89) for differentiating lung cancer patients from controls. The levels of all the markers were significantly higher in NSCLC patients with stage IV than in those with stages I-III. A Kaplan-Meier survival analysis showed that NSCLC cancer patients with higher levels of all markers showed poorer survival than those with lower levels. In Cox multivariate analysis of patients with NSCLC, independent prognostic factors for overall survival were CXCL9 and CXCL11. CXCL9 was the only independent prognostic factor for cancer-specific survival. Serum IFN-γ-inducible chemokines may be useful as clinical markers of metastasis and prognosis in NSCLC, and CXCL9 levels showed the most significant results.

TNF-α augments CXCL10/CXCR3 axis activity to induce Epithelial-Mesenchymal Transition in colon cancer cell

Chronic inflammation-induced metastases have long been regarded as one of the significant obstacles in treating cancer. Tumor necrosis factor-α (TNF-α), a main inflammation mediator within tumor microenvironment, affects tumor development by inducing multiple chemokines to establish a complex network. Recent reports have revealed that CXCL10/CXCR3 axis affects cancer cells invasiveness and metastases, and Epithelial-mesenchymal transition (EMT) is the main reason for frequent proliferation and distant organ metastases of colon cancer (CC) cells, However, it is unclear whether TNF-α- mediated chronic inflammation can synergically enhance EMT-mediated CC metastasis through promoting chemokine expression. According to this study, TNF-α activated the PI3K/Akt and p38 MAPK parallel signal transduction pathways, then stimulate downstream NF-κB pathway p65 into the nucleus to activate CXCL10 transcription. CXCL10 enhanced the metastases of CC-cells by triggering small GTPases such as RhoA and cdc42. Furthermore, overexpression of CXCL10 significantly enhanced tumorigenicity and mobility of CC cells in vivo. We further clarified that CXCL10 activated the PI3K/Akt pathway through CXCR3, resulting in suppression of GSK-3β phosphorylation and leading to upregulation of Snail expression, thereby regulating EMT in CC cells. These outcomes lay the foundation for finding new targets to inhibit CC metastases.

IP-10 (CXCL10) Can Trigger Emergence of Dormant Breast Cancer Cells in a Metastatic Liver Microenvironment

Metastatic breast cancer remains a largely incurable and fatal disease with liver involvement bearing the worst prognosis. The danger is compounded by a subset of disseminated tumor cells that may lie dormant for years to decades before re-emerging as clinically detectable metastases. Pathophysiological signals can drive these tumor cells to emerge. Prior studies indicated CXCR3 ligands as being the predominant signals synergistically and significantly unregulated during inflammation in the gut-liver axis. Of the CXCR3 ligands, IP-10 (CXCL10) was the most abundant, correlated significantly with shortened survival of human breast cancer patients with metastatic disease and was highest in those with triple negative (TNBC) disease. Using a complex ex vivo all-human liver microphysiological (MPS) model of dormant-emergent metastatic progression, CXCR3 ligands were found to be elevated in actively growing populations of metastatic TNBC breast cancer cells whereas they remained similar to the tumor-free hepatic niche in those with dormant breast cancer cells. Subsequent stimulation of dormant breast cancer cells in the ex vivo metastatic liver MPS model with IP-10 triggered their emergence in a dose-dependent manner. Emergence was indicated to occur indirectly possibly via activation of the resident liver cells in the surrounding metastatic microenvironment, as stimulation of breast cancer cells with exogenous IP-10 did not significantly change their migratory, invasive or proliferative behavior. The findings reveal that IP-10 is capable of triggering the emergence of dormant breast cancer cells within the liver metastatic niche and identifies the IP-10/CXCR3 as a candidate targetable pathway for rational approaches aimed at maintaining dormancy.

Systemic tumour suppression via the preferential accumulation of erythrocyte-anchored chemokine-encapsulating nanoparticles in lung metastases

Eliciting immune responses against primary tumours is hampered by their immunosuppressive microenvironment and by the greater inaccessibility of deeper intratumoural cells. However, metastatic tumour cells are exposed to highly perfused and immunoactive organs, such as the lungs. Here, by taking advantage of the preferential colocalization of intravenously administered erythrocytes with metastases in the lungs, we show that treatment with chemokine-encapsulating nanoparticles that are non-covalently anchored onto the surface of injected erythrocytes results in local and systemic tumour suppression in mouse models of lung metastasis. Such erythrocyte-anchored systemic immunotherapy led to the infiltration of effector immune cells into the lungs, in situ immunization without the need for exogenous antigens, inhibition of the progression of lung metastasis, and significantly extended animal survival and systemic immunity that suppressed the growth of distant tumours after rechallenge. Erythrocyte-mediated systemic immunotherapy may represent a general and potent strategy for cancer vaccination.

Tumor inhibition or tumor promotion? The duplicity of CXCR3 in cancer

Tumor tissue includes cancer cells and normal stromal cells such as vascular endothelial cells, connective tissue cells (cancer associated fibroblast, mesenchymal stem cell), and immune cells (tumor-infiltrating lymphocytes or TIL, dendritic cells, eosinophils, basophils, mast cells, tumor-associated macrophages or TAM, myeloid-derived suppressor cells or MDSC). Anti-tumor activity is mainly mediated by infiltration of NK cells, Th1 and CD8⁺ T cells, and correlates with expression of NK cell and T cell attracting chemokines. Nevertheless, cancer cells hijack tissue homeostasis through secretion of cytokines and chemokines that mediate not only the induction of an inflamed status that supports cancer cell survival and growth, but also the recruitment and/or activation of immune suppressive cells. CXCL9, CXCL10, and CXCL11 are known for their tumor-inhibiting properties, but their overexpression in several hematologic and solid tumors correlates with disease severity, suggesting a role in tumor promotion. The dichotomous nature of CXCR3 ligands activity mainly depends on several molecular mechanisms induced by cancer cells themselves able to divert immune responses and to alter the whole local environment. A deep understanding of the nature of such phenomenon may provide a rationale to build up a CXCR3/ligand axis targeting strategy. In this review, we will discuss the role of CXCR3 in cancer progression and in regulation of anti-tumor immune response and immunotherapy.

CXC Chemokine/Receptor Axis Profile and Metastasis in Prostate Cancer

In this study, the effects of the CXC chemokine/receptor axis on lymph node and distant metastases of prostate cancer (PC) were analyzed. Further, mRNA expression data of metastatic PC were extracted from the Stand Up To Cancer–Prostate Cancer Foundation Dream Team database and differences between metastatic sites were comprehensively analyzed. CXC chemokine/receptor mRNA expression data of primary PC included in the Cancer Genome Atlas were used to analyze the relationships of CXC chemokine/receptor expression with lymph node metastasis and cancer progression. In metastatic PC, significantly higher expression of ELR⁺ CXC chemokines/receptors and significantly lower expression of ELR⁻ CXC chemokines/receptors were observed in bone metastases relative to lymph node metastases. In primary PC, significantly higher ELR⁻ CXC chemokine/receptor expression and significantly lower ELR⁺ CXC chemokine/receptor expression were observed in patients with lymph node metastasis relative to those without. Multivariate logistic regression analysis identified CXCL10 expression as an independent predictor of lymph node metastasis. Furthermore, the log-rank test results revealed that co-expression of CXCL10/CXCR3 was associated with postoperative recurrence. These findings demonstrate heterogeneous expression of CXC chemokine/receptor genes in primary PC as well as differences in expression patterns according to the metastatic site.

The role of PKC in CXCL8 and CXCL10 directed prostate, breast and leukemic cancer cell migration

Migration of tumour cells is a fundamental process for the formation and progression of metastasis in malignant diseases. Chemokines binding to their cognate receptors induce the migration of cancer cells, however, the molecular signalling pathways involved in this process are not fully understood. Protein kinase C (PKC) has been shown to regulate cell migration, adhesion and proliferation. In order to identify a connection between PKC and tumour progression in breast, prostate and leukaemia cells, the effect of PKC on CXCL8 or CXCL10-mediated cell migration and morphology was analysed. We tested the speed of the migrating cells, morphology, and chemotaxis incubated with different PKC isoforms inhibitors- GF109203X, staurosporine and PKCζ pseudosubstrate inhibitor (PKCζi). We found that the migration of CXCL8-driven PC3 and MDA-MB231 cells in the presence of conventional, novel or atypical PKCs was not affected, but atypical PKCζ is crucial for THP-1 chemotaxis. The speed of CXCL10-activated PC3 and MDA-MB231 cells was significantly reduced in the presence of conventional, novel and atypical PKCζ. THP-1 chemotaxis was again affected by atypical PKCζi. On the other hand, cell area, circularity or aspect ratio were affected by staurosporine in CXCL8 or CXCL10-activated cells, demonstrating a role of PKCα in the rearrangement of the cytoskeleton regardless of the effect on the migration. Consequently, this allows the speculation that different PKC isoforms induce different outcomes in migration and actin cytoskeleton based on the chemokine receptor and/or the cell type.

Comprehensive analysis of the prognostic value and immune function of chemokine-CXC receptor family members in breast cancer

Recently, immune checkpoint inhibitors (ICIs) have been successfully used for treating melanoma. Unfortunately, many breast cancer (BC) patients show low response to ICIs due to the lack of infiltrating immune cells. Previous studies revealed that chemokine-CXC receptors (CXCRs) play a crucial role in leukocyte infiltration and promote cancer cell proliferation, migration, metastasis, and angiogenesis. However, the underlying functions of CXCRs in cancer-immunity cycle remain unclear. In this study, we firstly found that in comparison to normal tissues, BC tissues, especially basal-like BC, showed increased mRNA levels of CXCR3/4/5/6/8, but decreased CXCR1/2/7 expression using UALCAN and TIMER database. Interestingly, it's was found that the mRNA levels of CXCR3/4/5/6 were decreased in lymphocyte depleted of the BC immune subtype. Subsequently, functional enrichment analysis of distinct CXCRs indicated that CXCR3/4/5/6 were strongly associated to immune-related biological functions. Therefore, further analysis using TIMER and TISIDB database suggested that CXCR3/4/5/6 expression were strongly correlated with tumor-infiltrating lymphocytes (TILs) and immune checkpoints in BC. Finally, Kaplan-Meier Plotter analysis indicated that high mRNA expression of CXCR4 predicted worse relapse-free survival (RFS), whereas CXCR3/5/6 indicated better RFS in BC patients. These findings suggest a therapeutic value for CXCR3/4/5/6 in combination with ICIs for the treatment of BC.

Chemokine gene expression influences metastasis and survival time of female dogs with mammary carcinoma

Chemokines are signaling proteins secreted by immune cells which regulate leukocyte trafficking. The aberrant expression of chemokines and their receptors by neoplastic cells influences the behaviour of many human cancers. This study evaluated gene-expression of the chemokines: CCL5, CXCL10, CXCL12 and the chemokine receptors: CXCR3, CXCR4, CXCR7, CCR4, CCR9 in 41 histologically-malignant, outcome-known, canine mammary tumours. These chemokines and chemokine receptors were selected as all were previously shown to influence the behaviour of human breast cancers. The expression of chemokines CCL5 and CXCL12 were significantly higher in tumours which subsequently metastasised than tumours that did not metastasise (p < 0.05). Increased expression of these chemokines was also correlated with shorter survival times of the dogs (CCL5: r_s = -0.40, p = 0.02, CXCL12: r_s = -0.40, p = 0.03) while CCL5 was independently prognostic of survival times (p = 0.026). A significantly higher proportion of tumours that subsequently metastasised expressed CXCR3 (p = 0.037), CXCR4 (p = 0.026), CXCR7 (p = 0.025) and CCR9 (p = 0.039) receptors while the survival times of the dogs with tumours that expressed CXCR4 (p = 0.045) and CCR9 (p = 0.039) receptors were significantly shorter than dogs with tumours that did not express these receptors. Chemokine and chemokine receptor gene-expression has not been previously correlated with disease outcome of canine mammary tumours. These findings indicate that altered expression of chemokines and their receptors influences the behaviour of canine mammary tumours suggesting a potential role of them as prognostic markers or therapeutic targets.

C-X-C motif receptor 3A enhances proliferation and invasiveness of colorectal cancer cells, and is mediated by C-X-C motif ligand 10

The chemokine CXCL10 and its receptor CXCR3 have been demonstrated to be implicated in cancer cell proliferation and metastasis. CXCR3 has three splice variants: CXCR3A, CXCR3B and CXCR3-alt. CXCR3A and B serve multiple roles in the growth and invasiveness of a number of cancer types. However, the roles of CXCR3 isoforms in colorectal cancer (CRC) cells remain unclear. In the current study, the effects of CXCL10 and CXCR3 isoforms on proliferation and invasion of CRC cells was examined. Proliferation and invasiveness of the CRC cell line HCT116, which were transfected with CXCR3A or CXCR3B in the presence of CXCL10, were evaluated in vitro using MTT, scratch wound healing and transwell assays. MTT assay indicated that regardless of the presence or absence of CXCL10, the proliferative ability of CXCR3A-transfected HCT116 cells was enhanced compared with blank and mock cells. Scratch wound healing and transwell assays indicated that invasiveness of CXCR3A-transfected cells was greater compared with blank and mock cells. However, HCT116 cells transfected with CXCR3B did not exhibit changes in their proliferative or invasive ability. mRNA expression of MMP9, which is associated with signaling downstream of the CXCL10/CXCR3A pathway, was increased 4-fold in CXCR3A-transfected HCT116 cells compared with control cells. The results of the present study indicated that CXCL10-enhanced proliferation and invasiveness of the CRC cell line HCT116 was likely mediated by CXCR3A, but not by CXCR3B.

Metastasis-initiating cells induce and exploit a fibroblast niche to fuel malignant colonization of the lungs

Metastatic colonization relies on interactions between disseminated cancer cells and the microenvironment in secondary organs. Here, we show that disseminated breast cancer cells evoke phenotypic changes in lung fibroblasts, forming a supportive metastatic niche. Colonization of the lungs confers an inflammatory phenotype in metastasis-associated fibroblasts. Specifically, IL-1α and IL-1β secreted by breast cancer cells induce CXCL9 and CXCL10 production in lung fibroblasts via NF-κB signaling, fueling the growth of lung metastases. Notably, we find that the chemokine receptor CXCR3, that binds CXCL9/10, is specifically expressed in a small subset of breast cancer cells, which exhibits tumor-initiating ability when co-transplanted with fibroblasts and has high JNK signaling that drives IL-1α/β expression. Importantly, disruption of the intercellular JNK-IL-1-CXCL9/10-CXCR3 axis reduces metastatic colonization in xenograft and syngeneic mouse models. These data mechanistically demonstrate an essential role for the molecular crosstalk between breast cancer cells and their fibroblast niche in the progression of metastasis.

How cancer cells engage the microenvironment to establish metastasis is poorly understood. Here, the authors show that CXCR3-expressing breast cancer cells secrete IL-1 to induce a paracrine crosstalk with fibroblasts in the lung, which involves CXCL9/10 production and results in colonization of the lung.

Proteolytic chemokine cleavage as a regulator of lymphocytic infiltration in solid tumors

In the past decade, immune-based therapies such as monoclonal antibodies against tumor epitopes or immune checkpoint inhibitors have become an integral part of contemporary cancer treatment in many entities. However, a fundamental prerequisite for the success of such therapies is a sufficient trafficking of tumor-infiltrating lymphocytes into the tumor microenvironment. This infiltration is facilitated by chemokines, a group of about 50 small proteins capable of chemotactically guiding leukocytes. Proteolytic inactivation of chemokines leading to an impaired infiltration of immune effector cells appears to be an efficient immune escape mechanism of solid cancers.

The CXCR3 and CX3CR1 chemokine receptor ligands CXCL9-11 and CX3CL1, respectively, are mainly responsible for the tumor-suppressive lymphocytic infiltration into the tumor micromilieu. Their structure explains the biochemical basis of their proteolytic cleavage, while in vivo data from mouse models and patient samples shed light on the corresponding processes in cancer. The emerging roles of proteases, e.g., matrix metalloproteinases, cathepsins, and dipeptidyl peptidase 4, in chemokine inactivation define new resistance mechanisms against immunotherapies and identify attractive new targets to enhance immune intervention in cancer.

The CC and CXC chemokines: major regulators of tumor progression and the tumor microenvironment

Chemokines are a family of soluble cytokines that act as chemoattractants to guide the migration of cells, in particular of immune cells. However, chemokines are also involved in cell proliferation, differentiation, and survival. Chemokines are associated with a variety of human diseases including chronic inflammation, immune dysfunction, cancer, and metastasis. This review discusses the expression of CC and CXC chemokines in the tumor microenvironment and their supportive and inhibitory roles in tumor progression, angiogenesis, metastasis, and tumor immunity. We also specially focus on the diverse roles of CXC chemokines (CXCL9-11, CXCL4 and its variant CXCL4L1) and their two chemokine receptor CXCR3 isoforms, CXCR3-A and CXCR3-B. These two distinct isoforms have divergent roles in tumors, either promoting (CXCR3-A) or inhibiting (CXCR3-B) tumor progression. Their effects are mediated not only directly in tumor cells but also indirectly via the regulation of angiogenesis and tumor immunity. A full comprehension of their mechanisms of action is critical to further validate these chemokines and their receptors as biomarkers or therapeutic targets in cancer.

CXC Chemokine Receptors in the Tumor Microenvironment and an Update of Antagonist Development

Chemokine receptors, a diverse group within the seven-transmembrane G protein-coupled receptor superfamily, are frequently overexpressed in malignant tumors. Ligand binding activates multiple downstream signal transduction cascades that drive tumor growth and metastasis, resulting in poor clinical outcome. These receptors are thus considered promising targets for anti-tumor therapy. This article reviews recent studies on the expression and function of CXC chemokine receptors in various tumor microenvironments and recent developments in cancer therapy using CXC chemokine receptor antagonists.

Expression of E-cadherin and specific CXCR3 isoforms impact each other in prostate cancer

Background

Carcinoma cells shift between epithelial and mesenchymal phenotypes during cancer progression, as defined by surface presentation of the cell-cell cohesion molecule E-cadherin, affecting dissemination, progression and therapy responsiveness. Concomitant with the loss of E-cadherin during the mesenchymal transition, the predominant receptor isoform for ELR-negative CXC ligands shifts from CXCR3-B to CXCR3-A which turns this classical G-protein coupled receptor from an inhibitor to an activator of cell migration, thus promoting tumor cell invasiveness. We proposed that CXCR3 was not just a coordinately changed receptor but actually a regulator of the cell phenotype.

Methods

Immunoblotting, immunofluorescence, quantitative real-time PCR and flow cytometry assays investigated the expression of E-cadherin and CXCR3 isoforms. Intrasplenic inoculation of human prostate cancer (PCa) cells with spontaneous metastasis to the liver analyzed E-cadherin and CXCR3-B expression during cancer progression in vivo.

Results

We found reciprocal regulation of E-cadherin and CXCR3 isoforms. E-cadherin surface expression promoted CXCR3-B presentation on the cell membrane, and to a lesser extent increased its mRNA and total protein levels. In turn, forced expression of CXCR3-A reduced E-cadherin expression level, whereas CXCR3-B increased E-cadherin in PCa. Meanwhile, a positive correlation of E-cadherin and CXCR3-B expression was found both in experimental PCa liver micro-metastases and patients’ tissue.

Conclusions

CXCR3-B and E-cadherin positively correlated in vitro and in vivo in PCa cells and liver metastases, whereas CXCR3-A negatively regulated E-cadherin expression. These results suggest that CXCR3 isoforms may play important roles in cancer progression and dissemination via diametrically regulating tumor’s phenotype.

Metformin Inhibits Chemokine Expression Through the AMPK/NF-κB Signaling Pathway

Inflammation is mediated by cytokines and chemokines, which are considered targets of inflammatory diseases. Mounting evidence has demonstrated the anti-inflammatory benefits of metformin. However, the underlying mechanisms are not completely understood. In this study, we aim to elucidate the regulatory effects of metformin on chemokine expression and the possible mechanisms using RAW264.7 cells, a mouse macrophage cell line, as a model. First, we treated the cells with lipopolysaccharide (LPS), and found that the expression of CXCL10 and CXCL11 was markedly induced in a dose- and time-dependent fashion concurrent with the inhibition of AMPK activity. Then, we treated the cells with metformin, and analyzed the expression of CCL2, CXCL10, and CXCL11 by quantitative real-time polymerase chain reaction (PCR). We observed that metformin prevented the stimulating effect of LPS on these chemokines as well as IL-1 and IL-6. Second, the inhibitory effects of metformin on LPS-induced chemokine expression were diminished by Compound C, a chemical inhibitor of AMPK. Finally, we investigated whether the NF-κB signaling pathway is regulated by metformin in this setting. Our results showed that metformin inhibited the phosphorylation of I-κBα and p65 while it activated AMPK. Therefore, the results suggest that metformin inhibits LPS-induced chemokine expression through the AMPK and NF-κB signaling pathways.

The Chemokine Receptor CXCR3 Isoform B Drives Breast Cancer Stem Cells

We are seeking to identify molecular targets that are relevant to breast cancer cells with stem-like properties. There is growing evidence that cancer stem cells (CSCs) are supported by inflammatory mediators expressed in the tumor microenvironment. The chemokine receptor CXCR3 binds the interferon-γ-inducible, ELR-negative CXC chemokines CXCL9, CXCL10, and CXCL11 and malignant cells have co-opted this receptor to promote tumor cell migration and invasion. There are 2 major isoforms of CXCR3: CXCR3A and CXCR3B. The latter is generated from alternative splicing and results in a protein with a longer N-terminal domain. CXCR3 isoform A is generally considered to play a major role in tumor metastasis. When the entire tumor cell population is examined, CXCR3 isoform B is usually detected at much lower levels than CXCR3A and for this, and other reasons, was not considered to drive tumor progression. We have shown that CXCR3B is significantly upregulated in the subpopulation of breast CSCs in comparison with the bulk tumor cell population in 3 independent breast cancer cell lines (MDA-MB-231, SUM159, and T47D). Modulation of CXCR3B levels by knock in strategies increases CSC populations identified by aldehyde dehydrogenase activity or CD44⁺CD24⁻ phenotype as well as tumorsphere-forming capacity. The reverse is seen when CXCR3B is gene-silenced. CXCL11 and CXCL10 directly induce CSC. We also report that novel CXCR3 allosteric modulators BD064 and BD103 prevent the induction of CSCs. BD103 inhibited experimental metastasis. This protective effect is associated with the reversal of CXCR3 ligand-mediated activation of STAT3, ERK1/2, CREB, and NOTCH1 pathways. We propose that CXCR3B, expressed on CSC, should be explored further as a novel therapeutic target.

Increased cytoplasmatic expression of cancer immune surveillance receptor CD1d in anaplastic thyroid carcinomas

BACKGROUND

Anaplastic thyroid carcinomas are associated with rapid tumor growth, short survival time and without any promising therapy to improve the poor prognosis. In this study, expression of immunoregulative receptor CD1d and lymphocyte infiltration in different thyroid tumors as well as in healthy tissue were analyzed in order to find new targets for an immunotherapeutic approach.

METHODS

CD1d immunohistochemistry was performed in samples of 18 anaplastic, 17 follicular, 27 papillary, and 4 medullary thyroid carcinomas as well as in 19 specimens from normal thyroid tissue and additionally in 10 samples of sarcoma, seven malignant melanoma and three spindle-cell lung carcinoma. Furthermore, thyroid samples were stained with antibodies against CD3, CD20, CD56, CD68, and LCA in order to analyze lymphocyte infiltration.

RESULTS

For the first time CD1d receptor expression on normal thyroid tissue could be demonstrated. Moreover, anaplastic thyroid carcinomas showed significantly higher expression levels compared to other thyroid samples. Most astonishingly, CD1d expression disappeared from the cellular surface and was detected rather in the cytoplasm of anaplastic thyroid carcinoma cells. In addition, histologically similar tumors to anaplastic carcinoma like sarcoma and malignant melanoma revealed distinct CD1d staining patterns. Furthermore, infiltration of T cells, B cells, and macrophages in anaplastic thyroid carcinomas was different when compared to normal thyroid tissue and all other thyroid carcinomas.

CONCLUSIONS

Anaplastic thyroid carcinomas show significantly higher expression of CD1d, a receptor for NKT cells, which are subject of several anticancer therapy studies. These results may offer a novel approach to explore immunotherapeutic treatment options.

Identification of Alternatively-Activated Pathways between Primary Breast Cancer and Liver Metastatic Cancer Using Microarray Data

Alternatively-activated pathways have been observed in biological experiments in cancer studies, but the concept had not been fully explored in computational cancer system biology. Therefore, an alternatively-activated pathway identification method was proposed and applied to primary breast cancer and breast cancer liver metastasis research using microarray data. Interestingly, the results show that cytokine-cytokine receptor interaction and calcium signaling were significantly enriched under both conditions. TGF beta signaling was found to be the hub in network topology analysis. In total, three types of alternatively-activated pathways were recognized. In the cytokine-cytokine receptor interaction pathway, four active alteration patterns in gene pairs were noticed. Thirteen cytokine-cytokine receptor pairs with inverse activity changes of both genes were verified by the literature. The second type was that some sub-pathways were active under only one condition. For the third type, nodes were significantly active in both conditions, but with different active genes. In the calcium signaling and TGF beta signaling pathways, node E2F5 and E2F4 were significantly active in primary breast cancer and metastasis, respectively. Overall, our study demonstrated the first time using microarray data to identify alternatively-activated pathways in breast cancer liver metastasis. The results showed that the proposed method was valid and effective, which could be helpful for future research for understanding the mechanism of breast cancer metastasis.

Apoptotic caspases inhibit abscopal responses to radiation and identify a new prognostic biomarker for breast cancer patients

Caspase 3 (CASP3) has a key role in the execution of apoptosis, and many cancer cells are believed to disable CASP3 as a mechanism of resistance to cytotoxic therapeutics. Alongside, CASP3 regulates stress-responsive immunomodulatory pathways, including secretion of type I interferon (IFN). Here, we report that mouse mammary carcinoma TSA cells lacking Casp3 or subjected to chemical caspase inhibition were as sensitive to the cytostatic and cytotoxic effects of radiation therapy (RT) in vitro as their control counterparts, yet secreted increased levels of type I IFN. This effect originated from the accrued accumulation of irradiated cells with cytosolic DNA, likely reflecting the delayed breakdown of cells experiencing mitochondrial permeabilization in the absence of CASP3. Casp3^-/- TSA cells growing in immunocompetent syngeneic mice were more sensitive to RT than their CASP3-proficient counterparts, and superior at generating bona fide abscopal responses in the presence of an immune checkpoint blocker. Finally, multiple genetic signatures of apoptotic proficiency were unexpectedly found to have robust negative (rather than positive) prognostic significance in a public cohort of breast cancer patients. However, these latter findings were not consistent with genetic signatures of defective type I IFN signaling, which were rather associated with improved prognosis. Differential gene expression analysis on patient subgroups with divergent prognosis (as stratified by independent signatures of apoptotic proficiency) identified SLC7A2 as a new biomarker with independent prognostic value in breast cancer patients. With the caveats associated with the retrospective investigation of heterogeneous, public databases, our data suggest that apoptotic caspases may influence the survival of breast cancer patients (or at least some subsets thereof) via mechanisms not necessarily related to type I IFN signaling as they identify a novel independent prognostic biomarker that awaits prospective validation.

DNA Repair Deficiency in Breast Cancer: Opportunities for Immunotherapy

Historically the development of anticancer treatments has been focused on their effect on tumor cells alone. However, newer treatments have shifted attention to targets on immune cells, resulting in dramatic responses. The effect of DNA repair deficiency on the microenvironment remains an area of key interest. Moreover, established therapies such as DNA damaging treatments such as chemotherapy and PARP inhibitors further modify the tumor microenvironment. Here we describe DNA repair pathways in breast cancer and activation of innate immune pathways in DNA repair deficiency, in particular, the STING (STimulator of INterferon Genes) pathway. Breast tumors with DNA repair deficiency are associated with upregulation of immune checkpoints including PD-L1 (Programmed Death Ligand-1) and may represent a target population for single agent or combination immunotherapy treatment.

The Distinct Roles of CXCR3 Variants and Their Ligands in the Tumor Microenvironment

First thought to orchestrate exclusively leukocyte trafficking, chemokines are now acknowledged for their multiple roles in the regulation of cell proliferation, differentiation, and survival. Dysregulation of their normal functions contributes to various pathologies, including inflammatory diseases and cancer. The two chemokine receptor 3 variants CXCR3-A and CXCR3-B, together with their cognate chemokines (CXCL11, CXCL10, CXCL9, CXCL4, and CXCL4L1), are involved in the control but also in the development of many tumors. CXCR3-A drives the infiltration of leukocytes to the tumor bed to modulate tumor progression (paracrine axis). Conversely, tumor-driven changes in the expression of the CXCR3 variants and their ligands promote cancer progression (autocrine axis). This review summarizes the anti- and pro-tumoral activities of the CXCR3 variants and their associated chemokines with a focus on the understanding of their distinct biological roles in the tumor microenvironment.

The Role of CXCR3 in Neurological Diseases

BACKGROUND

Neurological diseases have become an obvious challenge due to insufficient therapeutic intervention. Therefore, novel drugs for various neurological disorders are in desperate need. Recently, compelling evidence has demonstrated that chemokine receptor CXCR3, which is a G protein-coupled receptor in the CXC chemokine receptor family, may play a pivotal role in the development of neurological diseases. The aim of this review is to provide evidence for the potential of CXCR3 as a therapeutic target for neurological diseases.

METHODS

English journal articles that focused on the invovlement of CXCR3 in neurological diseases were searched via PubMed up to May 2017. Moreover, reference lists from identified articles were included for overviews.

RESULTS

The expression level of CXCR3 in T cells was significantly elevated in several neurological diseases, including multiple sclerosis (MS), glioma, Alzheimer's disease (AD), chronic pain, human T-lymphotropic virus type 1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and bipolar disorder. CXCR3 antagonists showed therapeutic effects in these neurological diseases.

CONCLUSION

These studies provided hard evidence that CXCR3 plays a vital role in the pathogenesis of MS, glioma, AD, chronic pain, HAM/TSP and bipolar disorder. CXCR3 is a crucial molecule in neuroinflammatory and neurodegenerative diseases. It regulates the activation of infiltrating cells and resident immune cells. However, the exact functions of CXCR3 in neurological diseases are inconclusive. Thus, it is important to understand the topic of chemokines and the scope of their activity in neurological diseases.

Chemokines and Chemokine Receptors: Orchestrating Tumor Metastasization

Metastasis still represents the primary cause of cancer morbidity and mortality worldwide. Chemokine signalling contributes to the overall process of cancer growth and metastasis, and their expression in both primary tumors and metastatic lesions correlate with prognosis. Chemokines promote tumor metastasization by directly supporting cancer cell survival and invasion, angiogenesis, and by indirectly shaping the pre-metastatic niches and antitumor immunity. Here, we will focus on the relevant chemokine/chemokine receptor axes that have been described to drive the metastatic process. We elaborate on their role in the regulation of tumor angiogenesis and immune cell recruitment at both the primary tumor lesions and the pre-metastatic foci. Furthermore, we also discuss the advantages and limits of current pharmacological strategies developed to target chemokine networks for cancer therapy.

The Antitumor Mechanism of Paeonol on CXCL4/CXCR3-B Signals in Breast Cancer Through Induction of Tumor Cell Apoptosis

BACKGROUND

Paeonol, a phenolic component from the root bark of Paeonia moutan, has been identified to possess antitumor effects. However, the effect of paeonol and the mechanism of CXCL4/CXCR3-B signals in paeonol-induced breast cancer cell remain unknown.

MATERIALS AND METHODS

After MDA-MB-231 cells were pretreated with paeonol or DMSO, the proliferation activity was detected by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), Hoechst, Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), and Annexin-V/propidium iodide staining flow cytometry. Western blot and immunohistochemistry of human breast cancer and noncancerous tissues were performed to determine the molecular alteration of CXCL4/CXCR3-B signals.

RESULTS

Compared with the control, paeonol-treated breast cancer cells had low proliferation activity and high apoptotic index, indicating that paeonol induces breast cancer cell apoptosis. Western blot and immunohistochemistry showed that paeonol increased CXCR3-B signal, downregulated CXCL4, heme oxygenase (HO-1) with a corresponding increased BACH1, and decreased nuclear factor E2-related factor 2 (Nrf2).

CONCLUSIONS

Thus, CXCL4/CXCR3-B may be involved in the mechanism of apoptosis induced by paeonol in breast cancer cells by regulating the expression of BACH1 and Nrf2 to downregulating HO-1 and promote apoptosis. Therefore, the authors suggest paeonol has a significant growth inhibitory effect on breast cancer cells, which may be related to the induction of apoptosis.

CXCR3 is a prognostic marker and a potential target for patients with solid tumors: a meta-analysis

OBJECTIVE

To deeply verify the clinical significance of CXCR3 in prediction of cancer patients' prognosis.

DATA SOURCES

We performed a meta-analysis including 12 studies searched from PubMed, Web of Science, Embase, and Cochrane databases. A total of 1,751 patients were used to analyze the association between CXCR3 and patients' prognosis, based on either overall survival or time to tumor progression.

STUDY SELECTION

Studies evaluating CXCR3 expression for predicting prognosis in human solid tumors were included.

RESULTS

It showed that patients with higher expression of CXCR3 had significantly shorter OS (pooled hazard ratio =2.315, 95% CI: 1.162-4.611, P=0.017). In addition, higher CXCR3 expression was associated with distant metastasis (yes vs no: pooled relative ratio [RR] =1.828, 95% CI: 1.140-2.931, P=0.012) in solid tumors and indicated advanced tumor stage (III/IV vs I/II, RR =2.656, 95% CI: 1.809-3.900, P<0.001) and lymph node metastasis (yes vs no: RR =2.28, 95% CI: 1.61-3.25, P<0.001) in colorectal cancer.

CONCLUSION

Our study highlights the role of CXCR3 as a potential prognostic marker and a promising therapeutic target in solid tumors.

Molecular Mechanisms of Biased and Probe-Dependent Signaling at CXC-Motif Chemokine Receptor CXCR3 Induced by Negative Allosteric Modulators

Our recent explorations of allosteric modulators with improved properties resulted in the identification of two biased negative allosteric modulators, BD103 (N-1-{[3-(4-ethoxyphenyl)-4-oxo-3,4-dihydropyrido[2,3-d]pyrimi-din2yl]ethyl}-4-(4-fluorobutoxy)-N-[(1-methylpiperidin-4-yl)methyl}]butanamide) and BD064 (5-[(N-{1-[3-(4-ethoxyphenyl)-4-oxo-3,4-dihydropyrido[2,3-d]pyrimidin-2-yl]ethyl-2-[4-fluoro-3-(trifluoromethyl)phenyl]acetamido)methyl]-2-fluorophenyl}boronic acid), that exhibited probe-dependent inhibition of CXC-motif chemokine receptor CXCR3 signaling. With the intention to elucidate the structural mechanisms underlying their selectivity and probe dependence, we used site-directed mutagenesis combined with homology modeling and docking to identify amino acids of CXCR3 that contribute to modulator binding, signaling, and transmission of cooperativity. With the use of allosteric radioligand RAMX3 ([³H]N-{1-[3-(4-ethoxyphenyl)-4-oxo-3,4-dihydropyrido[2,3-d]pyrimidin-2-yl]ethyl}-2-[4-fluoro-3-(trifluoromethyl)phenyl]-N-[(1-methylpiperidin-4-yl)methyl]acetamide), we identified that F131^3.32 and Y308^7.43 contribute specifically to the binding pocket of BD064, whereas D186^4.60 solely participates in the stabilization of binding conformation of BD103. The influence of mutations on the ability of negative allosteric modulators to inhibit chemokine-mediated activation (CXCL11 and CXCL10) was assessed with the bioluminescence resonance energy transfer-based cAMP and β-arrestin recruitment assay. Obtained data revealed complex molecular mechanisms governing biased and probe-dependent signaling at CXCR3. In particular, F131^3.32, S304^7.39, and Y308^7.43 emerged as key residues for the compounds to modulate the chemokine response. Notably, D186^4.60, W268^6.48, and S304^7.39 turned out to play a role in signal pathway selectivity of CXCL10, as mutations of these residues led to a G protein-active but β-arrestin-inactive conformation. These diverse effects of mutations suggest the existence of ligand- and pathway-specific receptor conformations and give new insights in the sophisticated signaling machinery between allosteric ligands, chemokines, and their receptors, which can provide a powerful platform for the development of new allosteric drugs with improved pharmacological properties.

CXCL9, CXCL10, CXCL11/CXCR3 axis for immune activation - A target for novel cancer therapy

Chemokines are proteins which induce chemotaxis, promote differentiation of immune cells, and cause tissue extravasation. Given these properties, their role in anti-tumor immune response in the cancer environment is of great interest. Although immunotherapy has shown clinical benefit for some cancer patients, other patients do not respond. One of the mechanisms of resistance to checkpoint inhibitors may be chemokine signaling. The CXCL9, -10, -11/CXCR3 axis regulates immune cell migration, differentiation, and activation, leading to tumor suppression (paracrine axis). However, there are some reports that show involvements of this axis in tumor growth and metastasis (autocrine axis). Thus, a better understanding of CXCL9, -10, -11/CXCR3 axis is necessary to develop effective cancer control. In this article, we summarize recent evidence regarding CXCL9, CXCL10, CXCL11/CXCR3 axis in the immune system and discuss their potential role in cancer treatment.

The role of CXCR3/LRP1 cross-talk in the invasion of primary brain tumors

CXCR3 plays important roles in angiogenesis, inflammation, and cancer. However, the precise mechanism of regulation and activity in tumors is not well known. We focused on CXCR3-A conformation and on the mechanisms controlling its activity and trafficking and investigated the role of CXCR3/LRP1 cross talk in tumor cell invasion. Here we report that agonist stimulation induces an anisotropic response with conformational changes of CXCR3-A along its longitudinal axis. CXCR3-A is internalized via clathrin-coated vesicles and recycled by retrograde trafficking. We demonstrate that CXCR3-A interacts with LRP1. Silencing of LRP1 leads to an increase in the magnitude of ligand-induced conformational change with CXCR3-A focalized at the cell membrane, leading to a sustained receptor activity and an increase in tumor cell migration. This was validated in patient-derived glioma cells and patient samples. Our study defines LRP1 as a regulator of CXCR3, which may have important consequences for tumor biology.

Ligand activation induces different conformational changes in CXCR3 receptor isoforms as evidenced by plasmon waveguide resonance (PWR)

The chemokine receptor CXCR3 plays important roles in angiogenesis, inflammation and cancer. Activation studies and biological functions of CXCR3 are complex due to the presence of spliced isoforms. CXCR3-A is known as a pro-tumor receptor whereas CXCR3-B exhibits anti-tumor properties. Here, we focused on the conformational change of CXCR3-A and CXCR3-B after agonist or antagonist binding using Plasmon Waveguide Resonance (PWR). Agonist stimulation induced an anisotropic response with very distinct conformational changes for the two isoforms. The CXCR3 agonist bound CXCR3-A with higher affinity than CXCR3-B. Using various concentrations of SCH546738, a CXCR3 specific inhibitor, we demonstrated that low SCH546738 concentrations (≤1 nM) efficiently inhibited CXCR3-A but not CXCR3-B’s conformational change and activation. This was confirmed by both, biophysical and biological methods. Taken together, our study demonstrates differences in the behavior of CXCR3-A and CXCR3-B upon ligand activation and antagonist inhibition which may be of relevance for further studies aimed at specifically inhibiting the CXCR3A isoform.

The Eya phosphatase: Its unique role in cancer

The Eya proteins were originally identified as essential transcriptional co-activators of the Six family of homeoproteins. Subsequently, the highly conserved C-terminal domains of the Eya proteins were discovered to act as a Mg²⁺-dependent Tyr phosphatases, making Eyas the first transcriptional activators to harbor intrinsic phosphatase activity. Only two direct targets of the Eya Tyr phosphatase have been identified: H2AX, whose dephosphorylation directs cells to the DNA repair instead of the apoptotic pathway upon DNA damage, and ERβ, whose dephosphorylation inhibits its anti-tumor transcriptional activity. The Eya Tyr phosphatase mediates breast cancer cell transformation, migration, invasion, as well as metastasis, through targets not yet identified. Intriguingly, the N-terminal domain of Eya contains a separate Ser/Thr phosphatase activity implicated in innate immunity and in regulating c-Myc stability. Thus, Eya proteins are highly complex, containing two separable phosphatase domains and a transcriptional activation domain, thereby influencing tumor progression through multiple mechanisms.

SSeCKS/AKAP12 scaffolding functions suppress B16F10-induced peritoneal metastasis by attenuating CXCL9/10 secretion by resident fibroblasts

SSeCKS/Gravin/AKAP12 (SSeCKS) is a kinase scaffolding protein known to suppress metastasis by attenuating tumor-intrinsic PKC- and Src-mediated signaling pathways [1]. In addition to downregulation in metastatic cells, in silico analyses identified SSeCKS downregulation in prostate or breast cancer-derived stroma, suggesting a microenvironmental cell role in controlling malignancy. Although orthotopic B16F10 and SM1WT1[Braf^V600E] mouse melanoma tumors grew similarly in syngeneic WT or SSeCKS-null (KO) mice, KO hosts exhibited 5- to 10-fold higher levels of peritoneal metastasis, and this enhancement could be adoptively transferred by pre-injecting naïve WT mice with peritoneal fluid (PF), but not non-adherent peritoneal cells (PC), from naïve KO mice. B16F10 and SM1WT1 cells showed increased chemotaxis to KO-PF compared to WT-PF, corresponding to increased PF levels of multiple inflammatory mediators, including the Cxcr3 ligands, Cxcl9 and 10. Cxcr3 knockdown abrogated enhanced chemotaxis to KO-PF and peritoneal metastasis in KO hosts. Conditioned media from KO peritoneal membrane fibroblasts (PMF), but not from KO-PC, induced increased B16F10 chemotaxis over controls, which could be blocked with Cxcl10 neutralizing antibody. KO-PMF exhibited increased levels of the senescence markers, SA-β-galactosidase, p21^waf1 and p16^ink4a, and enhanced Cxcl10 secretion induced by inflammatory mediators, lipopolysaccharide, TNFα, IFNα and IFNγ. SSeCKS scaffolding-site mutants and small molecule kinase inhibitors were used to show that the loss of SSeCKS-regulated PKC, PKA and PI3K/Akt pathways are responsible for the enhanced Cxcl10 secretion. These data mark the first description of a role for stromal SSeCKS/AKAP12 in suppressing metastasis, specifically by attenuating signaling pathways that promote secretion of tumor chemoattractants in the peritoneum.

CXCR3 mediates ascites-directed tumor cell migration and predicts poor outcome in ovarian cancer patients

Intraabdominal tumor dissemination is a major hallmark of epithelial ovarian cancer (EOC), but the underlying mechanisms have not been fully elucidated. The CXCR3 chemokine receptor supports migration of tumor cells to metastatic sites, but its role in ovarian cancer metastasis is largely unknown. Herein, we first screened two independent cohorts of high-grade serous ovarian cancers (HGSCs, discovery set n=60, validation set n=117) and 102 metastatic lesions for CXCR3 expression. In primary tumors, CXCR3 was particularly overexpressed by tumor cells at the invasive front. In intraabdominal metastases, tumor cells revealed a strong CXCR3 expression regardless of its expression in the corresponding primary tumor, suggesting a selection of CXCR3-overexpressing cancer cells into peritoneal niches. In support of this, CXCR3 mediated the migration of tumor cell lines OVCAR3 and SKOV3 toward malignant ascites, which was inhibited by a monoclonal anti-CXCR3 antibody in vitro. These results were prospectively validated in ascites-derived tumor cells from EOC patients ex vivo (n=9). Moreover, tumor cell-associated overexpression of CXCR3 in advanced ovarian cancer patients was associated with a reduced progression-free survival (PFS) and overall survival (OS), which remained independent of optimal debulking, age, FIGO stage and lymph node involvement (PFS: hazard ratio (HR) 2.11, 95% confidence interval (CI) 1.30–3.45, P=0.003; OS: HR 2.36, 95% CI 1.50–3.71, P<0.001). These results in ovarian cancer patients identify CXCR3 as a potential new target to confine peritoneal spread in ovarian cancer after primary cytoreductive surgery.

An integrated method for the identification of novel genes related to oral cancer

Cancer is a significant public health problem worldwide. Complete identification of genes related to one type of cancer facilitates earlier diagnosis and effective treatments. In this study, two widely used algorithms, the random walk with restart algorithm and the shortest path algorithm, were adopted to construct two parameterized computational methods, namely, an RWR-based method and an SP-based method; based on these methods, an integrated method was constructed for identifying novel disease genes. To validate the utility of the integrated method, data for oral cancer were used, on which the RWR-based and SP-based methods were trained, thereby building two optimal methods. The integrated method combining these optimal methods was further adopted to identify the novel genes of oral cancer. As a result, 85 novel genes were inferred, among which eleven genes (e.g., MYD88, FGFR2, NF-κBIA) were identified by both the RWR-based and SP-based methods, 70 genes (e.g., BMP4, IFNG, KITLG) were discovered only by the RWR-based method and four genes (L1R1, MCM6, NOG and CXCR3) were predicted only by the SP-based method. Extensive analyses indicate that several novel genes have strong associations with cancers, indicating the effectiveness of the integrated method for identifying disease genes.

Induction of cathepsin B by the CXCR3 chemokines CXCL9 and CXCL10 in human breast cancer cells

Cathepsin B (CTSB) is a lysosomal cysteine protease that has been linked to the progression of breast cancer, for example by activation of other proteases and tumor-promoting cytokines, thereby supporting tumor invasion and metastasis. Previously, it was shown that CTSB cleaves and inactivates C-X-C motif chemokine receptor 3 (CXCR3) chemokines. As CXCR3 ligands have been demonstrated to induce proteases in cancer cells, the present study hypothesized that they may also affect CTSB in breast cancer cells. The results demonstrated that the human breast cancer tumor cell lines MCF-7 and MDA-MB-231 express the CXCR3 splice variants A and B and CTSB. Upon binding to CXCR3, the two chemokine ligands C-X-C motif chemokine ligand (CXCL) 9 and CXCL10 trigger upregulation of CTSB in these breast cancer cells, whereas the CXCR3-B-specific ligand CXCL4 has no such effect, suggesting the involvement of CXCR3-A in the regulation of CTSB. In early-stage human breast cancer specimens (n=81), overexpression of CXCR3 is associated with statistically significant poorer overall survival, independent of lymph node status, tumor size and nuclear grading (hazard ratio=1.99; 95% confidence interval=1.00–3.97; P=0.050). In conclusion, the data from the current study propose a so far unknown mechanism by which breast cancer cells may exploit tumor-suppressive chemokines to enhance their invasiveness and reduce immune cell infiltration by the degradation of these chemokines. This mechanism may support the established unfavorable prognostic feature of CXCR3 expression in breast cancer.

Pro-tumoural CXCL10/CXCR3-A autocrine loop in invasive mucinous lung adenocarcinoma

Invasive mucinous adenocarcinoma (IMA) is a mucinous variant of lepidic predominant lung adenocarcinoma (LPA) and associated with a worse prognosis. We postulated that cytokine expression would enable us to differentiate IMA from LPA in terms of prognosis and acquisition of pro-tumoural capacities.

A 30-cytokine panel was assessed in bronchoalveolar lavage fluids (BALF) from IMA (n=38), LPA (n=25) and control samples (n=7). We investigated the expression of differentially expressed cytokines and splice variants of their receptors in surgical samples. The presence of EGFR and KRAS mutations were determined. We also examined the expression of cytokines and splice variants of their receptors in different cell lines, exploring their functional impact on signalling pathways, proliferation and migration.

Only C-X-C motif chemokine 10 (CXCL10) was differentially expressed, namely overexpressed in IMA BALF compared with LPA. CXCL10 overexpression in BALF was linked to a worse prognosis. In surgical samples, CXCL10 and its receptor C-X-C motif chemokine receptor 3 (CXCR3) were overexpressed in IMA compared to LPA. A pro-tumoural CXCR3-A splice variant was overexpressed in IMA, suggesting a CXCL10/CXCR3-A autocrine loop in IMA. CXCL10 and CXCR3 expression were not correlated with EGFR or KRAS status. CXCL10 up-regulated CXCR3-A expression, Erk1/2 phosphorylation and enhanced migration in the mucinous H2228 cell line.

CXCL10/CXCR3-A may play a pro-tumoural role in IMA via an autocrine mechanism.

Invasive mucinous lung adenocarcinoma derived pro-tumoural advantages by means of a CXCL10/CXCR3-A autocrine loophttp://ow.ly/2Gjj308QxwK

CXCR3+ monocytes/macrophages are required for establishment of pulmonary metastases

We present a new foundational role for CXCR3⁺ monocytes/macrophages in the process of tumor engraftment in the lung. CXCR3 is associated with monocytic and lymphocytic infiltration of inflamed or tumor-bearing lung. Although the requirement for tumor-expressed CXCR3 in metastatic engraftment has been demonstrated, the role of monocyte-expressed CXCR3 had not been appreciated. In a murine model of metastatic-like melanoma, engraftment was coordinate with CXCR3⁺ monocyte/macrophage accumulation in the lungs and was sensitive to pharmacologic inhibition of CXCR3 signaling. Tumor engraftment to lung was impaired in CXCR3^−/− mice, and transient reconstitution with circulating CXCR3-replete monocytes was sufficient to restore engraftment. These data illustrate the paradoxical pro-tumor role for CXCR3 in lung immunobiology wherein the CXCR3 axis drives both the anti-tumor effector cell chemoattraction and pro-tumor infiltration of the lungs and suggests a potential therapeutic target for lung-tropic metastasizing cancers.

CXCR3 as a molecular target in breast cancer metastasis: inhibition of tumor cell migration and promotion of host anti-tumor immunity

Chemokines and chemokine receptors have critical roles in cancer metastasis and have emerged as one of the targeting options in cancer therapy. However, the treatment efficacy on both tumor and host compartments needs to be carefully evaluated. Here we report that targeting CXCR3 decreased tumor cell migration and at the same time improved host anti-tumor immunity. We observed an increased expression of CXCR3 in metastatic tumor cells compared to those from non-metastatic tumor cells. Knockdown (KD) of CXCR3 in metastatic tumor cells suppressed tumor cell migration and metastasis. Importantly, CXCR3 expression in clinical breast cancer samples correlated with progression and metastasis. For the host compartment, deletion of CXCR3 in all host cells in 4T1 mammary tumor model significantly decreased metastasis. The underlying mechanisms involve a decreased expression of IL-4, IL-10, iNOs, and Arg-1 in myeloid cells and an increased T cell response. IFN-γ neutralization diminished the metastasis inhibition in the CXCR3 knockout (KO) mice bearing 4T1 tumors, suggesting a critical role of host CXCR3 in immune suppression. Consistently, targeting CXCR3 using a small molecular inhibitor (AMG487) significantly suppressed metastasis and improved host anti-tumor immunity. Our findings demonstrate that targeting CXCR3 is effective in both tumor and host compartments, and suggest that CXCR3 inhibition is likely to avoid adverse effects on host cells.