Divergent roles of CXCR3 isoforms in promoting cancer stem-like cell survival and metastasis

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.

Role of CXCR3 in fibrotic tissue responses

Development of fibrosis leads to end stage diseases that defy treatments across all organs. This ensues as chronic inflammation is not dampened by physiologic processes that issue in the resolution phase of wound healing. Thus, these conditions can be considered diseases of "failure to heal". In the absence of broadly viable treatments, it is proposed to examine key switches in wound healing resolution to seek insights into novel approaches. Signaling through the GPCR CXCR3 has been shown to be one such critical player in this physiologic transition that limits and even reverses early fibrosis. As such, a number of investigators and early stage technology companies have posited that triggering this signaling network would limit fibrosis. While there are some conflicting results, a consensus is emerging that pharmacologic interventions that promote signaling through this pathway represent innovative ways to limit fibrotic diseases.

Expression profile and prognostic value of CXCR family members in head and neck squamous cell carcinoma

Background

CXC chemokine receptor gene family consists of seven well-established members which are broadly involved in biological functions of various cancers. Currently, limited studies have shed light on the expression profile of CXCR family members (CXCRs), as well as their prognostic value, in head and neck squamous cells carcinoma (HNSCC).

Methods

The data for this study were retrieved from the Cancer Genome Atlas database and other publicly available databases, including gene expression, methylation profiles, clinical information, immunological features, and prognoses. The expression pattern and prognostic values of CXCRs were identified, and the potential mechanism underlying CXCRs function in HNSCC was investigated by gene set enrichment analysis (GSEA).

Results

CXCRs were differentially expressed in HNSCC. As shown by Kaplan–Meier analysis, high CXCR3-6 expression was significantly associated with better prognostic outcomes of HNSCC patients, including overall survival and progression-free survival. According to the results of univariate and multivariate Cox proportional risk regression analysis, it was demonstrated that upregulation of CXCR3-6 was an independent factor for better prognosis, while the two other clinical features, age and stage, were factors for worse prognosis. A significant positive correlation between CXCR3-6 and tumor-infiltrated immune cells was revealed by results from Tumor Immune Estimation Resource and CIBERSORT analysis database. The main involvement of CXCRs in immune and inflammatory responses was further confirmed by GSEA.

Conclusions

Overall, this study provided a rationale for targeting CXCRs as a promising therapeutic strategy of HNSCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-022-02713-z.

Single-Cell Proteomic Profiling Identifies Nanoparticle Enhanced Therapy for Triple Negative Breast Cancer Stem Cells

Breast cancer remains a major cause of cancer-related deaths in women worldwide. Chemotherapy-promoted stemness and enhanced stem cell plasticity in breast cancer is a cause for great concern. The discovery of drugs targeting BCSCs was suggested to be an important advancement in the establishment of therapy that improves the efficacy of chemotherapy. In this work, by using single-cell mass cytometry, we observed that stemness in spheroid-forming cells derived from MDA-MB-231 cells was significantly increased after doxorubicin administration and up-regulated integrin αvβ3 expression was also observed. An RGD-included nanoparticle (CS-V) was designed, and it was found that it could promote doxorubicin’s efficacy against MDA-MB-231 spheroid cells. The above observations suggested that the combination of RGD-included nanoparticles (CS-V) with the chemo-drug doxorubicin could be developed as a potential therapy for breast cancer.

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.

CXCR3 Expression and Genome-Wide 3' Splice Site Selection in the TCGA Breast Cancer Cohort

CXCR3 is a chemokine receptor with two well-characterized isoforms that have unique, context-dependent roles: CXCR3-A and CXCR3-B, which are produced through alternative 3′ splice site selection (A3SS). RNA-seq data from The Cancer Genome Atlas (TCGA) were used to correlate CXCR3 expression with breast cancer progression. This analysis revealed significant CXCR3 expression patterns associated with survival and differential expression between the tumor and adjacent normal tissue. TCGA data were used to estimate abundance of immune cells in breast cancer, which demonstrated the association of CXCR3 with immune infiltration, particularly in the triple-negative subtype. Given the importance of A3SS in CXCR3, genome-wide analysis of A3SS events was performed to identify events that were differentially spliced between breast cancer tissue and adjacent normal tissue. A total of 481 splicing events in 424 genes were found to be differentially spliced. The parent genes of differentially spliced events were enriched in RNA processing and splicing functions, indicating an underappreciated role of A3SS in the integrated splicing network of breast cancer. These results further validated the role of CXCR3 in immune infiltration of tumors, while raising questions about the role of A3SS splicing.

The Effect of Hypoxia on the Expression of CXC Chemokines and CXC Chemokine Receptors-A Review of Literature

Hypoxia is an integral component of the tumor microenvironment. Either as chronic or cycling hypoxia, it exerts a similar effect on cancer processes by activating hypoxia-inducible factor-1 (HIF-1) and nuclear factor (NF-κB), with cycling hypoxia showing a stronger proinflammatory influence. One of the systems affected by hypoxia is the CXC chemokine system. This paper reviews all available information on hypoxia-induced changes in the expression of all CXC chemokines (CXCL1, CXCL2, CXCL3, CXCL4, CXCL5, CXCL6, CXCL7, CXCL8 (IL-8), CXCL9, CXCL10, CXCL11, CXCL12 (SDF-1), CXCL13, CXCL14, CXCL15, CXCL16, CXCL17) as well as CXC chemokine receptors—CXCR1, CXCR2, CXCR3, CXCR4, CXCR5, CXCR6, CXCR7 and CXCR8. First, we present basic information on the effect of these chemoattractant cytokines on cancer processes. We then discuss the effect of hypoxia-induced changes on CXC chemokine expression on the angiogenesis, lymphangiogenesis and recruitment of various cells to the tumor niche, including myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), regulatory T cells (T_regs) and tumor-infiltrating lymphocytes (TILs). Finally, the review summarizes data on the use of drugs targeting the CXC chemokine system in cancer therapies.

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.

Mechanisms of Tumor-Induced Lymphovascular Niche Formation in Draining Lymph Nodes

Enlargement of the lymphatic vascular network in tumor-draining lymph nodes (LNs) often precedes LN metastasis, likely providing a lymphovascular niche for tumor cells. We investigated morphological and molecular changes associated with the lymphatic remodeling process, using the 4T1 breast cancer and B16F10 melanoma models. Lymphatic expansion in tumor-draining LNs is mediated by sprouting and proliferation of lymphatic endothelial cells (LECs) as early as 4 days after tumor implantation. RNA sequencing revealed an altered transcriptional profile of LECs from tumor-draining compared to naive LNs with similar changes in both tumor models. Integrin αIIb is upregulated in LECs of tumor-draining LNs and mediates LEC adhesion to fibrinogen in vitro. LEC-associated fibrinogen was also detected in LNs in vivo, suggesting a role of integrin αIIb in lymphatic remodeling. Together, our results identify specific responses of LN LECs to tumor stimuli and provide insights into the mechanisms of lymphovascular niche formation in tumor-draining LNs.

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Lymph node lymphatic endothelial cells (LN LECs) dramatically react to tumor stimuli

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Cell adhesion molecules are among the strongest differentially regulated genes

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Itga2b is upregulated and associated with fibrinogen in tumor-draining LN LECs

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Itga2b mediates adhesion of LN LECs to fibrinogen

Effect of Vitamin D3 on Lung Damage Induced by Cigarette Smoke in Mice

Cigarette smoking is known to induce serious lung diseases, but there is not an effective method to solve this problem. The present study investigated vitamin D3 on over-expression of CXCR3 and CXCL10 in mice induced by cigarette smoking. A pulmonary airway model was designed, and morphological assessment of emphysema, IL-4, IFN-γ and CXCL10 concentration in bronchoalveolar lavage fluids, expression of CXCR3 and CXCL10 were detected. Emphysema of the mice only exposed to cigarette smoke was significant, and concentration of IL-4, IFN-γ and CXCL10 was also increased. In addition, CXCR3 and CXCL10 were over-expressed. The degree of emphysema, concentration of IL-4, IFN-γ and CXCL10, and expression of CXCR3 and CXCL10 in mice administrated with low dose vitamin D3 were similar to the normally treated mice. Low dose of vitamin D3 can effectively protect the lung from the damage induced by cigarette smoke.

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.

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.

Functions of the CXC ligand family in the pancreatic tumor microenvironment

Therapeutic resistance is the major contributor to the poor prognosis of and low survival from pancreatic cancer (PC). Cancer progression is a complex process reliant on interactions between the tumor and the tumor microenvironment (TME). Members of the CXCL family of chemokines are present in the pancreatic TME and seem to play a vital role in regulating PC progression. As pancreatic tumors interact with the TME and with PC stem cells (CSCs), determining the roles of specific members of the CXCL family is vital to the development of improved therapies. This review highlights the roles of selected CXCLs in the interactions between pancreatic tumor and its stroma, and in CSC phenotypes, which can be used to identify potential treatment targets.

Influence of transcriptional variants on metastasis

Cancer metastasis is defined as the dissemination of malignant cells from the primary tumor site, leading to colonization of distant organs and the establishment of a secondary tumor. Metastasis is frequently associated with chemoresistance and is the major cause of cancer-related mortality. Metastatic cells need to acquire the ability to resist to stresses provided by different environments, such as reactive oxygen species, shear stress, hemodynamic forces, stromal composition, and immune responses, to colonize other tissues. Hence, only a small population of cells has a metastasis-initiating potential. Several studies have revealed the misregulation of transcriptional variants during cancer progression, and many splice events can be used to distinguish between normal and tumoral tissue. These variants, which are abnormally expressed in malignant cells, contribute to an adaptive response of tumor cells and the success of the metastatic cascade, promoting an anomalous cell cycle, cellular adhesion, resistance to death, cell survival, migration and invasion. Understanding the different aspects of splicing regulation and the influence of transcriptional variants that control metastatic cells is critical for the development of therapeutic strategies. In this review, we describe how transcriptional variants contribute to metastatic competence and discuss how targeting specific isoforms may be a promising therapeutic strategy.

Upregulation of angiostatic chemokines IP-10/CXCL10 and I-TAC/CXCL11 in human obesity and their implication for adipose tissue angiogenesis

BACKGROUND/AIMS

Impaired angiogenesis is linked to adipose tissue (AT) dysfunction, inflammation, and insulin resistance in human obesity. Chemokine (C-X-C motif) receptor. (CXCR3) ligands are important regulators of angiogenesis in different disease contexts such as cancer; however, their role in human morbid obesity is unknown. We investigated the role of the CXCR3 axis in AT angiogenesis in morbidly obese patients.

SUBJECTS/METHODS

The study group comprised 50 morbidly obese patients (mean age 44 ± 1 years, body mass index 44 ± 1 kg/m²) who had undergone laparoscopic Roux-Y-gastric bypass surgery, and 25 age-matched non-obese control subjects. We measured the circulating levels of the CXCR3 ligands monokine induced by interferon-γ (MIG/CXCL9), interferon-γ inducible protein 10 (IP-10/CXCL10), and interferon-γ-inducible T-cell alpha chemoattractant (I-TAC/CXCL11) in all studied subjects. Additionally, the expression of CXCR3 ligands was analyzed in paired biopsies of subcutaneous and visceral AT obtained during the laparoscopic procedure in morbidly obese patients. Additionally, we explored the functional role of CXCR3 ligands on angiogenesis in AT from morbidly obese patients using an ex vivo assay.

RESULTS

Plasma levels of CXCL10 and CXCL11 were significantly higher in morbidly obese patients than in controls (p < 0.01). In ex vivo assays, angiogenic growth was markedly lower in visceral AT than in subcutaneous AT (p < 0.05), which was related to significant tissue upregulation of CXCL10, CXCL11 and CXCR3 (p < 0.05). CXCL10 or CXCL11 inhibited AT angiogenesis (p < 0.05), and blockade of CXCR3 function significantly increased capillary sprouting in visceral fat deposits (p < 0.05). Western blot analysis showed that the p38 mitogen-activated protein kinase signaling pathway was implicated in the angiostatic effects of CXCR3 in AT.

CONCLUSIONS

CXCL10 and CXCL11 may play. deleterious role in obesity as potential inhibitors of AT angiogenesis. Accordingly, pharmacological blockade of CXCR3 could represent. therapy to prevent AT dysfunction in obesity.

Platelet factor 4 is produced by subsets of myeloid cells in premetastatic lung and inhibits tumor metastasis

Bone marrow-derived myeloid cells can form a premetastatic niche and provide a tumor-promoting microenvironment. However, subsets of myeloid cells have also been reported to have anti-tumor properties. It is not clear whether there is a transition between anti- and pro- tumor function of these myeloid cells, and if so, what are the underlying molecular mechanisms. Here we report platelet factor 4 (PF4), or CXCL4, but not the other family members CXCL9, 10, and 11, was produced at higher levels in the normal lung and early stage premetastatic lungs but decreased in later stage lungs. PF4 was mostly produced by Ly6G+CD11b+ myeloid cell subset. Although the number of Ly6G+CD11b+ cells was increased in the premetastatic lungs, the expression level of PF4 in these cells was decreased during the metastatic progression. Deletion of PF4 (PF4 knockout or KO mice) led an increased metastasis suggesting an inhibitory function of PF4. There were two underlying mechanisms: decreased blood vessel integrity in the premetastatic lungs and increased production of hematopoietic stem/progenitor cells (HSCs) and myeloid derived suppressor cells (MDSCs) in tumor-bearing PF4 KO mice. In cancer patients, PF4 expression levels were negatively correlated with tumor stage and positively correlated with patient survival. Our studies suggest that PF4 is a critical anti-tumor factor in the premetastatic site. Our finding of PF4 function in the tumor host provides new insight to the mechanistic understanding of tumor metastasis.

Therapy-Educated Mesenchymal Stem Cells Enrich for Tumor-Initiating Cells

Stromal cells residing in the tumor microenvironment contribute to the development of therapy resistance. Here we show that chemotherapy-educated mesenchymal stem cells (MSC) promote therapy resistance via cross-talk with tumor-initiating cells (TIC), a resistant tumor cell subset that initiates tumorigenesis and metastasis. In response to gemcitabine chemotherapy, MSCs colonized pancreatic adenocarcinomas in large numbers and resided in close proximity to TICs. Furthermore, gemcitabine-educated MSCs promoted the enrichment of TICs in vitro and enhance tumor growth in vivo These effects were dependent on the secretion of CXCL10 by gemcitabine-educated MSCs and subsequent activation of the CXCL10-CXCR3 axis in TICs. In an orthotopic pancreatic tumor model, targeting TICs using nanovesicles (called nanoghosts) derived from MSC membranes and loaded with a CXCR3 antagonist enhanced therapy outcome and delayed tumor regrowth when administered in combination with gemcitabine. Overall, our results establish a mechanism through which MSCs promote chemoresistance, and propose a novel drug delivery system to target TICs and overcome this resistance.Significance: These results establish a mechanism by which mesenchyme stem cells in the tumor microenvironment promote chemoresistance, and they propose a novel drug delivery system to overcome this challenge. Cancer Res; 78(5); 1253-65. ©2018 AACR.

Multiple drug resistance-associated protein (MRP4) exports prostaglandin E2 (PGE2) and contributes to metastasis in basal/triple negative breast cancer

Cyclooxygenase-2 (COX-2) and its primary enzymatic product, prostaglandin E2 (PGE2), are associated with a poor prognosis in breast cancer. In order to elucidate the factors contributing to intratumoral PGE₂ levels, we evaluated the expression of COX-2/PGE₂ pathway members MRP4, the prostaglandin transporter PGT, 15-PGDH (PGE₂ metabolism), the prostaglandin E receptor EP4, COX-1, and COX-2 in normal, luminal, and basal breast cancer cell lines. The pattern of protein expression varied by cell line reflecting breast cancer heterogeneity. Overall, basal cell lines expressed higher COX-2, higher MRP4, lower PGT, and lower 15-PGDH than luminal cell lines resulting in higher PGE₂ in the extracellular environment. Genetic or pharmacologic suppression of MRP4 expression or activity in basal cell lines led to less extracellular PGE₂. The key finding is that xenografts derived from a basal breast cancer cell line with stably suppressed MRP4 expression showed a marked decrease in spontaneous metastasis compared to cells with unaltered MRP4 expression. Growth properties of primary tumors were not altered by MRP4 manipulation. In addition to the well-established role of high COX-2 in promoting metastasis, these data identify an additional mechanism to achieve high PGE₂ in the tumor microenvironment; high MRP4, low PGT, and low 15-PGDH. MRP4 should be examined further as a potential therapeutic target in basal breast cancer.

Differential expression profile of CXCR3 splicing variants is associated with thyroid neoplasia. Potential role in papillary thyroid carcinoma oncogenesis?

Papillary thyroid cancer (PTC) is the most prevalent endocrine neoplasia. The increased incidence of PTC in patients with thyroiditis and the frequent immune infiltrate found in PTC suggest that inflammation might be a risk factor for PTC development. The CXCR3-ligand system is involved in thyroid inflammation and CXCR3 has been found upregulated in many tumors, suggesting its pro-tumorigenic role under the inflammatory microenvironment. CXCR3 ligands (CXCL4, CXCL9, CXCL10 and CXCL11) trigger antagonistic responses partly due to the presence of two splice variants, CXCR3A and CXCR3B. Whereas CXCR3A promotes cell proliferation, CXCR3B induces apoptosis. However, the relation between CXCR3 variant expression with chronic inflammation and PTC development remains unknown. Here, we characterized the expression pattern of CXCR3 variants and their ligands in benign tumors and PTC. We found that CXCR3A and CXCL10 mRNA levels were increased in non-metastatic PTC when compared to non-neoplastic tissue. This increment was also observed in a PTC epithelial cell line (TPC-1). Although elevated protein levels of both isoforms were detected in benign and malignant tumors, the CXCR3A expression remained greater than CXCR3B and promoted proliferation in Nthy-ori-3-1 cells. In non-metastatic PTC, inflammation was conditioning for the CXCR3 ligands increased availability. Consistently, CXCL10 was strongly induced by interferon gamma in normal and tumor thyrocytes.

Our results suggest that persistent inflammation upregulates CXCL10 expression favoring tumor development via enhanced CXCR3A-CXCL10 signaling. These findings may help to further understand the contribution of inflammation as a risk factor in PTC development and set the basis for potential therapeutic studies.

Recombinant Parvoviruses Armed to Deliver CXCL4L1 and CXCL10 Are Impaired in Their Antiangiogenic and Antitumoral Effects in a Kaposi Sarcoma Tumor Model Due To the Chemokines' Interference with the Virus Cycle

Application of oncolytic viruses is a valuable option to broaden the armament of anticancer therapies, as these combine specific cytotoxic effects and immune-stimulating properties. The self-replicating H-1 parvovirus (H-1PV) is a prototypical oncolytic virus that, besides targeting tumor cells, also infects endothelial cells, thus combining oncolytic and angiostatic traits. To increase its therapeutic value, H-1PV can be armed with cytokines or chemokines to enhance the immunological response. Some chemokines-more specifically, the CXCR3 ligands CXCL4L1 and CXCL10-combine immune-stimulating properties with angiostatic activity. This study explores the therapeutic value of recombinant parvoviruses carrying CXCL4L1 or CXCL10 transgenes (Chi-H1/CXCL4L1 or Chi-H1/CXCL10, respectively) to inhibit the growth of the human Kaposi sarcoma cell line KS-IMM. KS-IMM cells infected by Chi-H1/CXCL4L1 or Chi-H1/CXCL10 released the corresponding chemokine and showed reduced migratory capacity. Therefore, the antitumoral capacity of Chi-H1/CXCL4L1 or Chi-H1/CXCL10 was tested in mice. Either in vitro infected KS-IMM cells were injected or subcutaneously growing KS-IMM xenografts were treated by peritumoral injections of the different viruses. Surprisingly, the transgenes did not increase the antitumoral effect of natural H-1PV. Further experiments indicated that CXCL4L1 and CXCL10 interfered with the expression of the viral NS1 protein in KS-IMM cells. These results indicate that the outcome of parvovirus-based delivery of CXCR3 ligands might be tumor cell type dependent, and hence its application must be considered carefully.

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.

Context Specific and Differential Gene Co-expression Networks via Bayesian Biclustering

Identifying latent structure in high-dimensional genomic data is essential for exploring biological processes. Here, we consider recovering gene co-expression networks from gene expression data, where each network encodes relationships between genes that are co-regulated by shared biological mechanisms. To do this, we develop a Bayesian statistical model for biclustering to infer subsets of co-regulated genes that covary in all of the samples or in only a subset of the samples. Our biclustering method, BicMix, allows overcomplete representations of the data, computational tractability, and joint modeling of unknown confounders and biological signals. Compared with related biclustering methods, BicMix recovers latent structure with higher precision across diverse simulation scenarios as compared to state-of-the-art biclustering methods. Further, we develop a principled method to recover context specific gene co-expression networks from the estimated sparse biclustering matrices. We apply BicMix to breast cancer gene expression data and to gene expression data from a cardiovascular study cohort, and we recover gene co-expression networks that are differential across ER+ and ER- samples and across male and female samples. We apply BicMix to the Genotype-Tissue Expression (GTEx) pilot data, and we find tissue specific gene networks. We validate these findings by using our tissue specific networks to identify trans-eQTLs specific to one of four primary tissues.

TNF-α augments CXCR2 and CXCR3 to promote progression of renal cell carcinoma

Within the tumour microenvironment, a complex network of chemokines and their receptors affects the initiation and progression of tumours. The higher levels of tumour necrosis factor‐alpha (TNF‐α) are associated with tumour progression and an anti‐TNF‐α monoclonal antibody has been used successfully to treat patients with renal cell carcinoma (RCC). However, the role of chemokines and their receptors in the TNF‐α‐promoted progression of RCC remains unclear. In this study, TNF‐α was found to enhance the migration, invasion and epithelial‐mesenchymal transition (EMT) of RCC cells. To further investigate the molecular mechanism of TNF‐α on the progression of RCC, reverse transcription and quantitative PCR was used to screen chemokines and chemokine receptors that were associated with tumorigenesis. The results showed that TNF‐α significantly increased the expressions of CXCR2 and CXCR3 and their related ligands in RCC cells. Subsequently, we used a lentiviral shRNA system to knockdown the expression of CXCR2 and/or CXCR3 in RCC cells. CXCR2 and CXCR3 silencing inhibited the induction of Slug and ZEB‐1 with TNF‐α treatment of RCC cells. In addition, the knockdown of both CXCR2 and CXCR3 resulted in a greater decrease in cell migration, invasion and clonogenic ability compared with either CXCR2 or CXCR3 knockdown alone. Moreover, CXCR2 and CXCR3 silencing significantly reduced the sphere‐forming ability of RCC cells. High expression levels of CXCR2 and CXCR3 in cancer tissues correlated with tumour progression of renal cell carcinoma. These findings suggest that TNF‐α augments CXCR2 and CXCR3 to promote the progression of renal cell carcinoma leading to a poor prognosis.

Radiofrequency ablation-increased CXCL10 is associated with earlier recurrence of hepatocellular carcinoma by promoting stemness

Radiofrequency ablation (RFA) represents a valuable choice in hepatocellular carcinoma (HCC); however, local recurrence of HCC is common after RFA. Here, 20 primary HCC patients treated by RFA were enrolled. Before (termed 0d) and after RFA treatment for 1 and 7 days (termed 1d and 7d, respectively), plasma and noncancerous tissue were collected. ELISA assay showed that plasma C-X-C motif chemokine 10 (CXCL10) was increased in ten patients (type I patients) but decreased in the other 10 patients (type II patients). The mean interval for HCC recurrence in type I patients was less than the mean interval in type II patients. Interestingly, a significant negative correlation between interval for HCC recurrence and fold change of plasma CXCL10 (1d/0d or 7d/0d) was identified, suggesting that RFA-induced CXCL10 is associated with earlier HCC recurrence. Immunofluorescence assay showed that the receptor of CXCL10, chemokine (C-X-C motif) receptor 3 (CXCR3), was significantly increased in type I, but not type II, patients after RFA. In vitro assay demonstrated that CXCL10 stimulus increased the rate of CD133(+) cancer stem cells (CSCs) in HepG2 cells by binding to CXCR3 and then inducing c-Myc expression. Many studies have reported that induction of CD133(+) CSCs contributes to HCC recurrence. Thus, CXCL10-increased CD133(+) CSCs by activating CXCR3/c-Myc pathway might accelerate HCC recurrence after RFA. These data might have potential implications for HCC therapy.