Stromal derived factor-1 (SDF-1/CXCL12) and CXCR4 in renal cell carcinoma metastasis

The Role of Ion Channels and Chemokines in Cancer Growth and Metastasis: A Proposed Mode of Action Using Peptides in Cancer Therapy

Metastasis (Met) largely contributes to the major cause of cancer deaths throughout the world, rather than the growth of the tumor mass itself. The present report brings together several of the pertinent contributors to cancer growth and metastatic processes from an activity standpoint. Such biological activities include the following: (1) cell adherence and detachment; (2) cell-to-cell contact; (3) contact inhibition; (4) the cell interfacing with the extracellular matrix (ECM); (5) tumor cell-to-stroma communication networks; (6) chemotaxis; and (7) cell membrane potential. Moreover, additional biochemical factors that contribute to cancer growth and metastasis have been shown to comprise the following: (a) calcium levels in the extracellular matrix and in intracellular compartments; (b) cation voltage and ATP-regulated potassium channels; (c) selective and non-selective cation channels; and (d) chemokines (cytokines) and their receptors, such as CXCL12 (SDF-1) and its receptor/binding partner, CXCR4. These latter molecular components represent a promising group of an interacting and synchronized set of candidates ideal for peptide therapeutic targeting for cancer growth and metastasis. Such peptides can be obtained from naturally occurring proteins such as alpha-fetoprotein (AFP), an onco-fetal protein and clinical biomarker.

DNA Damage-driven Inflammatory Cytokines: Reprogramming of Tumor Immune Microenvironment and Application of Oncotherapy

DNA damage occurs across tumorigenesis and tumor development. Tumor intrinsic DNA damage can not only increase the risk of mutations responsible for tumor generation but also initiate a cellular stress response to orchestrate the tumor immune microenvironment (TIME) and dominate tumor progression. Accumulating evidence documents that multiple signaling pathways, including cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) and ataxia telangiectasia-mutated protein/ataxia telangiectasia and Rad3-related protein (ATM/ATR), are activated downstream of DNA damage and they are associated with the secretion of diverse cytokines. These cytokines possess multifaced functions in the anti-tumor immune response. Thus, it is necessary to deeply interpret the complex TIME reshaped by damaged DNA and tumor-derived cytokines, critical for the development of effective tumor therapies. This manuscript comprehensively reviews the relationship between the DNA damage response and related cytokines in tumors and depicts the dual immunoregulatory roles of these cytokines. We also summarize clinical trials targeting signaling pathways and cytokines associated with DNA damage and provide future perspectives on emerging technologies.

The intricate role of annexin A2 in kidney: a comprehensive review

Annexin A2 (Anxa2) is a calcium (Ca2+)-regulated phospholipid binding protein composed of a variable N-terminus and a conserved core domain. This protein has been widely found in many tissues and fluids, including tubule cells, glomerular epithelial cells, renal vessels, and urine. In acute kidney injury, the expression level of this protein is markedly elevated in response to acute stress. Moreover, Anxa2 is a novel biomarker and potential therapeutic target with prognostic value in chronic kidney disease. In addition, Anxa2 is associated not only with clear-cell renal cell carcinoma differentiation but also the formation of calcium-related nephrolithiasis. In this review, we discuss the characteristics and functions of Anxa2 and focus on recent reports on the role of Anxa2 in the kidney, which may be useful for future research.

New Strategy for Promoting Vascularization in Tumor Spheroids in a Microfluidic Assay

Previous studies have developed vascularized tumor spheroid models to demonstrate the impact of intravascular flow on tumor progression and treatment. However, these models have not been widely adopted so the vascularization of tumor spheroids in vitro is generally lower than vascularized tumor tissues in vivo. To improve the tumor vascularization level, a new strategy is introduced to form tumor spheroids by adding fibroblasts (FBs) sequentially to a pre-formed tumor spheroid and demonstrate this method with tumor cell lines from kidney, lung, and ovary cancer. Tumor spheroids made with the new strategy have higher FB densities on the periphery of the tumor spheroid, which tend to enhance vascularization. The vessels close to the tumor spheroid made with this new strategy are more perfusable than the ones made with other methods. Finally, chimeric antigen receptor (CAR) T cells are perfused under continuous flow into vascularized tumor spheroids to demonstrate immunotherapy evaluation using vascularized tumor-on-a-chip model. This new strategy for establishing tumor spheroids leads to increased vascularization in vitro, allowing for the examination of immune, endothelial, stromal, and tumor cell responses under static or flow conditions.

New insights into fibrotic signaling in renal cell carcinoma

Fibrotic signaling plays a pivotal role in the development and progression of solid cancers including renal cell carcinoma (RCC). Intratumoral fibrosis (ITF) and pseudo-capsule (PC) fibrosis are significantly correlated to the disease progression of renal cell carcinoma. Targeting classic fibrotic signaling processes such as TGF-β signaling and epithelial-to-mesenchymal transition (EMT) shows promising antitumor effects both preclinically and clinically. Therefore, a better understanding of the pathogenic mechanisms of fibrotic signaling in renal cell carcinoma at molecular resolution can facilitate the development of precision therapies against solid cancers. In this review, we systematically summarized the latest updates on fibrotic signaling, from clinical correlation and molecular mechanisms to its therapeutic strategies for renal cell carcinoma. Importantly, we examined the reported fibrotic signaling on the human renal cell carcinoma dataset at the transcriptome level with single-cell resolution to assess its translational potential in the clinic.

Current Status of 68Ga-Pentixafor in Solid Tumours

Chemokine receptor CXCR4 is overexpressed in neoplasms and its expression is related to tumour invasion, metastasis and aggressiveness. ⁶⁸Ga-Pentixafor is used to non-invasively image the expression of CXCR4 in tumours and has been widely used in haematological malignancies. Recent evidence shows that therapies targeting CXCR4 can increase the chemosensitivity of the tumour as well as inhibit tumour metastasis and aggressiveness. ⁶⁸Ga-Pentixafor has shown promise as an elegant radiotracer to aid in the selection of patients whose tumours demonstrate CXCR4 overexpression and who therefore may benefit from novel therapies targeting CXCR4. In addition, its therapeutic partners ¹⁷⁷Lu- and ⁹⁰Y-Pentixather have been investigated in the treatment of patients with advanced haematological malignancies, and initial studies have shown a good treatment response in metabolically active lesions. ⁶⁸Ga-Pentixafor in solid tumours complements ¹⁸F-FDG by providing prognostic information and selecting patients who may benefit from therapies targeting CXCR4. This review summarises the available literature on the potential applications of ⁶⁸Ga-Pentixafor in solid tumours.

Evolving cancer-niche interactions and therapeutic targets during bone metastasis

Many cancer types metastasize to bone. This propensity may be a product of genetic traits of the primary tumour in some cancers. Upon arrival, cancer cells establish interactions with various bone-resident cells during the process of colonization. These interactions, to a large degree, dictate cancer cell fates at multiple steps of the metastatic cascade, from single cells to overt metastases. The bone microenvironment may even influence cancer cells to subsequently spread to multiple other organs. Therefore, it is imperative to spatiotemporally delineate the evolving cancer-bone crosstalk during bone colonization. In this Review, we provide a summary of the bone microenvironment and its impact on bone metastasis. On the basis of the microscopic anatomy, we tentatively define a roadmap of the journey of cancer cells through bone relative to various microenvironment components, including the potential of bone to function as a launch pad for secondary metastasis. Finally, we examine common and distinct features of bone metastasis from various cancer types. Our goal is to stimulate future studies leading to the development of a broader scope of potent therapies.

Exploring the synergistic effects of cabozantinib and a programmed cell death protein 1 inhibitor in metastatic renal cell carcinoma with machine learning

Clinical evidence supports the combination of cabozantinib with an immune checkpoint inhibitor for the treatment of metastatic clear cell renal cell carcinoma (mccRCC) and suggests a synergistic antitumour activity of this combination. Nevertheless, the biological basis of this synergy is not fully characterized. We studied the mechanisms underpinning the potential synergism of cabozantinib combined with a PD1 inhibitor in mccRCC and delved into cabozantinib monotherapy properties supporting its role to partner these combinations. To model physiological drug action, we used a machine learning-based technology known as Therapeutic Performance Mapping Systems, applying two approaches: Artificial Neural Networks and Sampling Methods. We found that the combined therapy was predicted to exert a wide therapeutic action in the tumour and the microenvironment. Cabozantinib may enhance the effects of PD1 inhibitors on immunosurveillance by modulating the innate and adaptive immune system, through the inhibition of VEGF-VEGFR and Gas6-AXL/TYRO3/MER (TAM) axes, while the PD1 inhibitors may boost the antiangiogenic and pro-apoptotic effects of cabozantinib by modulating angiogenesis and T-cell cytotoxicity. Cabozantinib alone was predicted to restore cellular adhesion and hamper tumour proliferation and invasion. These data provide a biological rationale and further support for cabozantinib plus PD1 inhibitor combination and may guide future nonclinical and clinical research.

Molecular Mechanisms of Resistance to Immunotherapy and Antiangiogenic Treatments in Clear Cell Renal Cell Carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most common histological subtype arising from renal cell carcinomas. This tumor is characterized by a predominant angiogenic and immunogenic microenvironment that interplay with stromal, immune cells, and tumoral cells. Despite the obscure prognosis traditionally related to this entity, strategies including angiogenesis inhibition with tyrosine kinase inhibitors (TKIs), as well as the enhancement of the immune system with the inhibition of immune checkpoint proteins, such as PD-1/PDL-1 and CTLA-4, have revolutionized the treatment landscape. This approach has achieved a substantial improvement in life expectancy and quality of life from patients with advanced ccRCC. Unfortunately, not all patients benefit from this success as most patients will finally progress to these therapies and, even worse, approximately 5 to 30% of patients will primarily progress. In the last few years, preclinical and clinical research have been conducted to decode the biological basis underlying the resistance mechanisms regarding angiogenic and immune-based therapy. In this review, we summarize the insights of these molecular alterations to understand the resistance pathways related to the treatment with TKI and immune checkpoint inhibitors (ICIs). Moreover, we include additional information on novel approaches that are currently under research to overcome these resistance alterations in preclinical studies and early phase clinical trials.

Systemic Fibrocyte Levels and Keloid Expression of the Chemoattractant CXCL12 Are Upregulated Compared With Patients With Normal Scar

BACKGROUND

Fibrocytes are bone marrow mesenchymal precursors with a surface phenotype compatible with leukocytes, fibroblasts, and hematopoietic progenitors that have been shown to traffic to wound healing sites in response to described chemokine pathways. Keloids are focal fibrotic responses to cutaneous trauma characterized by disordered collagen, which may be associated with elevated systemic fibrocyte levels and/or wound bed chemokine expression.

METHODS

Blood specimens from patients with longstanding keloids and those who form grossly normal scars were assayed by fluorescence activated cell sorting analysis for fibrocytes (CD45+, Col I+). The expression of the fibrocyte chemotactic cell surface marker CXCR4, intracellular markers of fibroblast differentiation (pSMAD2/3), and plasma levels of the CXCR4 cognate CXCL12 were compared. Keloid specimens and grossly normal scars were excised, and local expression of CXCL12 was assayed.

RESULTS

Keloid-forming patients demonstrated a significantly greater number of circulating fibrocytes (17.4 × 105 cells/mL) than control patients (1.01 × 105 cells/mL, P = 0.004). The absolute number of fibrocytes expressing CXCR4 was significantly greater (P = 0.012) in keloid-forming patients. Systemic CXCL12 levels were insignificantly greater in keloid-forming patients than controls. Keloid specimens had significantly greater CXCL12 expression (529.3 pg/mL) than normal scar (undetectable).

CONCLUSIONS

Systemic fibrocyte levels and the CXCR4/CXCL12 biologic axis responsible for fibrocyte trafficking to areas of regional fibrosis were both upregulated in patients who form keloids compared with controls. Keloids persistently expressed CXLC12, which serves both as the main chemoattractant for fibrocytes and a downstream mediator for local inflammation, suggesting a role for this biologic axis in keloid formation and possibly recurrence.

Clinical and prognostic relevance of CXCL12 expression in acute myeloid leukemia

Background

Accumulating studies have been made to understand the association between CXC chemokine ligand-12 (CXCL12)/CXC chemokine receptor 4 (CXCR4) and acute myeloid leukemia (AML). However, large-scale data analysis of potential relationship between CXCL12 and AML remains insufficient.

Methods

We collected abundant CXCL12 expression data and AML samples from several publicly available datasets. The CIBERSORT algorithm was used to quantify immune cell fractions and the online website of STRING was utilized for gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The statistical analysis and graphical work were mainly performed via the R software.

Results

CXCL12 expression was extremely down-regulated in AML. Clinically, low CXCL12 expression was correlated with higher white blood cells (WBCs) (P < 0.0001), more blasts in bone marrow (BM) (P < 0.001) and peripheral blood (PB) (P < 0.0001), FLT3-internal tandem duplications (FLT3-ITD) (P = 0.010) and NPM1 mutations (P = 0.015). More importantly, reduced CXCL12 expression predicted worse overall survival (OS) and event-free survival (EFS) in all AML, non-M3-AML, and cytogenetically normal (CN)-AML patients in three independent cohorts. As for immune cell infiltration, high CXCL12 expressed groups tended to harbor more memory B cells and plasma cells infiltration while low CXCL12 expressed groups exhibited more eosinophils infiltration. GO enrichment and KEGG pathways analysis revealed the potential biological progress the gene participating in.

Conclusions

CXCL12 is significantly down-regulated in AML and low CXCL12 expression is an independent and poor predictor of AML prognosis. CXCL12 expression level correlates with clinical and immune characteristics of AML, which could provide potential assistance for treatment. Prospective studies are needed to further validate the impact of CXCL12 expression before routine clinical application in AML.

Expression and prognostic value of CXCL12/CXCR4/CXCR7 axis in clear cell renal cell carcinoma

BACKGROUND

CXCL12 or stromal-derived factor-1 is a chemokine that binds to two receptors CXCR4 and CXCR7 and takes part in both physiological and pathological cell functions. The disruption of the CXCL12/CXCR4/CXCR7 chemokine axis is seen in various types of cancers.

METHODS

We have immunohistochemically analyzed the expression of CXCL12 and its receptors in clear cell renal cell carcinoma patients. The study included 85 tissue samples. Since samples exhibited heterogeneity of expression intensity and staining localization (cytoplasmatic and membranous), histoscores were calculated, and their associations with clinicopathological parameters were analyzed.

RESULTS

Both cytoplasmatic CXCR7 and CXCL12 histoscores were associated with greater tumour size, while CXCL12 staining was associated with a higher grade as well. Mortality was associated with tumour size and both membranous and cytoplasmatic CXCL12 histoscores. With each centimetre in tumour size, survival decreases 1.3 times, while CXCL12C histoscore higher than 73 was associated with 2.3 greater risk of mortality. CXCR4 histoscore could only be predicted by female gender and neither cytoplasmatic nor membranous CXCR4 expression was found to be a mortality predictor.

CONCLUSION

Our data suggest that regarding overall survival, CXCL12 could be considered a valuable prognostic marker.

At the Bench: Pre-clinical evidence for multiple functions of CXCR4 in cancer

Signaling through chemokine receptor, C-X-C chemokine receptor type 4 (CXCR4) regulates essential processes in normal physiology, including embryogenesis, tissue repair, angiogenesis, and trafficking of immune cells. Tumors co-opt many of these fundamental processes to directly stimulate proliferation, invasion, and metastasis of cancer cells. CXCR4 signaling contributes to critical functions of stromal cells in cancer, including angiogenesis and multiple cell types in the tumor immune environment. Studies in animal models of several different types of cancers consistently demonstrate essential functions of CXCR4 in tumor initiation, local invasion, and metastasis to lymph nodes and distant organs. Data from animal models support clinical observations showing that integrated effects of CXCR4 on cancer and stromal cells correlate with metastasis and overall poor prognosis in >20 different human malignancies. Small molecules, Abs, and peptidic agents have shown anticancer efficacy in animal models, sparking ongoing efforts at clinical translation for cancer therapy. Investigators also are developing companion CXCR4-targeted imaging agents with potential to stratify patients for CXCR4-targeted therapy and monitor treatment efficacy. Here, pre-clinical studies demonstrating functions of CXCR4 in cancer are reviewed.

The Role of CXCL12 in Kidney Diseases: A Friend or Foe?

Background

Chemokines are a family of proteins mainly mediating the homing and migration of various cells. The CXC chemokine CXCL12 is a member of low-weight-molecular chemokines. In the kidney, CXCL12 is pivotal for renal development and exerts a modulatory effect in kidney diseases under different etiologic settings by binding with CXC chemokine receptor 4 (CXCR4) or CXC chemokine receptor 7 (CXCR7). Besides, CXCL12 also exerts homeostasis influence in diverse physical conditions and various pathological situations. Thus, we conclude the complicated relationship between CXCL12 and kidney diseases in this review.

Summary

In renal development, CXCL12 contributes a lot to nephrogenesis and the formation of renal vasculature via correlating with CXCR4. CXCL12 also plays an essential role in renal recovery from acute kidney injury. However, the CXCL12/CXCR4 axis plays a dual regulatory role in the initiation and development of diabetic kidney disease as well as chronic allogeneic nephropathy after kidney transplantation through dialectical consideration. Additionally, the CXCL12/CXCR4 link is considered as a new risk factor for lupus nephritis and renal cell carcinoma.

Key Messages

Plenty of studies have presented the influence of CXCL12 and the relation with corresponding receptors in diverse biological and pathological statuses. Simultaneously, some drugs and antagonists targeting CXCL12/CXCR4 axis effectively treat various kidney diseases. However, more researches are needed to explore thorough influence and mechanisms, providing more cues for clinical treatments.

Intratumoral Fibrosis in Facilitating Renal Cancer Aggressiveness: Underlying Mechanisms and Promising Targets

Intratumoral fibrosis is a histologic manifestation of fibrotic tumor stroma. The interaction between cancer cells and fibrotic stroma is intricate and reciprocal, involving dysregulations from multiple biological processes. Different components of tumor stroma are implicated via distinct manners. In the kidney, intratumoral fibrosis is frequently observed in renal cell carcinoma (RCC). However, the underlying mechanisms remain largely unclear. In this review, we recapitulate evidence demonstrating how fibrotic stroma interacts with cancer cells and mechanisms shared between RCC tumorigenesis and renal fibrogenesis, providing promising targets for future studies.

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.

HIF-1α Metabolic Pathways in Human Cancer

Oxygen is directly involved in many key pathophysiological processes. Oxygen deficiency, also known as hypoxia, could have adverse effects on mammalian cells, with ischemia in vital tissues being the most significant (Michiels C. Physiological and pathological responses to hypoxia. Am J Pathol 164(6): 1875-1882, 2004); therefore, timely adaptive responses to variations in oxygen availability are essential for cellular homeostasis and survival. The most critical molecular event in hypoxic response is the activation and stabilization of a transcriptional factor termed hypoxia-induced factor-1 (HIF-1) that is responsible for the upregulation of many downstream effector genes, collectively known as hypoxia-responsive genes. Multiple key biological pathways such as proliferation, energy metabolism, invasion, and metastasis are governed by these genes; thus, HIF-1-mediated pathways are equally pivotal in both physiology and pathology.As we gain knowledge on the molecular mechanisms underlying the regulation of HIF-1, a great focus has been placed on elucidating the cellular function of HIF-1, particularly the role of HIF-1 in cancer pathogenesis pathways such as proliferation, invasion, angiogenesis, and metastasis. In cancer, HIF-1 is directly involved in the shift of cancer tissues from oxidative phosphorylation to aerobic glycolysis, a phenomenon known as the Warburg effect. Although targeting HIF-1 as a cancer therapy seems like an extremely rational approach, owing to the complex network of its downstream effector genes, the development of specific HIF-1 inhibitors with fewer side effects and more specificity has not been achieved. Therefore, in this review, we provide a brief background about the function of HIF proteins in hypoxia response with a special emphasis on the unique role played by HIF-1α in cancer growth and invasiveness, in the hypoxia response context.

The Role of the CXCL12/CXCR4/CXCR7 Chemokine Axis in Cancer

Chemokines are a family of small, secreted cytokines which regulate a variety of cell functions. The C-X-C motif chemokine ligand 12 (CXCL12) binds to C-X-C chemokine receptor type 4 (CXCR4) and C-X-C chemokine receptor type 7 (CXCR7). The interaction of CXCL12 and its receptors subsequently induces downstream signaling pathways with broad effects on chemotaxis, cell proliferation, migration, and gene expression. Accumulating evidence suggests that the CXCL12/CXCR4/CXCR7 axis plays a pivotal role in tumor development, survival, angiogenesis, metastasis, and tumor microenvironment. In addition, this chemokine axis promotes chemoresistance in cancer therapy via complex crosstalk with other pathways. Multiple small molecules targeting CXCR4/CXCR7 have been developed and used for preclinical and clinical cancer treatment. In this review, we describe the roles of the CXCL12/CXCR4/CXCR7 axis in cancer progression and summarize strategies to develop novel targeted cancer therapies.

CXCL12/CXCR4 axis in the microenvironment of solid tumors: A critical mediator of metastasis

Tumors are dynamic tissue masses, so requiring continuous exposure to the host cells, nurturing them into pave a path for tumor growth and metastasis. C-X-C chemokine ligand 12 (CXCL12)/C-X-C chemokine receptor type 4 (CXCR4) is the key signaling for such aim. Gathering knowledge about the activity within this axis would deepen our insight into the utmost importance this signaling taken to attract and cross-connect multiple cells within the tumor microenvironment (TME) aiming for tumor progression and metastasis. The concept behind this review is to underscore the multi-tasking roles taken by CXCL12/CXCR4 signaling in tumor metastasis, and to also suggest some strategies to target the activities within this axis.

Interaction between CXCR4 and EGFR and downstream PI3K/AKT pathway in lung adenocarcinoma A549 cells and transplanted tumor in nude mice

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related mortality all over the world, particularly in China. Metastasis is the main factor resulting in the poor prognosis of patients with NSCLC. CXCR4 and EGFR have been widely studied due to their critical role in tumor metastasis, but it remains more elusive then the relationship between CXCR4 and EGFR. Studies have demonstrated that many tumors have been found the existence of the "cross-talk" between EGFR and CXCR4 signaling pathways. In this context, we explored the relationship between EGFR and CXCR4 signaling pathways in lung cancer invasion and metastasis by both in vitro and in vivo experiments.

Effect of CXCL12 and Its Receptors on Unpredictable Renal Cell Carcinoma

Chemokines are chemotactic cytokines that participate in numerous cell functions during hematopoiesis, morphogenesis, inflammation, neovascularization, and autoimmune diseases and cancer. They achieve their functions on binding to their G protein-coupled receptors. CXCL12, or stromal cell-derived factor-1, is a homeostatic chemokine secreted by fibroblasts, macrophages, and endothelial cells. It binds to CXC receptor 4 (CXCR4), also known as fusin (CD184), and alternate CXC receptor 7 (CXCR7), also known as atypical chemokine receptor 3. The CXCL12/CXCR4 axis participates in homing of hematopoietic stem cells and the development and production of B and T lymphocytes, plasmacytoid dendritic cells, and natural killer cells. It has been examined in > 20 different malignancies. CXCL12 plays an important role in tumor metastasis because it mediates the migration of tumor cells through the endothelial vessel wall and extracellular matrix. Its expression has been highest in common metastatic sites such as the brain, bone marrow, lymph nodes, and liver. CXCR4 is expressed by tumor cells in prostate, breast, lung, and other malignancies. Numerous studies have shown its correlation with a poor prognosis, recurrence-free survival, and poor overall survival. The present review has addressed the structure and function of CXCL12 and its receptors and the effect CXCL12/CXCR4 axis has on the pathogenesis and clinical development of renal cell carcinoma, one of the most aggressive cancers in urology, with limited therapeutic options.

The role of cancer-associated fibroblasts in renal cell carcinoma. An example of tumor modulation through tumor/non-tumor cell interactions

Cancer-associated fibroblasts (CAF) are a cellular compartment of the tumor microenvironment (TME) with critical roles in tumor development. Fibroblast activation protein-α (FAP) is one of the proteins expressed by CAF and its immunohistochemical detection in routine practice is associated with tumor aggressiveness and shorter patient survival. For these reasons, FAP seems a good prognostic marker in many malignant neoplasms, including renal cell carcinoma (RCC). The start point of this Perspective paper is to review the role of CAF in the modulation of renal cell carcinoma evolution. In this sense, CAF have demonstrated to develop important protumor and/or antitumor activities. This apparent paradox suggests that some type of temporally or spatially-related specialization is present in this cellular compartment during tumor evolution. The end point is to remark that tumor/non-tumor cell interactions, in particular the symbiotic tumor/CAF connections, are permanent and ever-changing crucial phenomena along tumor lifetime. Interestingly, these interactions may be responsible of many therapeutic failures.

Clinicopathological and prognostic significance of CXCR4 high expression in renal cell carcinoma: A meta-analysis and literature review

INTRODUCTION

Previous results have indicated that CXCR4 is an oncogene in several types of human tumors including renal cell carcinoma (RCC). However, the correlation between CXCR4 expression and clinicopathological characteristics of RCC remains unclear.

MATERIALS AND METHODS

We conducted a meta-analysis to quantitatively evaluate the association of CXCR4 expression with the incidence of RCC and clinicopathological characteristics. Final analysis of 1203 patients with RCC from 14 eligible studies was performed.

RESULTS

We observed that CXCR4 expression is significantly higher in RCC than in normal renal tissue, and the pooled OR from 7 studies including 435 RCC and 297 normal renal tissues was OR = 46.23, 95% CI = 7.18-297.69, p < 0.0001. CXCR4 expression is not associated with gender status and clinical stages. However, CXCR4 expression was significantly associated with pathological grades, metastatic status, and overall survival in patients with RCC.

DISCUSSION

These results indicate that CXCR4 expression is associated with increased risk, progression, and prognosis for patients with RCC. The determination of CXCR4 expression may provide a biomarker for tumor risk evaluation, progression, and prognosis of patients with RCC.

The role of CXCR4 in multiple myeloma: Cells' journey from bone marrow to beyond

CXCR4 is a pleiotropic chemokine receptor which acts through its ligand CXCL12 to regulate diverse physiological processes. CXCR4/CXCL12 axis plays a pivotal role in proliferation, invasion, dissemination and drug resistance in multiple myeloma (MM). Apart from its role in homing, CXCR4 also affects MM cell mobilization and egression out of the bone marrow (BM) which is correlated with distant organ metastasis. Aberrant CXCR4 expression pattern is associated with osteoclastogenesis and tumor growth in MM through its cross talk with various important cell signalling pathways. A deeper insight into understanding of CXCR4 mediated signalling pathways and its role in MM is essential to identify potential therapeutic interventions. The current therapeutic focus is on disrupting the interaction of MM cells with its protective tumor microenvironment where CXCR4 axis plays an essential role. There are still multiple challenges that need to be overcome to target CXCR4 axis more efficiently and to identify novel combination therapies with existing strategies. This review highlights the role of CXCR4 along with its significant interacting partners as a mediator of MM pathogenesis and summarizes the targeted therapies carried out so far.

A feed-forward loop between nuclear translocation of CXCR4 and HIF-1α promotes renal cell carcinoma metastasis

CXC chemokine receptor 4 (CXCR4) has been suggested to play a critical role in cancer metastasis. Some studies have described CXCR4 nuclear localization in metastatic lesions of renal cell carcinoma (RCC), which has been suggested to be correlated with cancer metastasis. However, the underlying mechanism and clinical significance of CXCR4 nuclear localization remains unknown. Here, we show that CXCR4 nuclear localization is more likely to occur in RCC tissues, especially in metastases, and is associated with poor prognosis. CXCR4 nuclear localization requires its nuclear localization sequence (NLS, residues 146-RPRK-149). After the mutation of NLS in CXCR4, CXCR4 nuclear localization in RCC cells is lost. Nuclear localization of CXCR4 promoted RCC tumorigenicity both in vitro and in vivo. Mechanistically, we found that CXCR4 and hypoxia-inducible factor-1α (HIF-1α) colocalized in RCC cells and interacted with each other. Moreover, CXCR4 nuclear localization promoted nuclear accumulation of HIF-1α, thereby promoting the expression of genes downstream of HIF-1α. Reciprocally, nuclear HIF-1α promoted CXCR4 transcription, thus forming a feed-forward loop. Subcellular CXCR4 and HIF-1α expression levels were independent adverse prognostic factors and could be combined with TNM stage to generate a predictive nomogram of the clinical outcome of patients with RCC. Therefore, our findings indicate that CXCR4 nuclear translocation plays a critical role in RCC metastasis and may serve as a prognostic biomarker and potential therapeutic target.

Exploring Optic Nerve Axon Regeneration

Background:

Traumatic optic nerve injury is a leading cause of irreversible blindness across the world and causes progressive visual impairment attributed to the dysfunction and death of retinal ganglion cells (RGCs). To date, neither pharmacological nor surgical interventions are sufficient to halt or reverse the progress of visual loss. Axon regeneration is critical for functional recovery of vision following optic nerve injury. After optic nerve injury, RGC axons usually fail to regrow and die, leading to the death of the RGCs and subsequently inducing the functional loss of vision. However, the detailed molecular mechanisms underlying axon regeneration after optic nerve injury remain poorly understood.

Methods:

Research content related to the detailed molecular mechanisms underlying axon regeneration after optic nerve injury have been reviewed.

Results:

The present review provides an overview of regarding potential strategies for axonal regeneration of RGCs and optic nerve repair, focusing on the role of cytokines and their downstream signaling pathways involved in intrinsic growth program and the inhibitory environment together with axon guidance cues for correct axon guidance. A more complete understanding of the factors limiting axonal regeneration will provide a rational basis, which contributes to develop improved treatments for optic nerve regeneration. These findings are encouraging and open the possibility that clinically meaningful regeneration may become achievable in the future.

Conclusion:

Combination of treatments towards overcoming growth-inhibitory molecules and enhancing intrinsic growth capacity combined with correct guidance using axon guidance cues is crucial for developing promising therapies to promote axon regeneration and functional recovery after ON injury.

Cancer stem cell markers predict a poor prognosis in renal cell carcinoma: a meta-analysis

Background

Relevant markers of CSCs may serve as prognostic biomarkers of RCC. However, their actual prognostic significance remains inconclusive. Thus, a meta-analysis was performed to reevaluate the association of CSCs-relevant markers (CXCR4, CD133, CD44, CD105) expression with RCC prognosis more precisely.

Methods

PubMed and Embase were searched to look for eligible studies. The pooled hazard ratios (HR) with 95% confidence intervals (95% CI) were used to reassess the association of CSCs markers expression and RCC prognosis of overall survival (OS), cancer-specific survival (CSS), disease-free survival (DFS), and progression-free survival (PFS).

Results

There were 25 relevant articles, encompassing 2673 RCC patients, eligible for meta-analysis. Overall pooled analysis suggested that high CSCs markers expression predicted poor OS (HR, 2.10, 95% CI: 1.73–2.55) and DFS (HR, 3.77, 95% CI: 2.30–6.19). High CXCR4 expression predicted worse OS (HR, 2.57, 95% CI: 1.95–3.40), CSS (HR,1.97, 95% CI: 1.50–2.59), and DFS (HR, 5.82, 95% CI: 3.01–11.25). CD44 over-expression correlated with a poor OS(HR,1.58, 95% CI: 1.14–2.18), CSS (HR, 2.58, 95% CI: 1.27–5.23), and DFS (HR, 4.49, 95% CI: 2.12–9.53) in RCC patients. CD133 was an independent favorable prognostic factor for CSS (HR, 0.4, 95% CI: 0.29–0.54).

Conclusions

The presence of CSCs markers correlates with poor RCC outcome. CSCs may be potentially utilized as prognostic markers to stratify RCC patients, probably representing also a novel potential therapeutic target.

Biological/pathological functions of the CXCL12/CXCR4/CXCR7 axes in the pathogenesis of bladder cancer

CXC chemokine ligand 12 (CXCL12) is an important member of the CXC subfamily of chemokines, and has been extensively studied in various human body organs and systems, both in physiological and clinical states. Ligation of CXCL12 to CXCR4 and CXCR7 as its receptors on peripheral immune cells gives rise to pleiotropic activities. CXCL12 itself is a highly effective chemoattractant which conservatively attracts lymphocytes and monocytes, whereas there exists no evidence to show attraction for neutrophils. CXCL12 regulates inflammation, neo-vascularization, metastasis, and tumor growth, phenomena which are all pivotally involved in cancer development and further metastasis. Generation and secretion of CXCL12 by stromal cells facilitate attraction of cancer cells, acting through its cognate receptor, CXCR4, which is expressed by both hematopoietic and non-hematopoietic tumor cells. CXCR4 stimulates tumor progression by different mechanisms and is required for metastatic spread to organs where CXCL12 is expressed, thereby allowing tumor cells to access cellular niches, such as the marrow, which favor tumor cell survival and proliferation. It has also been demonstrated that CXCL12 binds to another seven-transmembrane G-protein receptor or G-protein-coupled receptor, namely CXCR7. These studies indicated critical roles for CXCR4 and CXCR7 mediation of tumor metastasis in several types of cancers, suggesting their contributions as biomarkers of tumor behavior as well as potential therapeutic targets. Furthermore, CXCL12 itself has the capability to stimulate survival and growth of neoplastic cells in a paracrine fashion. CXCL12 is a supportive chemokine for tumor neovascularization via attracting endothelial cells to the tumor microenvironment. It has been suggested that elevated protein and mRNA levels of CXCL12/CXCR4/CXCR7 are associated with human bladder cancer (BC). Taken together, mounting evidence suggests a role for CXCR4, CXCR7, and their ligand CXCL12 during the genesis of BC and its further development. However, a better understanding is still required before exploring CXCL12/CXCR4/CXCR7 targeting in the clinic.

Difference in CXCR4 expression between sporadic and VHL-related hemangioblastoma

Central nervous system hemangioblastomas occur sporadically and in patients with von Hippel–Lindau (VHL) disease due to a VHL germline mutation. This mutation leads to enhanced transcription of chemokine receptor 4 (CXCR4), its ligand (CXCL12) and vascular endothelial growth factor A (VEGFA). We aimed to determine in VHL-related and sporadic hemangioblastomas CXCR4, CXCL12, and VEGFA protein expression and to correlate this to hemangioblastoma size and expression in normal surrounding tissue. 27 patients with a hemangioblastoma were included for analysis of immunohistochemistry of tissue, MRI and DNA. Hemangioblastomas overexpress CXCR4, CXCL12, and VEGFA compared to normal surrounding tissue. In sporadic hemangioblastomas the mean percentage of CXCR4 positive hemangioblastoma cells was 16 %, SD 8.4, in VHL-related hemangioblastomas 8 %, SD 4.4 (P = 0.002). There was no relation between preoperative tumor size and CXCR4 or CXCL12 expression. Compared to normal surrounding tissue CXCR4, CXCL12, and VEGFA were overexpressed in hemangioblastomas. Most interestingly, sporadic hemangioblastomas overexpress CXCR4 compared to VHL-related hemangioblastoma.

PBRM1 regulates proliferation and the cell cycle in renal cell carcinoma through a chemokine/chemokine receptor interaction pathway

PBRM1 is a novel tumor suppressor gene that can inhibit cancer cell proliferation and predict the outcome of renal cell carcinoma (RCC), but its biological role needs further elucidation. We examined expression of the PBRM1 gene in RCC cell lines and the effect of PBRM1 on cell proliferation and cell cycle in RCC ACHN cells. Microarray processing and analysis was used to explore novel pathways involved in tumorigenesis related to PBRM1 knockdown. PBRM1 was expressed at high levels in RCC ACHN cells and lentivirus-mediated PBRM1 knockdown in these cells caused an increase in the proportion of cells in S phase of the cell cycle and promoted in vitro proliferation and migration. In vivo experiments showed that downregulation of PBRM1 promoted tumorigenesis in nude mice. In pathway gene chip analysis, the chemokine/chemokine receptor interaction pathway showed the greatest difference in gene expression upon PBRM1 knockdown. Protein levels of IL6ST and CCL2 were increased, whereas levels of interleukin (IL)-8, IL-6, and CXCL2 were decreased, in knockdown cells. Re-expression of IL-8 in PBRM1 knockdown ACHN cells could significantly decrease cell proliferation/migration and induced cell arrest in the G2/M phase. These findings indicate that PBRM1 alters cell cycle progression and inhibits proliferation and migration of ACHN cells through the chemokine/chemokine receptor pathway.

Notch signaling plays a crucial role in cancer stem-like cells maintaining stemness and mediating chemotaxis in renal cell carcinoma

Background

Cancer stem cells (CSCs) are correlated with the initiation, chemoresistance and relapse of tumors. Notch pathway has been reported to function in CSCs maintenance, but whether it is involved in renal cell carcinoma (RCC) CSCs maintaining stemness remain unclear. This study aims to explore the effect of Notch pathway on stemness of CSCs in RCC and the underlying mechanisms.

Methods

The CD133⁺/CD24⁺ cells were isolated from RCC ACHN and Caki-1 cell line using Magnetic-activated cell sorting and identified by Flow cytometry analysis. RT-PCR and immunoblot analyses were used for determining the stemness maker expression. The effect of Notch pathway on function of CSCs was assessed by self-renewal ability, chemosensitivity, invasive and migratory ability tumorigenicity in vivo using soft agar colony formation assay, sphere-forming assay, MTT assay, Transwell assay.

Results

Here, we found that the sorted CD133⁺/CD24⁺cells possessed elevated stemness maker CTR2, BCL-2, MDR1, OCT-4, KLF4, compared with parental cells, as well as enhanced self-renewal ability, stronger resistance to cisplatin and sorafenib, increased invasion and migration, and higher tumorigenesis in vivo, suggesting the CD133⁺/CD24⁺ cells have the stem-like characteristics of CSCs and thus identified as RCC CSCs. Then the enhanced notch1, notch2, Jagged1, Jagged2, DLL1 and DLL4 expression were detected in RCC CSCs and blockage of Notch1 or notch2 using pharmacological inhibitor MRK-003 or its endogenous inhibitor Numb resulted in loss of its stemness features: self-renewal, chemoresistance, invasive and migratory potential, and tumorigenesis in vivo. Moreover, it is confirmed that overexpression of notch1 up-regulated CXCR4 inRCC CSCs and augmented SDF-1-induced chemotaxis in RCC CSCs in vitro, which could be rescued when treatment of CXCR4 inhibitor, suggesting that notch signaling promotes the chemotaxis of RCC CSCs by SDF-1/CXCR4 axis.

Conclusions

Our results provide a new mechanism of RCC CSCs maintaining stemness via notch pathway as well as a potential therapeutic target in human RCC.

Targeting HIF2 in Clear Cell Renal Cell Carcinoma

Inactivation of the von Hippel-Lindau tumor-suppressor protein (pVHL) is the signature "truncal" event in clear cell renal cell carcinoma, which is the most common form of kidney cancer. pVHL is part of a ubiquitin ligase the targets the α subunit of the hypoxia-inducible factor (HIF) transcription factor for destruction when oxygen is available. Preclinical studies strongly suggest that deregulation of HIF, and particularly HIF2, drives pVHL-defective renal carcinogenesis. Although HIF2α was classically considered undruggable, structural and chemical work by Rick Bruick and Kevin Gardner at University of Texas Southwestern laid the foundation for the development of small molecule direct HIF2α antagonists (PT2385 and the related tool compound PT2399) by Peloton Therapeutics that block the dimerization of HIF2α with its partner protein ARNT1. These compounds inhibit clear cell renal cell carcinoma growth in preclinical models, and PT2385 has now entered the clinic. Nonetheless, the availability of such compounds, together with clustered regularly interspaced short palindromic repeat (CRISPR)-based gene editing approaches, has revealed a previously unappreciated heterogeneity among clear cell renal carcinomas and patient-derived xenografts with respect to HIF2 dependence, suggesting that predictive biomarkers will be needed to optimize the use of such agents in the clinic.

Targeting chemokine receptor CXCR4 for treatment of HIV-1 infection, tumor progression, and metastasis

The chemokine receptor CXCR4 is required for the entry of human immunodeficiency virus type 1 (HIV-1) into target cells and for the development and dissemination of various types of cancers, including gastrointestinal, cutaneous, head and neck, pulmonary, gynecological, genitourinary, neurological, and hematological malignancies. The T-cell (T)-tropic HIV-1 strains use CXCR4 as the entry coreceptor; consequently, multiple CXCR4 antagonistic inhibitors have been developed for the treatment of acquired immune deficiency syndrome (AIDS). However, other potential applications of CXCR4 antagonists have become apparent since its discovery in 1996. In fact, increasing evidence demonstrates that epithelial and hematopoietic tumor cells exploit the interaction between CXCR4 and its natural ligand, stromal cellderived factor (SDF)-1α, which normally regulates leukocyte migration. The CXCR4 and/or SDF-1α expression patterns in tumor cells also determine the sites of metastatic spread. In addition, the activation of CXCR4 by SDF-1α promotes invasion and proliferation of tumor cells, enhances tumor-associated neoangiogenesis, and assists in the degradation of the extracellular matrix and basement membrane. As such, the evaluation of CXCR4 and/or SDF-1α expression levels has a significant prognostic value in various types of malignancies. Several therapeutic challenges remain to be overcome before the use of CXCR4 inhibitors can be translated into clinical practice, but promising preclinical data demonstrate that CXCR4 antagonists can mobilize tumor cells from their protective microenvironments, interfere with their metastatic and tumorigenic potentials, and/or make tumor cells more susceptible to chemotherapy.

RNA interference-mediated silencing of speckle-type POZ protein promotes apoptosis of renal cell cancer cells

This study aimed to investigate the effects of silencing the speckle-type POZ protein (SPOP) gene on renal cell cancer (RCC) cells and to explore its possible mechanism. The A498 and ACHN RCC cells were transfected with small interference RNA (siRNA)-SPOP by lipofection methods. The silencing efficiency was monitored by quantitative real-time polymerase chain reaction and Western blot. The effects of SPOP silencing on cell apoptosis, cell viability, colony formation ability, cell migration ability, and chemosensitivity to Sorafenib were assessed by flow cytometry, an MTT assay, a colony formation assay, a trans-well migration assay, and a CCK-8 assay, respectively. Its effects on the expression of several cytokines were determined by a protein microarray. Relevant signaling pathways were also analyzed. Compared with the control group, the cell apoptosis rate was significantly higher; the cell viability, the colony formation, and migration ability were significantly decreased in the siRNA-SPOP group. The protein microarray screening showed that the expression of vascular endothelial growth factor receptor, matrix metallopeptidase-9, vascular cell adhesion molecule-1, and stromal cell-derived factor-1 in the siRNA group was significantly decreased and that the expression of granulocyte-macrophage colony-stimulating factor and E-cadherin was significantly increased (P<0.05). The relevant signaling pathways were the integrin-mediated cell surface interactions pathway and extracellular matrix organization signal pathway. SPOP gene silencing induced cell apoptosis, decreased cell viability, colony formation, and migration ability, and elevated the drug sensitivity in the RCC cells. A possible mechanism is that silencing SPOP induces the differential expression of E-cadherin, vascular endothelial growth factor receptor, matrix metallopeptidase-9, and vascular cell adhesion molecule, which are related to the integrin-mediated cell surface interactions and extracellular matrix organization signaling pathway.

Role of the tumor microenvironment in tumor progression and the clinical applications (Review)

Oncogene activation and tumor-suppressor gene inactivation are considered as the main causes driving the transformation of normal somatic cells into malignant tumor cells. Cancer cells are the driving force of tumor development and progression. Yet, cancer cells are unable to accomplish this alone. The tumor microenvironment is also considered to play an active role rather than simply acting as a by-stander in tumor progression. Through different pathways, tumor cells efficiently recruit stromal cells, which in turn, provide tumor cell growth signals, intermediate metabolites, and provide a suitable environment for tumor progression as well as metastasis. Through reciprocal communication, cancer cells and the microenvironment act in collusion leading to high proliferation and metastatic capability. Understanding the role of the tumor microenvironment in tumor progression provides us with novel approaches through which to target the tumor microenvironment for efficient anticancer treatment. In this review, we summarize the mechanisms involved in the recruitment of stromal cells by tumor cells to the primary tumor site and highlight the role of the tumor microenvironment in the regulation of tumor progression. We further discuss the potential approaches for cancer therapy.

Analysis of the expression of SDF-1 splicing variants in human colorectal cancer and normal mucosa tissues

C-X-C motif chemokine ligand 12 (CXCL12), also termed stromal cell-derived factor-1 (SDF-1) is a small protein 8-14 kDa in length that is expressed as six isoforms, consisting of SDF-1α, SDF-1β, SDF-1γ, SDF-1δ, SDF-1ε and SDF-1θ. All six isoforms are encoded by the single CXCL12 gene on chromosome 10. This gene regulates leukocyte trafficking and is variably expressed in a number of normal and cancer tissues. The potential role of the novel CXCL12 splice variants as components of the CXCR4 axis in cancer development is not fully understood. The present study aimed to analyze the expression profile of the various SDF-1 isoforms and SDF-1 polymorphisms, and the association with the clinicopathological features and overall survival of patients with colorectal cancer (CRC). SDF-1 polymorphism analysis was performed using restriction fragment length polymorphism (RFLP) analysis in 73 histologically confirmed human CRC tissue samples at various stages of disease. The expression pattern of the SDF-1 isoforms was analyzed by reverse transcription-polymerase chain reaction in 40 histologically confirmed human CRC tissue samples obtained at various stages of disease, as well as in matched adjacent normal mucosa samples. The presence of the CXCL12 gene polymorphism rs1801157 demonstrated an association with local progression of the primary tumor, as indicated by the T stage. The frequency of the GG genotype was slightly increased in patients with stage 3 and 4 tumors (78.0%) compared with the incidence of the GA/AA genotype (69.5%; P=0.067). The expression of SDF-1β was associated with the presence of metastases (P=0.0656) and the expression of SDF-1γ was significantly associated with tumor size (P=0.0423). The present study is the first to analyze the association between the expression profile of the chemokine CXCL12 splice variants in human CRC tissues and their clinical relevance. The present results reveal that the CXCL12 G801A polymorphism is a low-penetrance risk factor for the development of CRC, and was associated with the T stage. All six isoforms of SDF-1 were expressed in CRC tissues. The expression of SDF-1β was found to be associated with metastases and SDF-1γ appears to be a possible tumor marker for local tumor progression.

Involvement of hypoxia-inducible factors in the dysregulation of oxygen homeostasis in sepsis

Sepsis is a state of infection with serious systemic manifestations, and if severe enough, can be associated with multiple organ dysfunction and systemic hypotension, which can cause tissues to be hypoxic. Inflammation, as part of the multifaceted biological response to injurious stimuli, such as pathogens or damaged tissues and cells, underlies these biological processes. Prolonged and persistent inflammation, also known as chronic inflammation, results in progressive alteration in the various types of cells at the site of inflammation and is characterized by the simultaneous destruction and healing of tissue during the process. Tissue hypoxia during inflammation is not just a simple bystander process, but can considerably affect the development or attenuation of inflammation by causing the regulation of hypoxia-dependent gene expression. Indeed, the study of transcriptionally regulated tissue adaptation to hypoxia requires intense investigation to help control hypoxia-induced inflammation and organ failure. In this review, I have described the pathophysiology of sepsis with respect to oxygen metabolism and expression of hypoxia-inducible factor 1.

Obstructive sleep apnea and cancer: effects of intermittent hypoxia?

Obstructive sleep apnea (OSA) is a common disorder characterized by pauses in regular breathing. Apneic episodes lead to recurrent hypoxemia-reoxygenation cycles with concomitant cellular intermittent hypoxia. Studies suggest that intermittent hypoxia in OSA may influence tumorigenesis. This review presents recent articles on the potential role of OSA in cancer development. Relevant research has focused on: molecular pathways mediating the influence of intermittent hypoxia on tumor physiology, animal and epidemiological human studies linking OSA and cancer. Current data relating OSA to risk of neoplastic disease remain scarce, but recent studies reveal the potential for a strong relation. More work is, therefore, needed on the impact of OSA on many cancer-related aspects. Results may offer enlightenment for improved cancer diagnosis and treatment.

CXCL12/CXCR4 display an inverse mRNA expression profile in gastric carcinoma that correlates with tumor progression

Chemokines and their receptors have been shown to contribute to tumor growth and metastatic spread in various gastrointestinal cancer entities. In the present study, the mRNA expression profiles and clinical significance of chemokine ligand CXCL12 and its corresponding receptor CXCR4 were investigated in patients with gastric cancer (GC). Using quantitative polymerase chain reaction, the expression profile of CXCL12/CXCR4 was analyzed in resection specimens from the patients with GC (n=66) and in corresponding normal gastric tissues. Upon investigating CXCL12/CXCR4 mRNA expression levels in the GC tissues, significant downregulation of CXCL12 expression was demonstrated (P<0.05), whereas CXCR4 mRNA expression was shown to be significantly upregulated (P<0.05). Likewise, in gastric carcinoma patients undergoing neoadjuvant chemotherapy, CXCR4 expression was found to be significantly upregulated (P<0.05), whereas in GC patients with lymph and vein infiltration, CXCL12 mRNA expression was significantly downregulated (P<0.05). These results demonstrate a significant inverse association between the development and progress of GC and CXCL12/CXCR4 mRNA expression. CXCR4 mRNA upregulation was promoted under the effect of neoadjuvant chemotherapy prior to surgery in GC patients, whereas higher tumor stages with lymph and vein infiltration negatively affected CXCL12 mRNA expression.

Prognostic Value of High CXCR4 Expression in Renal Cell Carcinoma: A System Review and Meta-Analysis

Background. Recent studies have shown that CXC chemokine receptor 4 (CXCR4) is involved in the progression and metastasis of renal cell carcinoma (RCC). However, the prognostic value of CXCR4 expression in RCC remains controversial. The aim of our meta-analysis is to evaluate the prognostic value of high CXCR4 expression in RCC. Methods. Relevant studies focused on the relationship between high CXCR4 expression and the outcome of RCC were searched in PubMed and EMBASE/Cochrane Library database. Hazard ratios (HRs) of overall survival (OS) and progression-free survival (PFS) were our evaluation index. The individual and pooled HRs with 95% confidence intervals (CIs) were analyzed. Results. A total of 1068 patients from 7 studies were included in our meta-analysis. The results suggested that high CXCR4 expression predicted a poor OS (random effect model (REM) HR = 2.77, 95% CI = 1.80−4.27) and PFS (REM HR = 4.83, 95% CI = 2.30−10.15) for RCC patients. Conclusion. The results of meta-analysis indicated that high CXCR4 expression was correlated with worse OS and PFS for patients with RCC. However, some larger samples and well-matched studies should be designed to estimate the potential prognosis of RCC patients.

CXCR4 pharmacogical inhibition reduces bone and soft tissue metastatic burden by affecting tumor growth and tumorigenic potential in prostate cancer preclinical models

BACKGROUND

The majority of prostate cancer (Pca) patient morbidity can be attributed to bone metastatic events, which poses a significant clinical obstacle. Therefore, a better understanding of this phenomenon is imperative and might help to develop novel therapeutic strategies. Stromal cell-derived factor 1α (SDF-1α) and its receptor CXCR4 have been implicated as regulators of bone resorption and bone metastatic development, suggesting that agents able to suppress this signaling pathway may be used as pharmacological treatments. In this study we studied if two CXCR4 receptor antagonists, Plerixafor and CTE9908, may affect bone metastatic disease induced by Pca in preclinical experimental models

METHODS

To verify the hypothesis that CXCR4 inhibition affects Pca metastatic disease, selective CXCR4 compounds, Plerixafor, and CTE9908, were tested in preclinical models known to generate bone lesions. Additionally, the expression levels of CXCR4 and SDF-1α were analyzed in a number of human tissues derived from primary tumors, lymph-nodes and osseous metastases of Pca as well as in a wide panel of human Pca cell lines to non-tumorigenic and tumorigenic phenotype.

RESULTS

Bone-derived Pca cells express higher CXCR4 levels than other Pca cell lines. This differential expression was also observed in human Pca samples. In vitro evidence supports the hypothesis that factors produced by bone microenvironment differentially sustain CXCR4 and SDF1-α expression with respect to prostate microenvironment determining increased efficacy toward Plerixafor. The use of SDF1-α neutralizing antibodies greatly reduced the increase of CXCR4 expression in cells co-cultured with bone stromal cells (BMSc) and to a lesser extent in cells co-cultured with prostate stromal cells (HPSc) and partially reduced SDF1-α Plerixafor efficacy. SDF-1α induced tumor cell migration and invasion, as well as MMP-9, MMP-2, and uPA expression, which were reduced by Plerixafor. The incidence of X-ray detectable bone lesions was significantly reduced following Plerixafor and CTE9908 treatment Kaplan-Meier probability plots showed a significant improvement in the overall survival of mice treated with Plerixafor and CTE9908. The reduced intra-osseous growth of PC3 and PCb2 tumor cells after intratibial injection, as a result of Plerixafor and CTE9908 treatment, correlated with decreased osteolysis and serum levels of both mTRAP and type I collagen fragments (CTX), which were significantly lower with respect to controls.

CONCLUSIONS

Our report provides novel information on the potential activity of CXCR4 inhibitors on the formation and progression of Pca bone and soft tissue metastases and supports a biological rationale for the use of these inhibitors in men at high risk to develop clinically evident bone lesions.

Insights into the mechanism of CXCL12-mediated signaling in trophoblast functions and placental angiogenesis

The chemokine CXCL12 and its receptor CXCR4 are important signaling components required for human blastocyst implantation and the progression of pregnancy. Growing evidence indicates that the CXCL12/CXCR4 axis can regulate trophoblast function and uterine spiral artery remodeling, which plays a fundamental role in placentation and fetal outcome. The orphan receptor CXCR7 is also believed to partly regulate the function of the CXCL12/CXCR4 axis. Additionally, the CXCL12/CXCR4/CXCR7 axis can enhance the cross-talk between trophoblasts and decidual cells such as uterine natural killer cells and decidual stromal cells which are involved in regulation of trophoblast differentiation and invasion and placental angiogenesis. In addition, recent studies proved that CXCL12 expression is elevated in the placenta and mid-trimester amniotic fluid of pregnant women with preeclampsia, implying that dysregulation of CXCL12 plays a role in the pathogenesis of preeclampsia. Further understanding of the regulatory mechanisms of CXCL12-mediated signaling in trophoblast functions and placental angiogenesis may help to design novel therapeutic approaches for pregnancy-associated diseases.

CXCR4 in breast cancer: oncogenic role and therapeutic targeting

Chemokines are 8–12 kDa peptides that function as chemoattractant cytokines and are involved in cell activation, differentiation, and trafficking. Chemokines bind to specific G-protein-coupled seven-span transmembrane receptors. Chemokines play a fundamental role in the regulation of a variety of cellular, physiological, and developmental processes. Their aberrant expression can lead to a variety of human diseases including cancer. C-X-C chemokine receptor type 4 (CXCR4), also known as fusin or CD184, is an alpha-chemokine receptor specific for stromal-derived-factor-1 (SDF-1 also called CXCL12). CXCR4 belongs to the superfamily of the seven transmembrane domain heterotrimeric G protein-coupled receptors and is functionally expressed on the cell surface of various types of cancer cells. CXCR4 also plays a role in the cell proliferation and migration of these cells. Recently, CXCR4 has been reported to play an important role in cell survival, proliferation, migration, as well as metastasis of several cancers including breast cancer. This review is mainly focused on the current knowledge of the oncogenic role and potential drugs that target CXCR4 in breast cancer. Additionally, CXCR4 proangiogenic molecular mechanisms will be reviewed. Strict biunivocal binding affinity and activation of CXCR4/CXCL12 complex make CXCR4 a unique molecular target for prevention and treatment of breast cancer.

A meta-analysis for CXCR4 as a prognostic marker and potential drug target in non-small cell lung cancer

Background

Recent reports have shown that C-X-C chemokine receptor type 4 (CXCR4) is a candidate oncogene in several types of human tumors, including non-small cell lung cancer (NSCLC). However, the correlation between CXCR4 expression and clinicopathological characteristics of NSCLC remains controversial and has not been emphasized. The aim of this study is to quantitatively evaluate the association of CXCR4 expression with the incidence of NSCLC and clinicopathological characteristics by performing a meta-analysis.

Methods

A detailed literature search was carried out for related research publications. Only articles in which CXCR4 expression was detected by immunohistochemical staining were included. Odds ratio (OR) and hazard ratio (HR) with 95% confidence intervals (CIs) were calculated and summarized.

Results

Final analysis of 1,872 NSCLC patients from 19 eligible studies was performed. We observed that CXCR4 expression was significantly higher in NSCLC than in normal lung tissue, based on the pooled OR from ten studies, including 678 NSCLCs and 189 normal lung tissues (OR =16.66, 95% CI =6.94–40.02, P<0.00001). CXCR4 expression was also significantly associated with clinical stages, metastatic status, and overall survival (OS) in NSCLC patients. In addition, CXCR4 mRNA high expression was found to correlate with worse OS of all NSCLC patients followed for 20 years, HR =1.24, P=0.0047.

Conclusion

The present meta-analysis indicated that CXCR4 protein expression is associated with an increased risk and worse survival in NSCLC patients. The aberrant CXCR4 protein and mRNA expression play an important role in the carcinogenesis and metastasis of NSCLC.

The intricate role of CXCR4 in cancer

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

miR-181a Targets RGS16 to Promote Chondrosarcoma Growth, Angiogenesis, and Metastasis

Chondrosarcoma is the most common primary malignant bone tumor in adults, has no effective systemic treatment, and patients with this disease have poor survival. Altered expression of microRNA (miR) is involved in tumorigenesis; however, its role in chondrosarcoma is undetermined. miR-181a is overexpressed in high-grade chondrosarcoma, is upregulated by hypoxia, and increases VEGF expression. Here, the purpose was to determine the mechanism of miR-181a regulation of VEGF, determine whether miR-181a overexpression promotes tumor progression, and to evaluate an antagomir-based approach for chondrosarcoma treatment. Therapeutic inhibition of miR-181a decreased expression of VEGF and MMP1 in vitro, and angiogenesis, MMP1 activity, tumor growth, and lung metastasis, all by more than 50%, in a xenograft mouse model. A target of miR-181a is a regulator of G-protein signaling 16 (RGS16), a negative regulator of CXC chemokine receptor 4 (CXCR4) signaling. CXCR4 signaling is increased in chondrosarcoma, its expression is also increased by hypoxia, and is associated with angiogenesis and metastasis; however, receptor blockade is only partially effective. RGS16 expression is restored after miR-181a inhibition and partially accounts for the antiangiogenic and antimetastatic effects of miR-181a inhibition. These data establish miR-181a as an oncomiR that promotes chondrosarcoma progression through a new mechanism involving enhancement of CXCR4 signaling by inhibition of RGS16.

IMPLICATIONS

Targeting miR-181a can inhibit tumor angiogenesis, growth, and metastasis, thus suggesting the possibility of antagomir-based therapy in chondrosarcoma.

Three-dimensional (3D) culture of bone-derived human 786-O renal cell carcinoma retains relevant clinical characteristics of bone metastases

Bone metastases from renal cell carcinoma (RCC) are typically lytic, destructive, and resistant to treatment regimens. Current in vitro models for studying metastasis introduce artifacts that limit their usefulness. Many features of tumors growing in bone are lost when human RCC cells are cultured in two-dimensional (2D) plastic substrata. In this study, we established that RCC spheroids, consisting of aggregates of cells, can be grown in a three-dimensional (3D) hyaluronate hydrogel-based culture system. The bone-derived human 786-O RCC subline proliferated and survived long term in these hydrogels. Additionally, RCC spheroids in 3D hydrogels demonstrated lower proliferation rates than their counterparts grown in 2D. Overall, gene expression patterns of RCC spheroids in 3D more closely mimicked those observed in vivo than did those of cells grown in 2D. Of particular importance, selected adhesion molecules, angiogenesis factors, and osteolytic factors that have been shown to be involved in RCC bone metastasis were found to be expressed at higher levels in 3D than in 2D cultures. We propose that the 3D culture system provides an improved platform for RCC bone metastasis studies compared with 2D systems.