Development of a unique small molecule modulator of CXCR4

Informed by Cancer Stem Cells of Solid Tumors: Advances in Treatments Targeting Tumor-Promoting Factors and Pathways

Cancer stem cells (CSCs) represent a subpopulation within tumors that promote cancer progression, metastasis, and recurrence due to their self-renewal capacity and resistance to conventional therapies. CSC-specific markers and signaling pathways highly active in CSCs have emerged as a promising strategy for improving patient outcomes. This review provides a comprehensive overview of the therapeutic targets associated with CSCs of solid tumors across various cancer types, including key molecular markers aldehyde dehydrogenases, CD44, epithelial cellular adhesion molecule, and CD133 and signaling pathways such as Wnt/β-catenin, Notch, and Sonic Hedgehog. We discuss a wide array of therapeutic modalities ranging from targeted antibodies, small molecule inhibitors, and near-infrared photoimmunotherapy to advanced genetic approaches like RNA interference, CRISPR/Cas9 technology, aptamers, antisense oligonucleotides, chimeric antigen receptor (CAR) T cells, CAR natural killer cells, bispecific T cell engagers, immunotoxins, drug-antibody conjugates, therapeutic peptides, and dendritic cell vaccines. This review spans developments from preclinical investigations to ongoing clinical trials, highlighting the innovative targeting strategies that have been informed by CSC-associated pathways and molecules to overcome therapeutic resistance. We aim to provide insights into the potential of these therapies to revolutionize cancer treatment, underscoring the critical need for a multi-faceted approach in the battle against cancer. This comprehensive analysis demonstrates how advances made in the CSC field have informed significant developments in novel targeted therapeutic approaches, with the ultimate goal of achieving more effective and durable responses in cancer patients.

The CXCR4 might be a potential biomarker for esophageal squamous cell carcinoma: A meta-analysis

OBJECTIVE

To evaluate the relationship between CXCL12/CXCR4 and the progress, prognosis of esophageal squamous cell carcinoma (ESCC), providing evidence for potential early diagnosis, clinical treatment, prognosis evaluation, and therapeutic target of ESCC.

METHODS

Databases of PubMed, the Cochrane Library, Embase, and Web of Science were searched for the relationship between CXCL12/CXCR4 and clinicopathological characteristics and survival time of ESCC. Stata16.0 software was used to conduct meta-analysis.

RESULTS

A total of 10 studies involving 1216 cases of patients with ESCC were included in our study. The results indicated that high-level expression of CXCR4 was significantly correlated with tumor differentiation [OR = 0.69, 95% confidence interval (CI): (0.50, 0.97)], tumor infiltration [OR = 0.39, 95% CI: (0.25, 0.61)], lymph node metastasis [OR = 0.36, 95% CI: (0.21, 0.61)], clinical stage [OR = 0.33, 95% CI: (0.24, 0.45)] of ESCC. The expression of CXCR4 was also significantly correlated with OS [HR = 2.00, 95% CI: (1.63, 2.45)] and disease-free survival [HR = 1.76, 95% CI: (1.44, 2.15)] in patients of ESCC after surgical resection. No significant relationship was observed between the expression of CXCL12 and the clinicopathological characteristics of ESCC.

CONCLUSION

CXCR4 might be a potential biomarker for the progress and prognosis evaluation, and therapeutic target for ESCC.

Design of a New 99mTc-radiolabeled Cyclo-peptide as Promising Molecular Imaging Agent of CXCR4 Receptor: Molecular Docking, Synthesis, Radiolabeling, and Biological Evaluation

INTRODUCTION

C-X-C Chemokine receptor type 4 (CXCR4) is often overexpressed or overactivated in different types and stages of cancer disease. Therefore, it is considered a promising target for imaging and early detection of primary tumors and metastasis. In the present research, a new cyclo-peptide radiolabelled with 99mTc, 99mTc-Cyclo [D-Phe-D-Tyr-Lys (HYNIC)- D-Arg-2-Nal-Gly-Lys(iPr)], was designed based on the parental LY251029 peptide, as a potential in vivo imaging agent of CXCR4-expressing tumors.

METHODS

The radioligand was successfully prepared using the method of Fmoc solid-phase peptide synthesis and was evaluated in biological assessment. Molecular docking findings revealed high affinity (binding energy of -9.7 kcal/mol) and effective interaction of Cyclo [D-Phe- D-Tyr-Lys (HYNIC)-D-Arg-2-Nal-Gly-Lys(iPr)] in the binding pocket of CXCR4 receptor (PDB code: 3OE0) as well.

RESULT

The synthesized peptide and its purity were assessed by both reversed-phase high-performance liquid chromatography (RP-HPLC) and mass spectroscopy. High stability (95%, n = 3) in human serum and favorable affinity (Kd = 28.70 ± 13.56 nM and Bmax = 1.896 ± 0.123 fmol/mg protein) in the B16-F10 cell line resulted. Biodistribution evaluation findings and planar image interpretation of mice both showed high affinity and selectivity of the radiotracer to the CXCR4 receptors.

CONCLUSION

Therefore, the findings indicate this designed radioligand could be used as a potential SPECT imaging agent in highly proliferated CXCR4 receptor tumors.

CXC chemokine receptor 4 (CXCR4) blockade in cancer treatment

CXC chemokine receptor type 4 (CXCR4) is a member of the G protein-coupled receptors (GPCRs) superfamily and is specific for CXC chemokine ligand 12 (CXCL12, also known as SDF-1), which makes CXCL12/CXCR4 axis. CXCR4 interacts with its ligand, triggering downstream signaling pathways that influence cell proliferation chemotaxis, migration, and gene expression. The interaction also regulates physiological processes, including hematopoiesis, organogenesis, and tissue repair. Multiple evidence revealed that CXCL12/CXCR4 axis is implicated in several pathways involved in carcinogenesis and plays a key role in tumor growth, survival, angiogenesis, metastasis, and therapeutic resistance. Several CXCR4-targeting compounds have been discovered and used for preclinical and clinical cancer therapy, most of which have shown promising anti-tumor activity. In this review, we summarized the physiological signaling of the CXCL12/CXCR4 axis and described the role of this axis in tumor progression, and focused on the potential therapeutic options and strategies to block CXCR4.

CXCL12-CXCR4/CXCR7 Axis in Cancer: from Mechanisms to Clinical Applications

Cancer is a multi-step disease caused by the accumulation of genetic mutations and/or epigenetic changes, and is the biggest challenge around the world. Cytokines, including chemokines, exhibit expression changes and disorders in all human cancers. These cytokine abnormalities can disrupt homeostasis and immune function, and make outstanding contributions to various stages of cancer development such as invasion, metastasis, and angiogenesis. Chemokines are a superfamily of small molecule chemoattractive cytokines that mediate a variety of cellular functions. Importantly, the interactions of chemokine members CXCL12 and its receptors CXCR4 and CXCR7 have a broad impact on tumor cell proliferation, survival, angiogenesis, metastasis, and tumor microenvironment, and thus participate in the onset and development of many cancers including leukemia, breast cancer, lung cancer, prostate cancer and multiple myeloma. Therefore, this review aims to summarize the latest research progress and future challenges regarding the role of CXCL12-CXCR4/CXCR7 signaling axis in cancer, and highlights the potential of CXCL12-CXCR4/CXCR7 as a biomarker or therapeutic target for cancer, providing essential strategies for the development of novel targeted cancer therapies.

CXCR4-Targeted Radiopharmaceuticals for the Imaging and Therapy of Malignant Tumors

C-X-C chemokine receptor type 4 (CXCR4), also known as fusin or CD184, is a 7-transmembrane helix G-protein-coupled receptor that is encoded by the CXCR4 gene. Involved in various physiological processes, CXCR4 could form an interaction with its endogenous partner, chemokine ligand 12 (CXCL12), which is also named SDF-1. In the past several decades, the CXCR4/CXCL12 couple has attracted a large amount of research interest due to its critical functions in the occurrence and development of refractory diseases, such as HIV infection, inflammatory diseases, and metastatic cancer, including breast cancer, gastric cancer, and non-small cell lung cancer. Furthermore, overexpression of CXCR4 in tumor tissues was shown to have a high correlation with tumor aggressiveness and elevated risks of metastasis and recurrence. The pivotal roles of CXCR4 have encouraged an effort around the world to investigate CXCR4-targeted imaging and therapeutics. In this review, we would like to summarize the implementation of CXCR4-targeted radiopharmaceuticals in the field of various kinds of carcinomas. The nomenclature, structure, properties, and functions of chemokines and chemokine receptors are briefly introduced. Radiopharmaceuticals that could target CXCR4 will be described in detail according to their structure, such as pentapeptide-based structures, heptapeptide-based structures, nonapeptide-based structures, etc. To make this review a comprehensive and informative article, we would also like to provide the predictive prospects for the CXCR4-targeted species in future clinical development.

N-Alkylation of Amines by C1-C10 Aliphatic Alcohols Using A Well-Defined Ru(II)-Catalyst. A Metal-Ligand Cooperative Approach

A Ru(II)-catalyzed efficient and selective N-alkylation of amines by C1-C10 aliphatic alcohols is reported. The catalyst [Ru(L^1a)(PPh₃)Cl₂] (1a) bearing a tridentate redox-active azo-aromatic pincer, 2-((4-chlorophenyl)diazenyl)-1,10-phenanthroline (L^1a) is air-stable, easy to prepare, and showed wide functional group tolerance requiring only 1.0 mol % (for N-methylation and N-ethylation) and 0.1 mol % of catalyst loading for N-alkylation with C3-C10 alcohols. A wide array of N-methylated, N-ethylated, and N-alkylated amines were prepared in moderate to good yields via direct coupling of amines and alcohols. 1a efficiently catalyzes the N-alkylation of diamines selectively. It is even suitable for synthesizing N-alkylated diamines using (aliphatic) diols producing the tumor-active drug molecule MSX-122 in moderate yield. 1a showed excellent chemo-selectivity during the N-alkylation using oleyl alcohol and monoterpenoid β-citronellol. Control experiments and mechanistic investigations revealed that the 1a-catalyzed N-alkylation reactions proceed via a borrowing hydrogen transfer pathway where the hydrogen removed from the alcohol during the dehydrogenation step is stored in the ligand backbone of 1a, which in the subsequent steps transferred to the in situ formed imine intermediate to produce the N-alkylated amines.

Chemokine level predicts the therapeutic effect of anti-PD-1 antibody (nivolumab) therapy for malignant melanoma

Anti-programmed cell death protein 1 (PD-1) antibody drugs, nivolumab and pembrolizumab, are regarded as first-line therapies for advanced malignant melanoma. Anti-PD-1 therapy suppresses tumor immunity, and the therapeutic effect is frequently correlated with the number of tumor-infiltrating lymphocytes (TIL) and tumor mutation burden (TMB). However, sampling tumor tissues from the metastatic sites to examine the number of TILs and TMB level is often challenging. Herein, we focused on chemokines in blood to determine whether they can predict the therapeutic effect of anti-PD-1 (nivolumab) therapy. First, we measured 44 types of chemokines and cytokines in the blood of 8 advanced malignant melanomas before anti-PD-1 (nivolumab) treatment and examined the relationship between the levels of these proteins and therapeutic effect of the drug treatment, which suggested that C-C motif chemokine 5 (CCL5) and C-X-C motif chemokine ligand 12 (CXCL12) were candidates for biomarkers to predict the therapeutic effect of anti-PD-1 therapy. Next, we measured the blood levels of CCL5 and CXCL12 in 22 patients with advanced malignant melanomas before the administration of anti-PD-1 antibody. We evaluated tumor infiltration of CD8-positive T cells by immunostaining in nine patients in whom the metastatic site could be sampled at the beginning of the treatment. The patients with lower than average levels of CCL5 and CXCL12 had a large number of TILs (P = 0.04) and good disease-specific survival rate (P = 0.04). Therefore, CCL5 and CXCL12 could likely be used as biomarkers to predict the therapeutic effect of anti-PD-1 (nivolumab) therapy.

Recent Advances in CXCL12/CXCR4 Antagonists and Nano-Based Drug Delivery Systems for Cancer Therapy

Chemokines can induce chemotactic cell migration by interacting with G protein-coupled receptors to play a significant regulatory role in the development of cancer. CXC chemokine-12 (CXCL12) can specifically bind to CXC chemokine receptor 4 (CXCR4) and is closely associated with the progression of cancer via multiple signaling pathways. Over recent years, many CXCR4 antagonists have been tested in clinical trials; however, Plerixafor (AMD3100) is the only drug that has been approved for marketing thus far. In this review, we first summarize the mechanisms that mediate the physiological effects of the CXCL12/CXCR4 axis. Then, we describe the use of CXCL12/CXCR4 antagonists. Finally, we discuss the use of nano-based drug delivery systems that exert action on the CXCL12/CXCR4 biological axis.

Chemokines and NSCLC: Emerging role in prognosis, heterogeneity, and therapeutics

Lung cancer persists to contribute to one-quarter of cancer-associated deaths. Among the different histologies, non-small cell lung cancer (NSCLC) alone accounts for 85% of the cases. The development of therapies involving immune checkpoint inhibitors and angiogenesis inhibitors has increased patients' survival probability and reduced mortality rates. Developing targeted therapies against essential genetic alterations also translates to better treatment strategies. But the benefits still seem farfetched due to the development of drug resistance and refractory tumors. In this review, we have highlighted the interplay of different tumor microenvironment components, essentially discussing the chemokine families (CC, CXC, C, and CX3C) that regulate the tumor biology in NSCLC and promote tumor growth, metastasis, and associated heterogeneity. The development of therapeutics and prognostic markers is a complex and multipronged approach. However, some essential chemokines can act as critical players for being considered potential prognostic markers and therapeutic targets.

Production of human embryonic kidney 293T cells stably expressing C-X-C chemokine receptor type 4 (CXCR4) as a screening tool for anticancer lead compound targeting CXCR4

AIM

The C-X-C chemokine-receptor type 4 (CXCR4) is an emerging target for cancer drug discovery due to its high expression in cancer cells. The present study aimed to produce CXCR4 overexpressing HEK293T cells for a non-radioactive binding assay as a platform to identify drug candidates targeting CXCR4.

MAIN METHODS

HEK293T cells stably expressing human CXCR4 were constructed by transfection of CXCR4 plasmids from the human CXCR4 gene. The CXCR4 overexpressing HEK293T cells were obtained by fluorescence-activated sorting and verified by conducting the competition binding assay of a known CXCR4 inhibitor, AMD3100 (plerixafor), to determine the IC₅₀ value against monoclonal anti-human CD184 (hCD184) antibody tagged with fluorescence probe, phycoerythrin (PE). The non-radioactive binding assay using CXCR4 overexpressing HEK293T cells and PE-anti hCD184 was applied as a platform for identifying the target of natural compounds that exhibited cytotoxicity against cancer cell lines.

KEY FINDINGS

The CXCR4 overexpressing HEK293T cells were produced with high expression (99.8%). The IC₅₀ value of plerixafor determined by fluorescence tagged antibody-based competition assay using our developed cells agree with previously reported values using a radioligand binding assay. We observed no significant displacement of bound PE-anti-hCD184 by the test natural compounds which could be due to non-specific binding to other functional targets or organelles, low potency of the natural compounds, or binding to CXCR4 at deeper pockets.

SIGNIFICANCE

The verified non-radioactive binding assay can serve as an alternative screening tool for anticancer lead compounds targeting CXCR4 and an essential tool for proof of mechanism study in the drug discovery.

MSX-122: Is an effective small molecule CXCR4 antagonist in cancer therapy?

Chemokines, a subgroup of cytokines along with their receptors, are involved in various biologic processes and regulation of a wide range of immune responses in different physiologic and pathologic states such as tissue repair, infection, and inflammation. C-X-C motif chemokine receptor 4 (CXCR4), a G-protein-coupled receptor (GPCR), has one identified natural ligand termed stromal-derived factor-1(SDF-1 or CXCL12). Evidence demonstrated that the ligation of SDF-1 to CXCR4 initiates several intracellular signaling pathways, regulating cell proliferation, survival, chemotaxis, migration, angiogenesis, adhesion, as well as bone marrow (BM)-resident cells homing and mobilization. Additionally, CXCR4 is expressed by tumor cells in blood malignancies and solid tumors. Therefore, CXCR4 is considered a potential therapeutic target in cancer therapy, and CXCR4 antagonists, including AMD3100, MSX-122, BPRCX807, WZ811, Motixafortide, TN14003, AMD3465, and AMD1170, have been employed in experimental and clinical studies to enhance cancer therapy. MSX-122 is a specific small-molecule antagonist of CXCR4/CXCL12 and the only orally available non-peptide CXCR4 antagonist with promising anti-cancer properties. Studies have shown that MSX-122 is particularly important in treating metastatic cancers and has great therapeutic potential. Accordingly, this review summarized the characteristics of MSX-122 and its effects on the CXCL12/CXCR4 axis as well as cancer therapy.

Colorectal Cancer: The Contribution of CXCL12 and Its Receptors CXCR4 and CXCR7

Simple Summary

Many signaling pathways are involved in cancer progression, and among these pathways, the CXCL12 axis and its two receptors CXCR4 and CXCR7 are well described for many cancers. This review presents the current knowledge on the role played by each of the actors of this axis in colorectal cancer and on its consideration in the development of new therapeutic strategies.

Abstract

Colorectal cancer is one of the most common cancers, and diagnosis at late metastatic stages is the main cause of death related to this cancer. This progression to metastasis is complex and involves different molecules such as the chemokine CXCL12 and its two receptors CXCR4 and CXCR7. The high expression of receptors in CRC is often associated with a poor prognosis and aggressiveness of the tumor. The interaction of CXCL12 and its receptors activates signaling pathways that induce chemotaxis, proliferation, migration, and cell invasion. To this end, receptor inhibitors were developed, and their use in preclinical and clinical studies is ongoing. This review provides an overview of studies involving CXCR4 and CXCR7 in CRC with an update on their targeting in anti-cancer therapies.

A single domain i-body (AD-114) attenuates renal fibrosis through blockade of CXCR4

The G protein–coupled CXC chemokine receptor 4 (CXCR4) is a candidate therapeutic target for tissue fibrosis. A fully human single-domain antibody-like scaffold i-body AD-114-PA600 (AD-114) with specific high binding affinity to CXCR4 has been developed. To define its renoprotective role, AD-114 was administrated in a mouse model of renal fibrosis induced by folic acid (FA). Increased extracellular matrix (ECM) accumulation, macrophage infiltration, inflammatory response, TGF-β1 expression, and fibroblast activation were observed in kidneys of mice with FA-induced nephropathy. These markers were normalized or partially reversed by AD-114 treatment. In vitro studies demonstrated AD-114 blocked TGF-β1–induced upregulated expression of ECM, matrix metalloproteinase-2, and downstream p38 mitogen-activated protein kinase (p38 MAPK) and PI3K/AKT/mTOR signaling pathways in a renal proximal tubular cell line. Additionally, these renoprotective effects were validated in a second model of unilateral ureteral obstruction using a second generation of AD-114 (Fc-fused AD-114, also named AD-214). Collectively, these results suggest a renoprotective role of AD-114 as it inhibited the chemotactic function of CXCR4 as well as blocked CXCR4 downstream p38 MAPK and PI3K/AKT/mTOR signaling, which establish a therapeutic strategy for AD-114 targeting CXCR4 to limit renal fibrosis.

Non-invasive detection and complementary diagnosis of liver metastases via chemokine receptor 4 imaging

Noninvasive detection of early-stage liver metastases from different primary cancers is a pressing unmet medical need. The lack of both molecular biomarkers and the sensitive imaging methodology makes the detection challenging. In this study, we observed the elevated expression of chemokine receptor 4 (CXCR4) in uveal melanoma (UM) patient liver tissues, and high CXCR4 expression in liver metastases of UM murine models, regardless of the expression levels in the primary tumors. Based on these findings, we identified CXCR4 as an imaging biomarker and exploited a CXCR4-targeted MRI contrast agent ProCA32.CXCR4 for molecular MRI imaging. ProCA32.CXCR4 has strong CXCR4 binding affinity, high metal selectivity, and r1 and r2 relaxivities, which enables the sensitive detection of liver micrometastases. The MRI imaging capacity for detecting liver metastases was demonstrated in three UM models and one ovarian cancer model. The imaging results were validated by histological and immunohistochemical analysis. ProCA32.CXCR4 has strong potential clinical application for non-invasive diagnosis of liver metastases.

Nedd4-2-dependent Ubiquitination Potentiates the Inhibition of Human NHE3 by Cholera Toxin and Enteropathogenic Escherichia coli

BACKGROUND & AIMS

Diarrhea is one of the most common illnesses and is often caused by bacterial infection. Recently, we have shown that human Na⁺/H⁺ exchanger NHE3 (hNHE3), but not non-human NHE3s, interacts with the E3 ubiquitin ligase Nedd4-2. We hypothesize that this property of hNHE3 contributes to the increased severity of diarrhea in humans.

METHODS

We used humanized mice expressing hNHE3 in the intestine (hNHE3^int) to compare the contribution of hNHE3 and mouse NHE3 to diarrhea induced by cholera toxin (CTX) and enteropathogenic Escherichia coli (EPEC). We measured Na⁺/H⁺ exchange activity and fluid absorption. The role of Nedd4-2 on hNHE3 activity and ubiquitination was determined by knockdown in Caco-2bbe cells. The effects of protein kinase A (PKA), the primary mediator of CTX-induced diarrhea, on Nedd4-2 and hNHE3 phosphorylation and their interaction were determined.

RESULTS

The effects of CTX and EPEC were greater in hNHE3^int mice than in control wild-type (WT) mice, resulting in greater inhibition of NHE3 activity and increased fluid accumulation in the intestine, the hallmark of diarrhea. Activation of PKA increased ubiquitination of hNHE3 and enhanced interaction of Nedd4-2 with hNHE3 via phosphorylation of Nedd4-2 at S342. S342A mutation mitigated the Nedd4-2-hNHE3 interaction and blocked PKA-induced inhibition of hNHE3. Unlike non-human NHE3s, inhibition of hNHE3 by PKA is independent of NHE3 phosphorylation, suggesting a distinct mechanism of hNHE3 regulation.

CONCLUSIONS

The effects of CTX and EPEC on hNHE3 are amplified, and the unique properties of hNHE3 may contribute to diarrheal symptoms occurring in humans.

Target-Based Small Molecule Drug Discovery Towards Novel Therapeutics for Inflammatory Bowel Diseases

Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), is a class of severe and chronic diseases of the gastrointestinal (GI) tract with recurrent symptoms and significant morbidity. Long-term persistence of chronic inflammation in IBD is a major contributing factor to neoplastic transformation and the development of colitis-associated colorectal cancer. Conversely, persistence of transmural inflammation in CD is associated with formation of fibrosing strictures, resulting in substantial morbidity. The recent introduction of biological response modifiers as IBD therapies, such as antibodies neutralizing tumor necrosis factor (TNF)-α, have replaced nonselective anti-inflammatory corticosteroids in disease management. However, a large proportion (~40%) of patients with the treatment of anti-TNF-α antibodies are discontinued or withdrawn from therapy because of (1) primary nonresponse, (2) secondary loss of response, (3) opportunistic infection, or (4) onset of cancer. Therefore, the development of novel and effective therapeutics targeting specific signaling pathways in the pathogenesis of IBD is urgently needed. In this comprehensive review, we summarize the recent advances in drug discovery of new small molecules in preclinical or clinical development for treating IBD that target biologically relevant pathways in mucosal inflammation. These include intracellular enzymes (Janus kinases, receptor interacting protein, phosphodiesterase 4, IκB kinase), integrins, G protein-coupled receptors (S1P, CCR9, CXCR4, CB2) and inflammasome mediators (NLRP3), etc. We will also discuss emerging evidence of a distinct mechanism of action, bromodomain-containing protein 4, an epigenetic regulator of pathways involved in the activation, communication, and trafficking of immune cells. We highlight their chemotypes, mode of actions, structure-activity relationships, characterizations, and their in vitro/in vivo activities and therapeutic potential. The perspectives on the relevant challenges, new opportunities, and future directions in this field are also discussed.

PET Imaging Radiotracers of Chemokine Receptors

Chemokines and chemokine receptors have been recognized as critical signal components that maintain the physiological functions of various cells, particularly the immune cells. The signals of chemokines/chemokine receptors guide various leukocytes to respond to inflammatory reactions and infectious agents. Many chemokine receptors play supportive roles in the differentiation, proliferation, angiogenesis, and metastasis of diverse tumor cells. In addition, the signaling functions of a few chemokine receptors are associated with cardiac, pulmonary, and brain disorders. Over the years, numerous promising molecules ranging from small molecules to short peptides and antibodies have been developed to study the role of chemokine receptors in healthy states and diseased states. These drug-like candidates are in turn exploited as radiolabeled probes for the imaging of chemokine receptors using noninvasive in vivo imaging, such as positron emission tomography (PET). Recent advances in the development of radiotracers for various chemokine receptors, particularly of CXCR4, CCR2, and CCR5, shed new light on chemokine-related cancer and cardiovascular research and the subsequent drug development. Here, we present the recent progress in PET radiotracer development for imaging of various chemokine receptors.

CXCL12 Signaling in the Tumor Microenvironment

Tumor microenvironment (TME) is the local environment of tumor, composed of tumor cells and blood vessels, extracellular matrix (ECM), immune cells, and metabolic and signaling molecules. Chemokines and their receptors play a fundamental role in the crosstalk between tumor cells and TME, regulating tumor-related angiogenesis, specific leukocyte infiltration, and activation of the immune response and directly influencing tumor cell growth, invasion, and cancer progression. The chemokine CXCL12 is a homeostatic chemokine that regulates physiological and pathological process such as inflammation, cell proliferation, and specific migration. CXCL12 activates CXCR4 and CXCR7 chemokine receptors, and the entire axis has been shown to be dysregulated in more than 20 different tumors. CXCL12 binding to CXCR4 triggers multiple signal transduction pathways that regulate intracellular calcium flux, chemotaxis, transcription, and cell survival. CXCR7 binds with high-affinity CXCL12 and with lower-affinity CXCL11, which binds also CXCR3. Although CXCR7 acts as a CXCL12 scavenger through ligand internalization and degradation, it transduces the signal mainly through β-arrestin with a pivotal role in endothelial and neural cells. Recent studies demonstrate that TME rich in CXCL12 leads to resistance to immune checkpoint inhibitors (ICI) therapy and that CXCL12 axis inhibitors sensitize resistant tumors to ICI effect. Thus targeting the CXCL12-mediated axis may control tumor and tumor microenvironment exerting an antitumor dual action. Herein CXCL12 physiology, role in cancer biology and in composite TME, prognostic role, and the relative inhibitors are addressed.

Biased agonism at chemokine receptors

In the human chemokine system, interactions between the approximately 50 known endogenous chemokine ligands and 20 known chemokine receptors (CKRs) regulate a wide range of cellular functions and biological processes including immune cell activation and homeostasis, development, angiogenesis, and neuromodulation. CKRs are a family of G protein-coupled receptors (GPCR), which represent the most common and versatile class of receptors in the human genome and the targets of approximately one third of all Food and Drug Administration-approved drugs. Chemokines and CKRs bind with significant promiscuity, as most CKRs can be activated by multiple chemokines and most chemokines can activate multiple CKRs. While these ligand-receptor interactions were previously regarded as redundant, it is now appreciated that many chemokine:CKR interactions display biased agonism, the phenomenon in which different ligands binding to the same receptor signal through different pathways with different efficacies, leading to distinct biological effects. Notably, these biased responses can be modulated through changes in ligand, receptor, and or the specific cellular context (system). In this review, we explore the biochemical mechanisms, functional consequences, and therapeutic potential of biased agonism in the chemokine system. An enhanced understanding of biased agonism in the chemokine system may prove transformative in the understanding of the mechanisms and consequences of biased signaling across all GPCR subtypes and aid in the development of biased pharmaceuticals with increased therapeutic efficacy and safer side effect profiles.

CXCL12-PLGA/Pluronic Nanoparticle Internalization Abrogates CXCR4-Mediated Cell Migration

Chemokine-induced chemotaxis mediates physiological and pathological immune cell trafficking, as well as several processes involving cell migration. Among them, the role of CXCL12/CXCR4 signaling in cancer and metastasis is well known, and CXCR4 has been often targeted with small molecule-antagonists or short CXCL12-derived peptides to limit the pathological processes of cell migration and invasion. To reduce CXCR4-mediated chemotaxis, we adopted a different approach. We manufactured poly(lactic acid-co-glycolic acid) (PLGA)/Pluronic F127 nanoparticles through microfluidics-assisted nanoprecipitation and functionalized them with streptavidin to docking a biotinylated CXCL12 to be exposed on the nanoparticle surface. Our results show that CXCL12-decorated nanoparticles are non-toxic and do not induce inflammatory cytokine release in THP-1 monocytes cultured in fetal bovine and human serum-supplemented media. The cell internalization of our chemokine receptor-targeting particles increases in accordance with CXCR4 expression in FBS/medium. We demonstrated that CXCL12-decorated nanoparticles do not induce cell migration on their own, but their pre-incubation with THP-1 significantly decreases CXCR4⁺-cell migration, thereby antagonizing the chemotactic action of CXCL12. The use of biodegradable and immune-compatible chemokine-mimetic nanoparticles to reduce cell migration opens the way to novel antagonists with potential application in cancer treatments and inflammation.

Primary tumor and metastasis-sectioning the different steps of the metastatic cascade

Patients with lung cancer in the majority die of metastases. Treatment options include surgery, chemo- and radiotherapy, targeted therapy by tyrosine kinase inhibitors (TKIs), and immuno-oncologic treatment. Despite the success with these treatment options, cure of lung cancer is achieved in only a very small proportion of patients. In most patients’ recurrence and metastasis will occur, and finally kill the patient. Metastasis is a multistep procedure. It requires a change in adhesion of tumor cells for detachment from their neighboring cells. The next step is migration either as single cells [epithelial-mesenchymal transition (EMT)], or as cell clusters (hybrid-EMT or bulk migration). A combination of genetic changes is required to facilitate migration. Then tumor cells have to orient themselves along matrix proteins, detect oxygen concentrations, prevent attacks by immune cells, and induce a tumor-friendly switch of stroma cells (macrophages, myofibroblasts, etc.). Having entered the blood stream tumor cells need to adapt to shear stress, avoid being trapped by coagulation, but also use coagulation in small veins for adherence to endothelia, and express homing molecules for extravasation. Within a metastatic site, tumor cells need a well-prepared niche to establish a metastatic focus. Tumor cells again have to establish a vascular net for maintaining nutrition and oxygen supply, communicate with stroma cells, grow out and set further metastases. In this review the different steps will be discussed with a focus on pulmonary carcinomas. The vast amount of research manuscripts published so far are not easy to analyze: in most reports’ single steps of the metastatic cascade are interpreted as evidence for the whole process; for example, migration is interpreted as evidence for metastasis. In lung cancer most often latency periods are shorter, in between 1–5 years. In other cases, despite widespread migration occurs, tumor cells die within the circulation and do not reach a metastatic site. Therefore, migration is a requisite, but does not necessarily predict metastasis. The intention of this review is to point to these different aspects and hopefully provoke research directed into a more functional analysis of the metastatic process.

Microtiter plate-based antibody-competition assay to determine binding affinities and plasma/blood stability of CXCR4 ligands

C-X-C chemokine receptor type 4 (CXCR4) is involved in several intractable disease processes, including HIV infection, cancer cell metastasis, leukemia cell progression, rheumatoid arthritis, asthma and pulmonary fibrosis. Thus, CXCR4 represents a promising drug target and several CXCR4 antagonizing agents are in preclinical or clinical development. Important parameters in drug lead evaluation are determination of binding affinities to the receptor and assessment of their stability and activity in plasma or blood of animals and humans. Here, we designed a microtiter plate-based CXCR4 antibody competition assay that enables to measure inhibitory concentrations (IC₅₀ values) and affinity constants (K_i values) of CXCR4 targeting drugs. The assay is based on the observation that most if not all CXCR4 antagonists compete with binding of the fluorescence-tagged CXCR4 antibody 12G5 to the receptor. We demonstrate that this antibody-competition assay allows a convenient and cheap determination of binding affinities of various CXCR4 antagonists in living cells within just 3 h. Moreover, the assay can be performed in the presence of high concentrations of physiologically relevant body fluids, and thus is a useful readout to evaluate stability (i.e. half-life) of CXCR4 ligands in serum/plasma, and even whole human and mouse blood ex vivo. Thus, this optimized 12G5 antibody-competition assay allows a robust and convenient determination and calculation of various important pharmacological parameters of CXCR4 receptor-drug interaction and may not only foster future drug development but also animal welfare by reducing the number of experimental animals.

New CXCR4 Antagonist Peptide R (Pep R) Improves Standard Therapy in Colorectal Cancer

The chemokine receptor CXCR4 is overexpressed and functional in colorectal cancer. To investigate the role of CXCR4 antagonism in potentiating colon cancer standard therapy, the new peptide CXCR4 antagonist Peptide R (Pep R) was employed. Human colon cancer HCT116 xenograft-bearing mice were treated with chemotherapeutic agents (CT) 5-Fluorouracil (5FU) and oxaliplatin (OX) or 5FU and radio chemotherapy (RT-CT) in the presence of Pep R. After two weeks, CT plus Pep R reduced by 4-fold the relative tumor volume (RTV) as compared to 2- and 1.6-fold reductions induced, respectively, by CT and Pep R. In vitro Pep R addition to CT/RT-CT impaired HCT116 cell growth and further reduced HCT116 and HT29 clonal capability. Thus, the hypothesis that Pep R could target the epithelial mesenchyme transition (EMT) process was evaluated. While CT decreased ECAD and increased ZEB-1 and CD90 expression, the addition of Pep R restored the pretreatment expression. In HCT116 and HT29 cells, CT/RT-CT induced a population of CD133+CXCR4+ cells, supposedly a stem-resistant cancer cell population, while Pep R reduced it. Taken together, the results showed that targeting CXCR4 ameliorates the effect of treatment in colon cancer through inhibition of cell growth and reversal of EMT treatment-induced markers, supporting further clinical studies.

Novel CXCR4 Inhibitor CPZ1344 Inhibits the Proliferation, Migration and Angiogenesis of Glioblastoma

Glioblastoma (GBM) are life-threatening tumors with a poor prognosis and low cure rates. GBMs are malignant brain tumors that develop from astrocytes. Most GBMs are not inherited and occur sporadically. GBM recurrence after standard treatment has led to the assessment of agents targeting the CXCR4 chemokine receptor as alternative drug target for much needed GBM therapeutics. In present study, a novel CXCR4 inhibitor modified with a picolinamide scaffold (CPZ1344) was designed and synthesized. Its anti-GBM function was then evaluated. Our results showed that CPZ1344 reduced the growth of GBM cells in a concentration dependent manner. The anti-GBM activity of CPZ1344 was due to alteration in GBM-cell morphology and apoptotic induction in GBM cells. CPZ1344 inhibited the migration and angiogenesis of U87 cells, led to cell cycle arrest in the G1 phase and inhibited CXCR4 signaling. These findings demonstrate the anticancer effects of CPZ1344 and its potential as a novel anti-GBM therapeutic.

Discovery of novel aminopiperidinyl amide CXCR4 modulators through virtual screening and rational drug design

The C-X-C chemokine receptor type 4 (CXCR4) is a potential therapeutic target for HIV infection, metastatic cancer, and inflammatory autoimmune diseases. In this study, we screened the ZINC chemical database for novel CXCR4 modulators through a series of in silico guided processes. After evaluating the screened compounds for their binding affinities to CXCR4 and inhibitory activities against the chemoattractant CXCL12, we identified a hit compound (ZINC 72372983) showing 100 nM affinity and 69% chemotaxis inhibition at the same concentration (100 nM). To increase the potency of our hit compound, we explored the protein-ligand interactions at an atomic level using molecular dynamics simulation which enabled us to design and synthesize a novel compound (Z7R) with nanomolar affinity (IC₅₀ = 1.25 nM) and improved chemotaxis inhibition (78.5%). Z7R displays promising anti-inflammatory activity (50%) in a mouse edema model by blocking CXCR4-expressed leukocytes, being supported by our immunohistochemistry study.

The Role of Innate Immunity in the Pathogenesis of Breast Cancer

Background

Breast carcinoma is the most common malignant disease in the female population and one of the leading causes of death among women worldwide. One crucial hallmark of cancer is chronic inflammation where the immunosuppressive environment is dominant. The immunosuppressive environment is largely achieved by the interaction of tumor cells and infiltrating leukocytes.

Summary

Usually, human macrophages and natural killer cells are involved in antitumor immunity. The therapeutic potential of this population against cancers has stimulated their study and led to the discovery of several different tumor-associated macrophages and natural killer cell subsets, each of which is endowed with different immunoregulatory functions. Both heterogeneity and plasticity of the tumor-associated macrophages and natural killer cell compartment, which are both tightly linked to the tumor microenvironment of different breast cancer types.

Key Messages

The identification of specific tumor-associated macrophages and natural killer cell subsets endowed with particular functional capabilities might help monitor tumor-mediated responses in breast cancer patients. Currently, one of the most used strategies for breast cancer of newly diagnosed patients is neoadjuvant chemotherapy.

Mouse models of uveal melanoma: Strengths, weaknesses, and future directions

Uveal melanoma is the most common primary malignancy of the eye, and a number of discoveries in the last decade have led to a more thorough molecular characterization of this cancer. However, the prognosis remains dismal for patients with metastases, and there is an urgent need to identify treatments that are effective for this stage of disease. Animal models are important tools for preclinical studies of uveal melanoma. A variety of models exist, and they have specific advantages, disadvantages, and applications. In this review article, these differences are explored in detail, and ideas for new models that might overcome current challenges are proposed.

CXCR4 Antagonists as Stem Cell Mobilizers and Therapy Sensitizers for Acute Myeloid Leukemia and Glioblastoma?

Glioblastoma is the most aggressive and malignant primary brain tumor in adults and has a poor patient survival of only 20 months after diagnosis. This poor patient survival is at least partly caused by glioblastoma stem cells (GSCs), which are slowly-dividing and therefore therapy-resistant. GSCs are localized in protective hypoxic peri-arteriolar niches where these aforementioned stemness properties are maintained. We previously showed that hypoxic peri-arteriolar GSC niches in human glioblastoma are functionally similar to hypoxic peri-arteriolar hematopoietic stem cell (HSC) niches in human bone marrow. GSCs and HSCs express the receptor C-X-C receptor type 4 (CXCR4), which binds to the chemoattractant stromal-derived factor-1α (SDF-1α), which is highly expressed in GSC niches in glioblastoma and HSC niches in bone marrow. This receptor–ligand interaction retains the GSCs/HSCs in their niches and thereby maintains their slowly-dividing state. In acute myeloid leukemia (AML), leukemic cells use the SDF-1α–CXCR4 interaction to migrate to HSC niches and become slowly-dividing and therapy-resistant leukemic stem cells (LSCs). In this communication, we aim to elucidate how disruption of the SDF-1α–CXCR4 interaction using the FDA-approved CXCR4 inhibitor plerixafor (AMD3100) may be used to force slowly-dividing cancer stem cells out of their niches in glioblastoma and AML. Ultimately, this strategy aims to induce GSC and LSC differentiation and their sensitization to therapy.

A benzenesulfonamide derivative as a novel PET radioligand for CXCR4

CXCR4 is involved in various diseases such as inflammation, tumor growth, and cancer metastasis through the interaction with its natural endogenous ligand, chemokine CXCL12. In an effort to develop imaging probes for CXCR4, we developed a novel small molecule CXCR4-targeted PET agent (compound 5) by combining our established benzenesulfonamide scaffold with a labeling component by virtue of click chemistry. 5 shows nanomolar affinity (IC50 = 6.9 nM) against a known CXCR4 antagonist (TN14003) and inhibits more than 65% chemotaxis at 10 nM in vitro assays. Radiofluorinated compound 5 ([18F]5) demonstrates a competitive cellular uptake against CXCL12 in a dose-dependent manner. Further, microPET images of [18F]5 exhibits preferential accumulation of radioactivity in the lesions of λ-carrageenan-induced paw edema, human head and neck cancer orthotopic xenograft, and metastatic lung cancer of each mouse model.

Small molecule and peptide-based CXCR4 modulators as therapeutic agents. A patent review for the period from 2010 to 2018

Introduction: The chemokine receptor CXCR4 has been under intense study due to the central role it plays in immune system regulation and the pathology of many human diseases. The FDA approval of the first CXCR4 antagonist drug Plerixafor (i.e. AMD3100, Mozobil®) ushered in an increase in patent activity covering CXCR4 based therapeutic agents over the past decade.Areas covered: This article describes patent documents published during the period of 2010 through 2018 for both small molecules and peptide-based CXCR4 modulators as therapeutic agents. There is an expansion of intellectual property (IP) around existing and new small molecules of clinical interest, including new chemotypes featuring aromatic and aliphatic heterocycles. There is also significant IP covering peptide-based therapeutics, although about half as many in number as those covering small molecules.Expert opinion: In the last decade there has been significant interest in modulators of the CXCR4 receptor, as gauged by the number of patent filings and clinical investigations targeting this receptor for human disease intervention. Seven of the many CXCR4 modulators described herein, that are currently in human clinical trials, are likely to spur the creation of other FDA approved therapeutics in the near future, most likely as immune and oncology drugs.

CXCL12/CXCR4 signal transduction in diseases and its molecular approaches in targeted-therapy

Chemokines are small molecules called "chemotactic cytokines" and regulate many processes like leukocyte trafficking, homing of immune cells, maturation, cytoskeletal rearrangement, physiology, migration during development, and host immune responses. These proteins bind to their corresponding 7-membrane G-protein-coupled receptors. Chemokines and their receptors are anti-inflammatory factors in autoimmune conditions, so consider as potential targets for neutralization in such diseases. They also express by cancer cells and function as angiogenic factors, and/or survival/growth factors that enhance tumor angiogenesis and development. Among chemokines, the CXCL12/CXCR4 axis has significantly been studied in numerous cancers and autoimmune diseases. CXCL12 is a homeostatic chemokine, which is acts as an anti-inflammatory chemokine during autoimmune inflammatory responses. In cancer cells, CXCL12 acts as an angiogenic, proliferative agent and regulates tumor cell apoptosis as well. CXCR4 has a role in leukocyte chemotaxis in inflammatory situations in numerous autoimmune diseases, as well as the high levels of CXCR4, observed in different types of human cancers. These findings suggest CXCL12/CXCR4 as a potential therapeutic target for therapy of autoimmune diseases and open a new approach to targeted-therapy of cancers by neutralizing CXCL12 and CXCR4. In this paper, we reviewed the current understanding of the role of the CXCL12/CXCR4 axis in disease pathology and cancer biology, and discuss its therapeutic implications in cancer and diseases.

Targeting CXCL12/CXCR4 Axis in Tumor Immunotherapy

Chemokines, which have chemotactic abilities, are comprised of a family of small cytokines with 8-10 kilodaltons. Chemokines work in immune cells by trafficking and regulating cell proliferation, migration, activation, differentiation, and homing. CXCR-4 is an alpha-chemokine receptor specific for stromal-derived-factor-1 (SDF-1, also known as CXCL12), which has been found to be expressed in more than 23 different types of cancers. Recently, the SDF-1/CXCR-4 signaling pathway has emerged as a potential therapeutic target for human tumor because of its critical role in tumor initiation and progression by activating multiple signaling pathways, such as ERK1/2, ras, p38 MAPK, PLC/ MAPK, and SAPK/ JNK, as well as regulating cancer stem cells. CXCL12/CXCR4 antagonists have been produced, which have shown encouraging results in anti-cancer activity. Here, we provide a brief overview of the CXCL12/CXCR4 axis as a molecular target for cancer treatment. We also review the potential utility of targeting CXCL12/CXCR4 axis in combination of immunotherapy and/or chemotherapy based on up-to-date literature and ongoing research progress.

An Agonist of the CXCR4 Receptor Strongly Promotes Regeneration of Degenerated Motor Axon Terminals

The activation of the G-protein coupled receptor CXCR4 by its ligand CXCL12α is involved in a large variety of physiological and pathological processes, including the growth of B cells precursors and of motor axons, autoimmune diseases, stem cell migration, inflammation, and several neurodegenerative conditions. Recently, we demonstrated that CXCL12α potently stimulates the functional recovery of damaged neuromuscular junctions via interaction with CXCR4. This result prompted us to test the neuroregeneration activity of small molecules acting as CXCR4 agonists, endowed with better pharmacokinetics with respect to the natural ligand. We focused on NUCC-390, recently shown to activate CXCR4 in a cellular system. We designed a novel and convenient chemical synthesis of NUCC-390, which is reported here. NUCC-390 was tested for its capability to induce the regeneration of motor axon terminals completely degenerated by the presynaptic neurotoxin α-Latrotoxin. NUCC-390 was found to strongly promote the functional recovery of the neuromuscular junction, as assayed by electrophysiology and imaging. This action is CXCR4 dependent, as it is completely prevented by AMD3100, a well-characterized CXCR4 antagonist. These data make NUCC-390 a strong candidate to be tested in human therapy to promote nerve recovery of function after different forms of neurodegeneration.

Targeted Therapy of Uveal Melanoma: Recent Failures and New Perspectives

Among Uveal Melanoma (UM) driver mutations, those involving GNAQ or GNA11 genes are the most frequent, while a minor fraction of tumors bears mutations in the PLCB4 or CYSLTR2 genes. Direct inhibition of constitutively active oncoproteins deriving from these mutations is still in its infancy in UM, whereas BRAFV600E-targeted therapy has obtained relevant results in cutaneous melanoma. However, UM driver mutations converge on common downstream signaling pathways such as PKC/MAPK, PI3K/AKT, and YAP/TAZ, which are presently considered as actionable targets. In addition, BAP1 loss, which characterizes UM metastatic progression, affects chromatin structure via histone H2A deubiquitylation that may be counteracted by histone deacetylase inhibitors. Encouraging results of preclinical studies targeting signaling molecules such as MAPK and PKC were unfortunately not confirmed in early clinical studies. Indeed, a general survey of all clinical trials applying new targeted and immune therapy to UM displayed disappointing results. This paper summarizes the most recent studies of UM-targeted therapies, analyzing the possible origins of failures. We also focus on hyperexpressed molecules involved in UM aggressiveness as potential new targets for therapy.

Development and Evaluation of an 18F-Radiolabeled Monocyclam Derivative for Imaging CXCR4 Expression

In humans, C-X-C chemokine receptor type 4 (CXCR4) is a protein that is encoded by the CXCR4 gene and binds the ligand CXCL12 (also known as SDF-1). The CXCR4-CXCL12 interaction in cancer elicits biological activities that result in tumor progression and has accordingly been the subject of significant investigation for detection and treatment of the disease. Peptidic antagonists have been labeled with a variety of radioisotopes for the detection of CXCR4, but the methodology utilizing small molecules has predominantly used radiometals. We report here the development of a 18F-radiolabeled cyclam-based small molecule radioprobe, [18F]MCFB, for imaging CXCR4 expression. The IC50 value of [19F]MCFB for CXCR4 was similar to that of AMD3465 (111.3 and 89.8 nM, respectively). In vitro binding assays show that the tracer depicted a differential CXCR4 expression, which was blocked in the presence of AMD3465, demonstrating the specificity of [18F]MCFB. Positron emission tomography (PET) imaging studies showed a distinct uptake of the radioprobe in lymphoma and breast cancer xenografts. High liver and kidney uptakes were seen with [18F]MCFB, leading us to further examine the basis of its pharmacokinetics in relation to the tracer's cationic nature and thus the role of organic cation transporters (OCTs). Substrate competition following the intravenous injection of metformin led to a marked decrease in the urinary excretion of [18F]MCFB, with moderate changes observed in other organs, including the liver. Our results suggest involvement of OCTs in the renal elimination of the tracer. In conclusion, the 18F-radiolabeled monocyclam, [18F]MCFB, has potential to detect tumor CXCR4 in nonhepatic tissues.

Genome-wide analysis of canine oral malignant melanoma metastasis-associated gene expression

Oral malignant melanoma (OMM) is the most common canine melanocytic neoplasm. Overlap between the somatic mutation profiles of canine OMM and human mucosal melanomas suggest a shared UV-independent molecular aetiology. In common with human mucosal melanomas, most canine OMM metastasise. There is no reliable means of predicting canine OMM metastasis, and systemic therapies for metastatic disease are largely palliative. Herein, we employed exon microarrays for comparative expression profiling of FFPE biopsies of 18 primary canine OMM that metastasised and 10 primary OMM that did not metastasise. Genes displaying metastasis-associated expression may be targets for anti-metastasis treatments, and biomarkers of OMM metastasis. Reduced expression of CXCL12 in the metastasising OMMs implies that the CXCR4/CXCL12 axis may be involved in OMM metastasis. Increased expression of APOBEC3A in the metastasising OMMs may indicate APOBEC3A-induced double-strand DNA breaks and pro-metastatic hypermutation. DNA double strand breakage triggers the DNA damage response network and two Fanconi anaemia DNA repair pathway members showed elevated expression in the metastasising OMMs. Cross-validation was employed to test a Linear Discriminant Analysis classifier based upon the RT-qPCR-measured expression levels of CXCL12, APOBEC3A and RPL29. Classification accuracies of 94% (metastasising OMMs) and 86% (non-metastasising OMMs) were estimated.

Development of CXCR4 modulators based on the lead compound RB-108

The CXCR4/CXCL12 axis plays prominent roles in tumor metastasis and inflammation. CXCR4 has been shown to be involved in a variety of inflammation-related diseases. Therefore, CXCR4 is a promising potential target to develop novel anti-inflammatory agents. Taking our previously discovered CXCR4 modulator RB-108 as the lead compound, a series of derivatives were synthesized structurally modifying and optimizing the amide and sulfamide side chains. The derivatives successfully maintained potent CXCR4 binding affinity. Furthermore, compounds IIb, IIc, IIIg, IIIj, and IIIm were all efficacious in inhibiting the invasion of CXCR4-positive cells, displaying a much more potent effect than the lead compound RB-108. Notably, compound IIIm significantly decreased carrageenan-induced swollen volume and paw thickness in a mouse paw edema model. More importantly, IIIm exhibited satisfying PK profiles with a half-life of 4.77 h in an SD rat model. In summary, we have developed compound IIIm as a new candidate for further investigation based on the lead compound RB-108.

Advances in Molecular Mechanisms and Treatment of Radiation-Induced Pulmonary Fibrosis

Radiation-induced pulmonary fibrosis (RIPF) is a common complication in patients with lung cancer and breast cancer after receiving thoracic radiotherapy. The average incidence of RIPF is 16%-28% after radiotherapy. RIPF includes a heterogeneous group of lung disorders characterized by progressive and irreversible destruction of lung architecture and disruption of gas exchange. The clinical signs of RIPF include increasing dyspnea, deteriorating lung function, and accumulation of interstitial fluid, eventually leading to respiratory failure. No medical therapy for RIPF has been approved for routine clinical use despite the apparent need for an effective treatment. Numerous signaling pathways are involved in the initiation and progression of RIPF. Also, various approaches for RIPF treatments have focused on several aspects of the current understanding of the molecular pathology of RIPF. This review used the mechanistic categories of associated cell signaling pathways, epithelial cell dysfunction and senescence, abnormal lung remodeling, and aberrant innate and adaptive immunity to review the published literature on RIPF to date and then to identify potential areas for the effective treatment of RIPF.

CXCR4-directed theranostics in oncology and inflammation

Given its prominent role in inflammation and cancer biology, the C-X-C motif chemokine receptor 4 (CXCR4) has gained a lot of attention in the recent years. This review gives a short overview of the physiology and pathology of chemokines and chemokine receptors and then focuses on the current experience of targeting CXCR4, using radiolabeled receptor ligands suitable for positron emission tomography (PET) imaging, in both hematologic and solid malignancy as well as in inflammatory conditions. Additionally, CXCR4-directed endoradiotherapy (ERT) as a new treatment option is discussed.

Small molecule CXCR4 antagonists block the HIV-1 Nef/CXCR4 axis and selectively initiate the apoptotic program in breast cancer cells

The chemokine receptor CXCR4 plays an integral role in the development of highly metastatic breast cancer and in the pathogenesis of chronic HIV infection. In this study, we compared the effects of CXCR4 antagonists on apoptosis induction in hematopoietic cells and in tumor cells. We incubated cells expressing CXCR4 with a series of CXCR4 antagonists and subsequently exposed the cultures to a pro-apoptotic peptide derived from the HIV-1 Nef protein (NefM1). The NefM1 peptide contains residues 50-60 of Nef and was previously shown to be the sequence necessary for Nef to initiate the apoptotic program through CXCR4 signaling. We found that several of the compounds studied potently blocked Nef-induced apoptosis in Jurkat T-lymphocyte cells. Interestingly, many of the same compounds selectively triggered apoptosis in MDA-MB-231 breast cancer cells, in some cases at sub-nanomolar concentrations. None of the compounds were toxic to lymphocyte, monocyte or macrophage cells, suggesting that aggressive breast cancer carcinomas may be selectively targeted and eliminated using CXCR4-based therapies without additional cytotoxic agents. Our results also demonstrate that not all CXCR4 antagonists are alike and that the observed anti-Nef and pro-apoptotic effects are chemically tunable. Collectively, these findings suggest our CXCR4 antagonists have promising clinical utility for HIV or breast cancer therapies as well as being useful probes to examine the link between CXCR4 and apoptosis.

PET and SPECT imaging of melanoma: the state of the art

Melanoma represents the most aggressive form of skin cancer, and its incidence continues to rise worldwide. 18F-FDG PET imaging has transformed diagnostic nuclear medicine and has become an essential component in the management of melanoma, but still has its drawbacks. With the rapid growth in the field of nuclear medicine and molecular imaging, a variety of promising probes that enable early diagnosis and detection of melanoma have been developed. The substantial preclinical success of melanin- and peptide-based probes has recently resulted in the translation of several radiotracers to clinical settings for noninvasive imaging and treatment of melanoma in humans. In this review, we focus on the latest developments in radiolabeled molecular imaging probes for melanoma in preclinical and clinical settings, and discuss the challenges and opportunities for future development.

The good and bad faces of the CXCR4 chemokine receptor

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

An update on small molecules targeting CXCR4 as starting points for the development of anti-cancer therapeutics

CXCR4 (C-X-C Chemokine Receptor type 4) and its natural ligand SDF-1α (Stromal-Derived-Factor-1α) are involved in a number of physiological and pathological processes including cancer spread and progression. Over the past few years, numerous CXCR4 antagonists have been identified and currently are in different development stages as potential agents for the treatment of several diseases involving the CXCR4/SDF-1α axis. Herein, we focus on small molecules reported in literature between 2013 and 2017, claimed as CXCR4 antagonists and potentially useful in the treatment of cancer and other diseases where this receptor is involved. Most of the compounds resulted from a chemical optimization of previously identified molecules and some of them could represent suitable candidates for the development of advanced anticancer agents.

Inhibition of CXCL12/CXCR4 axis as a potential targeted therapy of advanced gastric carcinoma

The whole outcome for patients with gastric carcinoma (GC) is very poor because most of them remain metastatic disease during survival even at diagnosis or after surgery. Despite many improvements in multiple strategies of chemotherapy, immunotherapy, and targeted therapy, exploration of novel alternative therapeutic targets is still warranted. Chemokine receptor 4 (CXCR4) and its chemokine ligand 12 (CXCL12) have been identified with significantly elevated levels in various malignancies including GC, which correlates with the survival, proliferation, angiogenesis, and metastasis of tumor cells. Increasing experimental evidence suggests an implication of inhibition of CXCL12/CXCR4 axis as a promising targeted therapy, although there are rare trials focused on the therapeutic efficacy of CXCR4 inhibitors in GC until recently. Therefore, it is reasonable to infer that specific antagonists or antibodies targeting CXCL12/CXCR4 axis alone or combined with chemotherapy will be effective and worthy of further translational studies as a potential treatment strategy in advanced GC.