The significance of cancer cell expression of the chemokine receptor CXCR4

Monoclonal Antibody Therapies for Hematological Malignancies: Not Just Lineage-Specific Targets

Today, monoclonal antibodies (mAbs) are a widespread and necessary tool for biomedical science. In the hematological cancer field, since rituximab became the first mAb approved by the Food and Drug Administration for the treatment of B-cell malignancies, a number of effective mAbs targeting lineage-specific antigens (LSAs) have been successfully developed. Non-LSAs (NLSAs) are molecules that are not restricted to specific leukocyte subsets or tissues but play relevant pathogenic roles in blood cancers including the development, proliferation, survival, and refractoriness to therapy of tumor cells. In consequence, efforts to target NLSAs have resulted in a plethora of mAbs-marketed or in development-to achieve different goals like neutralizing oncogenic pathways, blocking tumor-related chemotactic pathways, mobilizing malignant cells from tumor microenvironment to peripheral blood, modulating immune-checkpoints, or delivering cytotoxic drugs into tumor cells. Here, we extensively review several novel mAbs directed against NLSAs undergoing clinical evaluation for treating hematological malignancies. The review focuses on the structure of these antibodies, proposed mechanisms of action, efficacy and safety profile in clinical studies, and their potential applications in the treatment of hematological malignancies.

Agonist-induced CXCR4 and CB2 Heterodimerization Inhibits Gα13/RhoA-mediated Migration

G-protein-coupled receptor (GPCR) heterodimerization has emerged as a means by which alternative signaling entities can be created; yet, how receptor heterodimers affect receptor pharmacology remains unknown. Previous observations suggested a biochemical antagonism between GPCRs, CXCR4 and CB2 (CNR2), where agonist-bound CXCR4 and agonist-bound CB2 formed a physiologically nonfunctional heterodimer on the membrane of cancer cells, inhibiting their metastatic potential in vitro However, the reduced signaling entities responsible for the observed functional outputs remain elusive. This study now delineates the signaling mechanism whereby heterodimeric association between CXCR4 and CB2, induced by simultaneous agonist treatment, results in decreased CXCR4-mediated cell migration, invasion, and adhesion through inhibition of the Gα13/RhoA signaling axis. Activation of CXCR4 by its cognate ligand, CXCL12, stimulates Gα13 (GNA13), and subsequently, the small GTPase RhoA, which is required for directional cell migration and the metastatic potential of cancer cells. These studies in prostate cancer cells demonstrate decreased protein expression levels of Gα13 and RhoA upon simultaneous CXCR4/CB2 agonist stimulation. Furthermore, the agonist-induced heterodimer abrogated RhoA-mediated cytoskeletal rearrangement resulting in the attenuation of cell migration and invasion of an endothelial cell barrier. Finally, a reduction was observed in the expression of integrin α5 (ITGA5) upon heterodimerization, supported by decreased cell adhesion to extracellular matrices in vitro Taken together, the data identify a novel pharmacologic mechanism for the modulation of tumor cell migration and invasion in the context of metastatic disease.Implications: This study investigates a signaling mechanism by which GPCR heterodimerization inhibits cancer cell migration. Mol Cancer Res; 16(4); 728-39. ©2018 AACR.

Biomarker discovery for renal cancer stem cells

Characterised by high intra- and inter-tumor heterogeneity, metastatic renal cell carcinoma (RCC) is resistant to chemo- and radiotherapy. Therefore, the development of new prognostic and diagnostic markers for RCC patients is needed. Cancer stem cells (CSCs) are a small population of neoplastic cells within a tumor which present characteristics reminiscent of normal stem cells. CSCs are characterised by unlimited cell division, maintenance of the stem cell pool (self-renewal), and capability to give rise to all cell types within a tumor; and contribute to metastasis in vivo (tumourigenicity), treatment resistance and recurrence. So far, many studies have tried to establish unique biomarkers to identify CSC populations in RCC. At the same time, different approaches have been developed with the aim to isolate CSCs. Consequently, several markers were found to be specifically expressed in CSCs and cancer stem-like cells derived from RCC such as CD105, ALDH1, OCT4, CD133, and CXCR4. However, the contribution of genetic and epigenetic mechanisms, and tumor microenvironment, to cellular plasticity have made the discovery of unique biomarkers a very difficult task. In fact, contrasting results regarding the applicability of such markers to the isolation of renal CSCs have been reported in the literature. Therefore, a better understanding of the mechanism underlying CSC may help dissecting tumor heterogeneity and drug treatment efficiency.

Inhibitors of HIF-1α and CXCR4 Mitigate the Development of Radiation Necrosis in Mouse Brain

PURPOSE

There is mounting evidence that, in addition to angiogenesis, hypoxia-induced inflammation via the hypoxia-inducible factor 1α (HIF-1α)-CXC chemokine receptor 4 (CXCR4) pathway may contribute to the pathogenesis of late-onset, irradiation-induced necrosis. This study investigates the mitigative efficacy of an HIF-1α inhibitor, topotecan, and a CXCR4 antagonist, AMD3100, on the development of radiation necrosis (RN) in an intracranial mouse model.

METHODS AND MATERIALS

Mice received a single-fraction, 50-Gy dose of hemispheric irradiation from the Leksell Gamma Knife Perfexion and were then treated with either topotecan, an HIF-1α inhibitor, from 1 to 12 weeks after irradiation, or AMD3100, a CXCR4 antagonist, from 4 to 12 weeks after irradiation. The onset and progression of RN were monitored longitudinally via noninvasive, in vivo magnetic resonance imaging (MRI) from 4 to 12 weeks after irradiation. Conventional hematoxylin-eosin staining and immunohistochemistry staining were performed to evaluate the treatment response.

RESULTS

The progression of brain RN was significantly mitigated for mice treated with either topotecan or AMD3100 compared with control animals. MRI-derived lesion volumes were significantly smaller for both of the treated groups, and histologic findings correlated well with the MRI data. By hematoxylin-eosin staining, both treated groups demonstrated reduced irradiation-induced tissue damage compared with controls. Furthermore, immunohistochemistry results revealed that expression levels of vascular endothelial growth factor, CXC chemokine ligand 12, CD68, CD3, and tumor necrosis factor α in the lesion area were significantly lower in treated (topotecan or AMD3100) brains versus control brains, while ionized calcium-binding adapter molecule 1 (Iba1) and HIF-1α expression was similar, though somewhat reduced. CXCR4 expression was reduced only in topotecan-treated mice, while interleukin 6 expression was unaffected by either topotecan or AMD3100.

CONCLUSIONS

By reducing inflammation, both topotecan and AMD3100 can, independently, mitigate the development of RN in the mouse brain. When combined with first-line, antiangiogenic treatment, anti-inflammation therapy may provide an adjuvant therapeutic strategy for clinical, postirradiation management of tumors, with additional benefits in the mitigation of RN development.

Engineering multifunctional protein nanoparticles by in vitro disassembling and reassembling of heterologous building blocks

The engineering of protein self-assembling at the nanoscale allows the generation of functional and biocompatible materials, which can be produced by easy biological fabrication. The combination of cationic and histidine-rich stretches in fusion proteins promotes oligomerization as stable protein-only regular nanoparticles that are composed by a moderate number of building blocks. Among other applications, these materials are highly appealing as tools in targeted drug delivery once empowered with peptidic ligands of cell surface receptors. In this context, we have dissected here this simple technological platform regarding the controlled disassembling and reassembling of the composing building blocks. By applying high salt and imidazole in combination, nanoparticles are disassembled in a process that is fully reversible upon removal of the disrupting agents. By taking this approach, we accomplish here the in vitro generation of hybrid nanoparticles formed by heterologous building blocks. This fact demonstrates the capability to generate multifunctional and/or multiparatopic or multispecific materials usable in nanomedical applications.

Cyclotides, a versatile ultrastable micro-protein scaffold for biotechnological applications

Cyclotides are fascinating microproteins (≈30-40 residues long) with a unique head-to-tail cyclized backbone, stabilized by three disulfide bonds forming a cystine knot. This unique topology makes them exceptionally stable to chemical, thermal and biological degradation compared to other peptides of similar size. Cyclotides have been also found to be highly tolerant to sequence variability, aside from the conserved residues forming the cystine knot, able to cross cellular membranes and modulate intracellular protein-protein interactions both in vitro and in vivo. These properties make them ideal scaffolds for many biotechnological applications. This article provides and overview of the properties of cyclotides and their applications as molecular imaging agents and peptide-based therapeutics.

The Role of Chemokines in Thyroid Carcinoma

The global incidence of thyroid cancer is increasing, and metastatic spread to the lymph nodes is common in papillary thyroid carcinoma. The metastatic course of thyroid carcinoma is an intricate process involving invasion, angiogenesis, cell trafficking, extravasation, organ specific homing, and growth. A key aspect in this process involves a multitude of interactions between chemokines and their receptors. Chemokines are a group of small proteins, which act to elicit normal physiologic and immune responses principally through recruitment of specific cell populations to the site of infection or malignancy. Thyroid cancer cells, like other tumors, possess the ability to corrupt the chemokine system to their advantage by altering cell movement into the tumor microenvironment and affecting all aspects of thyroid cancer progression.

In vivo Evaluation of an Engineered Cyclotide as Specific CXCR4 Imaging Reagent

The CXCR4 chemokine receptor plays a key regulatory role in many biological functions, including embryonic development and controlling leukocyte functions during inflammation and immunity. CXCR4 has been also associated with multiple types of cancers where its overexpression/activation promotes metastasis, angiogenesis, and tumor growth and/or survival. Furthermore, CXCR4 is involved in HIV replication, as it is a co-receptor for viral entry into host cells. Altogether, these features make CXCR4 a very attractive target for the development of imaging and therapeutic agents. Here, the in vivo evaluation of the MCoTI-based cyclotide, MCo-CVX-5c, for the development of imaging agents that target CXCR4 is reported. Cyclotide MCo-CVX-5c is a potent CXCR4 antagonist with a remarkable in vivo resistance to biological degradation in serum. A [64 Cu]-DOTA-labeled version of this cyclotide demonstrated high and significant uptake in U87-stb-CXCR4 tumors compared to the control U87 tumors. Furthermore, protracted imaging studies demonstrated radiotracer retention in the U87-stb-CXCR4 tumor at 24 h post injection. Uptake in U87-stb-CXCR4 tumors could be blocked by unlabeled MCo-CVX-5c, showing high in vivo specificity. These results demonstrate the in vivo specificity and retention of a bioactive molecularly targeted cyclotide and highlight the potential of bioactive cyclotides for the development of new imaging agents that target CXCR4.

The immune system in cancer metastasis: friend or foe?

Metastatic disease is the leading cause of death among cancer patients and involves a complex and inefficient process. Every step of the metastatic process can be rate limiting and is influenced by non-malignant host cells interacting with the tumor cell. Over a century ago, experiments first indicated a link between the immune system and metastasis. This phenomenon, called concomitant immunity, indicates that the primary tumor induces an immune response, which may not be sufficient to destroy the primary tumor, but prevents the growth of a secondary tumor or metastases. Since that time, many different immune cells have been shown to play a role in both inhibiting and promoting metastatic disease. Here we review classic and new observations, describing the links between the immune system and metastasis that inform the development of cancer therapies.

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.

Imaging CXCR4 Expression with (99m)Tc-Radiolabeled Small-Interference RNA in Experimental Human Breast Cancer Xenografts

PURPOSE

Noninvasive quantification of chemokine receptor 4 (CXCR4) expression could serve as a prognostic indicator and may be of value for the design of personalized therapies and posttreatment monitoring. The objective of the present study was to assess the use of (99m)Tc-radiolabeled small-interference RNA (siRNA) targeting CXCR4 to detect CXCR4 expression in vivo.

PROCEDURES

CXCR4 siRNAs were radiolabeled with (99m)Tc using the bifunctional chelator hydrazinonicotinamide (HYNIC), and the labeling efficiency, specific activity and radiochemical purity were determined. The stability of the probe in serum was assessed by measuring its radiochemical purity and inhibitory activity by RT-PCR and western blotting. Biodistribution studies and static imaging were performed in MDA-MB-231 tumor-bearing mice.

RESULTS

Radiochemical purity remained highly stable in PBS and fresh human serum at room temperature and at 37 °C. Radiolabeled siRNA1 showed strong inhibitory effects similar to those of unlabeled siRNA1 on both CXCR4 messenger RNA (mRNA) and protein in vitro. The excretion of the probe occurred mainly through the liver and kidneys. Tumors were clearly visualized at 1-10 h after injection of the probe, but not after injection of the control probe.

CONCLUSIONS

(99m)Tc-labeled CXCR4 siRNA1 shows tumor-specific accumulation and could be a promising strategy for the visualization of CXCR4 expression in human breast cancer.

Targeting the CXCR4/CXCL12 axis in treating epithelial ovarian cancer

Ovarian carcinoma is the most crucial and difficult target for available therapeutic treatments among gynecological malignancies, and great efforts are required to find an effective solution. Molecular studies showed that the chemokine stromal cell-derived factor-1 (also known as CXCL12) and its receptor, CXCR4, are key determinants of tumor initiation, progression and metastasis in ovarian carcinomas. Hence, it is generally believed that blocking the CXCR4/CXCL12 pathway could serve as a potential therapy for patients with ovarian cancer. Herein, we investigated the role of the CXCR4/CXCL12 axis in regulating ovarian cancer progression. Using flow cytometry, a real-time PCR and western blot analyses, we showed that the chemokine receptor CXCR4 protein and mRNA were overexpressed in human epithelial ovarian cancer cell lines, and these were closely correlated with poor outcomes. Moreover, silencing CXCR4 by small hairpin RNA in HTB75 cells reduced cell proliferation, migration and invasion and significantly reduced RhoA and Rac-1/Cdc42 expressions, whereas overexpression of CXCR4 in SKOV3 cells significantly increased cell migration and markedly increased RhoA, Rac-1/Cdc42 levels. Silencing CXCR4 also led to decreased in vitro cytotoxicity of AMD3100, a specific antagonist of CXCR4, which exerts its effect upon CXCR4 expression. Remarkably, knockdown of CXCR4 in HTB75 cells led to a significantly decreased capability to form tumors in vivo, and the Ki67 proliferation index of xenograft tumors showed a dramatic reduction. Our results revealed that the CXCR4/CXCL12 pathway represents a promising therapeutic target for epithelial ovarian carcinoma.

Targeting the CXCR4/CXCL12 axis with the peptide antagonist E5 to inhibit breast tumor progression

Emerging evidence has demonstrated that stromal cell-derived factor 1 (SDF-1) and its cognate receptor CXCR4 have critical roles in tumorigenesis, angiogenesis and metastasis. In this study, we demonstrated the significant inhibitory effects of a novel chemically synthetic peptide (E5) on the CXCR4/CXCL12 axis in breast cancer both in vitro and in vivo. E5 was capable of specifically binding to the murine breast cancer cell line 4T1, remarkably inhibiting CXCL12- or stromal cell (MS-5)-induced migration, and adhesion and sensitizing 4T1 cells to multiple chemotherapeutic drugs. Furthermore, E5 combined with either paclitaxel or cyclophosphamide significantly inhibited tumor growth in a breast cancer model. Mechanistic studies implied that E5 can inhibit the expression of CXCR4 to block the CXCL12-mediated recruitment of endothelial progenitor cells and repress CXCR4 downstream of the Akt and Erk signaling pathway, which are involved in tumor angiogenesis and progression. Further pharmacokinetic evaluation suggested that E5 has an acceptable stability, with a half-life of 10 h in healthy mice. In conclusion, E5 demonstrates a promising anti-tumor effect and could be a potential chemotherapeutic sensitizer to improve current clinical breast cancer therapies.

Anti-tumor activity of nanomicelles encapsulating CXCR4 peptide antagonist E5

Cancer is the leading cause of death worldwide, and metastasis is the main attribute to cancer death. CXCR4 and its natural ligand CXCL12 have been known to play a critical role in tumorigenesis, angiogenesis and metastasis. Therefore, designing a new CXCR4 antagonist to prevent tumor metastasis will be of great significance. Herein, a novel chemically synthesized peptide (E5) that has an ability to target CXCR4/CXCL12 axis was loaded in micelle glycol-phosphatidylethanolamine (PEG-PE) block copolymer to form micelle-encapsulated E5 (M-E5). We demonstrated that M-E5 exhibited higher affinity for CXCR4-overexpressing MCF-7 and HepG2 tumor cells as compared to free E5, and efficiently inhibited the tumor cells migration. Mechanistic studies implied that PEG-PE micelle can encapsulate E5 and improve E5 targeting efficiency for CXCR4 by accumulating E5 on the tumor cell membrane. Furthermore, through encapsulation of chemotherapeutic drug doxorubicin (Dox) in PEG-PE micelle, we proved that PEG-PE micelle could serve as a co-carrier for both E5 and Dox (M-E5-Dox). M-E5 enhanced the efficiency of Dox by down-regulating the phosphorylation level of Akt, Erk and p38/MAPK proteins. In conclusion, PEG-PE micelle demonstrated a promising delivery system for E5, and M-E5 is expected to be a potential therapeutic agent that will help to improve the clinical benefits in current therapies used for solid tumors.

Identification and expression analysis of <i>miR-144-5p</i> and <i>miR-130b-5p</i> in dairy cattle

Abstract. MicroRNAs (miRNAs) can coordinate the main pathways involved in innate and adaptive immune responses by regulating gene expression. To explore the resistance to mastitis in cows, miR-144-5p and miR-130b-5p were identified in bovine mammary gland tissue and 14 potential target genes belonging to the chemokine signaling pathway, the arginine and proline metabolism pathway and the mRNA surveillance pathway were predicted. Subsequently, we estimated the relative expression of miR-144-5p and miR-130b-5p in cow mammary tissues by using stem-loop quantitative real-time polymerase chain reaction. The results showed that the relative expression of miR-144-5p and miR-130b-5p in the mastitis-infected mammary tissues (n = 5) was significantly downregulated 0.14-fold (p < 0. 01) and upregulated 3.34-fold (p < 0. 01), respectively, compared to healthy tissues (n = 5). Our findings reveal that miR-144-5p and miR-130b-5p may have important roles in resistance to mastitis in dairy cattle.

Cyclotides: Overview and Biotechnological Applications

Cyclotides are globular microproteins with a unique head-to-tail cyclized backbone, stabilized by three disulfide bonds forming a cystine knot. This unique circular backbone topology and knotted arrangement of three disulfide bonds makes them exceptionally stable to chemical, thermal, and biological degradation compared to other peptides of similar size. In addition, cyclotides have been shown to be highly tolerant to sequence variability, aside from the conserved residues forming the cystine knot. Cyclotides can also cross cellular membranes and are able to modulate intracellular protein-protein interactions, both in vitro and in vivo. All of these features make cyclotides highly promising as leads or frameworks for the design of peptide-based diagnostic and therapeutic tools. This article provides an overview on cyclotides and their applications as molecular imaging agents and peptide-based therapeutics.

Targeting the CXCR4 pathway using a novel anti-CXCR4 IgG1 antibody (PF-06747143) in chronic lymphocytic leukemia

BACKGROUND

The CXCR4-CXCL12 axis plays an important role in the chronic lymphocytic leukemia (CLL)-microenvironment interaction. Overexpression of CXCR4 has been reported in different hematological malignancies including CLL. Binding of the pro-survival chemokine CXCL12 with its cognate receptor CXCR4 induces cell migration. CXCL12/CXCR4 signaling axis promotes cell survival and proliferation and may contribute to the tropism of leukemia cells towards lymphoid tissues and bone marrow. Therefore, we hypothesized that targeting CXCR4 with an IgG1 antibody, PF-06747143, may constitute an effective therapeutic approach for CLL.

METHODS

Patient-derived primary CLL-B cells were assessed for cytotoxicity in an in vitro model of CLL microenvironment. PF-06747143 was analyzed for cell death induction and for its potential to interfere with the chemokine CXCL12-induced mechanisms, including migration and F-actin polymerization. PF-06747143 in vivo efficacy was determined in a CLL murine xenograft tumor model.

RESULTS

PF-06747143, a novel-humanized IgG1 CXCR4 antagonist antibody, induced cell death of patient-derived primary CLL-B cells, in presence or absence of stromal cells. Moreover, cell death induction by the antibody was independent of CLL high-risk prognostic markers. The cell death mechanism was dependent on CXCR4 expression, required antibody bivalency, involved reactive oxygen species production, and did not require caspase activation, all characteristics reminiscent of programmed cell death (PCD). PF-06747143 also induced potent B-CLL cytotoxicity via Fc-driven antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity activity (CDC). PF-06747143 had significant combinatorial effect with standard of care (SOC) agents in B-CLL treatment, including rituximab, fludarabine (F-ara-A), ibrutinib, and bendamustine. In a CLL xenograft model, PF-06747143 decreased tumor burden and improved survival as a monotherapy, and in combination with bendamustine.

CONCLUSIONS

We show evidence that PF-06747143 has biological activity in CLL primary cells, supporting a rationale for evaluation of PF-06747143 for the treatment of CLL patients.

Molecular imaging probes derived from natural peptides

Covering: up to the end of 2015.Peptides are naturally occurring compounds that play an important role in all living systems and are responsible for a range of essential functions. Peptide receptors have been implicated in disease states such as oncology, metabolic disorders and cardiovascular disease. Therefore, natural peptides have been exploited as diagnostic and therapeutic agents due to the unique target specificity for their endogenous receptors. This review discusses a variety of natural peptides highlighting their discovery, endogenous receptors, as well as their derivatization to create molecular imaging agents, with an emphasis on the design of radiolabelled peptides. This review also highlights methods for discovering new and novel peptides when knowledge of specific targets and endogenous ligands are not available.

Targeting the CXCR4 pathway using a novel anti-CXCR4 IgG1 antibody (PF-06747143) in chronic lymphocytic leukemia

BACKGROUND

The CXCR4-CXCL12 axis plays an important role in the chronic lymphocytic leukemia (CLL)-microenvironment interaction. Overexpression of CXCR4 has been reported in different hematological malignancies including CLL. Binding of the pro-survival chemokine CXCL12 with its cognate receptor CXCR4 induces cell migration. CXCL12/CXCR4 signaling axis promotes cell survival and proliferation and may contribute to the tropism of leukemia cells towards lymphoid tissues and bone marrow. Therefore, we hypothesized that targeting CXCR4 with an IgG1 antibody, PF-06747143, may constitute an effective therapeutic approach for CLL.

METHODS

Patient-derived primary CLL-B cells were assessed for cytotoxicity in an in vitro model of CLL microenvironment. PF-06747143 was analyzed for cell death induction and for its potential to interfere with the chemokine CXCL12-induced mechanisms, including migration and F-actin polymerization. PF-06747143 in vivo efficacy was determined in a CLL murine xenograft tumor model.

RESULTS

PF-06747143, a novel-humanized IgG1 CXCR4 antagonist antibody, induced cell death of patient-derived primary CLL-B cells, in presence or absence of stromal cells. Moreover, cell death induction by the antibody was independent of CLL high-risk prognostic markers. The cell death mechanism was dependent on CXCR4 expression, required antibody bivalency, involved reactive oxygen species production, and did not require caspase activation, all characteristics reminiscent of programmed cell death (PCD). PF-06747143 also induced potent B-CLL cytotoxicity via Fc-driven antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity activity (CDC). PF-06747143 had significant combinatorial effect with standard of care (SOC) agents in B-CLL treatment, including rituximab, fludarabine (F-ara-A), ibrutinib, and bendamustine. In a CLL xenograft model, PF-06747143 decreased tumor burden and improved survival as a monotherapy, and in combination with bendamustine.

CONCLUSIONS

We show evidence that PF-06747143 has biological activity in CLL primary cells, supporting a rationale for evaluation of PF-06747143 for the treatment of CLL patients.

Immunological effects of vaccines combined with granulocyte colony-stimulating factor on a murine WEHI-3 leukemia model

Granulocyte colony-stimulating factor (G-CSF) mobilizes regulatory T cells (Tregs) from bone marrow into the peripheral blood, by reducing the expression of stromal cell-derived factor-1α (SDF-1α). However, G-CSF has rarely been studied in acute myeloid leukemia (AML) immunotherapy. The present study performed a Transwell migration assay in vitro to determine the contribution of SDF-1α to the migration of leukemia cells, and the effects of G-CSF were evaluated. The effects of G-CSF on SDF-1α and Tregs in the AML microenvironment were examined, by employing a WEHI-3-grafted BALB/c mouse AML model (AML-M4). It is evident that G-CSF reversed immunosuppression of the AML microenvironment by reducing SDF-1α in bone marrow and elevating Tregs in the peripheral blood in in vivo studies. Furthermore, AML mice treated with vaccines combined with G-CSF achieved a longer survival time than those treated with vaccines without G-CSF, showing the efficiency of the regimen. The present study demonstrates the effects of G-CSF on the mobilization of leukemia cells and Tregs into the peripheral blood. In addition, immunotherapy with G-CSF priming represents a promising therapeutic strategy of targeting the immunosuppression.

Comparison of cell-based assays for the identification and evaluation of competitive CXCR4 inhibitors

The chemokine receptor CXCR4 is activated by its unique chemokine ligand CXCL12 and regulates many physiological and developmental processes such as hematopoietic cell trafficking. CXCR4 is also one of the main co-receptors for human immunodeficiency virus (HIV) entry. Dysfunction of the CXCL12/CXCR4 axis contributes to several human pathologies, including cancer and inflammatory diseases. Consequently, inhibition of CXCR4 activation is recognized as an attractive target for therapeutic intervention. In this regard, numerous agents modifying CXCR4 activity have been evaluated in in vitro experimental studies and pre-clinical models. Here, we evaluated a CXCL12 competition binding assay for its potential as a valuable initial screen for functional and competitive CXCR4 inhibitors. In total, 11 structurally diverse compounds were included in a side-by-side comparison of in vitro CXCR4 cell-based assays, such as CXCL12 competition binding, CXCL12-induced calcium signaling, CXCR4 internalization, CXCL12-guided cell migration and CXCR4-specific HIV-1 replication experiments. Our data indicated that agents that inhibit CXCL12 binding, i.e. the anti-CXCR4 peptide analogs T22, T140 and TC14012 and the small molecule antagonists AMD3100, AMD3465, AMD11070 and IT1t showed inhibitory activity with consistent relative potencies in all further applied CXCR4-related assays. Accordingly, agents exerting no or very weak receptor binding (i.e., CTCE-9908, WZ811, Me6TREN and gambogic acid) showed no or very poor anti-CXCR4 inhibitory activity. Thus, CXCL12 competition binding studies were proven to be highly valuable as an initial screening assay and indicative for the pharmacological and functional profile of competitive CXCR4 antagonists, which will help the design of new potent CXCR4 inhibitors.

DC - SIGNR by influencing the lncRNA HNRNPKP2 upregulates the expression of CXCR4 in gastric cancer liver metastasis

Background

Profiling evidences of selectin demonstrate that they play an crucial role in cancer progression and metastasis. However, DC-SIGNR as a family member of selectin participates in gastric cancer liver metastasis remains unknown.

Methods

The serum level of DC-SIGNR was evaluated in gastric cancer patients by ELISA. Manipulation DC-SIGNR expression in BGC823 and SGC7901 cell lines was mediated by lentivirus. Investigation the biological effects of DC-SIGNR were verified by MTT, wounding and transwell in vitro and experiments on animals to confirm gastric cancer liver metastasis by IVIS. Insights of the mechanism were employed microarray and bioinformatic analysis. Further to confirm the results were conducted by qRT-PCR, western blot and by flow cytometry.

Results

DC-SIGNR serum level was significantly increased in gastric cancer patients compared with healthy group. Additionally, DC-SIGNR level was associated with an advanced pathological stage in gastric cancer patients. DC-SIGNR knockdown inhibited the proliferation, migration and invasion of gastric cancer cells in vitro and suppressed the liver metastasis in vivo. While, DC-SIGNR overexpression promoted cell proliferation, migration and invasion. In mechanism, HNRNPKP2 as a lncRNA was upregulated after DC-SIGNR knockdown. Importantly, STAT5A promoted HNRNPKP2 expression after knockdown DC-SIGNR. Furthermore after HNRNPKP2 depletion, the downstream target gene CXCR4 was downregulated.

Conclusions

DC-SIGNR promoted gastric cancer liver metastasis mediated with HNRNPKP2 which expression was regulated by STAT5A. And HNRNPKP2 decreased the expression of downstream target gene CXCR4. These findings indicated potential therapeutic candidates for gastric cancer liver metastasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0639-2) contains supplementary material, which is available to authorized users.

Efficacy of Omega Fatty Acid Supplementation on mRNA Expression Level of Tumor Necrosis Factor Alpha in Patients with Gastric Adenocarcinoma

PURPOSE

Tumor necrosis factor alpha (TNF-α), a multifunctional cytokine, is involved in apoptosis, cell proliferation, cell survival, and inflammation. It plays a dual role in cancer development and progression. It has been revealed that polyunsaturated fatty acids (PUFAs) modulate the production and activity of TNF family cytokines. The objective of the present study was to evaluate the effect of PUFAs on messenger RNA expression levels of TNF-α in patients with gastric adenocarcinoma.

METHODS

Thirty-four chemotherapy-naive patients diagnosed with gastric adenocarcinoma were randomly divided into two groups. The first group (17 individuals) received cisplatin without supplements and the second group (17 individuals) received cisplatin plus orally administered PUFA supplements for 3 weeks, based on treatment strategies. The gastric biopsy samples were obtained from all participants before and after treatment, and TNF-α mRNA expression levels were evaluated by quantitative real-time PCR procedure.

RESULTS

Our findings revealed that TNF-α mRNA expression is downregulated in group II, after receiving cisplatin and omega fatty acid supplement for 3 weeks. However, this difference is not statistically significant (p > 0.05). TNF-α mRNA expression did not show significant alteration in group I, after receiving cisplatin alone.

CONCLUSIONS

Taken together, we concluded that omega fatty acids reduce TNF-α expression at the mRNA level in patients with gastric adenocarcinoma. These data suggest that TNF-α may act as a potential target for the therapy of human gastric adenocarcinoma.

5T4 oncofoetal antigen: an attractive target for immune intervention in cancer

The natural history of a patient's cancer is often characterised by genetic diversity and sequential sweeps of clonal dominance. It is therefore not surprising that identifying the most appropriate tumour-associated antigen for targeted intervention is challenging. The 5T4 oncofoetal antigen was identified by searching for surface molecules shared between human trophoblast and cancer cells with the rationale that they may function to allow survival of the foetus as a semi-allograft in the mother or a tumour in its host. The 5T4 protein is expressed by many different cancers but rarely in normal adult tissues. 5T4 molecules are 72 kD, heavily N-glycosylated proteins with several leucine-rich repeats which are often associated with protein-protein interactions. 5T4 expression is associated with the directional movement of cells through epithelial mesenchymal transition, potentiation of CXCL12/CXCR4 chemotaxis and inhibition of canonical Wnt/beta-catenin while favouring non-canonical pathway signalling; all processes which help drive the spread of cancer cells. The selective pattern of 5T4 tumour expression, association with a tumour-initiating phenotype plus a mechanistic involvement with cancer spread have underwritten the clinical development of different immunotherapeutic strategies including a vaccine, a tumour-targeted superantigen and an antibody drug conjugate. In addition, a chimeric antigen receptor T cell approach targeting 5T4 expressing tumour cells is in pre-clinical development. A key challenge will include how best to combine each 5T4 targeted immunotherapy with the most appropriate standard of care treatment (or adjunct therapy) to maximise the recovery of immune control and ultimately eliminate the tumour.

CCR7 and CXCR4 Expression in Primary Head and Neck Squamous Cell Carcinomas and Nodal Metastases – a Clinical and Immunohistochemical Study

Background: Squamous cell carcinomas (SCCs) are common head and neck malignancies demonstrating lymph node LN involvement. Recently chemokine receptor overxpression has been reported in many cancers. Of particular interest, CCR7 appears to be a strong mediator of LN metastases, while CXCR4 may mediate distant metastases. Any relations between their expression in primary HNSCCs and metastatic lymph nodes need to be clarified. Aims: To investigate CCR7 andCXCR4 expression in primary HNSCCs of all tumor sizes, clinical stages and histological grades, as well as involved lymph nodes, then make comparisons, also with control normal oral epithelium. Materials and Methods: The sample consisted of 60 formalin-fixed, paraffin-embedded specimens of primary HNSCCs, 77 others of metastasi-positive lymph nodes, and 10 of control normal oral epithelial tissues. Sections were conventionally stained with H&E and immunohistochemically with monoclonal anti-CCR7 and monoclonal anti-CXCR4 antibodies. Positive cells were counted under microscopic assessment in four fields (X40) per case. Results: There was no variation among primary HNSCC tumors staining positive for CCR7 and CXCR4 with tumor size of for CCR7 with lymph node involvement. However, a difference was noted between primary HNSCC tumors stained by CXCR4 with a single as compared to more numerous node involvement. CXCR4 appear to vary with the clinical stagebut no links were noted with histological grades. Staining for primary HNSCC tumors and metastatic lymph nodes correlated.

Curcumin exhibits anti-tumor effect and attenuates cellular migration via Slit-2 mediated down-regulation of SDF-1 and CXCR4 in endometrial adenocarcinoma cells

Although curcumin shows anti-proliferative and anti-inflammatory activities in various cancers, the effect of curcumin on cellular migration in endometrial adenocarcinoma cells remains to be understood. The current investigation was aimed to explore the anti-proliferative and anti-migratory effects of curcumin and its mechanism of action in endometrial cancer cells. Our in-vitro and in-vivo experimental studies showed that curcumin inhibited the proliferation of endometrial cancer cells and suppressed the tumor growth in Ishikawa xenograft mouse model. Curcumin induced ROS-mediated apoptosis in endometrial cancer cells. Curcumin suppressed the migration rate of Ishikawa and Hec-1B cells as analyzed by scratch wound assay. In transwell migration studies, knock down of Slit-2 reversed the anti-migratory effect of curcumin in these cell lines. Curcumin significantly up-regulated the expression of Slit-2 in Ishikawa, Hec-1B and primary endometrial cancer cells while it down-regulated the expression of stromal cell-derived factor-1 (SDF-1) and CXCR4 which in turn, suppressed the expression of matrix metallopeptidases (MMP) 2 and 9, thus attenuating the migration of endometrial cancer cells. In summary, we have demonstrated that curcumin has inhibitory effect on cellular migration via Slit-2 mediated down-regulation of CXCR4, SDF-1, and MMP2/MMP9 in endometrial carcinoma cells. These findings helped explore the role of Slit-2 in endometrial cancer cells.

Prognostic and predictive value of circulating tumor cells and CXCR4 expression as biomarkers for a CXCR4 peptide antagonist in combination with carboplatin-etoposide in small cell lung cancer: exploratory analysis of a phase II study

Background Circulating tumor cells (CTCs) and chemokine (C-X-C motif) receptor 4 (CXCR4) expression in CTCs and tumor tissue were evaluated as prognostic or predictive markers of CXCR4 peptide antagonist LY2510924 plus carboplatin-etoposide (CE) versus CE in extensive-stage disease small cell lung cancer (ED-SCLC). Methods This exploratory analysis of a phase II study evaluated CXCR4 expression in baseline tumor tissue and peripheral blood CTCs and in post-treatment CTCs. Optimum cutoff values were determined for CTC counts and CXCR4 expression in tumors and CTCs as predictors of survival outcome. Kaplan-Meier estimates and hazard ratios were used to determine biomarker prognostic and predictive values. Results There was weak positive correlation at baseline between CXCR4 expression in tumor tissue and CTCs. Optimum cutoff values were H-score ≥ 210 for CXCR4⁺ tumor, ≥7% CTCs with CXCR4 expression (CXCR4⁺ CTCs), and ≥6 CTCs/7.5 mL blood. Baseline H-score for CXCR4⁺ tumor was not prognostic of progression-free survival (PFS) or overall survival (OS). Baseline CXCR4⁺ CTCs ≥7% was prognostic of shorter PFS. CTCs ≥6 at baseline and cycle 2, day 1 were prognostic of shorter PFS and OS. None of the biomarkers at their respective optimum cutoffs was predictive of treatment response of LY2510924 plus CE versus CE. Conclusions In patients with ED-SCLC, baseline CXCR4 expression in tumor tissue was not prognostic of survival or predictive of LY2510924 treatment response. Baseline CXCR4⁺ CTCs ≥7% was prognostic of shorter PFS. CTC count ≥6 at baseline and after 1 cycle of treatment were prognostic of shorter PFS and OS.

Structural Analysis of Chemokine Receptor-Ligand Interactions

This review focuses on the construction and application of structural chemokine receptor models for the elucidation of molecular determinants of chemokine receptor modulation and the structure-based discovery and design of chemokine receptor ligands. A comparative analysis of ligand binding pockets in chemokine receptors is presented, including a detailed description of the CXCR4, CCR2, CCR5, CCR9, and US28 X-ray structures, and their implication for modeling molecular interactions of chemokine receptors with small-molecule ligands, peptide ligands, and large antibodies and chemokines. These studies demonstrate how the integration of new structural information on chemokine receptors with extensive structure–activity relationship and site-directed mutagenesis data facilitates the prediction of the structure of chemokine receptor–ligand complexes that have not been crystallized. Finally, a review of structure-based ligand discovery and design studies based on chemokine receptor crystal structures and homology models illustrates the possibilities and challenges to find novel ligands for chemokine receptors.

CXCL12 methylation-mediated epigenetic regulation of gene expression in papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer, and its incidence rate is rapidly growing. It is necessary to understand the pathogenesis of PTC to develop effective diagnosis methods. Promoter methylation has been recognized to contribute to the alterations in gene expression observed in tumorigenesis. Our RNA-seq data identified 1191 differentially expressed mRNAs and 147 differentially expressed lncRNAs in PTC. Next, promoter methylation of these genes was detected by reduced representation bisulfite sequencing (RRBS) technology and comprehensively analyzed to identify differential methylation. In total, 14 genes (13 mRNAs and 1 lncRNA), in which methylation was intimately involved in regulating gene expression, were proposed as novel diagnostic biomarkers. To gain insights into the relationships among these 14 genes, a core co-function network was constructed based on co-expression, co-function and co-methylation data. Notably, CXCL12 was identified as an essential gene in the network that was closely connected with the other genes. These data suggested that CXCL12 down-regulation in PTC may be caused by promoter hypermethylation. Our study was the first to perform an RRBS analysis for PTC and suggested that CXCL12 may contribute to PTC development by methylation-mediated epigenetic regulation of gene expression.

CXCR4 inhibitors could benefit to HER2 but not to triple-negative breast cancer patients

The CXCR4 receptor and its ligand CXCL12 (also named stromal cell-derived factor 1, SDF1) have a critical role in chemotaxis and homing, key steps in cancer metastasis. Although myofibroblasts expressing CXCL12 are associated with the presence of axillary metastases in HER2 breast cancers (BC), the therapeutic interest of targeting CXCR4/CXCL12 axis in the different BC subtypes remains unclear. Here, we investigate this question by testing antitumor activity of CXCR4 inhibitors in patient-derived xenografts (PDX), which faithfully reproduce human tumor properties. We observed that two CXCR4 inhibitors, AMD3100 and TN14003, efficiently impair tumor growth and metastasis dissemination in both Herceptin-sensitive and Herceptin-resistant HER2 BC. Conversely, blocking CXCR4/CXCL12 pathway in triple-negative (TN) BC does not reduce tumor growth, and can even increase metastatic spread. Moreover, although CXCR4 inhibitors significantly reduce myofibroblast content in all BC subtypes, they decrease angiogenesis only in HER2 BC. Thus, our findings suggest that targeting CXCR4 could provide some therapeutic interest for HER2 BC patients, whereas it has no impact or could even be detrimental for TN BC patients.

Hormophysa triquerta polyphenol, an elixir that deters CXCR4- and COX2-dependent dissemination destiny of treatment-resistant pancreatic cancer cells

Therapy-resistant pancreatic cancer (PC) cells play a crucial role in tumor relapse, recurrence, and metastasis. Recently, we showed the anti-PC potential of an array of seaweed polyphenols and identified efficient drug deliverables. Herein, we investigated the benefit of one such deliverable, Hormophysa triquerta polyphenol (HT-EA), in regulating the dissemination physiognomy of therapy-resistant PC cells in vitro,and residual PC in vivo. Human PC cells exposed to ionizing radiation (IR), with/without HT-EA pre-treatment were examined for the alterations in the tumor invasion/metastasis (TIM) transcriptome (93 genes, QPCR-profiling). Utilizing a mouse model of residual PC, we investigated the benefit of HT-EA in the translation regulation of crucial TIM targets (TMA-IHC). Radiation activated 30, 50, 15, and 38 TIM molecules in surviving Panc-1, Panc-3.27, BxPC3, and MiaPaCa-2 cells. Of these, 15, 44, 12, and 26 molecules were suppressed with HT-EA pre-treatment. CXCR4 and COX2 exhibited cell-line-independent increases after IR, and was completely suppressed with HT-EA, across all PC cells. HT-EA treatment resulted in translational repression of IR-induced CXCR4, COX2, β-catenin, MMP9, Ki-67, BAPX, PhPT-1, MEGF10, and GRB10 in residual PC. Muting CXCR4 or COX2 regulated the migration/invasion potential of IR-surviving cells, while forced expression of CXCR4 or COX2 significantly increased migration/invasion capabilities of PC cells. Further, treatment with HT-EA significantly inhibited IR-induced and CXCR4/COX2 forced expression-induced PC cell migration/invasion. This study (i) documents the TIM blueprint in therapy-resistant PC cells, (ii) defines the role of CXCR4 and COX2 in induced metastatic potential, and (iii) recognizes the potential of HT-EA in deterring the CXCR4/COX2-dependent dissemination destiny of therapy-resistant residual PC cells.

Structural basis of ligand interaction with atypical chemokine receptor 3

Chemokines drive cell migration through their interactions with seven-transmembrane (7TM) chemokine receptors on cell surfaces. The atypical chemokine receptor 3 (ACKR3) binds chemokines CXCL11 and CXCL12 and signals exclusively through β-arrestin-mediated pathways, without activating canonical G-protein signalling. This receptor is upregulated in numerous cancers making it a potential drug target. Here we collected over 100 distinct structural probes from radiolytic footprinting, disulfide trapping, and mutagenesis to map the structures of ACKR3:CXCL12 and ACKR3:small-molecule complexes, including dynamic regions that proved unresolvable by X-ray crystallography in homologous receptors. The data are integrated with molecular modelling to produce complete and cohesive experimentally driven models that confirm and expand on the existing knowledge of the architecture of receptor:chemokine and receptor:small-molecule complexes. Additionally, we detected and characterized ligand-induced conformational changes in the transmembrane and intracellular regions of ACKR3 that elucidate fundamental structural elements of agonism in this atypical receptor.

Hybrid Imaging Labels: Providing the Link Between Mass Spectrometry-Based Molecular Pathology and Theranostics

Background: Development of theranostic concepts that include inductively coupled plasma mass spectrometry (ICP-MS) and laser ablation ICP-MS (LA-ICP-MS) imaging can be hindered by the lack of a direct comparison to more standardly used methods for in vitro and in vivo evaluation; e.g. fluorescence or nuclear medicine. In this study a bimodal (or rather, hybrid) tracer that contains both a fluorescent dye and a chelate was used to evaluate the existence of a direct link between mass spectrometry (MS) and in vitro and in vivo molecular imaging findings using fluorescence and radioisotopes. At the same time, the hybrid label was used to determine whether the use of a single isotope label would allow for MS-based diagnostics.

Methods: A hybrid label that contained both a DTPA chelate (that was coordinated with either ¹⁶⁵Ho or ¹¹¹In) and a Cy5 fluorescent dye was coupled to the chemokine receptor 4 (CXCR4) targeting peptide Ac-TZ14011 (hybrid-Cy5-Ac-TZ4011). This receptor targeting tracer was used to 1) validate the efficacy of (¹⁶⁵Ho-based) mass-cytometry in determining the receptor affinity via comparison with fluorescence-based flow cytometry (Cy5), 2) evaluate the microscopic binding pattern of the tracer in tumor cells using both fluorescence confocal imaging (Cy5) and LA-ICP-MS-imaging (¹⁶⁵Ho), 3) compare in vivo biodistribution patterns obtained with ICP-MS (¹⁶⁵Ho) and radiodetection (¹¹¹In) after intravenous administration of hybrid-Cy5-Ac-TZ4011 in tumor-bearing mice. Finally, LA-ICP-MS-imaging (¹⁶⁵Ho) was linked to fluorescence-based analysis of excised tissue samples (Cy5).

Results: Analysis with both mass-cytometry and flow cytometry revealed a similar receptor affinity, respectively 352 ± 141 nM and 245 ± 65 nM (p = 0.08), but with a much lower detection sensitivity for the first modality. In vitro LA-ICP-MS imaging (¹⁶⁵Ho) enabled clear discrimination between CXCR4 positive and negative cells, but fluorescence microscopy was required to determine the intracellular distribution. In vivo biodistribution patterns obtained with ICP-MS (¹⁶⁵Ho) and radiodetection (¹¹¹In) of the hybrid peptide were shown to be similar. Assessment of tracer distribution in excised tissues revealed the location of tracer uptake with both LA-ICP-MS-imaging and fluorescence imaging.

Conclusion: Lanthanide-isotope chelation expands the scope of fluorescent/radioactive hybrid tracers to include MS-based analytical tools such as mass-cytometry, ICP-MS and LA-ICP-MS imaging in molecular pathology. In contradiction to common expectations, MS detection using a single chelate imaging agent was shown to be feasible, enabling a direct link between nuclear medicine-based imaging and theranostic methods.

US28, a Virally-Encoded GPCR as an Antiviral Target for Human Cytomegalovirus Infection

Viruses continue to evolve a new strategy to take advantage of every aspect of host cells in order to maximize their survival. Due to their central roles in transducing a variety of transmembrane signals, GPCRs seem to be a prime target for viruses to pirate for their own use. Incorporation of GPCR functionality into the genome of herpesviruses has been demonstrated to be essential for pathogenesis of many herpesviruses-induced diseases. Here, we introduce US28 of human cytomegalovirus (HCMV) as the best-studied example of virally-encoded GPCRs to manipulate host GPCR signaling. In this review, we wish to summarize a number of US28-related topics including its regulation of host signaling pathways, its constitutive internalization, its structural and functional analysis, its roles in HCMV biology and pathogenesis, its proliferative activities and role in oncogenesis, and pharmacological modulation of its biological activities. This review will aid in our understanding of how pathogenic viruses usurp the host GPCR signaling for successful viral infection. This kind of knowledge will enable us to build a better strategy to control viral infection by normalizing the virally-dysregulated host GPCR signaling.

Peptide-binding induced inhibition of chemokine CXCL12

A designed peptide (W4) has a significant inhibitory effect on the CXCL12/CXCR4 axis by targeting CXCL12 with high binding affinity.

Neurotrophin Receptors and Perineural Invasion: Analyses in Select Lineage-Unrelated Cutaneous Malignancies With a Propensity for Perineural Invasion

In this chapter, we parse the literature on neurotrophins that have been implicated in the pathogenesis of perineural invasion (PNI) in select lineage-unrelated malignancies. We also detail evidence linking neurotrophins and their receptors (TrkA, RET, p75NGFR, and NCAM) to the pathogenesis of PNI in desmoplastic melanoma and cutaneous squamous cell carcinoma-both malignancies with an established propensity for PNI. Lastly, the clinical potential of neurotrophins as receptors for targeted therapies is explored.

Molecular Pathways: Deciphering Mechanisms of Resistance to Macrophage-Targeted Therapies

Tumor-associated macrophages (TAMs) are a major cellular component of numerous tumor types. TAM-targeted therapies include depletion strategies, inhibiting their effector functions or reprogramming toward an antitumorigenic phenotype, with varying degrees of efficacy. Here, we review preclinical and clinical strategies to target macrophages in cancer and discuss potential explanations for why some strategies are effective while other approaches have shown limited success. Clin Cancer Res; 23(4); 876-84. ©2016 AACR.

Differential somatostatin and CXCR4 chemokine receptor expression in MALT-type lymphoma of gastric and extragastric origin

PURPOSE

Whereas the different somatostatin receptor (SSTR) subtypes and the chemokine receptor CXCR4 are known to be expressed in a wide variety of human malignancies, comprehensive data are still lacking for MALT-type lymphomas.

METHODS

Overall, 55 cases of MALT-type lymphoma of both gastric and extragastric origin were evaluated for the SSTR subtype and CXCR4 expression by means of immunohistochemistry using novel monoclonal rabbit antibodies. The stainings were rated by means of the immunoreactive score and correlated with clinical data.

RESULTS

While the CXCR4 was detected in 92 % of the cases investigated, the SSTR subtypes were much less frequently present. The SSTR5 was expressed in about 50 % of the cases, followed by the SSTR3, the SSTR2A, the SSTR4 and the SSTR1, which were present in 35, 27, 18 or 2 %, respectively, of the tumors only. Gastric lymphomas displayed a significantly higher SSTR3, SSTR4 and SSTR5 expression than extragastric tumors. A correlation between CXCR4 and Ki-67 expression was seen in gastric lymphomas, whereas primarily in extragastric tumors SSTR5 negativity was associated with poor patient outcome.

CONCLUSIONS

The CXCR4 may serve as a promising target for diagnostics and therapy of MALT-type lymphomas, while the SSTRs appear not suitable in this respect.

β-Arrestin1 and Signal-transducing Adaptor Molecule 1 (STAM1) Cooperate to Promote Focal Adhesion Kinase Autophosphorylation and Chemotaxis via the Chemokine Receptor CXCR4

The chemokine receptor CXCR4 and its chemokine ligand CXCL12 mediate directed cell migration during organogenesis, immune responses, and metastatic disease. However, the mechanisms governing CXCL12/CXCR4-dependent chemotaxis remain poorly understood. Here, we show that the β-arrestin1·signal-transducing adaptor molecule 1 (STAM1) complex, initially identified to govern lysosomal trafficking of CXCR4, also mediates CXCR4-dependent chemotaxis. Expression of minigene fragments from β-arrestin1 or STAM1, known to disrupt the β-arrestin1·STAM1 complex, and RNAi against β-arrestin1 or STAM1, attenuates CXCL12-induced chemotaxis. The β-arrestin1·STAM1 complex is necessary for promoting autophosphorylation of focal adhesion kinase (FAK). FAK is necessary for CXCL12-induced chemotaxis and associates with and localizes with β-arrestin1 and STAM1 in a CXCL12-dependent manner. Our data reveal previously unknown roles in CXCR4-dependent chemotaxis for β-arrestin1 and STAM1, which we propose act in concert to regulate FAK signaling. The β-arrestin1·STAM1 complex is a promising target for blocking CXCR4-promoted FAK autophosphorylation and chemotaxis.

Constitutive activation of T cells by γ2-herpesviral GPCR through the interaction with cellular CXCR4

Members of the herpesviral family use multiple strategies to hijack infected host cells and exploit cellular signaling for their pathogenesis and latent infection. Among the most intriguing weapons in the arsenal of pathogenic herpesviruses are the constitutively active virally-encoded G protein-coupled receptors (vGPCRs). Even though vGPCRs contribute to viral pathogenesis such as immune evasion and proliferative disorders, the molecular details of how vGPCRs continuously activate cellular signaling are largely unknown. Here, we report that the vGPCR of Herpesvirus saimiri (HVS), an oncogenic γ2-herpesvirus, constitutively activates T cells via a heteromeric interaction with cellular CXCR4. Constitutive T cell activation also occurs with expression of the vGPCR of Kaposi's sarcoma-associated herpesvirus (KSHV), but not the vGPCR of Epstein-Barr virus. Expression of HVS vGPCR down-regulated the surface expression of CXCR4 but did not induce the degradation of the chemokine receptor, suggesting that vGPCR/CXCR4 signaling continues in cytosolic compartments. The physical association of vGPCR with CXCR4 was demonstrated by proximity ligation assay as well as immunoprecipitation. Interestingly, the constitutive activation of T cells by HVS vGPCR is independent of proximal T cell receptor (TCR) signaling molecules, such as TCRβ, Lck, and ZAP70, whereas CXCR4 silencing by shRNA abolished T cell activation by vGPCRs of HVS and KSHV. Furthermore, previously identified inactive vGPCR mutants failed to interact with CXCR4. These findings on the positive cooperativity of vGPCR with cellular CXCR4 in T cell activation extend our current understanding of the molecular mechanisms of vGPCR function and highlight the importance of heteromerization for GPCR activity.

SDF-1/CXCR7 axis regulates the proliferation, invasion, adhesion, and angiogenesis of gastric cancer cells

Background

More recent studies have revealed that chemokine receptor CXCR7 plays an important role in cancer development. However, little is known about the effect of CXCR7 on the process of gastric cancer cell invasion and angiogenesis. The aim of this study is to investigate the expression of CXCR7 in gastric cancer cell lines and to evaluate the role of CXCR7 in the proliferation, invasion, adhesion, and angiogenesis of gastric cancer cells.

Methods

Real-time PCR and Western blotting were used to examine the mRNA and protein levels of CXCR4 and CXCR7 in five gastric cancer cell lines (HGC-27, MGC-803, BGC-823, SGC-7901, and MKN-28). CXCR7-expressing shRNA was constructed and subsequently stably transfected into the human gastric cancer cells. In addition, the effect of CXCR7 inhibition on cell proliferation, invasion, adhesion, VEGF secretion, and tube formation was evaluated.

Results

The mRNA and protein of CXCR7 were expressed in all five gastric cancer cell lines; in particular, the expression of CXCR7 was the highest in SGC-7901 cells. Stromal cell-derived factor-1 (SDF-1) was found to induce proliferation, invasion, adhesion, and tube formation. Moreover, the VEGF secretion in SGC-7901 cells was also enhanced by SDF-1 stimulation. These biological effects were inhibited by the silencing of CXCR7 in SGC-7901 cells.

Conclusions

Increased CXCR7 expression was found in gastric cancer cells. Knockdown of CXCR7 expression by transfection with CXCR7shRNA significantly inhibits SGC-7901 cells’ proliferation, invasion, adhesion, and angiogenesis. This study provides new insights into the significance of CXCR7 in the invasion and angiogenesis of gastric cancer.

Molecular basis for the antagonistic activity of an anti-CXCR4 antibody

Antagonistic antibodies targeting the G-protein C-X-C chemokine receptor 4 (CXCR4) hold promising therapeutic potential in various diseases. We report for the first time the detailed mechanism of action at a molecular level of a potent anti-CXCR4 antagonistic antibody (MEDI3185). We characterized the MEDI3185 paratope using alanine scanning on all 6 complementary-determining regions (CDRs). We also mapped its epitope using CXCR4 mutagenesis to assess the relative importance of the CXCR4 N-terminal peptide, extracellular loops (ECL) and ligand-binding pocket. We show that the interaction between MEDI3185 and CXCR4 is mediated mostly by CDR3H in MEDI3185 and ECL2 in CXCR4. The MEDI3185 epitope comprises the entire ECL2 sequence, lacks any so-called ‘hot-spot’ and is remarkably resistant to mutations. The structure of MEDI3185 variable domains was modeled, and suggested a β-strand/β-strand interaction between MEDI3185 CDR3H and CXCR4 ECL2, resulting in direct steric hindrance with CXCR4 ligand SDF-1. These findings may have important implications for designing antibody therapies against CXCR4.