Development of novel CXCR4-based therapeutics

Induced interleukin-33 expression enhances the tumorigenic activity of rat glioma cells

BACKGROUND

Glioma development is a multistep process associated with progressive genetic alterations but also regulated by cellular and noncellular components in a tumor-associated niche.

METHODS

Using 2 rat C6 glioma cell clones with different tumorigenesis, named C6-1 and C6-2, this study characterized genes associated with enhanced tumorigenic features of glioma cells by comparative cDNA microarray analysis combined with Q-PCR. Neurospehere formation and clonogenicity were examined to determine the growth of tumorigenic C6 glioma cells. The lentivirus-mediated gene knockdown approach was conducted to determine the role of interleukin-33 (IL-33) in glioma cell proliferation and migration. Transwell cell invasion assay was used to examine microglia migration induced by tumorigenic C6 cells.

RESULTS

The functional analysis of gene ontology (GO) biological processes shows that the upregulated genes found in tumorigenic C6 (C6-1) cells are closely related to cell proliferation. Tumorigenic C6 cells expressed cytokines and chemokines abundantly. Among these genes, IL-33 was profoundly induced in tumorigenic C6 cells with the expression of IL-33 receptor ST2. Furthermore, the growth rate and colony formation of tumorigenic C6 cells were attenuated by the inhibition of IL-33 and ST2 gene expression. Moreover, IL-33 was involved in tumorigenic glioma cell migration and regulation of the expression of several glioma-associated growth factors and chemokines in tumorigenic C6 cells.

CONCLUSION

Accordingly, we concluded that glioma cells with abundant production of IL-33 grow rapidly; moreover, the interactions of multiple cytokines/chemokines induced by glioma cells may develop a microenvironment that facilitates microglia/macrophage infiltration and fosters glioma growth in the brain.

The Spiegelmer NOX-A12, a novel CXCL12 inhibitor, interferes with chronic lymphocytic leukemia cell motility and causes chemosensitization

The CXC chemokine ligand (CXCL12, or stromal cell-derived factor-1 as previously known) plays a critical role for homing and retention of chronic lymphocytic leukemia (CLL) cells in tissues such as the bone marrow (BM). In tissues, stromal cells constitutively secrete and present CXCL12 via cell-surface-bound glycosaminoglycans (GAGs), thereby attracting CLL cells and protecting them from cytotoxic drugs, a mechanism that may account for residual disease after conventional CLL therapy. NOX-A12, an RNA oligonucleotide in L-configuration (Spiegelmer) that binds and neutralizes CXCL12, was developed for interference with CXCL12 in the tumor microenvironment and for cell mobilization. Here, we examined effects of NOX-A12 on CLL cell migration and drug sensitivity. We found that NOX-A12 effectively inhibited CXCL12-induced chemotaxis of CLL cells. In contrast, NOX-A12 increased CLL migration underneath a confluent layer of BM stromal cells (BMSCs) due to interference with the CXCL12 gradient established by BMSCs. In particular, NOX-A12 competes with GAGs such as heparin for CXCL12 binding, leading to the release of CXCL12 from stromal cell-surface-bound GAGs, and thereby to neutralization of the chemokine. Furthermore, NOX-A12 sensitizes CLL cells toward bendamustine and fludarabine in BMSC cocultures. These data demonstrate that NOX-A12 effectively interferes with CLL cell migration and BMSC-mediated drug resistance, and establishes a rationale for clinical development of NOX-A12 in combination with conventional agents in CLL.

Discovery of tetrahydroisoquinoline-based CXCR4 antagonists

A de novo hit-to-lead effort involving the redesign of benzimidazole-containing antagonists of the CXCR4 receptor resulted in the discovery of a novel series of 1,2,3,4-tetrahydroisoquinoline (TIQ) analogues. In general, this series of compounds show good potencies (3-650 nM) in assays involving CXCR4 function, including both inhibition of attachment of X4 HIV-1IIIB virus in MAGI-CCR5/CXCR4 cells and inhibition of calcium release in Chem-1 cells. Series profiling permitted the identification of TIQ-(R)-stereoisomer 15 as a potent and selective CXCR4 antagonist lead candidate with a promising in vitro profile. The drug-like properties of 15 were determined in ADME in vitro studies, revealing low metabolic liability potential. Further in vivo evaluations included pharmacokinetic experiments in rats and mice, where 15 was shown to have oral bioavailability (F = 63%) and resulted in the mobilization of white blood cells (WBCs) in a dose-dependent manner.

The chemokine system, and its CCR5 and CXCR4 receptors, as potential targets for personalized therapy in cancer

Chemokines and their receptors regulate the trafficking of leukocytes in hematopoiesis and inflammation, and thus are fundamental to the immune integrity of the host. In parallel, members of the chemokine system exert a large variety of functions that dictate processes of cancer development and progression. Chemokines can act as pro-tumoral or anti-tumoral regulators of malignancy by affecting cells of the tumor microenvironment (leukocytes, endothelial cells, fibroblasts) and the tumor cells themselves (migration, invasion, proliferation, resistance to chemotherapy). Several of the chemokines are generally skewed towards the cancer-promoting direction, including primarily the CCR5-CCL5 (RANTES) and the CXCR4-CXCL12 (SDF-1) axes. This review provides a general view of chemokines and chemokine receptors as regulators of malignancy, describing their multi-faceted activities in cancer. The tumor-promoting activities of the CCR5-CCL5 and CXCR4-CXCL12 pathways are enlightened, emphasizing their potential use as targets for personalized therapy. Indeed, novel blockers of chemokines and their receptors are constantly emerging, and two chemokine receptor inhibitors were recently approved for clinical use: Maraviroc for CCR5 and Plerixafor for CXCR4. The review addresses ongoing pre-clinical and clinical trials using these modalities and others in cancer. Then, challenges and opportunities of personalized therapy directed against chemokines and their receptors in malignancy are discussed, demonstrating that such novel personalized cancer therapies hold many challenges, but also offer hope for cancer patients.

Emerging targets in cancer management: role of the CXCL12/CXCR4 axis

The chemokine CXCL12 (SDF-1) and its cell surface receptor CXCR4 were first identified as regulators of lymphocyte trafficking to the bone marrow. Soon after, the CXCL12/CXCR4 axis was proposed to regulate the trafficking of breast cancer cells to sites of metastasis. More recently, it was established that CXCR4 plays a central role in cancer cell proliferation, invasion, and dissemination in the majority of malignant diseases. The stem cell concept of cancer has revolutionized the understanding of tumorigenesis and cancer treatment. A growing body of evidence indicates that a subset of cancer cells, referred to as cancer stem cells (CSCs), plays a critical role in tumor initiation, metastatic colonization, and resistance to therapy. Although the signals generated by the metastatic niche that regulate CSCs are not yet fully understood, accumulating evidence suggests a key role of the CXCL12/CXCR4 axis. In this review we focus on physiological functions of the CXCL12/CXCR4 signaling pathway and its role in cancer and CSCs, and we discuss the potential for targeting this pathway in cancer management.

Sequential administration of the high affinity CXCR4 antagonist BKT140 promotes megakaryopoiesis and platelet production

Platelets are the terminal differentiation product of megakaryocytes (MKs). Cytokines, such as thrombopoietin (TPO), are known to influence different steps in MK development; however, the complex differentiation and platelet localization processes are not fully understood. MKs express the receptor CXCR4 and have been shown to migrate in response to CXCL12 and to increase their platelet production. In this study, we studied the role of CXCR4 in platelet production with the high affinity CXCR4 antagonist, BKT140. Single and sequential administration of BKT140 significantly increased the number of MKs and haematopoietic progenitors (HPCs) within the bone marrow (BM). Increased megakaryopoiesis was associated with increased platelet production. Single and sequential administration of BKT140 also increased the number of HPCs in the blood. In a model of 5-fluorouracil-induced thrombocytopenia, BKT140 significantly reduced the severity and duration of thrombocytopenia and cytopenia when administered before and after chemotherapy. Our results demonstrated that the CXCR4 antagonist, BKT140, mediated unique beneficial effects by stimulating megakaryopoiesis and platelet production. These results provide evidence for the possible therapeutic use of BKT140 for modulating platelet numbers in thrombocytopenic conditions.

Potential therapeutic biomarkers in plasma cell myeloma: a flow cytometry study

OBJECTIVE

To investigate the expression profile of potential therapeutic biomarkers in plasma cell myeloma (PCM) by multicolor flow cytometry analysis.

METHODS

Bone marrow (BM) specimens were collected consecutively and analyzed using a routine PCM panel (CD38/CD138/CD45/CD19/CD20/CD28/CD56/CD117, cyto-kappa/lambda). The specimens were further assessed for CD30, CD44, CD49d, CD70, CD105, and CD184 expression in cases containing a substantial number of neoplastic plasma cells.

RESULTS

Totally, 101 patient BM samples were assessed, including 58 men and 43 women, with a median age of 64 years (34-89). Twenty-nine patients had newly diagnosed/untreated PCM, 40 had persistent/residual disease undergoing various therapies and 32 had relapsed disease. CD49d was expressed brightly and uniformly in all 45 patients tested. Expression of CD44 and CD184 was more variable with a median percentage of 77% (1-100) and 65% (5-100) respectively. Using an arbitrary 20% cutoff, CD44 was positive in 74 (73%) and CD184 in 92 (91%) cases with a mean fluorescence intensity ratio of 42.8 and 21.4. A higher CD44 expression was observed in patients with recurrent/persistent disease (P = 0.028). Additionally, both CD44 (P = 0.002) and CD184 (P = 0.026) showed higher expressions in CD117-positive cases, but there was no correlation with cytogenetic groups. The CD30, CD70, and CD105 were expressed very infrequently in PCM, with a median expression of 0.2%, 0.2%, and 0.4% respectively.

CONCLUSIONS

CD49d, CD44, and CD184, are highly expressed in PCM. CD49d expression is bright and uniform, whereas CD44 and CD184 are more heterogeneous. In contrast, surface CD30, CD70, and CD105 are infrequent. These data provide useful preclinical information for the design of potential novel targeted therapies in PCM patients.

RNAi targeting CXCR4 inhibits proliferation and invasion of esophageal carcinoma cells

CXC chemokine receptor 4 was found to be expressed by many different types of human cancers and its expression has been correlated with tumor aggressiveness, poor prognosis and resistance to chemotherapy. However the effect of CXCR4 on the esophageal carcinoma cells remains unclear, the present study explored the effects of CXCR4 siRNA on proliferation and invasion of esophageal carcinoma KYSE-150 and TE-13 cells. Two siRNA sequence targeting CXCR4 gene were constructed and then were transfected into KYSE-150 and TE-13 cells by Lipofectamine™2000. Changes of CXCR4 mRNA and protein were analyzed by qRT-PCR and Western blot. Effect of CXCR4 siRNA on KYSE-150 and TE-13 cells proliferation was determined by MTT. Transwell invasion assay was used to evaluate the invasion and metastasis of KYSE-150 and TE-13 cells. Tumor growth was assessed by subcutaneous inoculation of cells into BALB/c nude mice. qRT-PCR and Western blot demonstrate that the expression level of CXCR4 gene were obviously decreased in KYSE-150 and TE-13 cells transfected with CXCR4 targeting siRNA expression vectors. The average amount of cells transfected with CXCR4 siRNA penetrating Matrigel was significantly decreased (p<0.05). Injection of CXCR4 siRNA transfected cells inhibited tumor growth in a xenograft model compared with blank and negative control groups (p <0.05). CXCR4 silenced by siRNA could suppress the proliferation, invasion and metastasis of esophageal carcinoma cell lines KYSE-150 and TE-13 in vitro and in vivo. The results provide a theoretical and experimental basis for the gene therapy of ESCC using RNAi technology based on CXCR4 target site.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/3502376691001138.

CXCR4/CXCL12 mediate autocrine cell- cycle progression in NF1-associated malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumors (MPNSTs) are soft tissue sarcomas that arise in connective tissue surrounding peripheral nerves. They occur sporadically in a subset of patients with neurofibromatosis type 1 (NF1). MPNSTs are highly aggressive, therapeutically resistant, and typically fatal. Using comparative transcriptome analysis, we identified CXCR4, a G-protein-coupled receptor, as highly expressed in mouse models of NF1-deficient MPNSTs, but not in nontransformed precursor cells. The chemokine receptor CXCR4 and its ligand, CXCL12, promote MPNST growth by stimulating cyclin D1 expression and cell-cycle progression through PI3-kinase (PI3K) and β-catenin signaling. Suppression of CXCR4 activity either by shRNA or pharmacological inhibition decreases MPNST cell growth in culture and inhibits tumorigenesis in allografts and in spontaneous genetic mouse models of MPNST. We further demonstrate conservation of these activated molecular pathways in human MPNSTs. Our findings indicate a role for CXCR4 in NF1-associated MPNST development and identify a therapeutic target.

Molecular imaging of chemokine receptor CXCR4

CXCR4 was found to be expressed by many different types of human cancers and its expression has been correlated with tumor aggressiveness, poor prognosis and resistance to chemotherapy. CXCR4 was also shown to contribute to metastatic seeding of organs that express its ligand CXCL12 and support the survival of these cells. These findings suggest that CXCR4 is a potentially attractive therapeutic target, and several antagonists and antibodies for this receptor were developed and are under clinical evaluation. Quantifying CXCR4 expression non-invasively might aid in prognostication as a mean for personalized therapy and post treatment monitoring. Multiple attempts were done over the recent years to develop imaging agents for CXCR4 using different technologies including PET, SPECT, fluorescent and bioluminescence, and will be reviewed in this paper.

CXCR4/CXCL12 axis in non small cell lung cancer (NSCLC) pathologic roles and therapeutic potential

Lung cancer is the second most common malignancy and the leading cause of cancer-related death in the western world. Moreover, despite advances in surgery, chemotherapy and radiotherapy, the death rate from lung cancer remains high and the reported overall five-year survival rate is only 15%. Thus, novel treatments for this devastating disease are urgently needed. Chemokines, a family of 48 chemotactic cytokines interacts with their 7 transmembrane G-protein-coupled receptors, to guide immune cell trafficking in the body under both physiologic and pathologic conditions. Tumor cells, which express a relatively restricted repertoire of chemokine and chemokine receptors, utilize and manipulate the chemokine system in a manner that benefits both local tumor growth and distant dissemination. Among the 19 chemokine receptors, CXCR4 is the receptor most widely expressed by malignant tumors and whose role in tumor biology is most thoroughly studied. The chemokine CXCL12, which is the sole ligand of CXCR4, is highly expressed in primary lung cancer as well as in the bone marrow, liver, adrenal glands and brain, which are all sites for lung cancer metastasis. This review focuses on the pathologic role of the CXCR4/CXCL12 axis in NSCLC and on the potential therapeutic implication of targeting this axis for the treatment of NSCLC.

Molecular mechanisms of curcumin action: gene expression

Curcumin derived from the tropical plant Curcuma longa has a long history of use as a dietary agent, food preservative, and in traditional Asian medicine. It has been used for centuries to treat biliary disorders, anorexia, cough, diabetic wounds, hepatic disorders, rheumatism, and sinusitis. The preventive and therapeutic properties of curcumin are associated with its antioxidant, anti-inflammatory, and anticancer properties. Extensive research over several decades has attempted to identify the molecular mechanisms of curcumin action. Curcumin modulates numerous molecular targets by altering their gene expression, signaling pathways, or through direct interaction. Curcumin regulates the expression of inflammatory cytokines (e.g., TNF, IL-1), growth factors (e.g., VEGF, EGF, FGF), growth factor receptors (e.g., EGFR, HER-2, AR), enzymes (e.g., COX-2, LOX, MMP9, MAPK, mTOR, Akt), adhesion molecules (e.g., ELAM-1, ICAM-1, VCAM-1), apoptosis related proteins (e.g., Bcl-2, caspases, DR, Fas), and cell cycle proteins (e.g., cyclin D1). Curcumin modulates the activity of several transcription factors (e.g., NF-κB, AP-1, STAT) and their signaling pathways. Based on its ability to affect multiple targets, curcumin has the potential for the prevention and treatment of various diseases including cancers, arthritis, allergies, atherosclerosis, aging, neurodegenerative disease, hepatic disorders, obesity, diabetes, psoriasis, and autoimmune diseases. This review summarizes the molecular mechanisms of modulation of gene expression by curcumin.

The chemokine superfamily revisited

The chemokine superfamily consists of a large number of ligands and receptors. At first glance, this family appears redundant and their ligand-receptor relationships promiscuous, making its study challenging. However, analyzing this family from the evolutionary perspective greatly simplifies understanding both the organization and function of this apparently complex system. In particular, the functions of a subgroup of chemokines (designated homeostatic chemokines) have played pivotal roles in advancing our understanding of the organization and function of the cellular networks that shape the immune system. Here, we update the full scope of the human and mouse chemokine superfamilies and their relationships and summarize several important roles that homeostatic chemokines play in the immune system.

Halting metastasis through CXCR4 inhibition

Metastasis occurs when cancer cells leave the primary tumor site and migrate to distant parts of the body. The CXCR4-SDF-1 pathway facilitates this migration, and its expression has become the hallmark of several metastatic cancers. Targeted approaches are currently being developed to inhibit this pathway, and several candidates are now in clinical trials. Continued exploration of CXCR4 inhibitors will generate compounds that have improved activity over current candidates.

SDF and GABA interact to regulate axophilic migration of GnRH neurons

Stromal derived growth factor (SDF-1) and gamma-aminobutyric acid (GABA) are two extracellular cues that regulate the rate of neuronal migration during development and may act synergistically. The molecular mechanisms of this interaction are still unclear. Gonadotropin releasing hormone-1 (GnRH) neurons are essential for vertebrate reproduction. During development, these neurons emerge from the nasal placode and migrate through the cribriform plate into the brain. Both SDF-1 and GABA have been shown to regulate the rate of GnRH neuronal migration by accelerating and slowing migration, respectively. As such, this system was used to explore the mechanism by which these molecules act to produce coordinated cell movement during development. In the present study, GABA and SDF-1 are shown to exert opposite effects on the speed of cell movement by activating depolarizing or hyperpolarizing signaling pathways, GABA via changes in chloride and SDF-1 via changes in potassium. GABA and SDF-1 were also found to act synergistically to promote linear rather than random movement. The simultaneous activation of these signaling pathways, therefore, results in tight control of cellular speed and improved directionality along the migratory pathway of GnRH neurons.

Intracellular CXCR4⁺ cell targeting with T22-empowered protein-only nanoparticles

BACKGROUND

Cell-targeting peptides or proteins are appealing tools in nanomedicine and innovative medicines because they increase the local drug concentration and reduce potential side effects. CXC chemokine receptor 4 (CXCR4) is a cell surface marker associated with several severe human pathologies, including colorectal cancer, for which intracellular targeting agents are currently missing.

RESULTS

Four different peptides that bind CXCR4 were tested for their ability to internalize a green fluorescent protein-based reporter nanoparticle into CXCR4⁺ cells. Among them, only the 18 mer peptide T22, an engineered segment derivative of polyphemusin II from the horseshoe crab, efficiently penetrated target cells via a rapid, receptor-specific endosomal route. This resulted in accumulation of the reporter nanoparticle in a fully fluorescent and stable form in the perinuclear region of the target cells, without toxicity either in cell culture or in an in vivo model of metastatic colorectal cancer.

CONCLUSION

Given the urgent demand for targeting agents in the research, diagnosis, and treatment of CXCR4-linked diseases, including colorectal cancer and human immunodeficiency virus infection, T22 appears to be a promising tag for the intracellular delivery of protein drugs, nanoparticles, and imaging agents.

Chemokine 25-induced signaling suppresses colon cancer invasion and metastasis

Chemotactic cytokines (chemokines) can help regulate tumor cell invasion and metastasis. Here, we show that chemokine 25 (CCL25) and its cognate receptor chemokine receptor 9 (CCR9) inhibit colorectal cancer (CRC) invasion and metastasis. We found that CCR9 protein expression levels were highest in colon adenomas and progressively decreased in invasive and metastatic CRCs. CCR9 was expressed in both primary tumor cell cultures and colon-cancer-initiating cell (CCIC) lines derived from early-stage CRCs but not from metastatic CRC. CCL25 stimulated cell proliferation by activating AKT signaling. In vivo, systemically injected CCR9+ early-stage CCICs led to the formation of orthotopic gastrointestinal xenograft tumors. Blocking CCR9 signaling inhibited CRC tumor formation in the native gastrointestinal CCL25+ microenvironment, while increasing extraintestinal tumor incidence. NOTCH signaling, which promotes CRC metastasis, increased extraintestinal tumor frequency by stimulating CCR9 proteasomal degradation. Overall, these data indicate that CCL25 and CCR9 regulate CRC progression and invasion and further demonstrate an appropriate in vivo experimental system to study CRC progression in the native colon microenvironment.

Imaging agents for the chemokine receptor 4 (CXCR4)

The interaction between the chemokine receptor 4 (CXCR4) and stromal cell-derived factor-1 (SDF-1, also known as CXCL12) is a natural regulatory process in the human body. However, CXCR4 over-expression is also found in diseases such as cancer, where it plays a role in, among others, the metastatic spread. For this reason it is an interesting biomarker for the field of diagnostic oncology, and therefore, it is gaining increasing interest for applications in molecular imaging. Especially "small-molecule" imaging agents based on T140, FC131 and AMD3100 have been extensively studied. SDF-1, antibodies, pepducins and bioluminescence have also been used to visualize CXCR4. In this critical review reported CXCR4 targeting imaging agents are described based on their affinity, specificity and biodistribution. The level wherein CXCR4 is up-regulated in cancer patients and its relation to the different cell lines and animal models used to evaluate the efficacy of the imaging agents is also discussed (221 references).