Ido D. Weiss

Involvement of the CXCL12/CXCR4 pathway in the advanced liver disease that is associated with hepatitis C virus or hepatitis B virus

Chronic hepatitis C virus (HCV) and hepatitis B virus (HBV) infection is accompanied by inflammation and fibrosis eventually leading to cirrhosis. The chemokine CXCL12 is involved in chronic inflammatory conditions. The role of the CXCL12/CXCR4 pathway in HCV‐ and HBV‐associated liver inflammation and fibrosis was therefore studied. The levels and tissue localization of CXCL12 in liver and plasma of HCV and HBV patients were tested using immunohistochemistry and ELISA. The expression and function of CXCR4 on liver‐infiltrating lymphocytes (LIL) were tested by FACS and transwell migration assays. We found that CXCL12 is expressed by bile duct epithelial cells in normal liver tissue. Bile duct proliferation and liver fibrosis in chronic HCV and HBV infection result in the anatomical re‐distribution of CXCL12 in the liver. Moreover, CXCL12 is up‐regulated in the endothelium of neo‐blood‐vessels formed in active inflammatory foci and is significantly elevated, compared with controls, in the plasma of patients with advanced liver fibrosis. Complementing these observations were others indicating that over 50% of LIL express CXCR4 and, in response to CXCL12, migrated and adhered to fibronectin. These observations suggest an important role for the CXCL12/CXCR4 pathway in recruitment and retention of immune cells in the liver during chronic HCV and HBV infection.

IFN-γ Acts on T Cells to Induce NK Cell Mobilization and Accumulation in Target Organs

The mechanism(s) that regulates NK cell mobilization and the significance of this process to NK cell activity are unknown. After Con A-induced hepatitis, NK cells are mobilized from the spleen and bone marrow into the periphery in an IFN-γ-dependent fashion. Intraperitoneal administration of IFN-γ stimulates the mobilization of NK cells into the circulation, but not their cell death or proliferation. Increased number of circulating NK cells was coupled with their accumulation in the peritoneum, liver, and tumor-bearing lung tissue. Furthermore, increased number of NK cells in the lung reduced metastasis of Lewis lung carcinoma cells (3LL cell line) resulting in significantly extended NK-dependent survival. Mobilization of NK cells was specific and required the presence of T cells. Moreover, mobilization and migration of spleen NK cells in response to IFN-γ treatment is dependent on the chemokine receptor CXCR3. Mechanistic insights regarding the role of IFN-γ in the regulation of NK cell mobilization and their accumulation at sites of tumor metastasis may lead to the development of novel immunotherapy for cancer.

64Cu-AMD3100 - A novel imaging agent for targeting chemokine receptor CXCR4

CXCR4 is a chemokine receptor which has been shown to be exploited by various tumors for increased survival, invasion, and homing to target organs. We developed a one step radiosynthesis for labeling the CXCR4-specific antagonist AMD3100 with Cu-64 to produce (64)Cu-AMD3100 with a specific activity of 11.28Ci/ micromol (417GBq/ micromol) at the end of radiosynthesis. Incorporation of Cu(II) ion into AMD3100 did not change its ability to inhibit cellular migration in response to the (only) CXCR4 ligand, SDF-1/CXCL12. (64)Cu-AMD3100 binding affinity to CXCR4 was found to be 62.7 microM. Biodistribution of (64)Cu-AMD3100 showed accumulation in CXCR4-expressing organs and tissues, a renal clearance pathway, and an anomalous specific accumulation in the liver. We conclude that (64)Cu-AMD3100 exhibits promise as a potential PET imaging agent for visualization of CXCR4-positive tumors and metastases and might be used to guide and monitor anti-CXCR4 tumor therapy.

CD4+CXCR4highCD69+ T cells accumulate in lung adenocarcinoma.

The chemokine receptor CXCR4 is involved in the growth and metastasis of tumor cells. However, the expression of its ligand, the chemokine CXCL12, in tumors and its role in regulating the accumulation of immune cells within the tumors is not clear. Using ELISA and immunohistochemistry we found that CXCL12 is expressed in the majority of nonsmall cell lung cancer tissue sections obtained from stage IA to IIB nonsmall cell lung cancer patients undergoing operation. Histopathologic examination of these sections indicated that high CXCL12 expression correlated with increased tumor inflammation. In addition, disease recurrence rates in a subgroup of adenocarcinoma patients showed a tendency to correlate with high CXCL12 expression in the tumor. Isolation of adenocarcinoma-infiltrating immune cells demonstrated an increase in the percentage of CD4+CD69+CXCR4+ T cells as compared with normal lung tissue. About 30% of these cells expressed the regulatory T cell markers CD25high and FoxP3. The percentage of CD8 T cells within the tumor did not change, however; the percentage of NK and NK T cells was significantly reduced. In correlation with CXCR4 expression, CD4 T cells showed increased migration in response to CXCL12 compared with CD8 T cells and NK cells. Overall, these observations suggest that CXCL12 expression may influence tumor progression by shaping the immune cell population infiltrating lung adenocarcinoma tumors.

CCR6 is required for epidermal trafficking of γδ T cells in an IL-23-induced model of psoriasiform dermatitis

A subset of CCR6+, γδ-low (GDL) T cells that express Th17 cytokines in mouse skin participates in IL-23-induced psoriasisform dermatitis. We use CCR6-deficient (KO) and wildtype (WT) mice to analyze skin trafficking patterns of GDL T cells and function-blocking mAbs to determine the role of CCR6 in IL-23-mediated dermatitis. Herein, CCL20 was highly upregulated in IL-23-injected WT mouse ear skin as early as 24 hours after initial treatment, and large numbers of CCR6+ cells were observed in the epidermis of IL-23-injected WT mice. Anti-CCL20 mAbs reduced psoriasiform dermatitis and blocked recruitment of GDL T cells to the epidermis. In CCR6 KO mice, GDL T cells failed to accumulate in the epidermis after IL-23 treatment, but total numbers of GDL T cells in the dermis of WT and CCR6 KO mice were equivalent. There was a ~70% reduction in the proportion of IL-22+ GDL T cells in the dermis of CCR6 KO mice (vs. WT mice), suggesting that effector function as well as epidermal recruitment of GDL T cells are impaired in CCR6-deficient mice. Thus, these data show CCR6 regulates epidermal trafficking of γδ T cell subsets in skin and suggest the potential of CCR6 as a therapeutic target for psoriasis.

IFN-γ treatment at early stages of influenza virus infection protects mice from death in a NK cell-dependent manner

Influenza pandemics are imminent and represent a major world health concern. Since vaccinations are expected to be less efficient in the coming years due to newly emerging influenza virus strains, novel antiviral therapies are urgently needed. Here, we show that influenza-infected mice, capable of clearing the virus in the early stages of infection, failed to control inflammation and death. Sequential administration of Interferon-gamma (IFN-gamma) at early stage of the infection protected infected mice from death in a NK cell-dependent manner. IFN-gamma treatment stimulated NK cell proliferation and function and increased their number in the bone marrow, blood, spleen, and infected lungs, keeping viral clearance intact. In parallel, IFN-gamma treatment significantly reduced the number of T cells and NKT cells in the lungs at the inflammatory phase following infection. Thus, rapidly clearing the virus and reducing inflammation by shaping the cellular and cytokine profiles in the early stages of infection may favorably change the fate of influenza pathogenesis.

Rapid and Simple One-Step F-18 Labeling of Peptides

Labeling biomolecules with ¹⁸F is usually done through coupling with prosthetic groups, which requires several time-consuming radiosynthesis steps and therefore in low labeling yield. In this study, we designed a simple one-step ¹⁸F-labeling strategy to replace the conventional complex and the long process of multiple-step radiolabeling procedure. Both monomeric and dimeric cyclic RGD peptides were modified to contain 4-NO₂-3-CF₃ arene as precursors for direct ¹⁸F labeling. Binding of the two functionalized peptides to integrin α(v)β₃ was tested in vitro using the MDA-MB-435 human breast cell line. The most promising functionalized peptide, the dimeric cyclic RGD, was further evaluated in vivo in an orthotopic MDA-MB-435 tumor xenograft model. The use of relatively low amount of precursor (~0.5 μmol) gave reasonable yield, ranging from 7 to 23% (decay corrected, calculated from the start of synthesis) after HPLC purification. Overall reaction time was 40 min, and the specific activity of the labeled peptide was high. Modification of RGD peptides did not significantly change the biological binding affinities of the modified peptides. Small animal PET and biodistribution studies revealed integrin specific tumor uptake and favorable biokinetics. We have developed a novel one-step ¹⁸F radiolabeling strategy for peptides that contain a specific arene group, which shortens reaction time and labor significantly, requires low amount of precursor, and results in specific activity of 79 ± 13 GBq/μmol. Successful introduction of 4-fluoro-3-trifluoromethylbenzamide into RGD peptides may be a general strategy applicable to other biologically active peptides and proteins.

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.

In vitro and in vivo therapeutic efficacy of CXCR4 antagonist BKT140 against human non–small cell lung cancer

OBJECTIVES CXCR4/CXCL12 interactions promote non-small cell lung cancer (NSCLC) growth and dissemination. Furthermore, this axis might promote NSCLC resistance to chemotherapy and/or radiotherapy. Therefore, the CXCR4/CXCL12 axis constitutes an attractive therapeutic target for the treatment of NSCLC. We aimed to characterize the therapeutic efficacy of the novel CXCR4 antagonist BKT140 against human NSCLC. METHODS We determined the CXCR4 expression in 5 NSCLC cell lines (H358, A549, H460, H1299, and L4). We then tested the colony-forming capacity and proliferation of these cells in the presence of CXCL12 and BKT140. Next, we measured the in vivo growth of A549 and H460 xenografts with or without BKT140 treatment. Finally, we examined, in vitro, the potential antiproliferative effect of BKT140 combined with cisplatin or paclitaxel and after irradiation of NSCLC cells. RESULTS All tested cell lines expressed CXCR4 and showed increased colony formation in response to CXCL12 stimulation. BKT140 reduced the colony-forming capacity of NSCLC cells. Proliferation assays demonstrated both cytotoxic and cytostatic properties for this peptide. H460 cells were the most sensitive to BKT140 and A549 cells the least. Subcutaneous administration of BKT140 significantly delayed the development of H460 xenografts and showed a similar trend for A549 xenografts. Finally, the antiproliferative effects of BKT140 appears to be additive to those of chemotherapeutic drugs and radiotherapy. CONCLUSIONS Targeting the CXCL12/CXCR4 axis with BKT140 attenuated NSCLC cells tumor growth and augmented the effects of chemotherapy and radiotherapy. Future research will benefit from delineating the downstream mechanism of BKT140 action and defining BKT140 susceptibility markers.

PET Imaging of Tenascin-C with a Radiolabeled Single-Stranded DNA Aptamer

Tenascin-C is an extracellular matrix glycoprotein that is expressed by injured tissues and by various cancers. Recent publications showed that tenascin-C expression by cancer lesions predicts tumor growth, metastasis, and angiogenesis, suggesting tenascin-C as a potential therapeutic target. Currently there is no noninvasive method to determine tumoral tenascin-C expression in vivo. To address the need for an agent to image and quantify tenascin-C, we report the development of a radioactive PET tracer based on a tenascin-C–specific single-stranded DNA aptamer (tenascin-C aptamer). Methods: Tenascin-C aptamer was radiolabeled with 18F and 64Cu. PET imaging studies for the evaluation of tumor uptake and pharmacokinetics of tenascin-C aptamer were performed in comparison to a nonspecific scrambled aptamer (Sc aptamer). Results: The labeled tenascin-C aptamer provided clear visualization of tenascin-C–positive but not tenascin-C–negative tumors. The uptake of tenascin-C aptamer was significantly higher than that of Sc aptamer in tenascin-C–positive tumors. The labeled tenascin-C aptamer had fast clearance from the blood and other nonspecific organs through the kidneys, resulting in high tumor contrast. Conclusion: Our data suggest that suitably labeled tenascin-C aptamer can be used as a PET tracer to image tumor expression of tenascin-C with a high tumor-to-background ratio and might provide insightful and personalized medical data that will help determine appropriate treatment and monitoring.