Eradication of Pre-Established Lymphoma Using Herpes Simplex Virus Amplicon Vectors

Applications of chemokines as adjuvants for vaccine immunotherapy

Vaccinations are expected to aid in building immunity against pathogens. This objective often requires the addition of an adjuvant with certain vaccine formulations containing weakly immunogenic antigens. Adjuvants can improve antigen processing, presentation, and recognition, thereby improving the immunogenicity of a vaccine by simulating and eliciting an immune response. Chemokines are a group of small chemoattractant proteins that are essential regulators of the immune system. They are involved in almost every aspect of tumorigenesis, antitumor immunity, and antimicrobial activity and also play a critical role in regulating innate and adaptive immune responses. More recently, chemokines have been used as vaccine adjuvants due to their ability to modulate lymphocyte development, priming and effector functions, and enhance protective immunity. Chemokines that are produced naturally by the body's own immune system could serve as potentially safer and more reliable adjuvant options versus synthetic adjuvants. This review will primarily focus on chemokines and their immunomodulatory activities against various infectious diseases and cancers.

AhR and Arnt differentially regulate NF-κB signaling and chemokine responses in human bronchial epithelial cells

Background

The aryl hydrocarbon receptor (AhR) has gradually emerged as a regulator of inflammation in the lung and other tissues. AhR may interact with the p65-subunit of the nuclear factor (NF)-κB transcription factors, but reported outcomes of AhR/NF-κB-interactions are conflicting. Some studies suggest that AhR possess pro-inflammatory activities while others suggest that AhR may be anti-inflammatory. The present study explored the impact of AhR and its binding partner AhR nuclear translocator (Arnt) on p65-activation and two differentially regulated chemokines, CXCL8 (IL-8) and CCL5 (RANTES), in human bronchial epithelial cells (BEAS-2B).

Results

Cells were exposed to CXCL8- and CCL5-inducing chemicals, 1-nitropyrene (1-NP) and 1-aminopyrene (1-AP) respectively, or the synthetic double-stranded RNA analogue, polyinosinic-polycytidylic acid (Poly I:C) which induced both chemokines. Only CXCL8, and not CCL5, appeared to be p65-dependent. Yet, constitutively active unligated AhR suppressed both CXCL8 and CCL5, as shown by siRNA knock-down and the AhR antagonist α-naphthoflavone. Moreover, AhR suppressed activation of p65 by TNF-α and Poly I:C as assessed by luciferase-assay and p65-phosphorylation at serine 536, without affecting basal p65-activity. In contrast, Arnt suppressed only CXCL8, but did not prevent the p65-activation directly. However, Arnt suppressed expression of the NF-κB-subunit RelB which is under transcriptional regulation by p65. Furthermore, AhR-ligands alone at high concentrations induced a moderate CXCL8-response, without affecting CCL5, but suppressed both CXCL8 and CCL5-responses by Poly I:C.

Conclusion

AhR and Arnt may differentially and independently regulate chemokine-responses induced by both inhaled pollutants and pulmonary infections. Constitutively active, unligated AhR suppressed the activation of p65, while Arnt may possibly interfere with the action of activated p65. Moreover, ligand-activated AhR suppressed CXCL8 and CCL5 responses by other agents, but AhR ligands alone induced CXCL8 responses when given at sufficiently high concentrations, thus underscoring the duality of AhR in regulation of inflammation. We propose that AhR-signaling may be a weak activator of p65-signaling that suppresses p65-activity induced by strong activators of NF-κB, but that its anti-inflammatory properties also are due to interference with additional pathways.

Chemokine-based immunotherapy: delivery systems and combination therapies

A major role of chemokines is to mediate leukocyte migration through interaction with G-protein-coupled receptors. Various delivery systems have been developed to utilize the chemokine properties for combating disease. Viral and mutant viral vectors expressing chemokines, genetically modified dendritic cells with chemokine or chemokine receptors, engineered chemokine-expressing tumor cells and pDNA encoding chemokines are among these methods. Another approach for inducing a targeted immune response is fusion of a targeting antibody or antibody fragment to a chemokine. In addition, chemokines induce more effective antitumor immunity when used as adjuvants. In this regard, chemokines are codelivered along with antigens or fused as a targeting unit with antigenic moieties. In this review, several chemokines with their role in inducing immune response against different diseases are discussed, with a major emphasis on cancer.

The therapeutic function of the chemokine RANTES on the H22 hepatoma ascites model

This study aimed at analyzing the therapeutic function of the chemokine RANTES on the H22 hepatoma ascites model and preliminarily explore the mechanism of RANTES in malignant ascites to provide an important reference for applying chemokines in anti-tumor therapy. The murine H22 hepatoma ascites model was used. Three treatment groups were analyzed: a RANTES treatment group, an IL-2 control group, and an NS control group. Two regimens of early treatment and late treatment were designed, and the therapeutic effect of RANTES on malignant ascites was studied by measuring changes in mouse body weight and abdominal circumference and observing the survival time. The expression of TNF-α, IFN-γ, TGF-β1, and MCP-1 in mouse ascites was detected by ELISA, and the chemotactic function of RANTES on B lymphocytes and T lymphocytes was analyzed by flow cytometry. In the early and late treatment regimens, RANTES could effectively inhibit the increase in mouse body weight and abdominal circumference in the murine H22 hepatoma ascites model. The secretion of TNF-α and IFN-γ, which had anti-tumor effects, was higher in the RANTES treatment group than in the control groups (P < 0.05), whereas the secretion of TGF-β1 and MCP-1, which promoted tumor growth, invasion, and metastasis, was lower than in the control groups (P < 0.05). RANTES had chemotactic effects on CD4(+) and CD8(+) T lymphocytes; therefore, the percentage of CD3, CD4, and CD8 in the mouse ascites in the RANTES treatment group was significantly higher than in the NS control and IL-2 treatment groups, and the CD4/CD8 ratio was also significantly higher. RANTES can effectively inhibit the increase in body weight and abdominal circumference and significantly extend survival time in mice in the H22 hepatoma ascites model.

Engineered herpes simplex virus vectors for antitumor therapy and vaccine delivery

Genetically modified herpes simplex viruses (HSVs) have been exploited for both antitumor therapy and vaccine delivery. These mutant viruses retain their ability to replicate and lyse permissive cells, including many tumor types, and are referred to as oncolytic HSVs. In addition, deletion of nonessential genes permits the introduction of foreign genes to augment the antitumor effect by either immune stimulation, targeting for select tumors, or expression of tumor or vaccine antigens. This article reviews the development of oncolytic HSVs as an anticancer therapy, as well as the application of HSV-1 vectors for delivery of targeted antigens or as vaccine adjuvants. The impact of these novel vectors with respect to enhanced antitumor activity and development of antitumor vaccination strategies is discussed.

CCL5 as an adjuvant for cancer immunotherapy

IMPORTANCE OF THE FIELD

To date cancer immunotherapy has only achieved limited clinical efficacy, thus more efficient immunotherapeutic approaches need to be explored. The CC chemokine CCL5 plays a role in chemoattraction and activation of immune cells implying its potential clinical application as an adjuvant for boosting anti-tumor immunity, although an effect on carcinogenesis and tumor cell invasiveness is also reported to be associated with CCL5.

AREAS COVERED IN THIS REVIEW

Recent progress in exploiting CCL5 as an adjuvant for cancer prevention and treatment, and updated understanding on how CCL5 is involved in tumor invasiveness and carcinogenesis.

WHAT THE READER WILL GAIN

CCL5 represents a natural adjuvant for enhancing anti-tumor immune responses. However, animal experiments and clinical reports suggest that CCL5 plays a role in carcinogenesis and invasiveness of tumor cells. Therefore, a CCL5-based cancer therapeutic approach needs to avoid the CCL5-associated potential detrimental effects.

TAKE HOME MESSAGE

CCL5 has a pre-eminent role in chemotaxis and activation of a wide spectrum of immune cells. CCL5 functions as an adjuvant to boost anti-tumor immunity by diverse protocols such as co-immunization of recombinant CCL5 protein with tumor-associated antigen, vaccination with CCL-5-expressing tumor cells, or viral vector delivery of CCL5 cDNA into growing tumor. CCL5 may also promote tumor cell survival, proliferation and invasion by different mechanisms.

Development of vaccination approaches for the treatment of neurological diseases

Several progressive neurodegenerative diseases share a common pathology: the accumulation of misfolded proteins within cells or neuropil of the brain. Characteristically, these misfolded proteins form organized beta-sheet-containing assemblies that have optical and biochemical properties of amyloid. Thus, the brain amyloidoses, Alzheimer's disease (AD), Parkinson's disease, and the prionoses or transmissible spongioform encelphalopathies (TSEs) all manifest putatively pathogenic misfolded proteins, suggesting that these proteins or their precursors may be targets for therapeutics development efforts. Two different biological approaches, both predicated on vaccination, are discussed in this monograph as preclinical approaches for the treatment of AD and a TSE. Herein, I first describe an active vaccination approach that exploits immune shaping to engender a prophylactic T(H)2 response to Abeta in AD mouse models. Second, I describe a passive vaccination strategy whereby recombinant adeno-associated virus vectored delivery of anti-prion single-chain fragment variable antibodies attenuates disease progression and promotes life extension in a mouse TSE model.

Chemokines and the microenvironment in neuroectodermal tumor-host interaction

Chemokines and chemokine receptors play an important role in immune homeostasis and surveillance. Altered or defective expression of chemokines and/or chemokine receptors could lead to a disease state including autoimmune disorder or cancer. Tumors from glioblastoma, melanoma, and neuroblastoma secrete high levels of chemokines that can promote tumor growth and progression or induce stromal cells present in the tumor microenvironment to produce cytokines or chemokines which, in turn, can regulate angiogenesis, tumor growth, and metastasis. On the other hand, chemokines secreted by tumor or stromal cells can also attract leukocytes such as dendritic cells, macrophages, neutrophils, and lymphocytes which may downmodulate tumor growth. New therapies that are aimed at limiting tumor growth and progression by attracting immune effector cells to the tumor site with chemokines may hold the key to the successful treatment of cancer, although this approach may be hampered by possible tumor growth-stimulating effects of chemokines.

Immune-directed gene therapeutic development for Alzheimer's, prion, and Parkinson's diseases

The development of novel immune-based therapeutics for neurodegenerative diseases is an area of intense focus. Neurodegenerative diseases represent a particular challenge since in many cases the onset of symptoms occurs after considerable degeneration has ensued. Based on human genetic and histopathological evidence from patients with neurodegenerative diseases, animal models that recapitulate specific pathologic features have been developed. Utilizing these animal models in combination with viral vector-based gene therapeutics, specific epochs of disease can be targeted. One common feature of several neurodegenerative diseases is misfolded proteins. The mechanism by which these altered protein conformers lead to neurodegeneration is not completely understood but much effort has been put forward to either degrade aberrant protein or prevent the formation of misfolded conformers. In this review, we will summarize work that employs viral vector gene therapeutics to modulate the brain's response to misfolded proteins with a specific focus on neurodegeneration.

RANTES-403 polymorphism is associated with reduced risk of gastric cancer in women

BACKGROUND

Men are more susceptible to gastric cancer (GC) than women. However, the genetic factors associated with the sex difference are not well understood. Chemokines have been shown to modulate tumor behavior, and the sex-specific effect of the chemokine polymorphisms on the host susceptibility to several diseases has been reported. We aimed to determine the role of chemokine polymorphisms on host susceptibility to GC, with special interest on their sex-specific effect.

METHODS

A hospital-based case-control study, including 177 patients with GC and 217 age-matched unaffected healthy controls, was performed in three major tertiary care hospitals. Genotyping for regulated upon activation, normal T-cell expressed and secreted (RANTES) -403 A/G and -28 C/G, CC chemokine receptor 5 (CCR5) deletion, and CCR2-V64I was performed using peripheral blood DNA.

RESULTS

The RANTES -403 GA and AA genotypes were independently associated with a 2.3-fold reduced risk of developing GC (OR=0.44, 95% CI 0.22-0.90, P=0.025) compared with GG genotype in women, but not in men. The RANTES -28C/G and CCR2-V64I polymorphisms were not associated with different risk of developing GC. The tumor stage, histological features, and survival rate were not different when stratified by RANTES -403 and -28 and CCR2-V64I genotypes.

CONCLUSIONS

Our data indicate that women who inherit A allele at RANTES -403 may be at reduced risk of GC.

Augmentation of anti-tumor responses of adoptively transferred CD8+T cells in the lymphopenic setting by HSV amplicon transduction

Treatment of cancer with cytotoxic agents may induce lymphopenia. Adoptively transferred T cells have been reported to display enhanced anti-tumor efficacy in the lymphopenic setting. We reasoned that the anti-tumor effects of adoptively transferred cells in the lymphopenic host could be further augmented through local provision of an innate stimulus in the tumor bed. Utilizing a model in which mice were irradiated to induce lymphopenia, with limited shielding to allow tumor growth, we demonstrate that "triple" therapy consisting of radiation-induced lymphopenia, adoptive transfer of naïve CD8+ T cells, and intra-tumoral HSV amplicon injection resulted in reduced tumor growth compared to the combination of any two of the aforementioned interventions. To gain insight into the mechanism underlying this effect we studied the effects of HSV amplicon transduction into tumors on cytokine expression and on anti-tumor specific T cells. HSV amplicon transduction specifically induced several cytokine mRNAs including IFN-gamma, and IP-10. Adoptively transferred transgenic OT-1 T cells directed against Ovalbumin were more effective against Ovalbumin-expressing tumors when combined with intra-tumoral HSV amplicon injections in the lymphopenic host. Following intra-tumoral HSV-amplicon injections, anti-tumor T cells secreted higher levels of interferon-gamma in response to in-vitro re-stimulation with tumor cells, implying that HSV amplicon injection provided a strong signal for T cell activation. Combining adoptive transfer of naïve T cells in the lymphopenic setting with local T cell stimulation may facilitate expansion and activation of anti-tumor T cell populations in vivo, resulting in enhanced anti-tumor responses without the need to resort to prolonged in vitro T cell culture and/or manipulation.

Adoptively transferred tumor-specific T cells stimulated ex vivo using herpes simplex virus amplicons encoding 4-1BBL persist in the host and show antitumor activity in vivo

4-1BB is a T-cell costimulatory receptor which binds its ligand 4-1BBL, resulting in prolonged T cell survival. We studied the antitumor effects of adoptively transferred tumor-specific T cells expanded ex vivo using tumors transduced with herpes simplex virus (HSV) amplicons expressing 4-1BBL as a direct source of antigen and costimulation. We constructed HSV amplicons encoding either the 4-1BBL (HSV.4-1BBL) or B7.1 (HSV.B7.1) costimulatory ligands. Lewis lung carcinoma cells expressing ovalbumin (LLC/OVA) were transduced with HSV.4-1BBL, HSV.B7.1, or control HSV amplicons and used to stimulate GFP+ OVA-specific CD8+ T cells (OT-1/GFP) ex vivo. Naive or ex vivo stimulated OT-1/GFP cells were adoptively transferred into LLC/OVA tumor-bearing mice. Higher percentages of OT-1/GFP cells were seen in the peripheral blood, spleen, and tumor bed of the HSV.4-1BBL-stimulated OT-1/GFP group compared with all other experimental groups. OT-1 cells identified within the tumor bed and draining lymph nodes of the HSV.4-1BBL-stimulated OT-1 group showed enhanced bromodeoxyuridine (BrdUrd) incorporation, suggesting ongoing expansion in vivo. Mice receiving HSV.4-1BBL-stimulated OT-1/GFP had significantly decreased tumor volumes compared with untreated mice (P<0.001) or to mice receiving naive OT-1/GFP (P<0.001). Transfer of HSV.B7.1-stimulated OT-1/GFP did not protect mice from tumor. Mice that received HSV.4-1BBL-stimulated OT-1/GFP exhibited increased cytolytic activity against LLC/OVA and higher percentages of Ly-6C+ OT-1/GFP in the spleen and tumor bed compared with controls. Tumor-specific T cells stimulated ex vivo using tumor transduced with HSV.4-1BBL expand in vivo following adoptive transfer, resulting in tumor eradication and the generation of tumor-specific CD44+Ly-6C+CD62L- effector memory T cells.

Differential regulation of RANTES and IL-8 expression in lung adenocarcinoma cells

In lung adenocarcinoma, expression of Regulated upon Activation, Normal T cell Expressed and presumably Secreted (RANTES) is a predictor of survival while that of interleukin (IL)-8 is associated with a poor prognosis. In several models, tumorigenesis is abolished by RANTES, while it is facilitated by IL-8. We studied the regulation of RANTES and IL-8 expression in A549 lung adenocarcinoma cells. The effects of tumor necrosis factor (TNF)-alpha and regulators of protein kinases C (PKC)alpha/beta were tested because these have been shown to modulate cancer development and progression. TNF-alpha stimulated expression of both chemokines, while the PKCalpha/beta activator 12-O-tetradecanoyl-phorbol-13-acetate (TPA) induced only expression of IL-8 and inhibited TNF-alpha-induced RANTES expression. The PKCalpha/beta inhibitor Gö 6976 increased TNF-alpha-induced RANTES production and prevented its down-regulation by TPA. In contrast, it decreased TNF-alpha or TPA-induced IL-8 release. The differential regulation of RANTES and IL-8 expression was further analyzed. Site-directed mutagenesis indicated that regulation of RANTES promoter activity required two nuclear factor (NF)-kappaB response elements but not its activator protein (AP)-1 binding sites. An AP-1 and a NF-kappaB recognition sites were necessary for full induction of IL-8 promoter activity by TNF-alpha and TPA. Moreover, electrophoretic mobility shift assays demonstrated that NF-kappaB response elements from the RANTES promoter were of lower affinity than that from the IL-8 promoter. Immunoblotting experiments showed that TPA was more potent than TNF-alpha to induce in a PKCalpha/beta dependent manner the p44/p42 mitogen-activated protein kinases (MAPK) signaling cascade which controls AP-1 activity. Conversely, TPA inhibited TNF-alpha-induced NF-kappaB signaling and was a weak activator of this pathway. Thus, TPA did not sufficiently activate NF-kappaB to increase transcription through the low affinity NF-kappaB binding sites on RANTES promoter and its inhibitory effect on TNF-alpha-induced NF-kappaB signaling resulted in a reduced transcription rate. On IL-8 promoter, increased transcription through the high affinity NF-kappaB binding site occurred even with poorly activated NF-kappaB and the functional AP-1 response element compensated any loss of transcription rate. These data provide a mechanistic insight into the differential regulation of IL-8 and RANTES expression by PKCalpha/beta in lung adenocarcinoma cells.

Spatial and temporal expression of herpes simplex virus type 1 amplicon-encoded genes: implications for their use as immunization vectors

There is great interest in developing new immunization vectors. Helper virus-free herpes amplicons, plasmid-based vectors that encode no viral gene products and have an extremely large coding capacity, are attractive viral vaccine candidates for expressing recombinant proteins in vivo for immunization. Earlier studies in mice, using amplicons encoding the gp120 protein of human immunodeficiency virus (HIV), resulted in strikingly robust cellular immune responses as measured by cytotoxicity and interferon gamma enzyme-linked immunospot assays. To begin to understand how such vectors function in vivo to generate an immune response, we used amplicons encoding reporter constructs including green fluorescent protein (GFP) and luciferase to examine the duration of expression after administration to mice. Luciferase expression, measured with the IVIS system from Xenogen/Caliper Life Sciences (Hopkinton, MA) and by enzymatic assays of tissue extracts, revealed that expression after injection of the HSVluc amplicons peaked earlier than 24 hr after injection into mice. HSVegfp injection resulted in peak accumulation of GFP 24 hr after administration in vivo. Thus, both reporter genes revealed a rather rapid and robust expression pattern of short duration. The short period of expression appears in part to be due to gene silencing. Examination of the cells transduced by amplicons encoding GFP and human B7.1 suggested that the amplicons transduce a variety of cells, including professional antigen-presenting cells. From this and previous work, we conclude that amplicons may engender a potent immune response by directly transducing dendritic cells as well as by cross-priming of antigen produced by other transduced host cells.

Optimal purification method for Herpes-based viral vectors that confers minimal cytotoxicity for systemic route of vector administration

Herpes simplex virus (HSV)-1 amplicon vectors could be packaged in the presence of replication-competent helper virus or in a helper virus-free system. In the latter system, cytotoxicity due to the expression of de novo viral gene expression is greatly reduced due to the absence of helper virus. However, the titers produced are relatively low in the range of 10(7) and 10(8)TU/ml after sucrose gradient concentration. This may become a limitation to certain gene transfer applications, such as brain disorder studies since the volume of vectors that could be administered is restricted. In contrast, amplicon viral vectors of high titers can be easily generated in the presence of helper viruses. Despite the potential cytotoxicity caused by the presence of helper virus in the latter method of viral packaging, studies involving vector targeting would still require the complementing function of helper virus for the generation of recombinant HSV-1 amplicon vectors with modified viral envelopes. In view of this, the optimal method of purifying Herpes-based viral vectors that confers minimal cytotoxicity for systemic route of viral vector administration is examined. Parameters such as the ratio of amplicon versus helper viruses, the percentage of viral lost, and the extent of liver cytotoxicity induced by these viral vectors purified using different methods were investigated. In addition, the maximum recombinant HSV-1 viral dosage was also determined in vivo. Taken together, these findings may be of importance to the efficient production of contaminant-free HSV-1 amplicon viral vectors required for animal and human studies.

Soluble human LAG-3 molecule amplifies the in vitro generation of type 1 tumor-specific immunity

The adjuvant activities of the human lymphocyte activation gene-3 (LAG-3) molecule have been evaluated in a human setting by investigating the ability of a soluble recombinant human LAG-3 protein (hLAG-3Ig) to enhance the in vitro induction of viral- and tumor-specific CTLs. We found that soluble human LAG-3 significantly sustained the generation and expansion of influenza matrix protein Melan-A/MART-1 and survivin-specific CD8+ T lymphocytes in peripheral blood mononuclear cells (PBMC) of both cancer patients and healthy donors, showing its ability to boost CD8+ T-cell memory response or to prime naive T cells in vitro. The peptide-specific T cells generated in the presence of hLAG-3Ig were endowed with cytotoxic activity and enhanced release of type 1 cytotoxic T (Tc1) cytokines and were able to recognize tumor cells expressing their nominal antigen. Phenotype and cytokine/chemokines produced by antigen-presenting cells (APC) of PBMCs exposed in vitro for 2 days to peptide and hLAG-3Ig indicate that the LAG-3-mediated adjuvant effect may depend on a direct activation of circulating APCs. Our data revealed the activity of hLAG-3Ig in inducing tumor-associated, antigen-specific CD8+ T-cell responses in a human setting and strongly support the conclusion that this recombinant protein is a potential candidate adjuvant for cancer vaccines.

Herpes simplex virus type-1 amplicon vectors for vaccine generation in acute lymphoblastic leukemia

For leukemia vaccine generation, high-efficiency gene transfer is required to express immunomodulatory molecules that stimulate potent antileukemic immune responses. In this context, herpes simplex virus type-1 (HSV-1)-derived vectors have proven to be a promising tool for genetic modification of lymphoblastic leukemia cells. Yet, vector-associated viral protein expression might inadvertently modulate vaccine efficacy facilitating both immune evasion and immune stimulation. To explore the issue of immune-stimulation versus immune-suppression in immature lymphoblastic leukemia cells, two types of HSV-1 amplicon vectors, helper virus-dependent and helper virus-free that express the immunomodulatory molecules CD70 and IL-2, were compared with regard to their vector-associated immunomodulatory potential. We first established that lymphoblastic cell lines and primary acute lymphoblastic leukemia (ALL) cells express HSV receptor genes. Lymphoblastic cell lines were transduced with high efficiency, and in primary ALL cells high gene transfer rates of 47+/-15 and 42+/-14% were obtained with helper virus-dependent and -free HSV-1 amplicon vectors, respectively. The efficacy of the two amplicon vectors to induce antineoplastic responses was assessed in a vaccine setting in mice with pre-existing highly malignant lymphoblastic disease. Treatment of mice with vaccine cells transgenically expressing CD70+IL2 significantly suppressed lymphoblastic cell proliferation and improved survival. Of note, when helper virus-dependent HSV-1 amplicon vectors were used for vaccine preparation, the high immunogenic potential of the vector itself, in the absence of transgenic CD70+IL2 expression, seemed to be sufficient to mediate protection comparable to the antineoplastic response achieved by expression of immunomodulatory molecules. Thus for vaccine generation in B lymphoblastic leukemia, the immunogenic potential of HSV-1 helper virus-dependent amplicon vectors does provide additional benefit to the high transduction efficiency of HSV-1-derived vectors.

Expression of CCL5 (RANTES) and CCR5 in prostate cancer

BACKGROUND

Expression of the inflammatory chemokine CCL5 (RANTES) by tumor cells is thought to correlate with the progression of several cancers. CCL5 was shown to induce breast cancer cell migration, mediated by the receptor CCR5. A CCR5 antagonist was demonstrated to inhibit experimental breast tumor growth. Recently, CCL5 and CCR5 mRNA expression was reported in prostate cancer (PCa) tissues. Herein, we characterized CCL5 and CCR5 expression in cultures of PCa cells and explored possible functions of CCL5 in PCa progression.

METHODS

Quantitative RT-PCR, ELISA, and immunohistochemical staining were performed to examine CCL5 expression in prostate cell lines. CCR5 expression was measured by flow cytometry. Proliferation and invasion assays were performed to determine potential functions of CCL5 and CCR5 in PCa.

RESULTS

Expression of CCL5 mRNA and protein was found in human PCa cell lines (PC-3; DU-145; LNCaP) and primary prostate adenocarcinoma cells. CCL5 and CCR5 were also detected in human PCa tissues. CCR5 expression was demonstrated on the cell surface of PCa cells, as well as in intracellular pools. Incubation with CCL5 (10-100 ng/ml) induced PCa cell proliferation, and the CCR5 antagonist TAK-779 inhibited CCL5-induced proliferation. CCL5 was found to stimulate PCa cell invasion, and TAK-779 blocked the effects of CCL5.

CONCLUSIONS

In light of evidence that inflammation influences the pathogenesis of PCa, these results suggest that inflammatory chemokines, such as CCL5, expressed by prostate cells may act directly on the growth and survival of PCa cells. Chemokine receptor antagonists may thus block autocrine mechanisms of PCa progression.

Oncolytic measles viruses for cancer therapy

New strategies using biological agents are being developed to treat cancer. Live viruses are among these new agents. Virotherapy uses replication-competent viral vectors with strong oncolytic properties. With the use of molecular virology techniques, viruses have been genetically engineered to replicate selectively in tumour cells and are under preclinical and clinical investigation at present. Measles virus (MV) is being used for this purpose. Replication-competent attenuated Edmonston B measles vaccine strain (MV-Edm) is non-pathogenic and has potent antitumour activity against several human tumours. The virus is selectively oncolytic in tumour cells, eliciting extensive cell-to-cell fusion and ultimately leading to cell death. Therefore, MV-Edm is a safe and efficient means to kill tumour cells. Further improvements in existing MV vectors may increase tumour selectivity and oncolytic activity. This review discusses the discovery and development of replication-competent oncolytic MV for cancer therapy.

Genome-wide analysis of molecular changes in IL-12-induced control of mammary carcinoma via IFN-gamma-independent mechanisms

IL-12 is a major activator of tumor-killing NK cells and CTL. IFN-gamma mediates most of the well-known immunological activities of IL-12. In this study, we report IFN-gamma-independent activities induced by therapeutic application of rIL-12 in restricting tumor growth and metastasis in the 4T1 murine mammary carcinoma model. IFN-gamma-deficient mice carrying 4T1 tumor exhibit no gross defect in the number of tumor-infiltrating lymphocytes but have exaggerated angiogenesis in the tumor. Administration of IL-12 is able to constrict blood vessels in the tumor in the absence of IFN-gamma, and retains certain therapeutic efficacy even when applied late during tumor progression. IL-12 exposure in vivo does not irreversibly alter the immunogenicity of the tumor. Finally, global gene expression analysis of primary tumors reveals IL-12-induced molecular patterns and changes, implicating a number of novel genes potentially important for IFN-gamma-independent immune responses against the tumor, for IL-12-mediated antiproliferation, antimetastasis, and antiangiogenesis activities.

A dual role for tumor-derived chemokine RANTES (CCL5)

To investigate the role of tumor-derived CCL5 (regulated upon activation, normal T cell expressed and secreted, RANTES) in tumor immunity we compared the T cell response to tumors derived from the 4T1 murine mammary carcinoma cell line that express different levels of CCL5. Tumors that expressed low levels of CCL5 exhibited a decrease in the in vivo, but not the in vitro, growth rate. In conjunction with the decreased growth rate the tumors that produced lower levels of CCL5 contained a greater number of tumor infiltrating lymphocytes compared to tumors that express normal levels of CCL5. One explanation for these findings was that a reduction in tumor-derived CCL5 prevented the tumor-associated alteration in T cell chemotactic activity. Tumors expressing lower levels of CCL5 also elicited a greater tumor-specific T cell response as evident by examination of recently activated T cells from tumor-draining lymph nodes. However, despite the enhanced T cell response, tumors expressing low levels of CCL5 still grew slower than tumors expressing normal levels of CCL5 in SCID mice. These data are consistent with the ability of CCL5 to upregulate transcription of matrix metalloproteinase-9 (MMP9), which can contribute to angiogenesis and thus, foster growth in vivo. Consequently, these data indicate that tumor-derived CCL5 can inhibit the T cell response and enhance the in vivo growth of murine mammary carcinoma.

Chemokines and antitumor immunity: walking the tightrope

Chemokines play an important role in the generation of the immune system and in virtually every aspect of an immune response. The role of chemokines in antitumor immunity has been less straightforward to discern. A dichotomy exists in the field. One area of research has focused on the impact of tumor-derived chemokines, implicating them in everything from metastases to immune suppression. Another area of research has been dedicated to the introduction of chemokines into tumor cells in order to facilitate immune cell recruitment. In this review these two areas of investigation will be explored.

Dendritic cells transduced with HSV-1 amplicons expressing prostate-specific antigen generate antitumor immunity in mice

There is currently much interest in generating cytotoxic T lymphocyte (CTL) responses against tumor antigens as a therapy for cancer. This work describes a novel gene transfer technique utilizing dendritic cells (DCs), an extremely potent form of antigen-presenting cell (APC), and herpes simplex virus-1 (HSV-1) amplicons. HSV-1 amplicons are plasmid-based viral vectors that are packaged into HSV-1 capsids, but lack viral coding sequences. Amplicon vectors have been constructed that encode the model tumor antigen ovalbumin (HSV-OVA) and human prostate-specific antigen (HSV-PSA), a protein that is expressed specifically in prostate epithelium and prostate carcinoma cells. These amplicons were packaged using a helper virus-free system that produces vector stocks that are devoid of contaminating cytotoxic helper virus. Transduction of DCs with HSV-OVA or HSV-PSA and co-culture with CTL hybridomas results in specific activation, indicating that transduced DCs express these transgenes and process the tumor antigens for class I MHC presentation to CTL. Mice immunized with HSV-PSA-transduced DCs generate a specific CTL response that can be detected in vitro by a (51)Cr-release assay and are protected from challenge with tumors that express PSA. These results indicate that DCs transduced with HSV-1 amplicon vectors may provide a tool for investigation of the biology of CTL activation by DCs and a new modality for immunotherapy of cancer.

Chemoattractants MDC and TARC are secreted by malignant B-cell precursors following CD40 ligation and support the migration of leukemia-specific T cells

The use of tumor cells as vaccines in cancer immunotherapy is critically dependent on their capacity to initiate and amplify tumor-specific immunity. Optimal responses may require the modification of the tumor cells not only to increase their immunogenicity but also to improve their ability to recruit effector cells to the tumor sites or sites of tumor antigen exposure. It has been reported that CD40 cross-linking of acute lymphoblastic leukemia (ALL) cells significantly increases their immunogenicity and allows the generation and expansion of autologous antileukemia cytotoxic T lymphocytes. This study demonstrates that the CD40 ligation of these tumor cells also induces the secretion of the CC-chemokines MDC and TARC. Supernatants from malignant cells cultured in the presence of sCD40L promote the migration of activated T cells that express CCR4, the common specific receptor for MDC and TARC. More importantly, the supernatants from CD40-stimulated tumor cells also support the transendothelial migration of autologous CCR4(+) antileukemia T cells. Therefore, the results demonstrate that the delivery to leukemia cells of a single physiologic signal, that is, CD40 cross-linking, simultaneously improves tumor cell immunogenicity and induces potent chemoattraction for T cells. (Blood. 2001;98:533-540)

Development of herpes simplex virus-1 amplicon-based immunotherapy for chronic lymphocytic leukemia

Herpes simplex virus (HSV)-based vectors have favorable biologic features for gene therapy of leukemia and lymphoma. These include high transduction efficiency, ability to infect postmitotic cells, and large packaging capacity. The usefulness of HSV amplicon vectors for the transduction of primary human B-cell chronic lymphocytic leukemia (CLL) was explored. Vectors were constructed encoding beta-galactosidase (LacZ), CD80 (B7.1), or CD154 (CD40L) and were packaged using either a standard helper virus (HSVlac, HSVB7.1, and HSVCD40L) or a helper virus-free method (hf-HSVlac, hf-HSVB7.1, and hf-HSVCD40L). Both helper-containing and helper-free vector stocks were studied for their ability to transduce CLL cells, up-regulate costimulatory molecules, stimulate allogeneic T-cell proliferation in a mixed lymphocyte tumor reaction, and generate autologous cytotoxic T lymphocytes (CTLs). Although helper-containing and helper-free amplicon stocks were equivalent in their ability to transduce CLL cells, a vigorous T-cell proliferative response was obtained using cells transduced with hf-HSVB7.1 but not with HSVB7.1. CLL cells transduced with either HSVCD40L or hf-HSVCD40L were compared for their ability to up-regulate resident B7.1 and to function as T-cell stimulators. Significantly enhanced B7.1 expression in response to CD40L was observed using hf-HSVCD40L but not with HSVCD40L. CLL cells transduced with hf-HSVCD40L were also more effective at stimulating T-cell proliferation than those transduced with HSVCD40L stocks and were successful in stimulating autologous CTL activity. It is concluded that HSV amplicons are efficient vectors for gene therapy of hematologic malignancies and that helper virus-free HSV amplicon preparations are better suited for immunotherapy.

Cytokine gene transfer enhances herpes oncolytic therapy in murine squamous cell carcinoma

Replication-competent, attenuated herpes simplex viruses (HSV) have been demonstrated to be effective oncolytic agents in a variety of malignant tumors. Cytokine gene transfer has also been used as immunomodulatory therapy for cancer. To test the utility of combining these two approaches, two oncolytic HSV vectors (NV1034 and NV1042) were designed to express the murine GM-CSF and murine IL-12 genes, respectively. These cytokine-carrying variants were compared with the analogous non-cytokine-carrying control virus (NV1023) in the treatment of murine SCC VII squamous cell carcinoma. All three viruses demonstrated similar infection efficiency, viral replication, and cytotoxicity in vitro. SCC VII cells infected by NV1034 and NV1042 effectively produced GM-CSF and IL-12, respectively. In an SCC VII subcutaneous flank tumor model in immunocompetent C3H/HeJ mice, intratumoral injection with each virus caused a significant reduction in tumor volume compared with saline injections. The NV1042-treated tumors showed a striking reduction in tumor volume compared with the NV1023- and NV1034-treated tumors. On subsequent rechallenge in the contralateral flank with SCC VII cells, 57% of animals treated with NV1042 failed to develop tumors, in comparison with 14% of animals treated with NV1023 or NV1034, and 0% of naive animals. The increased antitumor efficacy seen with NV1042 in comparison with NV1023 and NV1034 was abrogated by CD4(+) and CD8(+) lymphocyte depletion. NV1042 is a novel, attenuated, oncolytic herpesvirus that effectively expresses IL-12 and elicits a T lymphocyte-mediated antitumor immune response against murine squamous cell carcinoma. Such combined oncolytic and immunomodulatory strategies hold promise in the treatment of cancer.

Enhanced learning in mice parallels vector-mediated nerve growth factor expression in hippocampus

Spatial learning requires the integrity of the nerve growth factor (NGF)-responsive septohippocampal pathway. Loss of a single NGF allele at the mouse NGF locus (heterozygous null, ngf(+/-)) reduces septohippocampal NGF levels and NGF-regulated cholinergic neurotransmitter enzymes and results in spatial learning deficits in adult animals. A herpes simplex virus (HSV) amplicon vector was utilized to locally deliver NGF to the hippocampus of mice heterozygous and wild type (ngf(+/+)) at the NGF gene locus. NGF gene transfer produced transient increases in NGF protein levels and choline acetyltransferase activity in both ngf(+/-) and ngf(+/+) mice. However, spatial learning capability was improved only in ngf(+/-) mice. In aggregate, these findings suggest that amplicon-directed expression of NGF in subjects with baseline septohippocampal dysfunction can correct spatial learning deficits.

Advances in immunotherapy of hematologic malignancies: cellular and humoral approaches

Monoclonal antibodies have become an important modality for cancer therapy. Genetically engineered chimeric and humanized antibodies have demonstrated activity against overt lymphoma and leukemia, as well as minimal residual disease. Radioimmunotherapy in both nonmyeloablative and myeloablative regimens has produced significant responses and also minimized radiation exposure to normal tissues. Targeted alpha-particle therapy offers the possibility of selective tumor cell kill. Antibody-drug conjugates have produced remissions in acute leukemia. Many proteins potentially act as leukemia or lymphoma-specific antigens for major histocompatibility complex-restricted T cell cytotoxicity. These include the idiotype proteins, breakpoint cluster region (bcr)-abl and other fusion oncoproteins, myeloid-specific differentiation antigens and minor histocompatibility antigens. Clinical trials exploiting the new understanding of the T cell immunology are underway.