Suppression of tumor growth by viral vector-mediated gene transfer of N-terminal truncated platelet factor 4

Recombinant Parvoviruses Armed to Deliver CXCL4L1 and CXCL10 Are Impaired in Their Antiangiogenic and Antitumoral Effects in a Kaposi Sarcoma Tumor Model Due To the Chemokines' Interference with the Virus Cycle

Application of oncolytic viruses is a valuable option to broaden the armament of anticancer therapies, as these combine specific cytotoxic effects and immune-stimulating properties. The self-replicating H-1 parvovirus (H-1PV) is a prototypical oncolytic virus that, besides targeting tumor cells, also infects endothelial cells, thus combining oncolytic and angiostatic traits. To increase its therapeutic value, H-1PV can be armed with cytokines or chemokines to enhance the immunological response. Some chemokines-more specifically, the CXCR3 ligands CXCL4L1 and CXCL10-combine immune-stimulating properties with angiostatic activity. This study explores the therapeutic value of recombinant parvoviruses carrying CXCL4L1 or CXCL10 transgenes (Chi-H1/CXCL4L1 or Chi-H1/CXCL10, respectively) to inhibit the growth of the human Kaposi sarcoma cell line KS-IMM. KS-IMM cells infected by Chi-H1/CXCL4L1 or Chi-H1/CXCL10 released the corresponding chemokine and showed reduced migratory capacity. Therefore, the antitumoral capacity of Chi-H1/CXCL4L1 or Chi-H1/CXCL10 was tested in mice. Either in vitro infected KS-IMM cells were injected or subcutaneously growing KS-IMM xenografts were treated by peritumoral injections of the different viruses. Surprisingly, the transgenes did not increase the antitumoral effect of natural H-1PV. Further experiments indicated that CXCL4L1 and CXCL10 interfered with the expression of the viral NS1 protein in KS-IMM cells. These results indicate that the outcome of parvovirus-based delivery of CXCR3 ligands might be tumor cell type dependent, and hence its application must be considered carefully.

Using mice to unveil the genetics of cancer resistance

In the UK, four in ten people will develop some form of cancer during their lifetime, with an individual's relative risk depending on many factors, including age, lifestyle and genetic make-up. Much research has gone into identifying the genes that are mutated in tumorigenesis with the overwhelming majority of genetically-modified (GM) mice in cancer research showing accelerated tumorigenesis or recapitulating key aspects of the tumorigenic process. Yet if six out of ten people will not develop some form of cancer during their lifetime, together with the fact that some cancer patients experience spontaneous regression/remission, it suggests there are ways of 'resisting' cancer. Indeed, there are wildtype, spontaneously-arising mutants and GM mice that show some form of 'resistance' to cancer. Identification of mice with increased resistance to cancer is a novel aspect of cancer research that is important in terms of providing both chemopreventative and therapeutic options. In this review we describe the different mouse lines that display a 'cancer resistance' phenotype and discuss the molecular basis of their resistance.

The Ron receptor tyrosine kinase positively regulates angiogenic chemokine production in prostate cancer cells

Overexpression of the Ron receptor tyrosine kinase has recently been shown in a wide variety of human cancers. However, no studies have examined Ron receptor expression or function during prostate tumorigenesis. We report here that Ron is highly expressed in human prostate adenocarcinoma and metastatic lymph nodes compared to normal prostate or benign prostate hyperplasia. Furthermore, we show that Ron is overexpressed in PC-3 and DU145 prostate cancer cell lines, and that levels of angiogenic chemokines produced by prostate cancer cells positively correlates with Ron expression. Knockdown of Ron in PC-3 or DU145 cells results in a significant decrease in angiogenic chemokine production and is associated with decreased activation of the transcription factor NF-kappaB. Moreover, exogenous overexpression of Ron in LNCaP cells is sufficient to induce a significant increase in angiogenic chemokines that can be abrogated by inhibition of NF-kappaB signaling. Given that the function of angiogenic chemokines is important in the development of new blood vessels, we also examined the ability of Ron to modulate endothelial cell migration. Our data show that knockdown of Ron in prostate cancer cells results both in significantly less endothelial cell chemotaxis compared to Ron-expressing cells in vitro as well as in reduced tumor growth and decreased microvessel density following orthotopic transplantation into the prostate in vivo. In total, our data suggest that the Ron receptor is important in modulating prostate tumor growth by modulating angiogenic chemokine production and subsequent endothelial cell recruitment.

In vivo fate and therapeutic efficacy of PF‐4/CTF microspheres in an orthotopic human glioblastoma model

The correlation between glioma grade and angiogenesis suggests that antiangiogenic therapies are potentially therapeutically effective for these tumors. However, to achieve tumor suppression, antiangiogenic therapies need to be administered daily using high systemic quantities. We designed a biodegradable polymeric device that overcomes those barriers by providing sustained local delivery of a C-terminal fragment of platelet factor 4 (PF-4/CTF), an antiangiogenic agent. Fluorescent-labeled microspheres composed of poly lactic-coglycolic acid (PLGA) were loaded with rhodamine-labeled PF-4/CTF and formulated to release their contents over time. Fluorescent labeling enabled the correlation between the in vitro to the in vivo kinetic and release studies. PF-4/CTF microspheres were injected into established intracranial human glioma tumors in nude mice. Noninvasive magnetic resonance imaging (MRI) was used to assess the therapeutic response. Tumor size, microvessel density, proliferation, and apoptosis rate were measured by histological analysis. Intracranially, the microspheres were located throughout the tumor bed and continuously released PF-4/CTF during the entire experimental period. MRI and histological studies showed that a single injection of microspheres containing PF-4/CTF caused a 65.2% and 72% reduction in tumor volume, respectively, with a significant decrease in angiogenesis and an increase in apoptosis. Our data demonstrate that polymeric microspheres are an effective therapeutic approach for delivering antiangiogenic agents that result in the inhibition of glioma tumor growth.

Anti-angiogenic gene therapy of cancer: current status and future prospects

The discovery of endogenous inhibitors of angiogenesis has made it possible to test the hypothesis that blocking the angiogenic switch may keep tumor growth in check, and has added a new investigational arm to the field of cancer gene therapy. Angiogenesis inhibitors are heterogeneous in origin and potency, and their growing list includes proteolysis products of larger molecules with a different function, such as angiostatin, endostatin and vasostatin, modulators of vascular endothelial growth factor activity, such as sFLT-1, and some cytokines/chemokines with marked anti-endothelial activity, such as IL-12, IFN-alpha, and CXCL10. Pre-clinical studies have clearly indicated that these factors are essentially cytostatic and that they need long-term administration in order to obtain prolonged anti-tumor effects, representing a rational basis for their delivery by a gene therapy approach. The experimental approaches attempted to date, reviewed herein, indicate overall that anti-angiogenic gene therapy has efficacy mainly as an early intervention strategy and that a better understanding of the biological mechanisms underlying resistance to angiogenesis inhibition, as well as appropriate combined treatments, are required to generate a conceptual advancement which could drive the field towards successful management of established tumors.

Roles of platelet factor 4 in hematopoiesis and angiogenesis

Platelet factor 4 (PF4) has been recognized as a physiological inhibitor of megakaryocytopoiesis and angiogenesis for two decades. Structure-function studies have shown that the DLQ determinant in position 54-56 is necessary for megakaryocytic inhibition whereas mutations of these residues into ELR sequence and more importantly, into DLR sequence, induce a stronger inhibitory activity of peptide p47-70 on angiogenesis. The alpha-helix region of peptides may participate in the fixation of the effector to its cellular receptor and the other important structural domains would activate the receptor. In vivo, PF4 and its related peptides can protect hematopoiesis from chemotherapy by enhancing cell viability and suppress tumor growth through anti-angiogenic pathway. Several PF4 fragments and modified molecules exhibit antiangiogenesis properties and may become an alternative for further therapeutic angiogenesis.

4q loss is potentially an important genetic event in MM tumorigenesis: identification of a tumor suppressor gene regulated by promoter methylation at 4q13.3, platelet factor 4

In this study, we have elucidated the chromosomal imbalances in the multistep pathogenesis and delineated several critical tumor suppressor gene (TSG) loci in multiple myeloma (MM). By using comparative genomic hybridization, allelotyping, and multicolor interphase fluorescence in situ hybridization, 5 MM cell lines and bone marrow CD138+ plasma cells from 88 Chinese patients with monoclonal gammopathy of undetermined significance (MGUS) and early and advanced stages of MM were investigated. In all MGUS and MM samples, chromosome copy number abnormalities were detected. A higher number of chromosomal imbalances and specific genetic alterations are involved in MGUS to MM transition (−6q, +3p, and +1p) and MM progression (+2p and +9q). In addition to −13q, we first found high frequencies (42% to 46%) of −4q involving high percentages (70% to 74%) of clonal plasma cells in both MGUS and MM, suggesting that inactivation of TSG in this region is also a potentially critical genetic event in MM tumorigenesis. By high-resolution allelotyping, we defined a common deletion region on 4q13.3 and found that a candidate TSG, platelet factor 4, was frequently silenced by promoter hypermethylation in MM (15 of 28) and MM cell lines (5 of 5). These data have opened up a new approach in the molecular targeting therapy and provide novel insights into MM tumorigenesis.

Oncolytic HSV armed with platelet factor 4, an antiangiogenic agent, shows enhanced efficacy

Oncolytic herpes simplex viruses (HSV) have emerged as a promising platform for cancer therapy. However, efficacy as single agents has thus far been unsatisfactory. Tumor vasculature is critical in supporting tumor growth, but successful antiangiogenic approaches often require maintaining constant levels of antiangiogenic products. We hypothesized that oncolytic HSV has the potential to destroy tumor vasculature and that this effect can be enhanced by combination with antiangiogenic gene transfer. We examined the strategy of arming oncolytic HSV with an antiangiogenic transgene, platelet factor 4 (PF4). The PF4 transgene was inserted into oncolytic HSV G47Delta utilizing a bacterial artificial chromosome construction system. Whereas bG47Delta-empty showed robust cell killing and migration inhibition of proliferating endothelial cells (HUVEC and Py-4-1), the effect was further enhanced by PF4 expression. Importantly, enhanced potency did not impede viral replication. In vivo, bG47Delta-PF4 was more efficacious than its nonexpressing parent bG47Delta-empty at inhibiting tumor growth and angiogenesis in both human U87 glioma and mouse 37-3-18-4 malignant peripheral nerve sheath tumor models. Enhancing the antiangiogenic properties of oncolytic HSV through the expression of antiangiogenic factors such as PF4 is a powerful new strategy that targets both the tumor cells and tumor vasculature.

Kinase domain insert containing receptor promoter controlled suicide gene system selectively kills human umbilical vein endothelial cells

AIM: To study the selective killing of human umbilical vein endothelial cells (HUVECs) by a double suicide gene under the regulation of a kinase domain insert containing receptor (KDR) promoter and mediated by an adenoviral gene vector.

METHODS: Human KDR promoter was cloned by polymerase chain reaction (PCR), and two recombinant adenoviral plasmids pAdKDR-CdglyTK, pAdCMV-CDglyTK were constructed according to a two-step transformation protocol. These two newly constructed plasmids were then transfected into 293 packaging cells to grow adenovirus, which were further multiplied and purified. HUVECs and LoVo cells were infected with either of the two resultant recombinant adenoviruses (AdKDR-CDglyTK and AdCMV-CDglyTK) respectively, and the infection rates were estimated by detection of green fluorescent protein (GFP) expression. Infected cells were cultured in culture media containing different concentrations of 5-fluorocytosine (5-FC) and ganciclovir (GCV), and the killing effects were measured.

RESULTS: The two recombinant adenoviral plasmids pAdKDR-CdglyTK, pAdCMV-CDglyTK were successfully constructed and transfected into 293 cells. The resultant recombinant adenoviruses infected cells caused similar infection rates; and the infected cells exhibited different sensitivity to the prodrugs: HUVECs infected with AdCMV-CDglyTK and LoVo cells infected with AdCMV-CDglyTK were highly sensitive to the prodrugs, and HUVECs infected with AdKDR-CDglyTK were similarly sensitive but significantly more sensitive than the LoVo cells infected with AdKDR-CdglyTK (P < 0.001).

CONCLUSION: Selective killing of HUVECs may be achieved by gene transfer of double suicide gene under the regulation of the KDR promoter. This finding may provide an optional way to target gene therapy of malignant tumors by abrogation of tumor blood vessels.

Live Attenuated Salmonella Carrying Platelet Factor 4 cDNAs as Radioprotectors

To determine whether live attenuated Salmonella carrying platelet factor 4 cDNAs can protect mice from radiation damage, the attenuated Salmonella SL3261 was used as oral vector for targeted gene delivery. The recovery of mice receiving sublethal total-body irradiation (TBI) was investigated after the oral administration of attenuated Salmonella carrying cDNA for platelet factor 4 (PF4) or truncated PF4. This oral gene therapy protected mice from radiation damage after TBI. The number of bone marrow cells and high proliferative potential colony-forming cells (HPP-CFCs) increased significantly at day 7. Similarly, the administration of PF4 or PF4(17-70) protein also improved the survival of mice after TBI. Both PF4 gene therapy and protein administration accelerated hematopoietic recovery in vivo in mice after irradiation. In vitro, PF4 also promoted survival and proliferation of 5-fluorouracil-resistant hematopoietic stem/progenitor cells after irradiation. These data demonstrate a novel biological function of PF4 as a protector against radiation injury and suggest that attenuated Salmonella could be used in vivo as a PF4 DNA delivery vector in the management of radiation injury.

Liposome-mediated gene transfer of K1-5 suppresses tumor development and improves the prognosis of hepatocellular carcinoma in mice

It has been reported that kringle 1-5 (K1-5) has a potent and specific antiangiogenic activity. In the present study, we investigated the antitumor effect of gene transfer of K1-5 for hepatocellular carcinoma in mice. Inhibitory effect by the media of Cos-1 cells containing K1-5 on bovine capillary endothelial (BCE) cell proliferation was evaluated by a tetrazolium-based assay. For tumor growth, intrahepatic metastasis, and survival studies, intravenous injection of liposome-K1-5 cDNA complexes was performed to nude mice implanted with three hepatoma cell lines into the liver. Production of K1-5 was investigated by immunohistochemistry and Western blotting. The number of vessels in the tumor was counted in 0.125 mm2 fields. Expression of vascular endothelial growth factor (VEGF) and angiopoietin (Ang)-1 and -2 in tumors was investigated by Western blotting. Serum ALT levels and body weight of the mice were measured. Proliferation of BCE cells was inhibited by 44% in the media containing K1-5. Gene transfer of K1-5 suppressed tumor growth of the three hepatoma cell lines, respectively. In the K1-5-treated group, survival period was prolonged and the number of intrahepatic metastases was reduced. Expression of K1-5 protein was detected on hepatoma cells and hepatocytes. The number of vessels in tumor tissues was decreased by K1-5 transfection. Expression of angiopoietin-2 in tumor tissues was suppressed by K1-5 transfection. Serum ALT levels and body weight of mice were not influenced by K1-5 transfection. These findings suggest that antiangiogenic gene therapy with K1-5 cDNA will be a safe and effective strategy to suppress the growth of hepatocellular carcinoma.

Serological protein profiling of neuroblastoma by ProteinChip SELDI-TOF technology

Serological proteins of neuroblastoma were profiled and analyzed by ProteinChip-SELDI-TOF MS technology with five types of protein chips. By comparing with normal control, a number of protein or polypeptide signals were found significantly and consistently different in their intensities (expression levels) in tumor sera. Interestingly, nine polypeptide peaks in these proteomic features can be simultaneously detected with consistent variations by more than one type of protein chips. None of the expression differences of these nine polypeptides was found in similar comparisons between healthy controls and hepatomas. Preliminary protein identification showed hints for that some of these proteomic alterations may be closely related to the tumorigenesis of neuroblastoma. These results demonstrated the potential of serological biomarker identification for neuroblastoma by ProteinChip-SELDI technology.

Kinase domain insert containing receptor promotor controlled suicide gene system kills human umbilical vein endothelial cells

AIM: To evaluate the killing effect of double suicide gene mediated by adenovirus and regulated under kinase domain insert containing receptor (KDR) promoter on human umbilical vein endothelial cells.

METHODS: By PCR technology, human KDR promoter gene, Escherichia coli (E. coli) cytosine deaminase (CD) gene and the herpes simple virus-thymidine kinase (TK) gene were cloned. Plasmid pKDR-CDglyTK was constructed with them. Then, a recombinant adenoviral plasmid pAdKDR-CDglyTK was constructed in a “two-step transformation protocol”. The newly constructed plasmids were transfected to 293 packaging cells to grow adenoviruses, which were further propagated and purified. Human umbilical vein endothelial cells (HUVEC) were infected with a different multiplicity of infection (MOI) of resultant recombinant adenovirus, the infection rate was measured with the aid of (GFP) expression. Infected cells were cultured in culture media containing different concentrations of (GCV) and/or 5-(FC), and the killing effects were measured.

RESULTS: Recombinant adenoviruses AdKDR-CDglyTK were successfully constructed, and they infected HUVEC cells efficiently. Our data indicated that the infection rate was relevant to MOI of recombinant adenoviruses. HUVEC cells infected with AdKDR-CDglyTK were highly sensitive to the prodrugs, their survival rate correlated to both the concentration of the prodrugs and the MOI of recombinant adenoviruses. Our data also indicated that the two prodrugs used in combination were much more effective on killing transgeneic cells than GCV or 5-FC used alone.

CONCLUSION: Prodrug/KDR-CDglyTK system is effective on killing HUVEC cells, its killing effect correlates to the concentration of prodrugs and recombinant adenovirus’ MOI. Combined use of the two prodrugs confers better killing effects on transgeneic cells.

Angiogenesis inhibitors found within the haemostasis pathway

Angiogenesis, the development of new blood vessels from the existing vasculature, and haemostasis, the coagulation cascade leading to formation of a clot, are among the most consistent host responses associated with cancer. Importantly, these two pathways interrelate, with blood coagulation and fibrinolysis influencing tumor angiogenesis directly, thereby contributing to tumor growth. Moreover, many endogenous inhibitors of angiogenesis are found within platelets or harboured as cryptic fragments of haemostatic proteins. In this review we outline ways in which angiogenesis is coordinated and regulated by haemostasis in human cancer. Then we detail the experimental and pre-clinical evidence for the ability of many of these endogenous proteins to inhibit tumor angiogenesis and thus their potential to be anti-cancer agents, with particular reference to any clinical trials.

Antiangiogenic gene therapy of cancer: recent developments

With the role of angiogenesis in tumor growth and progression firmly established, considerable effort has been directed to antiangiogenic therapy as a new modality to treat human cancers. Antiangiogenic agents have recently received much widespread attention but strategies for their optimal use are still being developed. Gene therapy represents an attractive alternative to recombinant protein administration for several reasons. This review evaluates the potential advantages of gene transfer for antiangiogenic cancer therapy and describes preclinical gene transfer work with endogenous angiogenesis inhibitors demonstrating the feasibility of effectively suppressing and even eradicating tumors in animal models. Additionally, we describe the advantages and disadvantages of currently available gene transfer vectors and update novel developments in this field. In conclusion, gene therapy holds great promise in advancing antiangiogenesis as an effective cancer therapy and will undoubtedly be evaluated in human clinical trials in the near future.