Adenovirus-p53 gene therapy in human nasopharyngeal carcinoma xenografts

Adenovirus siMDM2 and NDRG2 Gene Therapy Inhibits Cell Proliferation and Induces Apoptosis of Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) is one of the most common skin cancers. In the present study, we explored the effects of depletion of murine double minute gene 2 (MDM2) together with overexpression of N-myc downstream-regulated gene 2 (NDRG2) on cutaneous SCC. In order to achieve high efficiency of gene knockdown and overexpression in SCC-13 cells, recombinant adenovirus carrying siMDM2 and NDRG2 expression construct was produced. We found Ad-siMDM2, Ad-NDRG2, and Ad-siMDM2-NDRG2 infections inhibit the growth of SCC-13 cells in vitro, and Ad-siMDM2-NDRG2 infection has the highest inhibitory effect. Subcutaneous injections of Ad-siMDM2, Ad-NDRG2, and Ad-siMDM2-NDRG2 into SCC-13 xenograft nude mice resulted in the reduction of tumor volume. Moreover, we found that apoptosis protein caspase 3 was up-regulated in the Ad-siMDM2-, Ad-NDRG2-, and Ad-siMDM2-NDRG2-treated groups. Our data indicate that the adenovirus-mediated MDM2 silencing and NDRG2 overexpression can synergistically inhibit local cancer cell proliferation, induce apoptosis, and further prevent metastases of SCC. Our study provides a promising method that can be further developed as a new therapeutic approach against SCC.

Experimental studies on the inhibition of adenovirus-ING4-OSM therapy on nasopharyngeal carcinoma proliferation in vitro and in vivo

In the present study, the effects of the co-transfer of the tumor growth inhibitor 4 gene (ING4) together with the Oncostatin M (OSM) were investigated on tumor regression and subsequent tumor recurrence. We constructed a recombinant adenovirus carrying ING4 and OSM, which could induce high-level expression of these three genes in NPC CNE-1 cells. Ad-ING4, Ad-OSM and Ad-ING4-OSM infection all inhibited the growth of CNE-1 cells in vitro, while the Ad-ING4-OSM exerted the strongest inhibitory effect. In CNE-1 xenograft tumor models mice, an intratumoral injection of Ad-ING4, Ad-OSM and Ad-ING4-OSM resulted in a reduced tumor burden, compared to normal saline controls. Therefore, we suggested that the introduction of adenovirus-mediated ING4 and OSM genes could synergistically decrease the recurrence or metastases and develop a control of NPC tumors, which advocate a promising therapeutic future in NPC treatment.

Inauhzin sensitizes p53-dependent cytotoxicity and tumor suppression of chemotherapeutic agents

Toxicity and chemoresistance are two major issues to hamper the success of current standard tumor chemotherapy. Combined therapy of agents with different mechanisms of action is a feasible and effective means to minimize the side effects and avoid the resistance to chemotherapeutic drugs while improving the antitumor effects. As the most essential tumor suppressor, p53 or its pathway has been an attractive target to develop a new type of molecule-targeting anticancer therapy. Recently, we identified a small molecule, Inauhzin (INZ), which can specifically activate p53 by inducing its deacetylation. In this study, we tested if combination with INZ could sensitize tumor cells to the current chemotherapeutic drugs, cisplatin (CIS) and doxorubicin (DOX). We found that compared with any single treatment, combination of lower doses of INZ and CIS or DOX significantly promoted apoptosis and cell growth inhibition in human non-small lung cancer and colon cancer cell lines in a p53-dependent fashion. This cooperative effect between INZ and CIS on tumor suppression was also confirmed in a xenograft tumor model. Therefore, this study suggests that specifically targeting the p53 pathway could enhance the sensitivity of cancer cells to chemotherapeutic agents and markedly reduce the doses of the chemotherapy, possibly decreasing its adverse side effects.

Role of p53 mutations, protein function and DNA damage for the radiosensitivity of human tumour cells

PURPOSE

The tumour suppressor protein p53 is considered to have an impact on the radiosensitivity of tumour cells. However, this concept does not easily translate to the tumour sensitivity in the clinics. The aim of the present study was to determine whether a functional or dysfunctional p53 is associated with a sensitive or resistant phenotype. It was further studied whether DNA damage might be an additive factor by which p53 has impact on cell survival.

MATERIALS AND METHODS

Nine human tumour cell lines were studied for p53 mutation by direct sequencing of exons 4-9. Regulation of p53 and p21(cip1/waf1) protein was assessed by immunoblotting and cell cycle effects by combining 5-bromodeoxyuridine incorporation and flow cytometry.

RESULTS AND CONCLUSION

Three strains (RT112, Du145, SCC4451) were found to have a missense-mutation in the core domain and one did not express p53 at all (HeLa), presumably due to HPV18 infection. Immunoblots of these cells showed neither a regulated p53 nor p21 expression. The cells did not arrest in G1 phase after X-irradiation but did arrest in G2/M. All cells expressing wild-type protein (LNCaP, T47D-B8, MCF-7 and sublines BB and Bus) showed an intact p53 and p21 regulation and a modest arrest in both G1 and G2/M. Thus, in contrast to other studies, all tumour cells investigated showed either a typical p53wt or mutant (mut) pattern. Protein function was compared with cell survival and DNA damage, as assessed previously. p53 wild-type cells were on average 1.3-times (n.s.) more radiosensitive than mutant cells, but there was a considerable overlap between both groups. Further, the 1.3-fold enhanced resistance of cells lacking wild-type p53 was paralleled by a 1.3-fold lower number of induced double-strand breaks. The results suggest that p53 could have impact on chromatin compaction and thus effect DNA damage induction and radiosensitivity of tumour cells.

Efficacy of systemically administered mutant vesicular stomatitis virus (VSVDelta51) combined with radiation for nasopharyngeal carcinoma

PURPOSE

Nasopharyngeal carcinoma (NPC) is a malignancy of the head and neck region that is associated with EBV latency. Curative treatments for NPC achieve modest survival rates, underscoring a need to develop novel therapies. We evaluated the therapeutic potential of a mutant vesicular stomatitis virus (VSVDelta51) as single treatment modality or in combination with ionizing radiation (RT) in NPC.

EXPERIMENTAL DESIGN

MTS assay was used to assess cell viability in vitro; apoptosis was measured using propidium iodide staining and caspase activation. In vivo experiments were conducted using tumor-bearing nude mice with or without local RT (4 Gy). Apoptosis was assessed in excised tumor sections with terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining.

RESULTS

Our data showed that NPC cells are exquisitely sensitive to VSVDelta51 oncolysis, which correlated with the presence of EBV. Efficacy of VSVDelta51 against NPC cells was further augmented when combined with RT. A single systemic injection of VSVDelta51 achieved 50% survival in treated mice, which increased to 83% when combined with local tumor RT. In addition to induction of apoptosis, an antiangiogenic effect of VSVDelta51 was observed in vivo, suggesting a novel tumoricidal mechanism for VSVDelta51. This virus also prevented growth of NPC sphere-forming cells in vitro, showing potential utility in targeting NPC-initiating cells.

CONCLUSIONS

Our data represent the first report showing that EBV-positive NPC cells are exquisitely sensitive to VSVDelta51 oncolysis and documenting the successful utilization of this combinatorial regimen as a novel curative therapeutic strategy for NPC.

Potential utility of BimS as a novel apoptotic therapeutic molecule

We have previously demonstrated a 1000-fold induction of gene expression exclusive to Epstein-Barr virus (EBV)-positive nasopharyngeal carcinoma (NPC) cells using an adenoviral vector (ad5.oriP). This platform allows us to explore tumor-specific gene therapy with BimS (ad5.oriP.BimS), a potent proapoptotic Bcl-2 family member. Ad5.oriP.BimS (25 infectious units (ifu)/cell) reduced C666-1 viability in a time- and dose-dependent manner to 15% survival. The effect was enhanced with radiation (6 Gy). Three days after infection, the proportion of apoptotic cells increased from 3.5% (control) to 47.5% (25 ifu/cell). Confocal microscopy demonstrated Bim colocalization to the mitochondria within 18 h of ad5.oriP.BimS infection. Ad5.oriP.BimS induced a 2.8-, 2.1-, and 1.85-fold increase in caspase-3, -8, and -9 activities, respectively. When C666-1 cells were infected with ad5.oriP.BimS (20 ifu/cell), no tumors formed in 7/9 mice followed for 100 days. Six intratumoral injections of ad5.oriP.BimS (1.5 x 10(9) ifu/dose) in combination with radiation were sufficient to cause almost complete disappearance of established C666-1 or C15 xenograft tumors. Intravenous injections of ad5.oriP.BimS (10(9) ifu) induced mild perturbation in liver function tests, associated with hepatocyte apoptoses and mitoses. This vector appears to be safe and effectively cytotoxic to EBV-positive NPC cells both in vitro and in vivo, mediated primarily through the induction of apoptosis.

Efficacy of targeted FasL in nasopharyngeal carcinoma

We have successfully achieved selective gene expression in human nasopharyngeal carcinoma (NPC) by exploiting the presence of the Epstein-Barr virus (EBV), utilizing a transcriptional targeting strategy (J. H. Li et al., 2002, Cancer Res. 62: 171). Building on this platform, we have generated a novel DeltaE1 adenoviral vector mediating the expression of a mutant noncleavable form of the FasL gene (HUGO-approved symbol TNFSF6) (ad5oriP.ncFasL). We observe that this therapy induces significant cytotoxicity in the EBV-positive NPC cell line C666-1, mediated by the induction of caspase-dependent apoptosis. The addition of ionizing radiation therapy (RT) causes additional cytotoxicity. Ex vivo infection of C666-1 cells with adv.oriP.ncFasL completely prevents tumor formation in SCID mice followed for up to 100 days. The combination of intratumoral adv.oriP.ncFasL with RT causes regression of established nasopharyngeal xenograft tumors for 2 weeks' duration. Systemic delivery of this targeted strategy achieves 50-fold higher gene expression in nasopharyngeal tumors than in normal organs. Intravenously injected adv.oriP.ncFasL results in mild perturbation of liver function that returns to normal 2 weeks after initial therapy. These results demonstrate the efficacy of our EBV-specific targeting strategy, which allows the potentially safe and effective utilization of a highly potent membrane-based apoptotic gene.

A Conditionally Replicating Adenovirus for Nasopharyngeal Carcinoma Gene Therapy

Successful attainment of tumor-specific gene expression was achieved in nasopharyngeal carcinoma (NPC) by exploiting the exclusive presence of the Epstein-Barr virus (EBV) genome in the cancer cells. In the current study, we have utilized an EBV-dependent transcriptional targeting strategy to construct a novel conditionally replicating adenovirus, adv.oriP.E1A. After treatment with adv.oriP.E1A, we observed extensive cell death in the EBV-positive NPC cell line C666-1. In contrast, no cytotoxicity was observed in a panel of other human EBV-negative cell lines, including fibroblasts from the nasopharynx. In vitro adenoviral replication was confirmed by the time-dependent increase in the expression of adenoviral capsid fiber protein and adenoviral DNA after C666-1 cells were infected with adv.oriP.E1A. Tumor formation was inhibited for more than 100 days after ex vivo infection of C666-1 cells with adv.oriP.E1A. Combination of local tumor radiation and adv.oriP.E1A caused complete disappearance of established tumors for at least 2 weeks in two distinct EBV-positive NPC xenograft models. Safety of this treatment was determined through the systemic delivery of adv.oriP.E1A in vivo, whereby minimal temporary perturbation of liver function was observed. We have successfully established a conditionally replicating adenovirus for EBV-positive NPC, which is both safe and efficacious, indicating a strategy that may be therapeutically applicable.

Heat-directed suicide gene therapy for breast cancer

Adjuvant hyperthermia can improve treatment outcome for locally recurrent breast cancer (LRBC). Previously, we demonstrated that infection of human breast cancer cells with a recombinant adenovirus expressing beta-galactosidase from the human hsp70b gene promoter (Ad.70b.betagal) results in 50- to 800-fold increases in reporter gene expression following heat treatment (30 minutes at 43 degrees C). Here, we describe a heat-directed suicide gene therapy strategy based on an adenoviral vector (Ad.70b.CDTK) in which expression of the dual prodrug-activating E. coli cytosine deaminase/herpes simplex virus thymidine kinase (CDTK) fusion gene is under the control of the hsp70b promoter. Treatment of T47D and MCF-7 breast cancer cells with mild hyperthermia (43 degrees C/30 minutes) and prodrugs (100 microg/ml 5-fluorocytosine and 10 microg/ml ganciclovir) following infection with Ad.70b.CDTK (10-100 PFU/cell) resulted in 30- to 60-fold decreases in clonogenic survival relative to control cultures treated with heat or prodrugs alone. Clonogenic survival declined even further (up to 240-fold) following heat treatment at 41.5 degrees C for 120 minutes. A decreased clonogenic survival was accompanied by tumor cell apoptosis. These results demonstrate that this combined treatment strategy can be highly effective against heat- and radiation-resistant breast tumor cells and supports the continued development of heat-directed CDTK suicide gene therapy strategies for LRBC.

Novel gene therapy approach for nasopharyngeal carcinoma

This article will provide an overview on the status of cancer gene therapy, focussed specifically on its potential application in nasopharyngeal carcinoma (NPC). The concepts and strategies behind the design of therapeutic targets such as p53, p16, and death genes will be described. One of the major challenges in cancer gene therapy is tumor-specific expression of therapeutic genes, and a transcriptional targeting approach will be reviewed, in reference to NPC. Specifically, the ability to exploit the presence of Epstein-Barr virus (EBV) will be emphasized. The currently available preclinical data on genetic therapeutic approaches for NPC will be reviewed, and an outline for its future role in management of NPC, in conjunction with existing cytotoxic modalities of ionizing radiation and chemotherapy will be provided.