HSV-tk gene therapy in head and neck squamous cell carcinoma. Enhancement by the local and distant bystander effect

Gene-directed enzyme prodrug therapy

As one targeting strategy of prodrug delivery, gene-directed enzyme prodrug therapy (GDEPT) promises to realize the targeting through its three key features in cancer therapy-cell-specific gene delivery and expression, controlled conversion of prodrugs to drugs in target cells, and expanded toxicity to the target cells' neighbors through bystander effects. After over 20 years of development, multiple GDEPT systems have advanced into clinical trials. However, no GDEPT product is currently marketed as a drug, suggesting that there are still barriers to overcome before GDEPT becomes a standard therapy. In this review, we first provide a general introduction of this prodrug targeting strategy. Then, we utilize the four most thoroughly studied systems to illustrate components, mechanisms, preclinical and clinical results, and further development directions of GDEPT. These four systems are herpes simplex virus thymidine kinase/ganciclovir, cytosine deaminase/5-fluorocytosine, cytochrome P450/oxazaphosphorines, and nitroreductase/CB1954 system. Later, we focus our discussion on bystander effects including local and distant bystander effects. Lastly, we discuss carriers that are used to deliver genes for GDEPT including virus carriers and non-virus carriers. Among these carriers, the stem cell-based gene delivery system represents one of the newest carriers under development, and may brought about a breakthrough to the gene delivery issue of GDEPT.

Suicide gene therapy in cancer: where do we stand now?

Suicide gene therapy is based on the introduction into tumor cells of a viral or a bacterial gene, which allows the conversion of a non-toxic compound into a lethal drug. Although suicide gene therapy has been successfully used in a large number of in vitro and in vivo studies, its application to cancer patients has not reached the desirable clinical significance. However, recent reports on pre-clinical cancer models demonstrate the huge potential of this strategy when used in combination with new therapeutic approaches. In this review, we summarize the different suicide gene systems and gene delivery vectors addressed to cancer, with particular emphasis on recently developed systems and associated bystander effects. In addition, we review the different strategies that have been used in combination with suicide gene therapy and provide some insights into the future directions of this approach, particularly towards cancer stem cell eradication.

Gene therapy and targeted toxins for glioma

The most common primary brain tumor in adults is glioblastoma. These tumors are highly invasive and aggressive with a mean survival time of 15-18 months from diagnosis to death. Current treatment modalities are unable to significantly prolong survival in patients diagnosed with glioblastoma. As such, glioma is an attractive target for developing novel therapeutic approaches utilizing gene therapy. This review will examine the available preclinical models for glioma including xenographs, syngeneic and genetic models. Several promising therapeutic targets are currently being pursued in pre-clinical investigations. These targets will be reviewed by mechanism of action, i.e., conditional cytotoxic, targeted toxins, oncolytic viruses, tumor suppressors/oncogenes, and immune stimulatory approaches. Preclinical gene therapy paradigms aim to determine which strategies will provide rapid tumor regression and long-term protection from recurrence. While a wide range of potential targets are being investigated preclinically, only the most efficacious are further transitioned into clinical trial paradigms. Clinical trials reported to date are summarized including results from conditionally cytotoxic, targeted toxins, oncolytic viruses and oncogene targeting approaches. Clinical trial results have not been as robust as preclinical models predicted; this could be due to the limitations of the GBM models employed. Once this is addressed, and we develop effective gene therapies in models that better replicate the clinical scenario, gene therapy will provide a powerful approach to treat and manage brain tumors.

Flt3L and TK gene therapy eradicate multifocal glioma in a syngeneic glioblastoma model

The disseminated characteristics of human glioblastoma multiforme (GBM) make it a particularly difficult tumor to treat with long-term efficacy. Most preclinical models of GBM involve treatment of a single tumor mass. For therapeutic outcomes to translate from the preclinical to the clinical setting, induction of an antitumor response capable of eliminating multifocal disease is essential. We tested the hypothesis that expression of Flt3L (human soluble FMS-like tyrosine kinase 3 ligand) and TK (herpes simplex virus type 1-thymidine kinase) within brain gliomas would mediate regression of the primary, treated tumor mass and a secondary, untreated tumor growing at a distant site from the primary tumor and the site of therapeutic vector injection. In both the single-GBM and multifocal-GBM models used, all saline-treated control animals succumbed to tumors by day 22. Around 70% of the animals bearing a single GBM mass treated with an adenovirus expressing Flt3L (AdFlt3L) and an adenovirus expressing TK (AdTK + GCV) survived long term. Approximately 50% of animals bearing a large primary GBM that were implanted with a second GBM in the contralateral hemisphere at the same time the primary tumors were being treated with AdFlt3L and AdTK also survived long term. A second multifocal GBM model, in which bilateral GBMs were implanted simultaneously and only the right tumor mass was treated with AdFlt3L and AdTK, also demonstrated long-term survival. While no significant difference in survival was found between unifocal and multifocal GBM-bearing animals treated with AdFlt3L and AdTK, both treatments were statistically different from the saline-treated control group (p < 0.05). Our results demonstrate that combination therapy with AdFlt3L and AdTK can eradicate multifocal brain tumor disease in a syngeneic, intracranial GBM model.

Gene therapy and targeted toxins for glioma

The most common primary brain tumor in adults is glioblastoma. These tumors are highly invasive and aggressive with a mean survival time of nine to twelve months from diagnosis to death. Current treatment modalities are unable to significantly prolong survival in patients diagnosed with glioblastoma. As such, glioma is an attractive target for developing novel therapeutic approaches utilizing gene therapy. This review will examine the available preclinical models for glioma including xenographs, syngeneic and genetic models. Several promising therapeutic targets are currently being pursued in pre-clinical investigations. These targets will be reviewed by mechanism of action, i.e., conditional cytotoxic, targeted toxins, oncolytic viruses, tumor suppressors/oncogenes, and immune stimulatory approaches. Preclinical gene therapy paradigms aim to determine which strategies will provide rapid tumor regression and long-term protection from recurrence. While a wide range of potential targets are being investigated preclinically, only the most efficacious are further transitioned into clinical trial paradigms. Clinical trials reported to date are summarized including results from conditionally cytotoxic, targeted toxins, oncolytic viruses and oncogene targeting approaches. Clinical trial results have not been as robust as preclinical models predicted, this could be due to the limitations of the GBM models employed. Once this is addressed, and we develop effective gene therapies in models that better replicate the clinical scenario, gene therapy will provide a powerful approach to treat and manage brain tumors.

Antitumor effect of secreted Flt3-ligand can act at distant tumor sites in a murine model of head and neck cancer

The Flt3 ligand (Flt3-L) manifests antitumor activity, presumably due to its capacity to recruit dendritic cells and cause their proliferation. To assess whether local production of Flt3-L can mediate a "distant bystander" effect, murine B4B8 squamous cell carcinoma cells were transfected with a plasmid encoding a secretory form of Flt3-L to produce B4B8FL cells. Similarly, B4B8FL and B4B8 cells were transfected with herpes simplex virus thymidine kinase (HSVTK) to produce B4B8TK and B4B8FL/TK cells, which should be sensitive to ganciclovir (GCV), to know whether the effects of Flt3-L and HSVTK/GCV would be synergistic. To test for a distant bystander effect in vivo, B4B8FL, B4B8TK, and B4B8FL/TK cells were injected subcutaneously into the left flank of syngeneic Balb/c mice, and naïve B4B8 cells were injected into the right flank. The formation of tumors derived from B4B8FL and B4B8FL/TK cells was significantly delayed in both flanks compared with naïve B4B8 and B4B8TK cells. Growth of B4B8TK tumors in the ipsilateral flank was retarded following GCV treatment, but in contrast to B4B8FL and B4B8FL/TK cells, no distant bystander effect in the contralateral flank was observed. Immunohistochemistry showed lymphocytic infiltrates in both flanks of the B4B8FL and B4B8FL/TK groups. The data indicate that in these cells, local secretion of Flt3-L is sufficient to evoke a distant bystander effect but that expression of HSVTK, even after GCV administration, is not. Furthermore, the combination of local Flt3-L and HSVTK production, together with GCV administration, does not enhance the distant bystander effect produced by Flt3-L alone.

Enhanced antitumor effect of RGD fiber-modified adenovirus for gene therapy of oral cancer

Current clinical success rates of adenoviral vector (Adv)-based gene therapy of squamous cell carcinoma (SCC) of the head and neck remain unsatisfactory. A major problem with this approach is thought to be related to low Adv transduction efficiency due to weak expression of the adenovirus receptor, coxsackie-adenovirus receptor (CAR), in SCC. To improve the limited infectivity of Adv in oral SCC, we constructed mutated Adv incorporating the integrin-binding motif, RGD, in the HI loop of the fiber knob. The mutated Adv infected target cells through integrins commonly expressed in oral SCC. LacZ marker gene expression after infection with this mutated Adv (Adv-F/RGD) in oral SCC cell lines that showed reduced expression of CAR was approximately 5-10 times higher than that obtained with the parental Adv containing wild-type fiber knob (Adv-F/wt). In an in vitro study, transduction of oral cancer cell lines with Adv-F/RGD expressing human IL-2 (AxCAhIL2-F/RGD) resulted in greater production of cytokine than AxCAhIL2-F/wt infection. In an in vivo therapeutic xenograft model of oral SCC in nude mice, AxCAhIL2-F/RGD demonstrated antitumor effects superior to those of AxCAhIL2-F/wt. These data suggest that exploitation of genetically altered adenovirus vectors with integrin-binding motifs may offer significant improvements in oral SCC gene therapy.

Efficacy of transfection rates on head and neck squamous cell cancer by a novel adenovirus: an in vivo and in vitro study

INTRODUCTION

Internalization of wild-type adenovirus is dependent on binding to a coxsackie-adenovirus receptor (CAR). Unfortunately, many tumors lack these receptors. We hypothesized that a novel RGD adenovirus, which binds by way of cellular integrins, would improve the transfection of head and neck cancers.

MATERIALS AND METHODS

Three squamous cell cancer lines were transfected with either the wild type or the novel RGD containing a luciferase reporter gene. After 48 hours, the transfection rate was determined. This was correlated with CAR and alphaVbeta3 and alphaVbeta5 integrin expression as determined by flow cytometry. A similar experiment was performed in a nude mouse model to determine in vivo differences of transfection rate.

RESULTS

Statistically significant increased rates of transfection were seen for the novel adenovirus at all multiplicities of infection (MOIs) in the CAL-27 and SCC-4 cell lines. Increased rates of transfection were seen at lower viral titers for the SCC-25 cells. Flow cytometry revealed low CAR expression in all cell lines but no consistent pattern of integrin expression. The nude mouse model demonstrated a 43-fold higher rate of transfection for the novel RGD adenovirus.

CONCLUSIONS

A modified RGD adenovirus increased the efficacy of transfection in specific cell lines and in the nude mouse model. It is possible that modified adenoviruses may improve gene delivery to patients with advanced or recurrent head and neck cancers.

[Antitumoral effect of HSV-tk suicide gene associated with ganciclovir in an experimental model of head and neck epidermoid carcinoma]

INTRODUCTION

We studied the transfection by adenoviral vectors and the antitumoral effect of HSV-tk gene associated with ganciclovir (AdCMVtk/GCV) in KB human oral cavity squamous cell carcinoma, in vitro and in vivo.

MATERIALS AND METHODS

Transfection was assessed by the X-gal stain. It was used in cell cultures and tumoral sections previously exposed to adenoviral vector AdCMVlacZ. In vitro, in order to study the antitumoral effect of AdCMVtk/GCV, survival of cell cultures exposed to AdCMVtk/GCV and to AdCMVlacZ/GCV was compared. In vivo, necrotic volume as a percentage of total tumoral volume, was compared between AdCMVtk/GCV treated group and AdCMVlacZ/GCV exposed group. Hepatic and renal toxicities were assessed.

RESULTS

In vitro, survival of cell cultures treated with AdCMVtk/GCV was less than AdCMVlacZ/GCV exposed cells. In vivo, necrotic volume was larger in AdCMVtk/GCV treated group than in AdCMVlacZ/GCV exposed group. No toxicity was found (hepatic, renal).

CONCLUSIONS

KB cells are transfected by adenoviral vectors and are killed by AdCMVtk/GCV, both in vitro and in vivo (no toxicity was found in the animal model).

Gene therapy for head and neck cancer

Head and neck cancer, because of its anatomic accessibility and poor overall survival rate, has become a frequent target of novel gene therapy intervention strategies. Viral and nonviral vectors have been used to transfer a variety of tumor suppressor genes, suicide genes, and immunologic genes into head and neck cancer cells in both the laboratory and clinical setting. Gene therapy as an isolated treatment modality will probably not replace standard treatment modalities in the management of head and neck cancer. It seems likely, however, that gene transfer will find its way into the multidisciplinary care of the head and neck cancer patient, where novel treatments are combined with standard therapies in order to maximize tumor response.

Naked DNA injection for liver metastases treatment in rats

The cytosine deaminase (CD) gene converts the nontoxic prodrug, 5-fluorocytosine (5-FC), into 5-fluorouracil (5-FU). We previously showed that injection of CD-bearing cancer cells followed by 5-FC treatment can act as an autologous tumor vaccine in a syngenic liver metastasis model in rats. In the present work, we analyzed the antitumor efficiency of a direct intratumoral injection of a CD-expressing plasmid. In rats bearing microscopic or macroscopic metastases in right and left liver lobes, an injection of a CD-expressing plasmid was performed in the left lobe tumor, followed by 5-FC treatment of the animals. A significant regression of the DNA-injected tumor was observed in 5-FC-treated rats, both in microscopic (P =.007) or advanced (P <.0001) tumor models. Moreover, this treatment also induced a potent distant bystander effect on untreated controlateral liver tumors and extrahepatic metastases, resulting in an increased survival compared with control animals in both tumor models (P <.05). In conclusion, these data suggest that direct intratumoral injection of a CD-expressing plasmid, associated to 5-FC administration, can constitute a powerful and innocuous alternative treatment for unresectable liver metastases from colon carcinoma.

Head and neck cancer: gene therapy approaches. Part II: genes delivered

In Part I, the review summarised the safety of adenoviral vectors and provided insight into approaches being undertaken to improve the specificity, durability and potency of adenoviral delivery vehicles. In Part II, brief discussions are held regarding results of preclinical and clinical trials with a variety of different genes, which have demonstrated antitumour activity in squamous cell carcinoma of the head and neck region (HNSCC). Studies have been performed with a variety of immune modulatory genes. Preliminary results demonstrate activity with several cytokine genes, tumour antigen genes and co-stimulatory molecule genes. Despite only preliminary results, thus far, a theoretical attractive feature for the use of gene therapy for the enhancement of immune modulation is that local injection of the gene product appears to be well tolerated. It is also successful in inducing systemic immune response, potentially providing effect to metastatic sites distal from the injected site. Animal studies have confirmed efficacy in the use of specific targeting of molecules regulating cancer growth (EGF receptor [EGFR], super oxide dismutase [SOD], cyclin D1, E1A and Bcl-2). These approaches are discussed. However, the most significant clinical advances for the use of gene therapy in advanced HNSCC involves two agents: Adp53 and ONYX-015. Preliminary Phase I and II results suggest evidence of efficacy and justify accrual Phase III trials, which are currently ongoing.

Emerging new therapies for chemotherapy-resistant cancer using adenoviral vectors

The treatment of cancer by genetic manipulation of either the tumor itself or the patient as a whole offers new avenues for the treatment of otherwise refractory cancers. Gene therapy seeks to correct underlying genetic defects in malignant tissue or to augment the host defense response or to promote selectivity of other therapies. Many innovative and exciting genetic targets have been recently identified. However, the field as a whole is still constrained by limitations of gene delivery. The most common vector for gene delivery is modified adenovirus. In this review, we survey a sampling of current therapeutic approaches that depend upon adenoviral delivery vehicles and outline the advantages and disadvantages of this vector system.

Adenovirus calcium phosphate coprecipitates enhance squamous cell carcinoma gene transfer

OBJECTIVES/HYPOTHESIS

Adenoviral-mediated gene transfer offers a potential new treatment strategy for squamous cell cancer of the head and neck (SCCHN). Initial studies on some SCCHN cell lines have shown that these cells can be resistant to adenovirus-mediated gene transfer, requiring large amounts of vector and long infection times. The objectives of this study were to identify the barriers to gene transfer in three SCCHN lines, FaDu, SCC-9, and SCC-15, and to develop a method to circumvent the obstacles. We hypothesized that a low expression of adenovirus receptors may limit adenovirus infection and this may be overcome by using adenovirus complexed with calcium phosphate coprecipitates.

METHODS

Using standard cell and molecular biology techniques, the infectability of SCCHN cells was investigated.

RESULTS

Using Cy3-labeled adenovirus, we found minimal binding of adenovirus to FaDu cells and variable levels of binding among SCC-9 and SCC-15 cells. Northern blot analysis indicated that messenger RNA (mRNA) transcripts for coxsackie-adenovirus receptor, which binds adenovirus, were absent in FaDu cells but present in SCC-9 and SCC-15 cells. Integrin alphavbeta5, which binds and facilitates internalization of adenovirus, were expressed at low levels in all three cell types. We overcame these barriers by using adenovirus complexed with calcium phosphate precipitates. Total transgene expression and the number of cells expressing transgene were increased in all three cancer lines using adenovirus complexed with calcium phosphate precipitates compared with adenovirus that was not complexed.

CONCLUSIONS

Data in the present study suggest that adenovirus-mediated gene transfer to SCCHN cell lines is a result of limited viral receptors. Delivering adenovirus in a calcium phosphate coprecipitate enhanced gene transfer and, perhaps, the therapeutic index.

Gene directed enzyme/prodrug therapy of cancer: historical appraisal and future prospectives

Gene therapy of cancer is a novel approach with the potential to selectively eradicate tumour cells, whilst sparing normal tissue from damage. In particular, gene-directed enzyme prodrug therapy (GDEPT) is based on the delivery of a gene that encodes an enzyme which is non-toxic per se, but is able to convert a prodrug into a potent cytotoxin. Several GDEPT systems have been investigated so far, demonstrating effectiveness in both tissue culture and animal models. Based on these encouraging results, phase I/II clinical trials have been performed and are still ongoing. The aim of this review is to summarise the progress made in the design and application of GDEPT strategies. The most widely used enzyme/prodrug combinations already in clinical trials (e.g., herpes simplex 1 virus thymidine kinase/ganciclovir and cytosine deaminase/5-fluorocytosine), as well as novel approaches (carboxypeptidase G2/CMDA, horseradish peroxidase/indole-3-acetic acid) are described, with a particular attention to translational research and early clinical results.

Suicide gene therapy: possible applications in haematopoietic disorders

Although the treatment results for some forms of haematologic malignancies are excellent, especially for the childhood acute leukaemias, there is still a significant fraction of patients that will not benefit from the therapy available today. The identification of new techniques, such as gene therapy, may therefore be of great importance for future therapeutic applications. Suicide gene therapy is one of several gene therapeutic approaches to treat cancer. A suicide gene is a gene encoding a protein, frequently an enzyme, that in itself is nontoxic to the genetically modified cell. However, when a cell is exposed to a specific nontoxic prodrug, this is selectively converted by the gene product into toxic metabolites that kill the cell. The suicide gene most commonly employed, both in experimental and a clinical settings, is herpes simplex thymidine kinase (HSVtk). Some suicide gene products also induce a so-called 'bystander effect', i.e. a toxic effect on adjacent nongene modified tumour cells and sometimes also on more distant tumour cells. The bystander effect is most evident in tumour cells that have a high number of gap junctions, cellular channels build up by proteins called connexins. Many tumours, amongst them many haematological ones, have a low number of gap junctions. Therefore, it is important to develop gap junction independent drug delivery systems. Suicide gene technology may also be used for the ex vivo purging of tumour cells in bone marrow or peripheral blood stem cell autografts or for inactivation of effector cells, such as antitumour T donor lymphocytes in allogeneic transplantation to prevent severe graft versus host reactions. New constructs, e.g. combining suicide genes and immune response enhancing genes or suicide genes and connexin inducing genes may further improve the value of suicide gene therapy.

Efficient suicide gene therapy of transduced and distant untransduced ovary tumors is correlated with significant increase of intratumoral T and NK cells

Gene therapy using herpes simplex type 1 thymidine kinase gene (HSV1-TK) transfer followed by ganciclovir (GCV) treatment has revealed an important intratumoral and regional bystander effect that is at least partly immune-mediated. The aim of this work was to study the modifications of T lymphocyte subpopulations in a model of distant bystander effect occurring between ovary tumors. Bilateral ovarian tumors were generated in 21 WKY rats by injection in the ovarian pouch of either parental or HSV1-TK-expressing DWA-OC-1 ovarian cancer cells. After 14 days, rats were treated for two weeks with GCV (75 mg/kg x 2/d) or saline. All rats were killed at day 29 for pathological examination. The tumor-infiltrating mononuclear cells were analyzed by semi-quantitative immunohistochemistry. As compared to rats receiving saline, GCV-treated animals exhibited a complete disappearance of the HSV1-TK+ tumors with residual fibrotic scars (ovary weights: 0.46 +/- 0.4 g vs 10.11 +/- 1.5 g, P < 0.001). Interestingly, the contralateral HSV1-TK negative tumor showed a significant regression (12.39 +/- 1.93 g vs 22.24 +/- 237 g, P < 0.014). Furthermore, a lower incidence of tumoral ascitis was found in the GCV-receiving group (20% vs 90% P < 0.02). Within both TK- and TK+ tumors, there was a significant increase of CD4+, CD8+ and NK cells in the GCV-treated group compared to the saline-treated group. This study thus indicates that a distant bystander effect not only acts between close tumors within a given organ such as the liver, but also between more distant tumors in the peritoneal cavity. This effect is associated with significant infiltration of the tumor by immune system cells, supporting the notion that the distant bystander effect is immune-mediated.

[Vaccination by suicide gene therapy against a model of hepatic metastasis from colon cancer in the rat]

Suicide gene therapy consists of transferring into tumor cells a viral or bacterial gene encoding for an enzyme which converts a non-toxic product into a lethal drug.

STUDY AIM

To analyze the therapeutic potential of vaccination with tumor cells expressing the bacterial cytosine deaminase (CD) gene and 5-fluorocytosine (5-FC) treatment in a rat liver metastasis model.

MATERIAL AND METHOD

We used a rat colon carcinoma cell line which, after subcapsular or intraportal injection in syngenic animals, generates single or multiple experimental liver metastases, respectively. We have shown that introduction of a vector expressing the CD gene in this colon carcinoma cell line results in 5-FC sensitivity (PRObCD).

RESULTS

Intrahepatic subcapsular injection of PRObCD tumor cells, followed by 5-FC treatment, induces total regression of a wild-type tumor pre-established in the contralateral liver lobe in 45% of animals with a 96% decrease in mean volume (p < 0.0001), demonstrating the existence of a distant bystander effect. This vaccination significantly increased the survival of rats with single (log-rank p < 0.0001) or multiple (log-rank p = 0.01) liver metastasis

CONCLUSIONS

These results suggest that suicide gene-modified tumor cells can act as potent therapeutic vaccines against liver metastasis from colon carcinoma.

A radiation-controlled molecular switch for use in gene therapy of cancer

Ionising radiation induces the expression of a number of radiation-responsive genes and there is current interest in exploiting this to regulate the expression of exogenous therapeutic genes in gene therapy strategies for cancer. However, the radiation-responsive promoters used in these approaches are often associated with low and transient levels of therapeutic gene expression. We describe here a novel radiation-triggered molecular switching device based on promoter elements from the radiation-responsive Egr-1 gene and the cre-LoxP site-specific recombination system of the P1 bacteriophage. Using this system, a single, minimally toxic dose of radiation induced cre-mediated excision of a lox-P flanked stop cassette in a silenced expression vector and this resulted in amplified levels of CMV-promoter-driven expression of the exogenous tumour-sensitising gene, HSV-tk. This strategy could be used in combination with targeted delivery and tumour-specific promoters to elicit the tumour-targeted and prolonged expression of a variety of tumour-sensitising genes and provide an unprecedented level of control and tumour selectivity.

Gene therapy for head and neck cancer

OBJECTIVES/HYPOTHESIS

New treatment methods are needed for head and neck cancer to improve survival without increasing morbidity. Gene therapy is a potential method of improving patient outcome. Progress in gene therapy for cancer is reviewed with emphasis on the limitations of vector technology and treatment strategies. Given the current technological vector limitations in transmitting the therapeutic genes, treatments that require the fewest number of cells to be altered by the new gene are optimal. Therefore an immune-based gene therapy strategy was selected in which the tumors were transfected with the gene for an alloantigen, human leukocyte antigen (HLA)-B7, a class I major histocompatibility complex (MHC). This would restore an antigen presentation mechanism in the tumor to induce an antitumor response. This gene therapy strategy was tested in patients with advanced, unresectable head and neck cancer.

STUDY DESIGN

Prospective trial.

METHODS

Twenty patients with advanced head and neck cancer who had failed conventional therapy and did not express HLA-B7 were treated with gene therapy using a lipid vector by direct intratumoral injection. The gene therapy product contained the HLA-B7 gene and the beta2-microglobulin gene, which permits complete expression of the class I MHC at the cell surface. Patients were assessed for any adverse effects, for changes in tumor size, for time to disease progression, and for survival. Biopsy specimens were assessed for pathological response, HLA-B7 expression, apoptosis, cellular proliferation, CD-8 cells, granzyme, and p53 status.

RESULTS

There were no adverse effects from the gene therapy. At 16 weeks after beginning gene therapy, four patients had a partial response and two patients had stable disease. Two of the tumors completely responded clinically, but tumor was still seen on pathological examination. The time to disease progression in the responding patients was 20 to 80 weeks. The median survival in patients who completed gene therapy was 54 weeks, compared with 21 weeks in patients whose tumors progressed after the first cycle of treatment. One patient survived for 106 weeks without any additional therapy. HLA-B7 was demonstrated in the treated tumors, and increased apoptosis was seen in the responding tumors.

CONCLUSION

Significant advances have been made in the field of gene therapy for cancer. Alloantigen gene therapy has had efficacy in the treatment of cancer and can induce tumor responses in head and neck tumors. Alloantigen gene therapy has significant potential as an adjunctive treatment of head and neck cancer.

Replication-competent herpes simplex virus vector G207 and cisplatin combination therapy for head and neck squamous cell carcinoma

Replication-competent virus vectors are attractive therapeutic agents for cancer. G207, a second-generation, multimutated herpes simplex virus type 1 (HSV-1), is one such vector that is safe in primates and efficacious against human tumors in athymic mice. Squamous cell carcinoma is the most frequently encountered malignancy of the head and neck, and the chemotherapeutic agent cisplatin is a standard treatment for recurrent head and neck cancer. In this study we examine the therapeutic potential of G207, alone and in combination with cisplatin, against squamous cell carcinoma. Human squamous cell carcinoma cell lines are sensitive to G207 replication and cytotoxicity in vitro at a multiplicity of infection of 0.01, including cisplatin sensitive (UMSCC-22A), moderately sensitive (UMSCC-38), and weakly sensitive (SQ20B) cell lines. Cisplatin did not inhibit the cytopathic effect of G207. G207 inhibited the growth of established subcutaneous head and neck tumors in athymic mice. The therapeutic effects of cisplatin and G207 in vivo were independent. However, in cisplatin-sensitive tumors (UMSCC-38), combination therapy resulted in 100% cures in contrast to 42% with G207 or 14% with cisplatin alone. We conclude that G207 should be considered for the treatment of head and neck cancer and that combination with chemotherapeutic agents may improve efficacy.

Effects of herpes simplex virus on human oral cancer cells, and potential use of mutant viruses in therapy of oral cancer

The herpes simplex virus type-1 (HSV-1) might be useful in treatment of oral cancer because it is strongly cytolytic, and its natural target tissue is the source of oral squamous cell carcinomas. Use of a wild-type virus would be limited by its spread and neurotoxicity, but it might be possible to develop mutants whose range could be restricted to oral cancers. Thus we have investigated the effects of HSV-1 on human oral cancer cells and have used both wild-type virus and a mutant that lacks UL42--an essential gene of the virus. Growth of the oral cancer cell line 686LN was readily inhibited by wild-type HSV-1, with only 10(2) plaque forming units (pfu) per milliliter required for 50% inhibition. In contrast, the mutant HSV-1 required a titer of 10(6) pfu/ml for 50% inhibition of growth. The mutant virus did, however, inhibit cell growth through the activation of ganciclovir and thus might be able to amplify its cytotoxicity through a bystander effect. When wild-type HSV-1 was injected into 686LN cells which were growing as tumors in nude mice, the virus spread through the tumor. Treated tumors were smaller, of lower weight, and significantly more necrotic than either untreated tumors or tumors which had been treated with the mutant virus. The wild-type virus spread to the skin and nervous system of most animals causing zosteriform skin rash, neurological symptoms and death, while the mutant virus produced none of these side-effects. These results show that HSV-1 might be used to treat oral cancer if its replication could be limited to the tumor cells, and that controlled expression of the UL42 gene would be one way to obtain that limitation.

Induction of anti-tumour immunity by suicide-gene-modified HPV-16-transformed hamster cells

From K3/II, which is a highly oncogenic HPV16-transformed Syrian hamster cell line, thymidine-kinase(TK)-less cells, denoted B 49, were derived. B49 cells were transfected by a plasmid containing the herpes-simplex-virus TK gene (HSV TK) and several sub-lines expressing this gene were isolated from the transfected cultures. The HSV TK+ cells were highly sensitive to ganciclovir (GCV) and other anti-viral substances whose inhibitory effect is based on their phosphorylation by HSV TK. One of the cell lines, denoted KL1/6, exhibited relatively high stability of the HSV TK+ phenotype and was used in subsequent experiments. When KL1/6 cells were co-cultivated in the presence of GCV with various other cell lines of hamster, mouse or monkey origin, the by-stander effect (BE) was observed. GCV treatment of hamsters prevented development of tumours after the administration of KL1/6 cells but not K3/II cells. The treatment of animals with already established KL1/6-induced tumours resulted in tumour regression in all instances, but complete regression was observed only in animals carrying small tumours. The BE of KL1/6 cells on K3/II cells was also seen in vivo. In addition, concomitant immunity was observed in animals simultaneously inoculated with KL1/6 cells and K3/11 cells at 2 separate sites of the body. This effect was evident not only in animals in which KL1/6 tumours developed, but also in those in which tumour outgrowth was prevented by GCV treatment. In other experiments it was demonstrated that one KL1/6 + GCV treatment resulted in partial resistance, 2 such treatments in complete resistance to the challenge with K3/II cells.

Prospects for future studies in head and neck cancer

Present therapy of head and neck cancer patients includes surgical procedures, radiotherapy and sometimes chemotherapy. Over recent decades no dramatic improvements have been obtained with these treatment modalities with respect to efficacy and associated morbidity. Of patients with early stage disease (stage I and II), about 25% cannot be cured, while for patients with advanced disease (stage III and IV) this percentage may be as high as 70%. However, owing to advances in our knowledge of molecular biology, immunology, (bio)chemistry and biology of head and neck squamous cell carcinoma (HNSCC), new perspectives on therapy are arising. After several years of optimization several new therapeutic approaches are leaving their infancy and are being evaluated in clinical trials with HNSCC patients. Among other approaches, photodynamic therapy, gene therapy and antibody-based therapy are attracting most attention. The basic concepts and the potential applications of these treatment modalities in the management of head and neck cancer are discussed in this paper.

An academic centre for gene therapy research with clinical grade manufacturing capability

Huddinge University Hospital is a major teaching hospital affiliated with the Karolinska Institute in Southern Stockholm. For the past few years several groups have been working there in different areas of gene therapy relating to cancer, genetic and infectious diseases. However, a facility to produce clinical grade material under good manufacturing practice was lacking. To this end, Huddinge University Hospital has taken the initiative to open a Gene Therapy Research Center in 1996. This facility, which is unique of its kind in Scandinavia, is located in the Novum Research Park, Huddinge, and is a part of the existing Clinical Research Center. The newly built centre will allow clinicians and researchers to develop and produce vectors (viral and nonviral) for clinical trials and do basic research to understand the mechanisms of diseases. Although the centre will primarily serve the academic institutions it will also extend its facilities to other investigators in this field. The production unit is run in collaboration with the Faculty of Medicine, University of Lund. On-going projects include production of plasmid vectors for prevention of postangioplasty restenosis, DNA vaccine for HIV-1, cationic liposome DNA complexes for cystic fibrosis and retroviral vectors for HIV-1.

A "distant" bystander effect of suicide gene therapy: regression of nontransduced tumors together with a distant transduced tumor

Antitumor gene therapy using herpes simplex type 1 thymidine kinase (TKh) and ganciclovir (GCV) treatment has revealed an important intratumoral bystander effect. A whole tumor can be eliminated when only a fraction of its tumor cells express TKh. We now report that the bystander effect not only acts within a tumor, but also between distant tumors. One TKh+ tumor was generated simultaneously with one or multiple TKh- tumors in different rat liver lobes such that there was no contact between the resulting tumors. Both the TKh+ and the TKh- tumors regressed after GCV treatment and showed infiltration with macrophages and T lymphocytes. This distant bystander effect, which is likely immune mediated, should be of major importance for gene therapy of disseminated tumors.