Active immunization of metastatic melanoma patients with interleukin-2-transduced allogeneic melanoma cells: evaluation of efficacy and tolerability

Comparative antitumor effect of preventive versus therapeutic vaccines employing B16 melanoma cells genetically modified to express GM-CSF and B7.2 in a murine model

Cancer vaccines have always been a subject of gene therapy research. One of the most successful approaches has been working with genetically modified tumor cells. In this study, we describe our approach to achieving an immune response against a murine melanoma model, employing B16 tumor cells expressing GM-CSF and B7.2. Wild B16 cells were injected in C57BL6 mice to cause the tumor. Irradiated B16 cells transfected with GM-CSF, B7.2, or both, were processed as a preventive and therapeutic vaccination. Tumor volumes were measured and survival curves were obtained. Blood samples were taken from mice, and IgGs of each treatment group were also measured. The regulatory T cells (Treg) of selected groups were quantified using counts of images taken by confocal microscopy. Results: one hundred percent survival was achieved by preventive vaccination with the group of cells transfected with p2F_GM-CSF. Therapeutic vaccination achieved initial inhibition of tumor growth but did not secure overall survival of the animals. Classical Treg cells did not vary among the different groups in this therapeutic vaccination model.

Overview of Tumor Cell–Based Vaccines

Whole-cell tumor vaccines have been investigated for more than 20 years for their efficacy in both preclinical models and in clinical trials in humans. There are clear advantages of whole-cell/polyepitope vaccination over those types of immunotherapy that target specific epitopes. Multiple and unknown antigens may be targeted to both the innate and adaptive immune system, and this may be further augmented by genetic modification of the vaccine cells to provide cytokines and costimulation. In this review, we give an overview of the field including the preclinical and clinical advances using unmodified and modified tumor-cell vaccines.

Clinical application of dendritic cells and interleukin-2 and tools to study activated T cells in horses--first results and implications for quality control

Dendritic cells (DCs) are antigen-presenting cells, which are well known for their capacity to stimulate immunity. The ex vivo generation of myeloid DC from monocytes has facilitated the development of DC-vaccination protocols which have been extensively evaluated in tumour immunology and are regarded by some as a gold mine for clinical research. However, there is a considerable amount of work required to overcome the potential risks associated with such therapy. It is therefore mandatory to characterize the system to be applied and to study the reactions, particularly at the level of T cell responses. The first objective of the current study was to test if tumour lysates loaded autologous DC or recombinant human IL-2 are well tolerated in horses and performed an exploratory phase I study on equine sarcoids and squamous cell carcinomas. We consequently intended to establish a robust protocol for the magnetic separation of monocytes such as in use in human clinical studies. Finally we intended to address the limits in the reagents to study equine T cell based immune reactions, and analysed markers for CD25 and FoxP3. The data showed that local application of DC or IL-2 did not cause side effects. Additionally our data show that a polyclonal approach to detect antigens such as CD25 might be successful, where mAbs are not available. Our data also demonstrate that the mAb FJK16s, which has been used successfully in rodents, humans, and dogs, can also be applied in horses. We finally wish to share our concerns regarding quality control for clinical studies and encourage multi-central studies such as in human medicine to ensure that progress along established standards is made for the benefit of veterinary medicine.

Experimental study of specific immunotherapy induced by H22 autologous tumor as whole tumor cell vaccine

This study explores the novel H22 whole-cell vaccine of active specific immunotherapy in the treatment of hepatocellular carcinoma. H22 hepatoma tumor vaccine modified by human interleukin-2 (hIL-2) and mouse granulocyte-monocyte colony-stimulating factor (mGM-CSF) fusion gene was prepared to study its specific anti-tumor immunity. Mice were inoculated by these vaccines. Then tumor cells were injected into mouse models. The (51)Cr release assay was used to examine the cytotoxicities of the splenocytes to H22 hepatoma cells in immunized mice, tumor-bearing mice and control mice. The blood was needed to test the level of IL-10 and interferon (IFN)-gamma in serum. Survival time of mice was calculated. Specific cytotoxicity rate of splenocytes from the immunized mice to H22 cancer cell was 38%, significantly higher than 13.6% in the tumor-bearing group, 7.5% in the control group, and 9.1% in S180 cells (p<0.05). Serum IFN-gamma in the immunized group was significantly increased compared with other groups (p<0.01), and serum IL-10 in the immunized group was significantly decreased compared with other groups (p<0.01). The survival time of the transgenic vaccinated group was significantly longer.

Translational research in melanoma

Current treatment of malignant melanoma exemplifies not only the need for translational research but also many of the challenges of moving from bench to bedside. Melanoma remains unique among solid tumors in that its treatment primarily is surgical. Radiation is of limited benefit, and chemotherapy has been disappointing in both the adjuvant and metastatic settings. This leaves clinicians with few options for reducing the chance of recurrence after surgery and for treating unresectable disease. With this in mind, there has been a fervent attempt to identify novel approaches to melanoma therapy and translate them into clinical use.

Does melanoma behave differently in younger children than in adults? A retrospective study of 33 cases of childhood melanoma from a single institution

OBJECTIVE

To ascertain whether childhood melanoma presents any peculiar clinical features or differences in prognosis with respect to adults, we retrospectively analyzed the data from 33 patients who were up to 14 years of age and treated for cutaneous melanoma at the Istituto Nazionale Tumori, Milan, over a 25-year period.

METHODS

Primary lesions were amelanotic in half of the cases and raised in 73%. Lower extremities were the most common primary sites. Histologically, 9 cases were classified as nodular type, and median thickness was 2.5 mm. Nine children had nodal involvement at diagnosis, 2 in-transit metastases, and 1 distant spread. Surgery was the mainstay of treatment; 9 patients underwent lymph node dissection, 3 received chemotherapy, and 2 received radiotherapy.

RESULTS

With a median follow-up of 122 months, 5-year event-free survival and overall survival were 60% and 70%, respectively. Age seemed to correlate with survival, event-free survival being 90% in children under 10 and 47% in older patients, although the initial microstaging seemed worse in the former.

CONCLUSION

By comparison with adult cases, childhood melanoma can have a higher percentage of atypical clinical features (amelanotic and raised lesions), nodular histotype, and thick lesions. Although we have no data to support any suggestion of biological differences between young children and adolescents or adults, our findings give the impression that melanoma behaves differently in the younger age group.

Peripheral Blood CD4+ T-Cell Response Before Postoperative Active Immunotherapy Correlates with Clinical Outcome in Metastatic Melanoma

BACKGROUND

Canvaxin polyvalent specific active immunotherapeutic (CancerVax Corp., Carlsbad, CA) is a minimally toxic adjuvant after resection of regional metastatic melanoma. Because Canvaxin immunotherapeutic requires induction of an immune response, we hypothesized that survival would be directly correlated with cellular immune responses to Canvaxin cells prior to immunization.

METHODS

We randomly selected 54 patients from a study of Canvaxin therapy after complete resection of American Joint Committee on Cancer (AJCC) stage III melanoma. Peripheral blood lymphocytes (PBLs) collected before immunotherapy were co-cultured with Canvaxin cells; cellular response was determined by flow cytometric measurement of the production of intracellular interleukin 4 (IL4) or interferon gamma (IFNgamma) by CD4(+) T-cells. Results were calculated as percent positive for double staining of CD4(+) plus IL4(+) or CD4(+) plus IFNgamma(+).

RESULTS

The mean (+/- SD) increase in cytokine-producing CD4(+) T-cells after Canvaxin stimulation was 4.8 +/- 2.3% for an IFN response and 5.1 +/- 2.0% for an IL4 response. Both increases were significantly correlated with overall survival by univariate analysis (P = .0471 for IFNgamma and 0.002 for IL4). There was no significant correlation between unstimulated IFNgamma/IL4 responses and overall survival. Multivariate analysis showed that a CD4(+) T-cell IL4 response before Canvaxin therapy was a significant independent prognostic variable.

CONCLUSIONS

In vitro cellular immune response to Canvaxin cells directly correlates with survival after subsequent initiation of immunotherapy for AJCC stage III melanoma. This finding will be evaluated in a multicenter phase III trial of Canvaxin plus bacille Calmette-Guerin (BCG) versus placebo plus BCG after resection of stage III melanoma.

[Gene therapy of melanoma: review of published clinical trials]

INTRODUCTION

Melanoma frequency increases. Conventional antitumoral treatments fail. Gene therapy for metastatic melanoma is studied in 17 phase I-II clinical trials. ACTUALITES ET POINTS FORTS: Sixteen use cytokine genes. These studies are heterogenous as far as methodology is concerned. Gene therapy clinical tolerance is acceptable. Security is rarely discuted. In these studies overall response rate is 8%, with histological complete responses.

PERSPECTIVES

Presently, three new studies are opened in United States.

Tumor vaccines: a role in preventing recurrence in melanoma?

Patients presenting with thick primary melanomas or those with regional nodal metastases have a high risk of recurrence after surgery alone. Chemotherapy has limited efficacy in the adjuvant setting, and while the use of high-dose interferon in the adjuvant setting has been reported to improve survival, treatment with interferon is not without significant cost and toxicity. Mounting evidence suggests a prominent role for the immune system in the natural history of melanoma, and the clinical success of interferon highlights the potential for immunotherapy to prevent recurrence. Many researchers hope to use melanoma vaccines to reduce recurrence without significant toxicity, and many different vaccine strategies are under investigation. Peptide vaccines attempt to induce immunity to melanoma MHC-restricted peptide antigens by delivering the peptide to the patient along with an immune adjuvant meant to induce inflammation and stimulate immunity. While peptide vaccines have advantages with regard to cost and feasibility, it is still unclear whether highly purified peptides will stimulate an adequate immune response. An alternative approach is the use of cellular vaccines. Autologous cellular vaccines present all biologically relevant antigens to the immune system, but this is limited to individuals with sufficient tumor to prepare a vaccine. Allogeneic cellular vaccines are based on the fact that melanoma-associated antigens are shared among a large number of patients, so a vaccine prepared from a cultured cell line could stimulate an anti-tumor immune response in many patients. Allogeneic vaccines are available for all patients, and can be standardized, preserved and distributed in a manner akin to any other therapeutic agent. Because of this, they are more readily available for evaluation in large trials, and there are two major allogeneic vaccines presently being evaluated as an adjuvant therapy for melanoma. Several additional approaches to vaccine therapies are being investigated including among others ganglioside vaccines, viral oncolysates, cytokine gene-modified tumor cell vaccines, dendritic cell vaccines, anti-idiotype antibodies and DNA vaccines. While there appears to be tremendous potential for vaccines, it must be remembered that there has been significant interest in immunotherapy for melanoma for over 50 years and, to date, no large prospective, randomized trial has shown a survival benefit.

Cancer vaccines

Although cancer immunotherapy was initiated by William Coley more than a century ago, the field of cancer vaccines is in an early stage of development. Only recently, major advances in cellular and molecular immunology have allowed a comprehensive understanding of the complex and high rate of interactions between the immune system and tumor cells. We have learned that these tumor-immune system interactions may result either in strong immune antitumor response or tolerance to tumor-associated antigens. This article will discuss the profound interest in cancer vaccines derived from their potential to induce antitumor responses in vivo. Substantial data from several preclinical models and early human clinical trials have confirmed the ability of cancer vaccines to induce immune responses that are tumor-specific and, in some cases, associated with clinical responses. One future challenge will be to determine how to appropriately stimulate the pathways leading to effective interaction among antigen-presenting cells, T lymphocytes, and tumor cells. It also is critical to develop monitoring strategies that may allow the identification of patients who may benefit from cancer vaccines.

Cancer immunogene therapy: a review

Although immunotherapy has long held out promise as a specific, potent approach to cancer therapy, clinical applications have been unrewarding to date. However, advances in gene transfer technology and basic immunology have opened new avenues to stimulate antitumor immune responses including immunogene therapy. Many different approaches to immunogene therapy have been identified. These include transferring genes encoding proinflammatory proteins to tumor cells, suppressing immunosuppressive gene expression, and transferring proinflammatory genes and/or tumor antigen genes to professional antigen-presenting cells. In some cases, genes are transferred to tumor or antigen-presenting cells in situ. In others, gene transfer is performed ex vivo as part of preparing an anticancer vaccine. We discuss the underlying approach, relative success, and clinical application of various cancer immunogene therapy strategies, paying particular attention to immunogene therapy vaccines. Large numbers of preclinical studies have been reported, but only scattered clinical trial results have appeared in the literature. Although very successful preclinically, the ideal cancer immunogene therapy approach remains to be determined and will likely vary with tumor type. Clinical impact may be improved in the future as treatment protocols are refined.

Gene-based immunotherapy of skin cancers

Skin cancers continue to present a major therapeutic challenge to physicians. Recent advances in molecular genetics and improved understanding of immune responses to tumors have generated an interest in using gene-based immunotherapy for treating these malignancies. Two major forms of gene-based immunotherapy are currently being investigated. One focuses on genetic modification of some target cell populations of the host using immunostimulatory genes such as cytokines, in order to improve tumor immunogenicity and antitumor responses; the other is genetic immunization with the genes coding for melanoma-associated antigens recognized by cytotoxic T cells. This paper reviews these novel strategies and summarizes the most recent data recorded in either experimental studies or clinical trials.

Noninterferon-based adjuvant therapy for high-risk melanoma

High-dose interferon is the only treatment approved by the FDA for adjuvant therapy of melanoma. However, its efficacy in this setting is questionable and its administration is associated with considerable toxicity. Many new agents are being tested clinically that hold the promise of greater efficacy and less toxicity but none of these have yet shown efficacy in controlled trials. These include biologics such as vaccines, cytokines, monoclonal antibodies, gene transfer, cellular therapies and angiogenesis inhibitors as well as chemotherapy combinations.

Gene-based therapy of malignant melanoma

Melanoma continues to present a major therapeutic challenge to oncologists, oncologic surgeons, and dermatologists. Recent advances in molecular genetics and improvement in our understanding of immune responses to tumors have generated an interest in using gene-based treatment strategies to fight melanoma. Several basic strategies have emerged: (1) strengthening of the immune response against tumors by genetic modification of some target cell populations of the host using immunostimulatory genes such as cytokines and by genetic immunization with the genes coding for melanoma-associated antigens recognized by cytotoxic T cells; (2) interference with signaling cascades; and (3) suicide gene strategies. This article reviews these novel strategies and summarizes the most recent data generated by European groups either in experimental studies or in clinical trials.

Tumour cell-based vaccines for the treatment of melanoma

Melanoma is generally resistant to chemotherapy and radiation therapy. Its unique immunological properties lend support to developing innovative new therapies via manipulation of the patient's own immune system. The use of whole-cell-based tumour vaccines, including autologous, whole-cell allogeneic and cytokine gene-modified vaccines, as well as tumour lysate vaccines, for active specific immunotherapy of melanoma, is discussed in detail with regard to rationale and available clinical data. Although phase II data on the use of melanoma vaccine in the adjuvant setting show promise, there is no randomised phase III trial demonstrating the efficacy of active specific immunotherapy for melanoma. The coming years will bring the results of several pivotal multicentre phase III trials testing the clinical utility of active specific immunotherapy in the management of melanoma.

Advances in the non-surgical treatment of melanoma

Immune responses appear to play a role in the natural history of melanoma and immunotherapy has therefore been the subject of a number of studies. The results of several large randomised studies using allogeneic melanoma vaccines have shown minimal benefit and Phase I/II studies with gene transfected melanoma cells do not appear particularly encouraging. The majority of current interest now centres on development of vaccines using defined melanoma antigens recognised by T-cells and given as dendritic vaccines or injected directly as melanoma peptides or DNA. It can be expected that the most effective antigens and method of administration will become apparent over the next few years. It is clear, however, that melanoma shows low response rates to immunotherapy, as for chemotherapy. Both forms of therapy appear to kill melanoma by induction of apoptosis, so it is possible that resistance to apoptosis may underlie the low responses to these forms of therapy. Much is already known about agents that may sensitise melanoma to apoptosis and combining these with chemotherapy and/or immunotherapy provides a promising new approach in treatment of melanoma.

Induction of effective antitumor immune responses in a mouse bladder tumor model by using DNA of an alpha antigen from mycobacteria

One of the main objectives of cancer immunotherapy is the activation and increase in number of antitumor effector cells. Recently, genetically modified tumor cell vaccines have been proposed for elicitation of antitumor effector cells. Native alpha antigen (alpha Ag) (also known as MPT59 and antigen 85B) of mycobacteria, which cross-reacts among mycobacteria species, may play an important biological role in host-pathogen interaction because it elicits various helper T-cell type 1 immune responses. To assess the induction of antitumor immune responses by alpha Ag, mouse tumor cell lines transfected with cDNA of alpha Ag from Mycobacterium kansasii were established, and the possibility of producing a tumor cell vaccine for induction of antitumor effects was explored. Transfection of tumor cell lines with an alpha Ag gene lead to primary tumor rejection and the establishment of protective immunity to nontransfected original tumor cell lines in Mycobacterium bovis bacillus Calmette-Gurin (BCG)-primed and unprimed mice. Mice immunized with tumor cell lines transfected with the alpha Ag gene showed delayed-type hypersensitivity responses in vivo and proliferative responses together with induction of interferon-gamma of spleen cells against nontransfected wild-type tumor cell lines in in vitro experiments. Moreover, immunization of mice with alpha Ag-expressing tumor cells elicited tumor-specific and cytotoxic T lymphocyte (CTL) epitope peptide-specific CD8+ CTLs. The results of this study provided evidence of the potential usefulness of alpha Ag in tumor cell vaccines.

Efficacy of cytokine gene transfection may differ for autologous and allogeneic tumour cell vaccines

Whole tumour cells are a logical basis for generating immunity against the cancers they comprise or represent. A number of human trials have been initiated using cytokine-transfected whole tumour cells of autologous (patient-derived) or allogeneic [major histocompatibility complex (MHC)-disparate] origin as vaccines. Although precedent exists for the efficacy of autologous-transfected cell vaccines in animal models, little preclinical evidence confirms that these findings will extrapolate to allogeneic-transfected cell vaccines. In order to address this issue a murine melanoma cell line (K1735) was transfected to secrete interleukin (IL)-2, IL-4, IL-7 or granulocyte-macrophage colony-stimulating factor (GM-CSF); cytokines currently in use in trials. The efficacy of these cells as irradiated vaccines was tested head-to-head in syngeneic (C3H) mice and in MHC-disparate (C57BL/6) mice, the former being subsequently challenged with K1735 cells and the latter with naturally cross-reactive B16-F10 melanoma cells. Whilst the GM-CSF-secreting vaccine was the most effective at generating protection in C3H mice, little enhancement in protection above the wild-type vaccine was seen with any of the transfections for the allogeneic vaccines, even though the wild-type vaccine was more effective than the autologous B16-F10 vaccine. Anti-tumour cytotoxic T-lymphocyte (CTL) activity was detected in both models but did not correlate well with protection, whilst in vitro anti-tumour interferon-gamma (IFN-gamma) secretion tended to be higher following the GM-CSF-secreting vaccine. Cytokine transfection of vaccines generally increased anti-tumour CTL activity and IFN-gamma secretion (T helper type 1 response). Further studies in other model systems are required to confirm this apparent lack of benefit of cytokine transduction over wild-type allogeneic vaccines, and to determine which in vitro assays will correlate best with protection in vivo.

Cytokine-secreting tumor cell vaccines

Modification of the tumor microenvironment with gene transfer techniques stimulates two immune mechanisms that effectuate tumor destruction. One involves improved tumor-antigen presentation for the development of specific cellular and humoral immunity. The second involves compromise of the tumor vasculature by soluble factors and leukocytes.

Autologous, allogeneic tumor cells or genetically engineered cells as cancer vaccine against melanoma

Melanoma is a prototype of immunogenic tumor to which various types of immunotherapy have been applied extensively over the past decades. Melanoma vaccines are designed for the purpose of immune modulation and subsequent anti-tumor effects in the process of an active specific immunotherapy. Previous attempts of these vaccines include immunization with whole tumor cells/cell lysates admixed with nonspecific adjuvants. While these vaccines generated enhanced anti-tumor immunity in a subset of patients, some of which showing prolonged survival compared to historical controls, no clinical benefit has so far been demonstrated in a properly controlled phase III study. New-generation melanoma vaccines, which are based on genetic modifications of tumor cells to express cytokines, generated long-lasting systemic anti-tumor immunity in animal models. Translation of these preclinical results primarily into melanoma patients with advanced diseases, shows the potential of these vaccines to induce systemic anti-tumor immune responses and in some instances tumor regression with acceptably low toxicity. Higher efficacy of this novel vaccine approach would be expected when used in a postsurgical adjuvant setting when the tumor load is small. Also other novel vaccine approaches such as dendritic cell-based therapy hold promise for the treatment of melanoma. But the clinical value of all these new approaches has to be analysed in prospectively randomized clinical studies.

Management problems in oncology

Man has evolved sophisticated defence mechanisms over millions of years to combat insertion of foreign DNA into his cells. However, gene therapy carries huge potential for the treatment of cancer. The challenge is therefore to translate our scientific knowledge into a clinical reality.

Immunology and immunotherapy of human cancer: present concepts and clinical developments

Immunotherapy of cancer is entering into a new phase of active investigation both at the pre-clinical and clinical level. This is due to the exciting developments in basic immunology and tumour biology that have allowed a tremendous increase in our understanding of mechanisms of interactions between the immune system and tumour cells. This review briefly summarizes the state of the art in basic tumour immunology before discussing the clinical applications of the new concepts in the clinical setting. Clinical approaches are diverse but can now be based on strong scientific rationales. The analysis of the available clinical results suggests that, despite some disappointments, there is room for optimism that both active immunotherapy (vaccination) and adoptive immunotherapy may soon become part of the therapeutic arsenal to combat cancer in a more efficient way.

Vaccination of melanoma patients with an allogeneic, genetically modified interleukin 2-producing melanoma cell line

Thirty-three metastatic melanoma patients were vaccinated according to a phase I-II study with an allogeneic melanoma cell line that was genetically modified by transfection with a plasmid containing the gene encoding human interleukin 2 (IL-2). The cell line expresses the major melanoma-associated antigens and the HLA class I alleles HLA-A1, -A2, -B8, and Cw7. All patients shared one or more HLA class I alleles with this cell line vaccine. Patients were immunized by three vaccinations, each consisting of 60 x 106 irradiated (100 Gy) melanoma cells (secreting 120 ng of IL-2/10(6) cells/24 hr) administered subcutaneously at weekly intervals for 3 consecutive weeks. Side effects of treatment consisted of swelling of locoregional lymph nodes and induration at the site of injection, i.e., a delayed-type hypersensitivity (DTH) reaction. In three patients, vaccination induced inflammatory responses in distant metastases containing necrosis or apoptosis along with T cell infiltration. Apoptosis occurred only in Bcl-2-negative areas, not in Bcl-2-expressing parts of the metastases. Two other patients experienced complete or partial regression of subcutaneous metastases. Seven patients had protracted stabilization (4 to >46 months) of soft tissue metastases, including one patient who developed vitiligo after vaccination. Immune responses to the vaccine could be detected in 67% of the 27 patients measured. Vaccination was shown to induce a variable change in the number of anti-vaccine cytotoxic T lymphocytes (CTLs) in peripheral blood, which did not correlate with response to treatment. However, in two of five patients the frequency of anti-autologous tumor CTLs measured was significantly higher than before vaccination. This study demonstrates the feasibility, safety, and therapeutic potential of vaccination of humans with allogeneic, gene-modified tumor cells, and that frequencies of vaccine-specific CTLs among patient lymphocytes can be determined by using a modified limited dilution analysis (LDA).

Development of transferrin-polycation/DNA based vectors for gene delivery to melanoma cells

We describe the comparison of non-viral polycation transfection reagents, adenovirus-enhanced transferrinfection (AVET), polyethylenimine (PEI800) and transferrin-conjugated PEI800 (Tf-PEI800) in their ability to transfect murine and primary human melanoma cell lines. Expression of a reporter gene, cell surface marker and secreted protein (interleukin-2) was assessed for each vector system. Testing for luciferase reporter gene expression in murine and primary human cell lines, AVET and Tf-PEI800, both showed high levels of expression and comparable activity. Furthermore, when the melanoma cell line B16F10 was transfected with a cell surface marker up to approximately 97% of the cells expressed the protein on the cell surface. Assessing the levels of secreted IL-2 in murine cell lines, AVET/IL-2, Tf-PEI800/IL-2 and PEI800/IL-2 all expressed high levels of the cytokine (up to 20 microg IL-2/10(6) cells/24 h). In primary human melanoma cell lines, AVET/IL-2 transfected cells secreted more IL-2 than cells transfected with either Tf-PEI800/IL-2 or PEI800/IL-2. In murine melanoma cell culture experiments, positively charged PEI800/DNA and Tf-PEI800/DNA complexes gave similar transfection efficiencies. However, when subcutaneous tumors in mice were injected with the luciferase reporter gene complexed with either Tf-PEI800 or AVET, higher transfection activity was measured in the tumors as compared to ligand free PEI800/DNA complexes.

Immunotherapy of advanced malignancy by direct gene transfer of an interleukin-2 DNA/DMRIE/DOPE lipid complex: phase I/II experience

PURPOSE

We have completed a phase I study, followed by three phase I/II studies, in patients with metastatic melanoma, renal cell carcinoma (RCC), and sarcoma in order to evaluate the safety, toxicity, and antitumor activity of Leuvectin (Vical Inc, San Diego, CA), a gene transfer product containing a plasmid encoding human interleukin (IL)-2 formulated with the cationic lipid 1, 2-dimyristyloxypropyl-3-dimethyl-hydroxyethyl ammonium bromide/dioleyl-phosphatidyl-ethanolamine (DMRIE/DOPE) and administered intratumorally.

PATIENTS AND METHODS

Twenty-four patients were treated in the phase I study. Leuvectin doses were 10 microg, 30 microg, or 300 microg weekly for 6 weeks. In three subsequent phase I/II studies, a total of 52 patients (18 with melanoma, 17 with RCC, and 17 with sarcoma) were treated with further escalating doses of Leuvectin: 300 microg twice a week for 3 weeks, 750 microg weekly for 6 weeks, and 1,500 microg weekly for 6 weeks.

RESULTS

There were no drug-related grade 4 toxicities and only one grade 3 toxicity, but the majority of patients experienced mild constitutional symptoms after treatment. In the phase I/II studies, 45 patients were assessable for response (14 with RCC, 16 with melanoma, and 15 with sarcoma). Two patients with RCC and one with melanoma have achieved partial responses lasting from 16 to 19 months and continuing. In addition, two RCC, three melanoma, and six sarcoma patients had stable disease lasting from 3 to 18 months and continuing. The plasmid was detected by polymerase chain reaction assay in the posttreatment samples of 29 of 46 evaluated patients. Immunohistochemistry studies on serial biopsy specimens showed increased IL-2 expression and CD8(+) infiltration after treatment in the tumor samples of several patients (12 and 16, respectively).

CONCLUSION

Direct intratumoral injection of Leuvectin is a safe and possibly effective immunotherapeutic approach in the treatment of certain tumor types.

Immunotherapy of metastatic malignant melanoma by a vaccine consisting of autologous interleukin 2-transfected cancer cells: outcome of a phase I study

We performed a phase I trial to evaluate the safety and tolerability of repeated skin injections of IL-2-transfected autologous melanoma cells into patients with advanced disease. Cell suspensions, propagated from excised metastases, were IL-2 gene transfected by adenovirus-enhanced transferrinfection and X-irradiated prior to injection. Vaccine production was successful in 54% of the patients. Fifteen patients (37%) received two to eight skin vaccinations of either 3 x 10(6) (intradermal) or 1 x 10(7) (half intradermal, half subcutaneous) transfected melanoma cells per vaccination (secreting 140-17,060 biological response modifier program units of IL-2/10(6) cells/24 hr). Analyses of safety and efficacy were carried out in 15 and 14 patients, respectively. Overall, the vaccine was well tolerated. All patients displayed modest local reactions (erythema, induration, and pruritus) and some experienced flu-like symptoms. Apart from newly appearing (4 of 14) and increasing (5 of 14) anti-adenovirus and newly detectable anti-nuclear antibody titers (1 of 15), recipients developed de novo or exhibited increased melanoma cell-specific delayed-type hypersensitivity (DTH) reactions (8 of 15) and vitiligo (3 of 15) and showed signs of tumor regression (3 of 15). This supports the idea of a vaccine-induced or -amplified anti-cancer immune response. None of the patients exhibited complete or partial regressions, but five of them experienced periods of disease stabilization. Three of these individuals received more than the four planned vaccinations and their mean survival time was 15.7 +/- 3.5 months as compared to 7.8 +/- 4.6 months for the entire patient cohort. These data indicate that IL-2-producing, autologous cancer cells can be safely administered to stage IV melanoma patients and could conceivably be of benefit to patients with less advanced disease.

Cancer vaccines

It has been more than 100 years since the first reported attempts to activate a patient's immune system to eradicate developing cancers. Although a few of the subsequent vaccine studies demonstrated clinically significant treatment effects, active immunotherapy has not yet become an established cancer treatment modality. Two recent advances have allowed the design of more specific cancer vaccine approaches: improved molecular biology techniques and a greater understanding of the mechanisms involved in the activation of T cells. These advances have resulted in improved systemic antitumor immune responses in animal models. Because most tumor antigens recognized by T cells are still not known, the tumor cell itself is the best source of immunizing antigens. For this reason, most vaccine approaches currently being tested in the clinics use whole cancer cells that have been genetically modified to express genes that are now known to be critical mediators of immune system activation. In the future, the molecular definition of tumor-specific antigens that are recognized by activated T cells will allow the development of targeted antigen-specific vaccines for the treatment of patients with cancer.

Cytokine gene therapy: hopes and pitfalls

Transduction of a cytokine gene into neoplastic cells elicits a strong inflammatory host reaction that impairs tumor growth, and a long-lasting immune memory is established following their rejection. These findings have aroused great enthusiasm and expectations. Despite their enhanced immunogenicity, however, the immune reaction provoked by repeated injections of these engineered cells can do little more than inhibit the growth of initial tumors and metastases and is only minimally effective against established forms. Better therapeutic activity is thus being sought by combining such cells with tumor cells engineered with other genes.

Advances in cancer vaccine development

Traditionally, cancer vaccines have used whole tumour cells administered in adjuvant or infected with viruses to increase the immunogenicity of the cells. With the identification of tumour-associated and tumour-specific antigens (TAA, TSA), antigen and epitope-specific vaccines have been designed. Compared to tumour cell vaccines, antigen and epitope vaccines are more specific and easier to produce in large quantities but may display lower immunogenicity and lead to the in vivo selection of antigen or epitope-negative escape tumour variant cells. The optimal vaccine will elicit both humoral and cellular immunity in the patients as both parameters have been positively correlated with the induction of beneficial clinical responses. The choice of adjuvant, costimulation and delivery mode greatly determines the outcome of vaccinations and may favour the induction of T-cell responses of T helper (Th)1, Th2, or both Th1 and Th2 types. Animal models of TAA vaccines must take into account the normal tissue expression of TAA, which may induce immunological tolerance to TAA. With the identification of homologues of human TAA in animals, novel experimental models of cancer vaccines which mimic the condition in patients are now available. Several vaccines comprising tumour cells, TAA or anti-idiotypic antibodies mimicking TAA have recently entered phase III of clinical evaluation.

Gene therapy for melanoma in humans

As melanoma evolves, it interacts with the immune system. Based on this immunobiology, there are now a number of rationally designed attempts to develop genetically modified melanoma vaccines. This article outlines immunologic and other strategies in gene therapy for melanoma and provides an overview of current clinical trials.