Melanoma vaccines

The treatment and prevention of mouse melanoma with an oral DNA vaccine carried by attenuated Salmonella typhimurium

Therapeutic vaccines of cancer are attractive for their capacity of breaking the immune tolerance and invoking long-term immune response targeting cancer cells without autoimmunity. An efficient antigen delivery system is the key issue of developing an effective cancer vaccine. Attenuated Salmonella typhimurium as the carrier of cancer vaccine are able to transfer DNA from the prokaryote to the eukaryote and preferentially replicate within the tumor tissue. Heat shock protein 70 delivers the tumor-associated antigens to antigen presenting cells through its polypeptide-binding domain and breaks immune tolerance of the cancer cells. Here we described a novel low-copy-number DNA vaccine based on the Hsp70-TAA complex and carried by the attenuated S. typhimurium strain SL3261. Oral administration of this vaccine elicited specific CTL-mediated lysis of the melanoma tumor cells and marked activation of the T-cells. The therapeutic vaccine effectively protected 57.1% C57BL/6J mice from lethal challenge with B16F10 melanoma tumor cells in prophylactic settings and eraicated 62.5% tumor growth in therapeutic settings. This approach may provide a new strategy for the prevention and treatment of cancer.

Role of radiation therapy in cutaneous melanoma

Cutaneous melanoma is a disease that often has an aggressive and unpredictable course. It was historically thought to be a radioresistant neoplasm; however, substantial radiobiologic and clinical evidence has emerged to refute this notion. Improved local control has been demonstrated with the use of adjuvant radiation therapy delivered to the primary site or regional lymphatics in patients with high-risk clinical or pathologic features. Despite improved local control, high-risk cutaneous melanoma often spreads systemically, leading to poor survival. In the setting of systemic progression, radiation therapy can frequently palliate symptomatic sites of metastatic disease.

Phase I Study of a Plasmid DNA Vaccine Encoding MART-1 in Patients with Resected Melanoma at Risk for Relapse

Immunization with plasmid DNA represents an attractive method for increasing cellular immune responses against cancer antigens. The safety and immunologic response of a plasmid encoding the MART-1 melanocyte differentiation antigen was evaluated in 12 patients with resected melanoma at risk for relapse. As a control, patients were also administered a plasmid encoding hepatitis B surface antigen (HBsAg). After establishing immunologic activity of the vaccines in mice, groups of three to six HLA-A2-positive patients were enrolled into one of three cohorts in which they received intramuscular injections of the MART-1 plasmid into the right deltoid and the HBsAg plasmid into the left deltoid at doses of 0.1, 0.3, or 1.0 mg on days 1, 43, 85, and 127. Injections were well tolerated. Toxicity was limited to grade 1 pain and injection site tenderness. Systemic toxicity was not observed. Although baseline MART-1-specific lymphoproliferative and ELISPOT responses were evident, no patient manifested increases after injection of the MART-1 plasmid. Furthermore, changes in MART-1-specific precursors were not evident after immunization as assessed by an in vitro stimulation assay. No patients manifested a lymphoproliferative response to HBsAg antigen, and significant antibody responses to HBsAg were also not observed. Although injections were safe, the authors could not show significant immunologic responses to plasmid encoding MART-1 or HBsAg using the dose, schedule, and route of administration applied. This study underscores species differences in the ability to respond to plasmid immunogens.

Fighting Cancer with Vaccinia Virus: Teaching New Tricks to an Old Dog

Vaccinia virus has played a huge part in human beings' victory over smallpox. With smallpox being eradicated and large-scale vaccination stopped worldwide, vaccinia has assumed a new role in our fight against another serious threat to human health: cancer. Recent advances in molecular biology, virology, immunology, and cancer genetics have led to the design of novel cancer therapeutics based on vaccinia virus backbones. With the ability to infect efficiently a wide range of host cells, a genome that can accommodate large DNA inserts and express multiple genes, high immunogenicity, and cytoplasmic replication without the possibility of chromosomal integration, vaccinia virus has become the platform of many exploratory approaches to treat cancer. Vaccinia virus has been used as (1) a delivery vehicle for anti-cancer transgenes, (2) a vaccine carrier for tumor-associated antigens and immunoregulatory molecules in cancer immunotherapy, and (3) an oncolytic agent that selectively replicates in and lyses cancer cells.

Phase I/II Trial of Melanoma Patient–Specific Vaccine of Proliferating Autologous Tumor Cells, Dendritic Cells, and GM-CSF: Planned Interim Analysis

AIM

The aim of this study was to investigate the feasibility, safety, and clinical efficacy of patient-specific dendritic cell vaccines in patients with metastatic melanoma. A planned interim analysis was conducted on the first 20 patients.

METHODS

Tumor cell lines were established from metastatic tumor, expanded to 200 million cells, and then incubated with interferon-gamma for patients who were candidates for therapy. Cells were irradiated and cryopreserved. Patients underwent leukapheresis to obtain mononuclear cells that were cultured in the presence of IL-4 and GM-CSF to produce dendritic cells, which were incubated with cryopreserved, irradiated tumor cells, and then stored in aliquots of about 20 million cells for subcutaneous (s.c.) injections with GM-CSF once a week for 3 weeks, then once a month for 5 months.

RESULTS

The first 20 eligible patients included 10 men and 10 women, with a median age of 48 years (range, 16-79 years). Three (3) patients had brain metastases, and 13 patients had experienced disease progression after biochemotherapy. At the time of vaccine treatment, 6 patients had evaluable metastatic disease, while 14 patients lacked measurable disease. Vaccine therapy was well tolerated, except for what appeared to be GM-CSF-related allergic reactions in 2 patients. Delayed-type hypersensitivity (DTH) tests to irradiated tumor cells were positive in 0 of 20 patients tested at baseline, but converted to positive in 8 patients (40%). At a median follow-up of 13.8 months, there is a 95% overall survival and a 48% progression-free survival. Four (4) patients have already survived more than 3.0 years since starting the vaccine.

CONCLUSION

Based on tolerability, rate of tumor DTH conversion, and encouraging survival, the trial will continue accrual to at least 19 patients with measurable disease and 40 patients who lack measurable disease at the time of treatment.

Poxvirus vaccines for cancer and HIV therapy

The poxviridae have a long history of causing disease in society, and their biological effects in humans and other mammals have been extensively studied. In the 1980s, genetic engineering techniques were applied to vaccinia in order to create replicating recombinant vectors that could express inserted genes encoding influenza virus proteins. In animal models, these recombinant viruses were able to deliver their foreign antigens to the immune system and elicit a specific adaptive immune response. Since then, improvements in our understanding of immunobiology, as well as technical advances in bioengineering, have led to the creation and clinical testing of a large number of recombinant poxviruses as candidate vaccines. Poxviruses can infect a broad range of cells, replicate with high efficiency and elicit strong immune responses - factors that make them especially well-suited as vaccines for the prevention and treatment of human immunodeficiency virus (HIV) and cancer. Both of these diseases are characterised by chronic antigen expression in the setting of focal or global deficits in the immune system that hamper the generation of protective immunity. This review traces the history of poxviruses as pathogens and immunogens, examines some of the approaches that have been taken to design poxviral vaccines for HIV and cancer and summarises the results of existing clinical trials of these vectors. In addition, the review aims to identify some of the factors that may shape the development of future therapies based on recombinant poxviruses.

Novel therapeutic agents under investigation for malignant melanoma

Malignant melanoma presents a therapeutic challenge. Patients at high risk for recurrence (stage III) are eligible for adjuvant treatment with IFN-alpha or may enrol in a clinical trial. Both options offer no meaningful survival advantage. Patients with metastatic disease (stage IV) have a 5-year survival of < 10% and have no effective treatment options. Despite aggressive investigations into vaccine therapy, no vaccine has yet received FDA approval. Biological therapies with IFN-alpha and IL-2 have demonstrated a real but minimal effect. Chemotherapeutic options are even more dismal. Single-agent chemotherapy yields a 15-20% response rate of short lived duration. Combination chemotherapy alone or with immunological adjuvants yields response rates of 35-45% but with significant toxicity and no significant improvement in survival. Novel treatment agents that target metabolic pathways, angiogenesis inhibitors, antisense therapies, gene therapies and innovative vaccines may offer hope for an otherwise grave disease.