Cancer vaccines and immunotherapies: emerging perspectives

Peptide-Based Therapeutics in Cancer Therapy

A monster called cancer is still one of the most challenging human problems and one of the leading causes of death in the world. Different types of treatment methods are used for cancer therapy; however, there are challenges such as high cost and harmful side effects in using these methods. Recent years have witnessed a surge in the development of therapeutic peptides for a wide range of diseases, notably cancer. Peptides are preferred over antibiotics, radiation therapy, and chemotherapy in the treatment of cancer due to a number of aspects, including flexibility, easy modification, low immunogenicity, and inexpensive cost of production. The use of therapeutic peptides in cancer treatment is a novel and intriguing strategy. These peptides provide excellent prospects for targeted drug delivery because of their high selectivity, specificity, small dimensions, good biocompatibility, and simplicity of modification. Target specificity and minimal toxicity are benefits of therapeutic peptides. Additionally, peptides can be used to design antigens or adjuvants for vaccine development. Here, types of therapeutic peptides for cancer therapy will be discussed, such as peptide-based cancer vaccines and tumor-targeting peptides (TTP) and cell-penetrating peptides (CPP).

Cytotoxic T-lymphocyte elicited therapeutic vaccine candidate targeting cancer against MAGE-A11 carcinogenic protein

Immunotherapy is a breakthrough approach for cancer treatment and prevention. By exploiting the fact that cancer cells have overexpression of tumor antigens responsible for its growth and progression, which can be identified and removed by boosting the immune system. In silico techniques have provided efficient ways for developing preventive measures to ward off cancer. Herein, we have designed a potent cytotoxic T-lymphocyte epitope to elicit a desirable immune response against carcinogenic melanoma-associated antigen-A11. Potent epitope was predicted using reliable algorithms and characterized by advanced computational avenue CABS molecular dynamics simulation, for full flexible binding with HLA-A*0201 and androgen receptor to large-scale rearrangements of the complex system. Results showed the potent immunogenic construct (KIIDLVHLL), from top epitopes using five algorithms. Molecular docking analyses showed the strong binding of epitope with HLA-A*0201 and androgen receptor with docking score of -780.6 and -641.06 kcal/mol, respectively. Molecular dynamics simulation analysis revealed strong binding of lead epitope with androgen receptor by involvement of 127 elements through atomic-model study. Full flexibility study showed stable binding of epitope with an average root mean square deviation (RMSD) 2.21 Å and maximum RMSD value of 6.48 Å in optimal cluster density area. The epitope also showed remarkable results with radius of gyration 23.0777 Å, world population coverage of 39.08% by immune epitope database, and transporter associated with antigen processing (TAP) affinity IC50 value of 2039.65 nm. Moreover, in silico cloning approach confirmed the expression and translation capacity of the construct within a suitable expression vector. The present study paves way for a potential immunogenic construct for prevention of cancer.

Lipid/polymer-based nanocomplexes in nucleic acid delivery as cancer vaccines

Cancer vaccines consist of nucleic acid derivatives such as plasmid DNA, small interfering RNA and mRNA, and can be customized according to the patient's needs. Nanomedicines have proven to be exceptionally good as miniaturized drug carriers, and thus they offer great advantages for delivering cancer vaccines. This review provides an overview of the literature on cancer vaccines, from their inception to current developments in the field.

Tumor Microenvironment-Regulating Immunosenescence-Independent Nanostimulant Synergizing with Near-Infrared Light Irradiation for Antitumor Immunity

The combination of photothermal therapy (PTT) and toll-like receptor (TLR)-mediated immunotherapy can elicit antitumor immunity and modulate the immunosuppressive tumor microenvironment (TME). Unlike other TLRs, TLR-5 is a promising target for immune activation, as its expression is well-maintained even during immunosenescence. Here, we developed a unique tumor microenvironment-regulating immunosenescence-independent nanostimulant consisting of TLR-5 adjuvant Vibrio vulnificus flagellin B (FlaB) conjugated onto the surface to an IR 780-loaded hyaluronic acid-stearylamine (HIF) micelles. These HIF micelles induced immune-mediated cell death via PTT when irradiated with a near-infrared laser. In comparison with PTT alone, the combination of in situ-generated tumor-associated antigens produced during PTT and the immune adjuvant FlaB demonstrated enhanced vaccine-like properties and modulated the TME by suppressing immune-suppressive regulatory cells (Tregs) and increasing the fraction of CD103+ migratory dendritic cells, which are responsible for trafficking tumor antigens to draining lymph nodes (DLNs). This combinatorial strategy (i.e., applying a TLR-5 adjuvant targeted to immunosenescence-independent TLR-5 and the in situ photothermal generation of tumor-associated antigens) is a robust system for next-generation immunotherapy and could even be applied in elderly patients, thus broadening the clinical scope of immunotherapy strategies.

Peptide-based combination nanoformulations for cancer therapy

Research in cancer therapy is moving towards the use of biomolecules in combination with conventional approaches for improved disease outcome. Among the biomolecules explored, peptides are strong contenders due to their small size, high specificity, low systemic toxicity and wide inter/intracellular targets. The use of nanoformulations for such combination approaches can lead to further improvement in efficacy by reducing off-target cytotoxicity, increasing circulation time, tumor penetration and accumulation. This review focuses on nanodelivery systems for peptide-based combinations with chemo, immuno, radiation and hormone therapy. It gives an overview of the latest therapeutic research being conducted using combination nanoformulations with anticancer peptides, cell penetrating/tumor targeting peptides, peptide nanocarriers, peptidomimetics, peptide-based hormones and peptide vaccines. The challenges hindering clinical translation are also discussed.

Peptide-Based Therapeutics for Oncology

The development of peptide-based drugs, which are usually synthetic analogues of endogenous peptides, is currently one of the most topical directions in drug development. Among them, antitumor peptide-based drugs are of great interest. Anticancer peptides can be classified into three main groups based on their mechanism of action: inhibitory, necrosis-inducing and pro-apoptotic peptides. As an antitumor therapy, peptides are considered to have at least the same efficacy as chemotherapy or surgical treatment, but offer advantages in terms of safety and tolerability, given that chemotherapy is usually characterized by severe adverse effects, and surgery carries additional risks for patients. Short peptides have a number of benefits over other molecules. First, compared with full-length proteins and antibodies, short peptides are less immunogenic, more stable ex-vivo (prolonged storage at room temperature), and have better tumor or organ permeability. Moreover, the production of such short peptide-based drugs is more cost effective. Second, in comparison with small organic molecules, peptides have higher efficacy and specificity. Finally, due to the fact that the main products of peptide metabolism are amino acids, these drugs are usually characterized by lower toxicity. Short peptides have a highly selective mechanism of action, thereby demonstrating low toxicity. Furthermore, with the addition of different stabilizing structural modifications, as well as novel drug delivery systems, the peptide-based drugs are proving to be promising therapeutics for cancer mono- or polytherapy. However, challenges remain including that endogenous and synthetic peptide molecules can be oncogenic. Therefore, it is important to investigate whether peptides contribute to tumor growth. In order to answer such questions, numerous preclinical and clinical studies of peptide-based therapeutics are currently being conducted.

Whole leukemia cell vaccines: Past progress and future directions

It has long been recognized that allogeneic hematopoietic stem cell transplantation can reduce the risk of leukemia relapse by inducing the graft-versus-leukemia effect. However, allogeneic stem cell transplantation is also known to be able to cause graft-versus-host disease, which can cause considerable morbidity and even mortality in patients receiving allogeneic hematopoietic stem cell transplantation. Therefore, to elicit leukemia-specific immune responses without alloimmune reaction, the possibilities of active immunotherapy methods such as leukemia vaccines have been studied for decades. Among various types of leukemia vaccines, whole leukemia cell vaccines are known to be able to induce immune responses against multiple unknown antigens without the need for adoptive transfer of dendritic cells. In this review, we will discuss the past progress of whole leukemia cell vaccines, with a focus on strategies to enhance their immunogenicity. We will also present the future directions of whole leukemia cell vaccines along with addressing newly emerging concepts, such as immunogenic cell death and necroptosis. We will not discuss in detail other factors that can reduce the therapeutic efficacy of whole leukemia cell vaccines such as various immunosuppressive mechanisms of leukemia.

Barata T, Gaspar M, Brocchini S, Zloh M, Peppas NA, Satchi-Fainaro R, F. Florindo H. α-Galactosylceramide and peptide-based nano-vaccine synergistically induced a strong tumor suppressive effect in melanoma

α-Galactosylceramide (GalCer) is a glycolipid widely known as an activator of Natural killer T (NKT) cells, constituting a promising adjuvant against cancer, including melanoma. However, limited clinical outcomes have been obtained so far. This study evaluated the synergy between GalCer and major histocompatibility complex (MHC) class I and MHC class II melanoma-associated peptide antigens and the Toll-Like Receptor (TLR) ligands CpG and monophosphoryl lipid A (MPLA), which we intended to maximize following their co-delivery by a nanoparticle (NP). This is expected to improve GalCer capture by dendritic cells (DCs) and subsequent presentation to NKT cells, simultaneously inducing an anti-tumor specific T-cell mediated immunity. The combination of GalCer with melanoma peptides and TLR ligands successfully restrained tumor growth. The tumor volume in these animals was 5-fold lower than the ones presented by mice immunized with NPs not containing GalCer. However, tumor growth was controlled at similar levels by GalCer entrapped or in its soluble form, when mixed with antigens and TLR ligands. Those two groups showed an improved infiltration of T lymphocytes into the tumor, but only GalCer-loaded nano-vaccine induced a prominent and enhanced infiltration of NKT and NK cells. In addition, splenocytes of these animals secreted levels of IFN-γ and IL-4 at least 1.5-fold and 2-fold higher, respectively, than those treated with the mixture of antigens and adjuvants in solution. Overall, the combined delivery of the NKT agonist with TLR ligands and melanoma antigens via this multivalent nano-vaccine displayed a synergistic anti-tumor immune-mediated efficacy in B16F10 melanoma mouse model.

STATEMENT OF SIGNIFICANCE

Combination of α-galactosylceramide (GalCer), a Natural Killer T (NKT) cell agonist, with melanoma-associated antigens presented by MHC class I (Melan-A:26) and MHC class II (gp100:44) molecules, and Toll-like Receptor (TLR) ligands (MPLA and CpG), within nanoparticle matrix induced a prominent anti-tumor immune response able to restrict melanoma growth. An enhanced infiltration of NKT and NK cells into tumor site was only achieved when the combination GalCer, antigens and TLR ligands were co-delivered by the nanovaccine.

Peptide-guided targeting of GPR55 for anti-cancer therapy

Expression of the lysophosphatidylinositol receptor GPR55 correlates with invasive potential of metastatic cells and bone metastasis formation of different types of tumors. These findings suggest a role for GPR55 signaling in cancer progression, including in lymphoproliferative diseases. Here, we screened a M13-phage-displayed random library using the bait of HEK293 cells that heterologously expressed full-length HA-GPR55. We selected a set of phagotopes that carried 7-mer insert peptides flanked by a pair of cysteine residues, which resulted in cyclized peptides. Sequencing of selected phagotopes dictated the primary structure for the synthetic FITC-labeled peptide P1, which was analyzed for binding specificity to immunoprecipitated HA-GPR55, and to endogenously expressed GPR55, using cells interfered or not for GPR55, as well as for co-localization imaging with HA-GPR55 at the membrane level. The peptide P1 stimulated GPR55 endocytosis and inhibited GPR55-dependent proliferation of EHEB and DeFew cells, two human B-lymphoblastoid cell lines. Our data support the potential therapeutic application of peptide ligands of GPR55 for targeting and inhibiting growth of neoplastic cells, which overexpress GPR55 and are dependent on GPR55 signaling for their proliferation.

Blood brain barrier: a challenge for effectual therapy of brain tumors

Brain tumors are one of the most formidable diseases of mankind. They have only a fair to poor prognosis and high relapse rate. One of the major causes of extreme difficulty in brain tumor treatment is the presence of blood brain barrier (BBB). BBB comprises different molecular components and transport systems, which in turn create efflux machinery or hindrance for the entry of several drugs in brain. Thus, along with the conventional techniques, successful modification of drug delivery and novel therapeutic strategies are needed to overcome this obstacle for treatment of brain tumors. In this review, we have elucidated some critical insights into the composition and function of BBB and along with it we have discussed the effective methods for delivery of drugs to the brain and therapeutic strategies overcoming the barrier.

Cancer immunotherapy: nanodelivery approaches for immune cell targeting and tracking

Cancer is one of the most common diseases afflicting people globally. New therapeutic approaches are needed due to the complexity of cancer as a disease. Many current treatments are very toxic and have modest efficacy at best. Increased understanding of tumor biology and immunology has allowed the development of specific immunotherapies with minimal toxicity. It is important to highlight the performance of monoclonal antibodies, immune adjuvants, vaccines and cell-based treatments. Although these approaches have shown varying degrees of clinical efficacy, they illustrate the potential to develop new strategies. Targeted immunotherapy is being explored to overcome the heterogeneity of malignant cells and the immune suppression induced by both the tumor and its microenvironment. Nanodelivery strategies seek to minimize systemic exposure to target therapy to malignant tissue and cells. Intracellular penetration has been examined through the use of functionalized particulates. These nano-particulate associated medicines are being developed for use in imaging, diagnostics and cancer targeting. Although nano-particulates are inherently complex medicines, the ability to confer, at least in principle, different types of functionality allows for the plausible consideration these nanodelivery strategies can be exploited for use as combination medicines. The development of targeted nanodelivery systems in which therapeutic and imaging agents are merged into a single platform is an attractive strategy. Currently, several nanoplatform-based formulations, such as polymeric nanoparticles, micelles, liposomes and dendrimers are in preclinical and clinical stages of development. Herein, nanodelivery strategies presently investigated for cancer immunotherapy, cancer targeting mechanisms and nanocarrier functionalization methods will be described. We also intend to discuss the emerging nano-based approaches suitable to be used as imaging techniques and as cancer treatment options.

Immune system targeting by biodegradable nanoparticles for cancer vaccines

The concept of therapeutic cancer vaccines is based on the activation of the immune system against tumor cells after the presentation of tumor antigens. Nanoparticles (NPs) have shown great potential as delivery systems for cancer vaccines as they potentiate the co-delivery of tumor-associated antigens and adjuvants to dendritic cells (DCs), insuring effective activation of the immune system against tumor cells. In this review, the immunological mechanisms behind cancer vaccines, including the role of DCs in the stimulation of T lymphocytes and the use of Toll-like receptor (TLR) ligands as adjuvants will be discussed. An overview of each of the three essential components of a therapeutic cancer vaccine - antigen, adjuvant and delivery system - will be provided with special emphasis on the potential of particulate delivery systems for cancer vaccines, in particular those made of biodegradable aliphatic polyesters, such as poly(lactic-co-glycolic acid) (PLGA) and poly-ε-caprolactone (PCL). Some of the factors that can influence NP uptake by DCs, including size, surface charge, surface functionalization and route of administration, will also be considered.

Changes in the local tumor microenvironment in recurrent cancers may explain the failure of vaccines after surgery

Each year, more than 700,000 people undergo cancer surgery in the United States. However, more than 40% of those patients develop recurrences and have a poor outcome. Traditionally, the medical community has assumed that recurrent tumors arise from selected tumor clones that are refractory to therapy. However, we found that tumor cells have few phenotypical differences after surgery. Thus, we propose an alternative explanation for the resistance of recurrent tumors. Surgery promotes inhibitory factors that allow lingering immunosuppressive cells to repopulate small pockets of residual disease quickly. Recurrent tumors and draining lymph nodes are infiltrated with M2 (CD11b(+)F4/80(hi)CD206(hi) and CD11b(+)F4/80(hi)CD124(hi)) macrophages and CD4(+)Foxp3(+) regulatory T cells. This complex network of immunosuppression in the surrounding tumor microenvironment explains the resistance of tumor recurrences to conventional cancer vaccines despite small tumor size, an intact antitumor immune response, and unaltered cancer cells. Therapeutic strategies coupling antitumor agents with inhibition of immunosuppressive cells potentially could impact the outcomes of more than 250,000 people each year.

Cancer treatment using peptides: current therapies and future prospects

This paper discusses the role of peptides in cancer therapy with special emphasis on peptide drugs which are already approved and those in clinical trials. The potential of peptides in cancer treatment is evident from a variety of different strategies that are available to address the progression of tumor growth and propagation of the disease. Use of peptides that can directly target cancer cells without affecting normal cells (targeted therapy) is evolving as an alternate strategy to conventional chemotherapy. Peptide can be utilized directly as a cytotoxic agent through various mechanisms or can act as a carrier of cytotoxic agents and radioisotopes by specifically targeting cancer cells. Peptide-based hormonal therapy has been extensively studied and utilized for the treatment of breast and prostate cancers. Tremendous amount of clinical data is currently available attesting to the efficiency of peptide-based cancer vaccines. Combination therapy is emerging as an important strategy to achieve synergistic effects in fighting cancer as a single method alone may not be efficient enough to yield positive results. Combining immunotherapy with conventional therapies such as radiation and chemotherapy or combining an anticancer peptide with a nonpeptidic cytotoxic drug is an example of this emerging field.

NKT ligand-loaded, antigen-expressing B cells function as long-lasting antigen presenting cells in vivo

We had previously shown that activated NKT cells licensed B cells to be immunogenic antigen-presenting cells and helped to elicit a wide spectrum of cancer targeted immune responses. In the current study, we sought to verify the safety of αGalCer-loaded, and adenovirus-transduced B cell-based vaccines, together with mechanism of action. Intravenously injected αGalCer-loaded, antigen-expressing B cells rapidly localized in the spleen and directly primed CD8(+) T cells in an antigen-specific manner. The transferred antigen was sustained for at least 30 days. While some injected B cells produced nonspecific IgG, the antigen-specific IgG response was completely dependent on endogenous B cells. The liver was one of the main tissues where injected B cells were retained; however, we could not find the signs of liver toxicity. Our results demonstrate that αGalCer-loaded, antigen-expressing B cells behave as "antigen-presenting" cells that stimulate endogenous antigen-specific T cells and B cells in vivo without significant toxicity.

Irradiated CIITA-positive mammary adenocarcinoma cells act as a potent anti-tumor-preventive vaccine by inducing tumor-specific CD4+ T cell priming and CD8+ T cell effector functions

In the present study, we investigated the possibility to use irradiated, non-replicating class II transcriptional activator (CIITA)-transfected tumor TS/A cells as a cell-based vaccine. Eighty-three percent of TS/A-CIITA-vaccinated mice were completely protected from tumor growth and the remaining 17% displayed significant reduction of tumor growth. In contrast, only 30% of mice injected with irradiated TS/A parental cells were protected from tumor growth, whereas the remaining 70% of animals remained unprotected. Immunity generated in the TS/A-CIITA-vaccinated mice correlated with an efficient priming of CD4(+) T cells and consequent triggering and maintenance of CD8(+) CTL effectors, as assessed by adoptive transfer assays. Important qualitative differences were observed between the two cell-based vaccines, as TS/A-CIITA-vaccinated mice developed a CTL response containing a large proportion of anti-gp70 AH1 epitope-specific cells, completely absent in TS/A-vaccinated mice, and a mixed T(h)1/T(h)2 type of response as opposed to a T(h)2 type of response in TS/A-vaccinated mice. Finally, in TS/A-CIITA-vaccinated mice, a statistically significant reduction in the percentage and absolute number of CD4(+) CD25(+) T regulatory cells as compared with those of untreated mice with growing tumors (P < 0.001) or mice vaccinated with TS/A parental cells were observed. These results let to envisage the use of CIITA-transfected non-replicating tumor cells as a vaccination strategy for prevention and, possibly, adjuvant immunotherapy in human settings.

Peptides as tools and drugs for immunotherapies

Peptides are essential tools for discovery and pre-clinical and pharmaceutical development of viral and cancer vaccines ('active immunotherapies') as well as for therapeutic antibodies ('passive immunotherapies'). They help to trigger and analyze immune responses at a molecular level (B-cell, T-helper and CTL epitopes). They contribute largely to the design of new vaccine candidates and to the generation of monoclonal antibodies. They are also valuable analytical reference compounds for the structural characterisation by liquid chromatography and mass spectrometry of recombinant proteins used as biopharmaceuticals. As for other therapeutic applications, formulation, solubilisation, batch consistency and stability, issues have to be addressed to allow the pre-clinical and clinical development of this class of compounds as immunotherapeutic drugs. In the present review, three case studies dealing with (i) the design and the characterisation of Respiratory Syntycial Virus subunit vaccines, (ii) peptide-based melanoma vaccines, and (iii) therapeutic monoclonal antibodies, all investigated in clinical trials, are reported and discussed.

Receptor expression in orbital inflammatory syndromes and implications for targeted therapy

To investigate the expression of multiple therapeutic targets in tissue specimens from patients with orbital inflammatory syndromes, the clinical records of 16 patients treated for orbital inflammation between January 2003 and November 2005 for whom tissue blocks were available were reviewed retrospectively. Immunohistochemical staining was performed on archived specimens using commercially available monoclonal antibodies against CD3, CD20, CD22, CD23, CD25, and CD52 antigens. The histologic diagnoses were confirmed, and the immunohistochemical staining patterns were agreed upon by both collaborating pathologists (JLJ and PC-B). The study included 13 women and 3 men who ranged in age from 4 to 79 years (mean, 46 years). The histologic diagnoses were as follows: orbital pseudotumor in six patients; sarcoidosis, three; eosinophilic granuloma, one; necrobiotic xanthogranuloma, one; nonspecified granulomatous inflammation, one; Graves' ophthalmopathy, one; Wegener's granulomatosis, one; and reactive lymphoid hyperplasia, two. One orbital lymphoma specimen and one foreign body reaction specimen were used as controls. CD20 was strongly expressed in all specimens except three (Wegener's granulomatosis, eosinophilic granuloma, and nonspecified granulomatous inflammation specimens), and CD25 was strongly expressed in all specimens except the Wegener's granulomatosis specimen, in which this antigen was only moderately expressed. CD20 and CD25 were strongly or moderately expressed in most of the tested specimens of orbital inflammation. If our findings are confirmed in a larger study, rituximab, which targets CD20, and denileukin diftitox (ONTAK), which targets CD25, should be considered for future clinical trials for orbital inflammatory syndromes.

Human papillomavirus vaccine: progress and the future

A vaccine to prevent infection by human papillomavirus is available in the US. This article reviews the biology of human papillomavirus that allows for the development of both therapeutic and prophylactic vaccines. Issues that may delay the acceptance of the vaccine are discussed.

Prospects for exosomes in immunotherapy of cancer

Exosomes are nanometer sized membrane vesicles invaginating from multivesicular bodies and secreted from epithelial and hematopoietic cells. They were first described "in vitro" but vesicles with the hallmarks of exosomes are present in vivo in germinal centers and biological fluids. Their protein and lipid composition are unique and could account for their expanding functions such as eradication of obsolete proteins, antigen presentation or "Trojan horses" for viruses or prions. Exosome secretion could be a regulated process participating in the transfer of molecules inbetween immune cells. Despite numerous questions pertaining to their biological relevance, the potential of dendritic cell derived-exosomes as cell-free cancer vaccines is currently being assessed. This review will summarize the composition and formation of exosomes, preclinical data, Phase I trials and optimization protocols for improving their immunogenicity in tumor bearing patients.

N-terminally truncated WT1 protein with oncogenic properties overexpressed in leukemia

WT1 was originally identified as an inactivated gene in Wilms tumor, a childhood kidney cancer. Alternative splicing of the WT1 transcript generates four major protein isoforms, each having different functional properties. Here we characterized a short transcript originating from a second promoter located within intron 1 of WT1. This 2.3-kb sWT1 transcript encodes a protein of approximately 35-37 kDa that retains intact DNA-binding and transactivation domains but lacks the 147 amino acids at the N terminus required for transcriptional repression. We found sWT1 to be a more potent transcriptional activator than WT1 for cyclin E and insulin-like growth factor 1 receptor promoters, which are normally repressed by WT1. The expression patterns of the sWT1 and WT1 transcripts differed slightly in various organs; we found sWT1 protein in tissue samples from adult testis and fetal kidney, with low-level expression in adult kidney as well. The sWT1 transcript, but not the full-length transcript, was over-expressed in the leukemia samples tested. sWT1-specific small interfering RNA retarded the proliferation of leukemia cell line K562 in vitro. Finally, sWT1 cooperated with Ras in transforming primary fibroblasts in vitro. Further studies are needed to clarify the oncogenic behavior of this isoform and to determine the mechanism underlying its up-regulation in leukemia and other forms of cancer.

Adenoviral vectors--how to use them in cancer gene therapy?

Gene therapy is most often described as a technique for introducing the foreign genetic material into cells with a correction of a dysfunctional gene as its final goal. Today, it is well known that cancer is one of the leading causes of mortality in the world. Besides classical methods for cancer treatment new strategies against cancer are needed. Although originally being designed as a treatment for monogenetic illness, soon after, gene therapy appeared as a potential new strategy in cancer therapy. One of the widely used vectors for cancer gene therapy is adenovirus. In this review we have described molecular biology of adenoviruses and basis for construction of adenoviral vectors. We have also described concepts for cancer gene therapy including their in vitro and in vivo application. Special attention is drawn toward retargeting of adenovirus as a new approach in vector design for cancer gene therapy, in order to restrict transgene expression in tumor tissue. This approach uses biophysical as well as genetic characteristics of tumor itself and its supporting tissue, allowing new "bypass" in cancer gene therapy.

The rationale for prophylactic cancer vaccines and need for a paradigm shift

This review summarizes clinical experience with infectious disease vaccines and data from animal tumor models that support a paradigm shift for cancer vaccines from therapeutic to prevention applications.

Cycloxygenase-2 inhibition augments the efficacy of a cancer vaccine

Tumor-derived cyclooxygenase-2 (COX-2) and its product, prostaglandin E2, exert strong immunoinhibitory effects that block dendritic cell function and CD4+ and CD8+ T-cell proliferation and function. We have shown previously that the addition of an oral COX-2 inhibitor to immunogene therapy using IFN-beta markedly augmented therapeutic efficacy in murine tumor models. In this study, we hypothesized that COX-2 inhibition might also augment an antitumor vaccination strategy. Mice bearing tumors derived from TC1 cells, a tumor line that expresses the human papillomavirus (HPV) E7 protein, were thus vaccinated with an adenoviral vector expressing HPV E7 protein (Ad.E7). This vaccine approach effectively generated E7-specific CD8+ cells and slowed the growth of small tumors but had little effect on large tumors. However, feeding mice with the COX-2 inhibitor, rofecoxib, restored the effectiveness of the vaccine against large tumors and prolonged survival. This effect was accompanied by a larger percentage of E7-specific CD8+ cells in the regional draining lymph nodes and a markedly increased number of tumor-infiltrating E7-specific CD8+ cells (as determined by flow cytometry) and total CD8+ T cells (as determined by immunohistochemical staining). Increased immunocyte trafficking was likely mediated by the generation of a Th1-type tumor microenvironment because COX-2 inhibition increased expression levels of mRNA for IFN-gamma, interleukin-12, IP-10, and MIG while lowering the expression of vascular endothelial growth factor within tumors. This study shows that the effectiveness of a cancer vaccine can be significantly improved by adding COX-2 inhibition.