Cancer therapy and vaccination

Cancer remains one of the leading causes of death worldwide, both in developed and in developing nations. It may affect people at all ages, even fetuses, but the risk for most varieties increases with age. Current therapeutic approaches which include surgery, chemotherapy and radiotherapy are associated with adverse side effects arising from lack of specificity for tumors. The goal of any therapeutic strategy is to impact on the target tumor cells with limited detrimental effect to normal cell function. Immunotherapy is cancer specific and can target the disease with minimal impact on normal tissues. Cancer vaccines are capable of generating an active tumor-specific immune response and serve as an ideal treatment due to their specificity for tumor cells and long lasting immunological memory that may safeguard against recurrences. Cancer vaccines are designed to either prevent (prophylactic) or treat established cancer (therapeutic). Identification of tumor-associated antigens (TAAs) and tumor-specific antigens (TSAs) has led to increased efforts to develop vaccination strategies. Vaccines may be composed of whole cells or cell extracts, genetically modified tumor cells to express costimulatory molecules, dendritic cells (DCs) loaded with TAAs, immunization with soluble proteins or synthetic peptides, recombinant viruses or bacteria encoding tumor-associated antigens, and plasmid DNA encoding TSAs or TAAs in conjunction with appropriate immunomodulators. All of these antitumor vaccination approaches aim to induce specific immunological responses and localized to TAAs, destroying tumor cells alone and leaving the vast majority of other healthy cells of the body untouched.     

Cancer therapy with DNA-based vaccines

The development of DNA-based vaccines arises from the knowledge that weakly immunogenic, tumor-associated antigens (TAAs), the products of mutant or dysregulated genes in the malignant cells, are expressed in a highly immunogenic form by antigen presenting cells. We successfully prepared vaccines that were effective in the treatment of cancer in mice by transfection of DNA from breast cancer cells into a mouse fibroblast cell line (LM). Fibroblasts express MHC class I-determinants along with B7.1, a co stimulatory molecule. (Classic studies indicate that transfection of genomic DNA can stably alter both the genotype and the phenotype of the cells that take-up the exogenous DNA.) The fibroblasts were transfected with sheared, unfractionated genomic DNA from a breast adenocarcinoma that arose spontaneously in a C3H/He mouse (H-2(k)). To increase their non-specific immunogenic properties, the fibroblasts were modified before transfection to express allogeneic MHC-determinants (H-2K(b)) and to secrete IL-2. Afterward, the IL-2-secreting semi allogeneic cells were co transfected with DNA from the spontaneous breast neoplasm, along with a plasmid (pHyg) conferring resistance to hygromycin. Pooled colonies of hygromycin-resistant cells were then tested in C3H/He mice for their immunotherapeutic properties against the growth of the breast neoplasm. The results indicated that tumor-bearing mice immunized with the transfected cells survived significantly longer than mice in various control groups. Similar beneficial effects were seen in C57BL/6 mice injected with a syngeneic melanoma cells and semi allogeneic, IL-2-secreting fibroblasts transfected with DNA from the melanoma cells. The immunity was mediated by CD8(+) T cells and was specific for the type to tumor from which the DNA was obtained.     

Cancer gene therapy by adenovirus-mediated gene transfer

Cancer arises as a direct result of genetic mutations. It therefore stands to reason that cancer should be well suited for the correction through gene therapy. Recent advances in the understanding of the molecular pathogenesis of cancer and the rapid development of recombinant DNA technology have made cancer gene therapy feasible in the clinical setting. The current efforts for cancer gene therapy mainly focus on immunogene therapy, chemogene therapy, restoration of tumor suppressor gene function, and oncolytic virus therapy. Central to all these therapies is the development of efficient vectors for gene delivery--this remains a work in progress. These vectors can be classified as viral and non-viral vectors. This paper will concentrate on viral vectors because of their practical advantages over non-viral vectors. Of the viral vectors, by far the most important are the human adenoviruses as is reflected by the enormous data and literature accumulated by studies relating to animal tumor models and clinical trials. In this review, we examine the recent progress in adenovirus-mediated cancer gene therapy with regard to cytokine gene, tumor suppressor gene, chemogene, and oncolytic adenovirus. We also discuss the current limitations of the adenoviral vector system and how they may be circumvented in future developments relating to targeted gene delivery.     

Cancer gene therapy through autonomous parvovirus--mediated gene transfer

Parvoviruses are small nuclear replicating DNA viruses. The rodent parvoviruses are usually weakly pathogenic in adult animals, bind to cell surface receptors which are fairly ubiquitously expressed on cells, and do not appear to integrate into host chromosomes during either lytic or persistent infection. The closely related rodent parvoviruses MVM, H-1 and LuIII efficiently infect human cell lines. Most interesting, malignant transformation of human and rodent cells was often found to correlate with a greater susceptibility to parvovirus-induced killing (oncolysis) and with an increase in the cellular capacity for amplifying and / or expressing the incoming parvoviral DNA. These and other interesting properties make these autonomous rodent parvoviruses and recombinant derivatives promising candidate antitumor vectors. Capsid replacement vectors have been produced from MVM or H-1 virus that carry transgenes encoding either therapeutic products (cytokines/chemokines, Apoptin, herpes simplex virus thymidine kinase) or marker proteins (green fluorescent protein, chloramphenicolacetyl transferase, luciferase). This review describes the current state of the art regarding the potential application of wild-type parvoviruses and derived vectors for the treatment of cancer. In particular, recent successes with the development of replication-competent virus-free vector stocks are discussed and results from pre-clinical studies using recombinant parvoviruses transducing various cytokines/chemokines are presented.     

Cancer suicide gene therapy with TK.007: superior killing efficiency and bystander effect

Suicide gene therapy is a promising concept in oncology. We have recently introduced a novel suicide gene, TK.007, which was shown to excel established herpes simplex virus thymidine kinase (HSVtk) variants when used for donor-lymphocyte modification in adoptive immunotherapy models. Here, the potential of TK.007 in killing cancer cells was studied. Initially, we transduced tumour cell lines derived from different neoplasias (glioblastoma, melanoma, lung cancer, colon cancer) with lentiviral LeGO vectors encoding TK.007 or the splice-corrected (sc)HSVtk together with an eGFP/Neo-marker. Based on direct in vitro comparison, we found that TK.007 facilitates more efficient tumour cell killing at significantly lower ganciclovir doses in all tumour cell lines tested. Also, using different readout systems, we found a significantly stronger bystander effect of TK.007 as compared to scHSVtk. Importantly, in vitro data were confirmed in vivo using a subcutaneous G62 glioblastoma model in NOD/SCID mice. In mice transplanted with scHSVtk-positive tumours, treatment with low (10 mg/kg) or standard (50 mg/kg) ganciclovir doses resulted only in short-term growth inhibition or transient tumour remission, respectively. In striking contrast, in the TK.007 group, all animals achieved continuous complete remission after both standard and low-dose ganciclovir. Finally, a substantial bystander effect for TK.007 was also confirmed with the G62 model in vivo, where significantly prolonged survival for mice bearing tumours containing only 10% or 50% TK.007-expressing cells was observed. In summary, our data indicate strongly improved anti-tumour activity of TK.007 as compared to conventional HSVtk. We therefore suppose that TK.007 is an excellent candidate for cancer suicide gene therapy.     

Cancer therapy using tumor-associated antigens to reduce side effects

Tumor-associated antigens recently have become very popular in cancer therapy. They can be targeted to reduce side effects of traditional cancer therapy. In this review, ten promising tumor-associated antigens are being discussed in detail. The characteristics of each one are being reviewed in detail. Monoclonal antibodies attached to traditional anticancer agents can target a specific type of cancer cells thereby reducing the amount of traditional anticancer agents reaching normal tissues. This sort of cancer targeting can be a very attractive anticancer therapy because it substantially reduces the amount of side effects normally caused by traditional anticancer agents.     

Cancer and radiation therapy: current advances and future directions

In recent years remarkable progress has been made towards the understanding of proposed hallmarks of cancer development and treatment. However with its increasing incidence, the clinical management of cancer continues to be a challenge for the 21st century. Treatment modalities comprise of radiation therapy, surgery, chemotherapy, immunotherapy and hormonal therapy. Radiation therapy remains an important component of cancer treatment with approximately 50% of all cancer patients receiving radiation therapy during their course of illness; it contributes towards 40% of curative treatment for cancer. The main goal of radiation therapy is to deprive cancer cells of their multiplication (cell division) potential. Celebrating a century of advances since Marie Curie won her second Nobel Prize for her research into radium, 2011 has been designated the Year of Radiation therapy in the UK. Over the last 100 years, ongoing advances in the techniques of radiation treatment and progress made in understanding the biology of cancer cell responses to radiation will endeavor to increase the survival and reduce treatment side effects for cancer patients. In this review, principles, application and advances in radiation therapy with their biological end points are discussed.     

Cancer gene therapy utilizing interleukin-13 receptor alpha2 chain

Cancer cells are known to express cell surface molecules such as specific antigens or cytokine receptors, e.g., EGFR, Fas/CD95, gp100, HER-2/neu, IL-13Ralpha2, and MAGE. Among them, interleukin-13 receptor (IL-13R) alpha2 chain is expressed on certain types of cancer cells including glioblastoma, AIDS Kaposi's sarcoma, and head and neck cancer. This protein is one of the receptor components for IL-13, a Th2 cell-derived pleiotropic immune regulatory cytokine. IL-13Ralpha2 chain on these cancer cells can be targeted with a receptor-directed cytotoxin termed IL13-PE to induce specific cancer cell killing, however, this molecule does not mediate cytotoxicity to cells that do not express or express low levels of IL-13Ralpha2. In order to achieve a broad therapeutic window for IL13-PE, plasmid-mediated gene transfer of IL-13Ralpha2 in cancer cells was employed in vitro and in vivo. Cancer cells transfected with IL-13Ralpha2 demonstrated increased binding to IL-13 and sensitivity to IL13-PE in vitro. In vivo intratumoral gene transfer of IL-13Ralpha2 profoundly enhanced the antitumor activity of IL13-PE, providing complete elimination of established tumor in some xenografts. In this review article, current findings from IL-13Ralpha2 gene transfer in a variety of human cancer models in nude mice are summarized. In addition, safety issues and possible future directions utilizing this therapeutic approach are discussed.     

Cancer risk assessment.

Increasing efforts to reduce the burden of cancer have brought into sharp relief the relevance of cancer risk assessment in preventing the occurrence and, when that is not possible, preventing the progression of the disease. Methods for estimating human cancer risk have evolved steadily over the past few decades as more has been learned about molecular, genetic, and biological aspects of cancer. These methods have been applied with increasing frequency in community-based approaches to reduce the risk of environmentally provoked cancers. At the same time, patients are showing increased interest in estimates of their likelihood of developing cancer during the next 10, 20, or 30 years. This interest is involving more physicians in human cancer risk assessment in clinical counseling settings.