Local delivery for gene therapy

Anticancer therapy targeting the apoptotic pathway

Apoptosis, or programmed cell death, has an essential role in controlling cell number in many developmental and physiological settings and in chemotherapy-induced tumour-cell killing. It is a genetically regulated biological process, guided by the ratio of proapoptotic and antiapoptotic proteins. Recently, inducers of apoptosis have been used in cancer therapy. Several studies have attempted to induce apoptosis by triggering the tumour-necrosis-factor-related apoptosis-inducing ligand receptor and the BCL2 family of proteins, and others have targeted the caspases, and proteins that inhibit apoptosis. Most of these therapies are still in preclinical development because of their low efficacy and susceptibility to drug resistance, but some of them have shown promising results. In this article, we review the development and clinical efficacy of proapoptotic drugs that have shown promise.

Oropharyngeal cancer: the role of chemotherapy

Successful management of squamous cell cancer of the oropharynx must address two, sometimes conflicting, treatment goals. The first goal is disease eradication, and the second is preservation of oropharyngeal function. For early cancers, definitive surgical excision often represents the most effective and least morbid approach. When surgery is likely to result in functional deficits of speech or swallowing, definitive radiation therapy can also be used successfully. Often the choice of treatment modality is based on institutional expertise and bias. However, for the more frequent patients with advanced disease, treatment choices become more complex. Historically, surgery and radiation therapy have been used together, often with suboptimal control of locoregional disease and significant long-term functional deficits, reflecting surgical excision, radiation-induced long-term toxicities, and any initial functional impairment resulting from the tumor. The addition of systemic chemotherapy to definitive radiation has now been demonstrated to produce a significant survival benefit for patients with advanced squamous cell head and neck cancer originating in the oropharynx and elsewhere. Although there are still specific indications for primary surgical resection, the use of chemotherapy and radiation has become a standard of care for the management of patients with this disease, with surgery often reserved for salvage of those who fail definitive nonoperative treatment. Debate continues as to the best tolerated and most successful combination of chemotherapy drugs, radiation fractionation schema, and coordination of treatment modalities; however, a reproducible survival benefit has been demonstrated only for the concomitant, platinum-based treatment schedules. The focus of future investigation must be on optimizing these multimodality approaches, minimizing toxicities and functional deficits while maximizing treatment success. It is hoped that the addition of the newer therapeutic approaches, including epidermal growth factor receptor inhibition and gene therapy, may further improve the results of more traditional treatment combinations. Continued enrollment of patients in well-designed and conducted clinical trials is of paramount importance.

Recombinant adenovirus vectors for gene therapy and clinical trials

In the last decade adenovirus (AdV) vectors have emerged as promising technology in gene therapy. They have been used for genetic modification of a variety of somatic cells in vitro and in vivo. They have been widely used as gene delivery vectors in experiments both with curative and preventive purposes. AdV vectors have been used in the experimental and in some extent in the clinical gene therapy of a variety of cancers. The combination of recombinant AdV technology with chemotherapy (pro drug system) seems to be promising, too. AdV vectors offer several advantages over other vectors. Replication defective vectors can be produced in very high titers (10(11) pfu/ml) thus allowing a substantially greater efficiency of direct gene transfer; they have the capacity to infect both replicating and nonreplicating (quiescent) cells from a variety of tissues and species. Several important limitations of adenovirus mediated gene transfer are also known, such as the relatively short-term (transient) expression of foreign genes, induction of the host humoral and cellular immune response to viral proteins and viral infected cells, which may substantially inhibit the effect of repeated treatment with AdV vectors, the limited cloning capacity and the lack of target cell specificity. However, the well-understood structure, molecular biology and host cell interactions of AdV-s offer some potential solutions to these limitations.