Preface

Gene therapy provides great promises for cancer treatment. Two essential components are absolutely necessary in current gene therapy: an effective therapeutic gene that can be expressed at a target site, and an efficient and safe delivery system.

This book aims to provide an up-to-date report in gene delivery research. With the multidisciplinary contribution in gene delivery, the book covers: (1) various gene delivery systems, like cationic lipids, cationic polymers and silica nanoparticles; (2) methods to enhance delivery, such as ultrasound and microbubble; (3) materials with modification and multifunction for the tumor or tissue targeting.

The book provides an introductory text for nonspecialists in gene delivery, and prepares readers to perform well-controlled experiments with appropriate controls. It illustrates ideas and models with more than 100 figures, including 64 photomicrographs.

Many specialists are not familiar with both drug delivery and the molecular biology of DNA vectors. In this book, molecular biologists will gain a basic knowledge of lipids, liposome, and other gene delivery vehicles and lipids, while drug delivery scientists will better understand DNA, molecular biology, and DNA manipulation.

We acknowledge our contributors and section editors for generously sharing their expertise and scientific skills. We hope this book can help the researchers come up with new ideas and finally bring the gene therapy approaches to the clinical trials.

> **Xu-bo Yuan**  Tianjin University China

**1** 

*Greece*

**Non-Viral Gene Therapy Vectors** 

Gene therapy is the use of genes or DNA for the treatment of diseases. For the treatment of inherited disorders, DNA carrying a functional gene is introduced into the cells of a patient to reverse the defect of the corresponding malfunctioning endogenous gene. Previous genetic characterization of the disease and cloning of the gene that causes it are necessary. In most cases, the cDNA of the therapeutic gene is cloned into a bacterial plasmid under the control of a strong heterologous promoter (often of viral origin). However, such constructs, called mini-genes, lack introns, promoters, enhancers, and long-range controlling elements

For gene therapy of some diseases it is important to achieve expression of the therapeutic gene at specific levels. Expression at lower levels than normal might not be sufficient to correct the defect and at higher levels could result in undesirable effects. In other cases, tissue-specific expression may be very important. The elements responsible for controlled and tissue-specific expression of a gene usually lie within the introns and the sequences before and after the gene. Therefore, the use of genomic constructs which contain the introns and flanking DNA of the therapeutic gene is expected to be more effective than that of minigene constructs in gene therapy for certain genetic diseases where precise levels of the gene product are required (reviewed by (Pérez-Luz & Díaz-Nido, 2010)). Bacterial Artificial Chromosomes (BACs), originating from the human genome project, contain genomic loci of approximately 180 kb on average and cover the entire human genome (Osoegawa et al., 2001). These sequenced BACs can accommodate most genes along with their regulatory

Gene therapy as a modern therapeutic tool should provide a permanent cure to the patient by long-term maintenance and expression of the administered gene. This can be achieved either by integration of the transgene into the natural chromosomes or by other mechanisms

One of the most important aspects of gene therapy is the choice of the vector that will deliver and express the corrective gene in the appropriate cells. Current vectors fall into two categories: viral and non-viral. Apart from determining the method of delivery, the type of vector also determines the fate of the therapeutic gene within the cells. For instance, the vector may have the ability to remain extra-chromosomally. Non-viral artificial chromosome vectors and adeno-associated viral, adenoviral, Herpes viral and EBV vectors are all

that precisely control the temporal and spatial expression of the endogenous gene.

elements and can serve as tools in gene therapy using genomic constructs.

for its replication and nuclear retention.

**1. Introduction** 

**Carrying Genomic Constructs** 

George Kotzamanis, Hassan Abdulrazzak, Athanassios Kotsinas and Vassilis G. Gorgoulis

*University of Athens, Medical School*
