**1. Introduction**

498 Non-Viral Gene Therapy

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Chemotherapeutic drugs are fundamental in cancer management and are responsible for most cases of adjuvant treatment in patients after surgical procedures. However, the median overall survival does not increase in patients treated by concurrent chemo-radiotherapy. Consequently, further studies that could enhance the therapeutic effect should be encouraged [1].

Although the biological functions of microRNAs (miRNA) are not completely revealed, there is growing evidence that miRNA pathways are a new mechanism of gene regulation in both normal and diseased conditions [2]. Recent evidence has shown that miRNA mutations or aberrant expression patterns correlate with various diseases, such as cancer, viral infections, cardiovascular and indicates that miRNAs can function as tumor suppressors and oncogenes and oretically become a target to enhance the chemotherapeutic effect in cancer therapy.

However, although much work has been accomplished, the development of an efficient delivery system still remain a major challenge for the wide application of miRNA. In the following sections -- after a brief introduction of the miRNA strategies -- the potential and contributions of dendrimers in the development of effective non-viral delivery systems for combined the microRNA therapy with drug delivery will be discussed.
