The p53 gene located in human chromosome 17, suspends the cell cycle when there is DNA damage. If there is a mutation in p53, the cell cycle continues unrestrained and reproduces the damaged DNA, leading to uncontrolled cell proliferation and cancer tumors. The p53 protein is a transcription factor and its pivotal role in maintaining genomic integrity has earned it the nickname “guardian of the genome”. p53 gene is mutated in about 50% of human cancers of breast, colon, lung, liver, prostate, bladder, and skin. Since the loss of p53 function is so prevalent in human cancer, this protein is an ideal candidate for cancer therapy. Several gene therapeutic strategies have been employed in the attempt to restore p53 function to cancerous cells.