) Gene addition therapy: aims at introducing normal or functional copy of gene into genome so as to restore the normal function of the cell. Several genetic alternations are seen in oral squamous cell carcinoma like mutation of p53, p21 and p16. Since the p53 plays a important role in regulating cell cycle and apoptosis, p53 gene transfer was initially tested in carcinoma patients by injecting primary tumour with an adenoviral vector expressing wild type