Cancer is the second leading cause of mortality worldwide after cardiovascular diseases, predominantly due to the lack of early symptoms and early diagnosis, and high relapse rate after radical surgery and conventional therapies. Therefore, novel approaches such as gene therapy have raised hope to significantly improve the survival rate of patients with cancers. This review aims to provide up-to-date information concerning gene therapy including improved vectors, suicide genes, cancer suppressor genes, anti-tumor angiogenesis, gene silencing, oncolytic virotherapy, and gene-editing technology. Although specific issues still exist before gene therapy can completely cure cancers, here we highlight the potential of gene therapy in cancer treatment and expect to see continuous breakthroughs in techniques and methodologies of gene therapy.