Representative gene therapy strategies include (1) introduction and forced expression of tumor suppressor genes (p53, p27, p21, p16, and RB) in cancer cells [63,64]; (2) expression control of cancer-related genes (BCL-family, Myc, Fos, and RAS) [65]; (3) immunotherapy [66,67]; (4) prodrug therapy targeting cancer cells [63]; (5) inhibition of tumor angiogenesis genes (HIF1α, VEGF) [64,68]; and (6) administration of cancer nucleic acid vaccines [69]. Here, RB1 is linked to cancer.