MYCN and osteosarcoma: Experiments supported E2F-Sp1 interactions near: dihydrofolate reductase in Chinese hamster [59], dihydrofolate reductase in human osteosarcoma [60], fibroblast CTP:phosphocholine cytidylyltransferase in mouse embryo [61], thymidine kinase in mouse [62], RIP140 in human [63], CDKN2A [64], HMGA1 [65], MYCN [66], and CDKN2C [67].