We focused on miR-34a because not only previous reports demonstrated that the expression of miR-34a was significantly decreased in primary osteosarcoma samples as compared with adjacent normal tissues [23], but also the mutations of p53 tumor suppressor gene, which directly regulates the expression of miR-34a, was also found in 20–60% of sporadic osteosarcomas [16], [37]. The gene discussed is TP53; the disease is osteosarcoma.