STAT3 and osteosarcoma: A plenty of studies showed that elevated STAT3 expression in tumor tissue was correlated with poor survival of patients with various solid tumors such as gastric cancer [22–29], lung cancer [30–37], gliomas [38–42], colorectal cancer [43], ovarian cancer [44], cervical cancer [45], hepatocellular carcinoma [46, 47], melanoma [48], esophageal cancer [49], osteosarcoma [50, 51], pancreatic cancer [52, 53], thymic epithelial tumor [54], astrocytomas [55], lingual squamous cell carcinoma [56], nasopharyngeal carcinoma [57], prostate cancer [58], renal cell carcinoma [59] and Wilms' tumor [60].