KLF4 and osteosarcoma: Additionally, KLF4 bi-directionally regulates genes that are involved in cell cycle regulation and epithelium differentiation [15]; functions as a tumor suppressor in malignant tumors, such as colorectal cancer and pancreatic ductal carcinoma [16, 17]; and functions as an oncogene in multiple cancers, including osteosarcoma, melanoma, and bladder cancer [18–20].