FOXO3 and breast cancer: For example, circ-Foxo3 functions as a tumor suppressor gene by positively regulating the expression of its host gene Foxo3 in breast cancer and non-small cell lung cancer [16, 25], however, it functions as an oncogene through a circ-Foxo3-miR-143-3p-USP44 axis independent of its host gene in gastric carcinoma [134].