RAN and neoplasm: The vast majority of tumor suppressor proteins should be located in the nucleus to exercise their appropriate functions; however, in malignant cells, tumor suppressors tend to be translocated to the cytoplasm, resulting in the inactivation of suppressed proteins and the development of malignant tumors.22 Four important factors are related to nuclear transport: nucleoporins, RanGTPase, karyopherins (importin/exportin/transportin), and nuclear localization signals (NLSs) or nuclear export signals (NESs) in cargo molecules.