STAT3 and neoplasm: Emerging studies demonstrate that constitutive photomorphogenesis 1 (COP1), as an E3 ligase, is abnormally expressed in a wealth of tumor types, leading to the dysregulation of proteins related to tumor suppressor genes p53, p27, 14-3-3σ [8–10] as well as oncogenes c-Jun, signal transducer and activator of transcription 3 (STAT3), E-twenty-six (ETS) family members [11–13], etc. The knowledge highlights the involvement of COP1 in tumorigenesis [14, 15].