SMAD6 and lung carcinoma: The 3′UTR markers for which lengthening indicates poorer prognosis include PPIC, ZCCHC14, RTN1, PRCK8, CLIC2, CXCL8 and SMAD6. Among them, SMAD6 and CLIC2 are both related to the TGF-β pathway, and SMAD6 is associated with favorable survival in lung cancer [21, 22].