CD274 and neoplasm: In patients with melanoma (Taube et al., 2012), colorectal cancer (Droeser et al., 2013), or Merkel-cell carcinoma (Lipson et al., 2013), higher PD-L1 expression was significantly correlated with improved survival, indicating that tumor cell-intrinsic PD-L1 may exert either pro- or anti-tumor functions, and that its roles might be tissue- or tumor-type dependent.