Background: Blocking the programmed death-1 (PD-1) pathway has clinical benefit in
metastatic cancer and has led to the approval of the mAbs to treat several cancer
types. Expression of PD-1 ligand (PD-L1) on the cell surface of tumor cells is generally
associated with a higher likelihood of response to PD-1 blockade in multiple studies.
We analyzed distribution of PD-L1 in a wide variety of tumor types, studied underlying
mechanisms of expression and compared methods of detection.