Understanding PD-L1

Cancer immunotherapy is one of the most exciting areas of research, and has the potential to redefine the clinical care landscape for people with many types of cancer. This is because it is designed to help your own immune system recognize and fight cancer cells. There are many ways to interact the immune response, and in this story we’ll be describing one potentially important player: the PD-L1 protein.

A Tale of Two Receptors

First, some background. Our immune system has T cells that help fight off diseases. T cells are like soldiers that help the body fight infections and other diseases, including cancer.

However, cancer cells can escape this attack by expressing a protein called PD-L1. PD-L1 works like a “stop sign” to inactivate T cells.1

PD-L1 works by attaching to receptors on T cells called PD-1 and B7.1. Both PD-1 and B7.1 can inactivate T cells.2

One approach to fighting cancer is blocking the PD-L1 protein, which may prevent cancer cells from inactivating T cells through both PD-1 and B7.1.1

Targeting PD-L1

The PD-L1 protein is an important target in cancer research. Blocking PD-L1 can prevent cancer cells from inactivating T cells through both PD-1 and B7.1. However, healthy cells may also be affected by an increased immune response.3


1 Chen DS, Irving BA, Hodi FS. Molecular pathways: next-generation immunotherapy—inhibiting programmed death-ligand 1 and programmed death-1. Clin Cancer Res. 2012;18:6580-6587.

2 Keir ME, Butte MJ, Freeman GJ, Sharpe AH. PD-1 and its ligand in tolerance and immunity. Annu Rev Immunol. 2008;26:677-704.

3 Chen DS, Mellman I. Oncology meets immunology: the cancer-immunity cycle. Immunity. 2013;39:1-10.