How PD-1 and PD-L1 Act in Various Cancers

Antoni Ribas, MD, PhD, the director of the Tumor Immunology Program Area at UCLA's Jonsson Comprehensive Cancer Center, discusses PD-1 and PD-L1 in various cancers.

PD-1 is a negative regulator of the immune system, preventing it from overactivating. The cancer takes advantage of this, Ribas says, by expressing PD-L1 and preventing an attack from the immune system. New anti-PD-1 and anti-PD-L1 agents re-expose the cancer to the immune system.

Clinical Pearls I

Not all cancers and all histologies express PD-L1, Ribas says. PD-L1 has been analyzed in many cancers, including melanoma, kidney cancer, lung cancer, head and neck cancer, and ovarian cancer, allowing for the possibility of broad activity. Agents in this space release a brake of the immune system, meaning that the immune system must be activated against the cancer for these agents to be effective. This remains an evolving paradigm, Ribas notes.

• PD-1 is a negative regulator of the immune system
• A cancer expresses PD-L1 to prevent an attack from the immune system

Clinical Pearls II

• Not all cancers and histologies express the ligand PD-L1
• Agents in this space release a brake of the immune system
• The immune system must be activated against the cancer for these agents to be effective