Inflamed Tumour Markers
Tumour-infiltrating immune cells are observed in chronic inflamed tumours and their microenvironments.
Programmed death ligand 1 (PD-L1) is a protein ligand that binds to programmed death receptor-1 (PD-1). PD-1 is an immune checkpoint receptor. PD-L1 is expressed by lymphoid, endothelial, and epithelial cells. Expression of PD-L1 on tumour cells helps in evading immune response by inhibiting the activity of cytotoxic T cells.
Programmed death ligand 2 (PD-L2) is a protein ligand for the immune checkpoint receptor PD-1. PD-L2 competes with PD-L1 to bind to PD-1 (expressed by cytotoxic T cells). PD-L2 is expressed by different types of immune cells (antigen-presenting cells such as macrophages and dendritic cells), nonimmune cells and tumour cells Compared to PD-L1, PD-L2 has higher affinity for PD-1 receptor but is expressed at a lower level. Expression of PD-L2 by tumour cells downregulates T cell proliferation and functioning, by binding with PD-1.
Tumour infiltrating lymphocytes (TILs) are immune cell population comprising of cytotoxic T cells and natural killer cells that invade the tumour and its microenvironment. Tumour infiltrating lymphocytes is associated with tumour inflammation.
Inflammation Gene Signatures
Tumour inflammation gene signatures are gene expression profiles (GEPs) that can be used to understand immune cell infiltration and other inflammation signatures of tumour microenvironment. They can be used as powerful diagnostic tool to differentiate different stages of tumour progression and assess immune response.