Understanding the Cancer-Associated Fibroblast (CAF) and Its Biomarker Fibroblast Activation Protein (FAP), and Aspects in Human Liver Cancer

Tumours contain many fibroblasts, endothelial cells, and leukocytes that are emerging as therapeutic targets complementary to targeting genetically unstable cancer cells. Immunotherapies directed towards this tumour microenvironment (TME) are increasingly effective. Targeting the endothelium has shown success, particularly in hepatocellular carcinoma (HCC). Cancer-associated fibroblasts (CAFs) are also attracting novel nascent therapeutic approaches, and fibroblast activation protein (FAP), which is specific to activated mesenchyme, is prominent amongst CAF markers. This review places emphasis upon FAP, human HCC, and FAP-targeting approaches for therapeutic benefit, including FAP inhibitors, radioligand therapy, T cell and antibody-dependent cytotoxicity/immunotherapy, and FAP-activated prodrugs.