CTSG and neoplasm: Besides fMLP, ligands for FPR1 also include non-microbial endogenous host-derived peptides such as mitochondrial formylated peptides fMMYALF, fMLKLIV and fMFADRW, Annexin A1 and Cathepsin G [5, 34, 35], that may be released by necrotic cells within the tumor microenvironment.