LOXL4 (lysyl oxidase like 4) is a secreted copper-dependent amine oxidase that catalyzes the oxidative deamination of lysine and hydroxylysine residues in collagen and elastin, resulting in covalent cross-linkages that stabilize extracellular matrix (ECM) components 1. The protein contains a conserved C-terminal region with a copper-binding site and characteristic lysyl and tyrosyl residues, plus four N-terminal scavenger receptor cysteine-rich (SRCR) domains, one of which contains a unique 13 amino acid insertion 2. LOXL4 plays a critical role in pathological collagen cross-linking and fibrosis development, particularly in lung fibrosis where it serves as the main lysyl oxidase activity underlying pathological ECM remodeling 3. In cancer, LOXL4 exhibits bidirectional regulatory roles depending on tumor type - it is upregulated in gastric, breast, ovarian, and colorectal cancers but downregulated in bladder and lung cancers where it functions as a tumor suppressor by inhibiting the Ras/ERK signaling pathway 14. LOXL4 expression is regulated by promoter methylation and shows tissue-specific patterns, being highly expressed in pancreas and testis 2. Its dual role in fibrosis and cancer makes it a potential therapeutic target and prognostic marker 5.