Abstract
Lipocalins represent a group of about 20 diverse secreted proteins that exhibit limited amino acid sequence similarity but share a highly conserved 3D structure containing an enclosed calyx, which is capable to transport and present ligands, and bind to cellular receptors. NGAL is a prominent member of the lipocalin family, originally identified as a 25-kDa neutrophil glycoprotein bound to matrix metalloproteinase-9 (MMP-9) in hu-man neutrophils.
Thus, it is also referred to as neutrophil gelatinase-associated lipocalin (NGAL). NGAL can bind to the siderophores which are secreted by bacteria to capture PLS_85_2019.indd 2925.09.19 13:15 30iron which prevents bacteria from iron acquisition and inhibits bacterial growth.
The re-cent identification of a mammalian siderophore reacting with NGAL provides an alter-native to transferrin-dependent iron delivery to mammalian cells. Furthermore, NGAL has been assigned critical roles in pathological organ conditions including inflammation, ischemic and metabolic diseases, renal damage, intoxications and organ transplantations.
NGAL participates, as well, in a variety of cellular processes, including cell proliferation, differentiation and apoptosis. NGAL is overexpressed in non-microbe-associated cancers and haematological malignancies and elevated levels in most cancers appear significantly correlated with disease severity and poor survival.
However, a growing body of evidence is pointing to NGAL s paradoxical, i.e. both beneficial and detrimental effects on distinct processes associated with tumour development .