Extracellular melanin

Extracellular melanin is a complex biopolymer located outside the cell cytoplasm, primarily found within the cell walls of melanized pathogenic fungi or released into the extracellular environment during tissue damage and malignancy. In fungal pathogens such as Cryptococcus neoformans, melanin serves as a potent virulence factor that shields the organism from host immune defenses, including phagocytosis and oxidative bursts, while also providing resistance to various antifungal agents (Eisenman & Casadevall, 2012, PMID: 22461443). In oncology, particularly melanoma, extracellular melanin represents a unique antigenic target because it is often accessible to the systemic circulation due to the disorganized nature of tumor vasculature and cell death (Dadachova et al., 2004, PMID: 15319400). Therapeutic approaches have focused on using monoclonal antibodies, such as 18B7 or 6D2, to bind this pigment and deliver cytotoxic radionuclides directly to the site of infection or tumor (Nosanchuk & Casadevall, 2003, PMID: 12855493). While this strategy offers a novel way to treat resistant infections and metastatic melanoma, the ubiquitous presence of melanin in healthy tissues like the skin and eyes poses a significant risk for off-target toxicity. Furthermore, the release of neuromelanin into the extracellular space in the brain is associated with pro-inflammatory responses in neurodegenerative conditions like Parkinson's disease, making its clearance a potential therapeutic goal (Zhang et al., 2011, PMID: 21415394).

Other names

Fungal melaninCell wall melaninNeuromelanin (extracellular)EumelaninPheomelanin

Targeted delivery of radionuclides via radio-immunotherapy (RIT) or antibody-mediated opsonization and growth inhibition.