Expression of 12-lipoxygenase as a biomarker for melanoma carcinogenesis

12-Lipoxygenase (12-LOX), through its metabolite 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE], has been demonstrated to play a pivotal role in experimental melanoma invasion and metastasis, and 12-LOX expression may be important in early human melanoma carcinogenesis. We have studied the differences in 12-LOX protein expression during the progression of melanoma from human melanocytic cells to benign and dysplastic naevi to malignant metastatic disease. 12-LOX expression was determined in normal human skin melanocytes and in melanocytes found in compound naevi, dysplastic naevi and melanomas using a platelet-type 12-LOX antibody with a diaminobenzidine immunoperoxidase system detection system and was quantified using the analysis software NIH Image 1.62. Mean cellular pixel densities for 12-LOX staining (n = 50 cells/histological type) were unchanged in compound naevi (P = 0.14) and were increased in dysplastic naevi and melanomas compared with normal skin melanocytes (P = 0.03 and P = 0.01, respectively). Similarly, melanomas had higher levels of expression compared with dysplastic naevi (P = 0.03). 12-LOX expression was significantly different between compound naevus and dysplastic naevus melanocytes (P = 0.01). These data suggest that 12-LOX may be an important novel marker for cancer progression within the melanoma system, and therefore could be a useful biomarker and therapeutic target for melanoma chemoprevention.