PLG and melanoma: Notably, two serine proteases—plasminogen (Plg) and the CAAX prenyl protease 1 homolog (Zmpste24)—were detected only in melanoma, while two metabolic serine hydrolases—phospholipase B-like 1 (Plbd1) and carboxylesterase 1F (Ces1f)—were found only in normal skin.