Seladin-1/DHCR24 is implicated in melanoma progression through lipid rafts-dependent cross-talk with notch signaling

Background Malignant melanoma aggressive growth and cell resistance to apoptosis derive from aberrant activation of cell signals dependent from lipid rafts, cholesterol-rich membrane microdomains able to activate molecules involved in signal transduction. The identification of deranged gene expression is crucial to understand the melanoma pathogenesis. Seladin-1/DHCR24, an antiapoptotic protein which catalyses the last step of cholesterol biosynthesis, is more expressed in melanoma metastases vs. primary lesions, protecting cells against apoptosis. Melanoma tumorigenesis is also associated with up-regulation of Notch receptors and ligands. The aim of the study was to characterize Seladin-1 expression in normal skin, melanocytic nevi and melanoma and identify molecular mechanisms that link Seladin-1 with tumour progression. Methods Immunohistochemistry with anti-Seladin-1 Ab was performed on the different tissue specimens. Primary (A375) and metastatic (WM266-4) melanoma cell lines were used. Gene expression was determined by quantitative S284 Virchows Arch (2009) 455 (Suppl 1):S1–S482real time PCR and cell cholesterol by GC/MS. Lipid rafts distribution was visualised by confocal microscopy. Results and conclusions Seladin-1 was more expressed and differently localized in primary and metastatic tumours vs. normal skin and benign lesions. Higher Seladin-1 gene expression and cell cholesterol were found in WM266-4 vs. A375. Increase of lipid rafts after transient transfection of Seladin-1 in A375 suggests a raft-dependent activation of pro-oncogenic signals. Different gene expression of Notch receptors, ligands and target genes (HES1, HEY1) indicate a stronger activation of Notch signalling in metastatic vs. primary melanoma cell lines suggesting a raft-dependent crosstalk between this pathway and Seladin-1.