Up-regulation of flotillin-2 is associated with melanoma progression and modulates expression of the thrombin receptor protease activated receptor 1

• Published in: Cancer research (Chicago, Ill.) Vol. 64; no. 20; pp. 7361 - 7369
• Main Authors: HAZARIKA, Parul, MCCARTY, Marya F, PRIETO, Victor G, GEORGE, Saira, BABU, Daniel, KOUL, Dimpy, BAR-ELI, Menashe, DUVIC, Madeleine
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 15.10.2004
• Subjects: Animals; Antineoplastic agents; Biological and medical sciences; Cell Division - physiology; Cell Line, Tumor; Disease Progression; DNA, Complementary - genetics; Humans; Male; Medical sciences; Melanoma - blood supply; Melanoma - genetics; Melanoma - metabolism; Melanoma - pathology; Membrane Proteins - biosynthesis; Membrane Proteins - genetics; Mice; Mice, Inbred BALB C; Mice, Nude; Neoplasm Metastasis; Neovascularization, Pathologic - genetics; Neovascularization, Pathologic - metabolism; Pharmacology. Drug treatments; Receptor, PAR-1 - biosynthesis; Receptor, PAR-1 - genetics; RNA, Messenger - biosynthesis; RNA, Messenger - genetics; Transfection; Tumors; Up-Regulation; Peptidases; Protease activated receptor 1; Regulation(control); Serine endopeptidases; Enzyme; Flotillin; Tumor progression; Hydrolases; Thrombin; Gene expression; Biological receptor
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/0008-5472.CAN-04-0823

Flotillin 2 (flot-2) is a highly conserved protein isolated from caveolae/lipid raft domains that tether growth factor receptors linked to signal transduction pathways. Flot-2 protein and mRNA were increased in tumorigenic and metastatic melanoma cell lines in vitro, and the immunostaining intensity increased substantially across a tissue array of melanocytic lesions. Flot-2 transfection transformed SB2 melanoma cells from nontumorigenic, nonmetastatic to highly tumorigenic and metastatic in a nude mouse xenograft model. SB2 cells stably transfected with the flot-2 cDNA (SB2-flot)-2 cells proliferated faster in the absence of serum, and their migration through Matrigel was additionally enhanced by thrombin. When SB2-flot-2 cells were compared with SB2-vector-control cells on a cancer gene pathway array, SB2-flot-2 cells had increased expression of protease activated receptor 1 (PAR-1) mRNA, a transmembrane, G-protein-coupled receptor involved in melanoma progression. PAR-1 and flot-2 were coimmunoprecipitated from SB2-flot-2 cells. Up-regulation of PAR-1 was additionally confirmed in SB2-flot-2 cells and melanoma cell lines. SB2-flot-2 cells transfected with flot-2-specific small-interfering RNAs made substantially less flot-2 and PAR-1 mRNA. In conclusion, flot-2 overexpression is associated with melanoma progression, with increased PAR-1 expression, and with transformation of SB2 melanoma cells to a highly metastatic line. Flot-2 binds to PAR-1, a known upstream mediator of major signal transduction pathways implicated in cell growth and metastasis, and may thereby influence tumor progression.