title: Protease activated receptor-1 inhibits the Maspin tumor-suppressor gene to determine the melanoma metastatic phenotype.
abstract: The thrombin receptor protease activated receptor-1 (PAR-1) is overexpressed in metastatic melanoma cell lines and tumor specimens. Previously, we demonstrated a significant reduction in tumor growth and experimental lung metastasis after PAR-1 silencing via systemic delivery of siRNA encapsulated into nanoliposomes. Gene expression profiling identified a 40-fold increase in expression of Maspin in PAR-1-silenced metastatic melanoma cell lines. Maspin promoter activity was significantly increased after PAR-1 silencing, suggesting that PAR1 negatively regulates Maspin at the transcriptional level. ChIP analyses revealed that PAR-1 decreases binding of Ets-1 and c-Jun transcription factors to the Maspin promoter, both known to activate Maspin transcription. PAR-1 silencing did not affect Ets-1 or c-Jun expression; rather it resulted in increased expression of the chromatin remodeling complex CBP/p300, as well as decreased activity of the CBP/p300 inhibitor p38, resulting in increased binding of Ets-1 and c-Jun to the Maspin promoter and higher Maspin expression. Functionally, Maspin expression reduced the invasive capability of melanoma cells after PAR-1 silencing, which was abrogated after rescuing with PAR-1. Furthermore, tumor growth and experimental lung metastasis was significantly decreased after expressing Maspin in a metastatic melanoma cell line. Moreover, silencing Maspin in PAR-1-silenced cells reverted the inhibition of tumor growth and experimental lung metastasis. Herein, we demonstrate a mechanism by which PAR-1 negatively regulates the expression of the Maspin tumor-suppressor gene in the acquisition of the metastatic melanoma phenotype, thus attributing an alternative function to PAR-1 other than coagulation.
authors.affiliation: Department of Cancer Biology, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Gabriel J
authors.initials: GJ
authors.lastname: Villares
authors.forename: Maya
authors.initials: M
authors.lastname: Zigler
authors.forename: Andrey S
authors.initials: AS
authors.lastname: Dobroff
authors.forename: Hua
authors.initials: H
authors.lastname: Wang
authors.forename: Renduo
authors.initials: R
authors.lastname: Song
authors.forename: Vladislava O
authors.initials: VO
authors.lastname: Melnikova
authors.forename: Li
authors.initials: L
authors.lastname: Huang
authors.forename: Russell R
authors.initials: RR
authors.lastname: Braeuer
authors.forename: Menashe
authors.initials: M
authors.lastname: Bar-Eli
mesh_terms: D000818:Animals; D002843:Chromatin / Q000737:chemistry; D018450:Disease Progression; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology; D008545:Melanoma / Q000473:pathology*; D051379:Mice; D008819:Mice, Nude; D009362:Neoplasm Metastasis; D010641:Phenotype; D050784:Proto-Oncogene Protein c-ets-1 / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D044463:Receptor, PAR-1 / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D015843:Serpins / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D002843:Chromatin; C494041:ETS1 protein, human; D050784:Proto-Oncogene Protein c-ets-1; D016755:Proto-Oncogene Proteins c-jun; D044463:Receptor, PAR-1; D043562:Receptors, G-Protein-Coupled; C085344:SERPIN-B5; D015843:Serpins