title: The helicase HAGE expressed by malignant melanoma-initiating cells is required for tumor cell proliferation in vivo.
abstract: Malignant melanoma-initiating cells (MMIC) are a subpopulation of cells responsible for melanoma tumor growth and progression. They are defined by the expression of the ATP-binding cassette (ABC) subfamily B member 5 (ABCB5). Here, we identified a critical role for the DEAD-box helicase antigen (HAGE) in ABCB5+ MMIC-dependent tumorigenesis and show that HAGE-specific inactivation inhibits melanoma tumor growth mediated by this tumor-initiating population. Knockdown of HAGE led to a significant decrease in RAS protein expression with a concomitant decrease in activation of the AKT and ERK signaling pathways implicated to play an important role in melanoma progression. To confirm that the reduction in NRAS (Neuroblastoma RAS) expression was dependent on the HAGE helicase activity, we showed that NRAS, effectively silenced by siRNA, could be rescued by reintroduction of HAGE in cells lacking HAGE. Furthermore, we provide a mechanism by which HAGE promotes NRAS unwinding in vitro. We also observed using tumor transplantation in Non-obese diabetic/severe combined immunodeficiency mice that the HAGE knockdown in a ABCB5+ melanoma cell line displayed a significant decrease in tumor growth and compared with the control. Our results suggest that the helicase HAGE is required for ABCB5+ MMIC-dependent tumor growth through promoting RAS protein expression and that cancer therapies targeting HAGE helicase may have broad applications for treating malignant melanoma and potentially other cancer types.
authors.affiliation: The John van Geest Cancer Research Centre, School of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham NG11 8NS, United Kingdom.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Linley
authors.forename: Morgan G
authors.initials: MG
authors.lastname: Mathieu
authors.forename: Amanda K
authors.initials: AK
authors.lastname: Miles
authors.forename: Robert C
authors.initials: RC
authors.lastname: Rees
authors.forename: Stephanie E B
authors.initials: SE
authors.lastname: McArdle
authors.forename: Tarik
authors.initials: T
authors.lastname: Regad
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis*; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis*; D000818:Animals; D000951:Antigens, Neoplasm / Q000096:biosynthesis*; D002454:Cell Differentiation; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D053487:DEAD-box RNA Helicases / Q000096:biosynthesis*; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008545:Melanoma / Q000276:immunology* / Q000378:metabolism*; D051379:Mice; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D009368:Neoplasm Transplantation; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection
chemical_list: C480744:ABCB5 protein, human; C573563:ABCB5 protein, mouse; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D000951:Antigens, Neoplasm; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; C412324:DDX43 protein, human; C573562:HAGE protein, mouse; D053487:DEAD-box RNA Helicases