title: Apoptosis of human melanoma cells induced by inhibition of B-RAFV600E involves preferential splicing of bimS.
abstract: Bim is known to be critical in killing of melanoma cells by inhibition of the RAF/MEK/ERK pathway. However, the potential role of the most potent apoptosis-inducing isoform of Bim, Bim(S), remains largely unappreciated. Here, we show that inhibition of the mutant B-RAF(V600E) triggers preferential splicing to produce Bim(S), which is particularly important in induction of apoptosis in B-RAF(V600E) melanoma cells. Although the specific B-RAF(V600E) inhibitor PLX4720 upregulates all three major isoforms of Bim, Bim(EL), Bim(L), and Bim(S), at the protein and mRNA levels in B-RAF(V600E) melanoma cells, the increase in the ratios of Bim(S) mRNA to Bim(EL) and Bim(L) mRNA indicates that it favours Bim(S) splicing. Consistently, enforced expression of B-RAF(V600E) in wild-type B-RAF melanoma cells and melanocytes inhibits Bim(S) expression. The splicing factor SRp55 appears necessary for the increase in Bim(S) splicing, as SRp55 is upregulated, and its inhibition by small interfering RNA blocks induction of Bim(S) and apoptosis induced by PLX4720. The PLX4720-induced, SRp55-mediated increase in Bim(S) splicing is also mirrored in freshly isolated B-RAF(V600E) melanoma cells. These results identify a key mechanism for induction of apoptosis by PLX4720, and are instructive for sensitizing melanoma cells to B-RAF(V600E) inhibitors.
authors.affiliation: Immunology and Oncology Unit, Calvary Mater Newcastle Hospital, Newcastle, New South Wales, Australia.
authors.forename: C C
authors.initials: CC
authors.lastname: Jiang
authors.forename: F
authors.initials: F
authors.lastname: Lai
authors.forename: K H
authors.initials: KH
authors.lastname: Tay
authors.forename: A
authors.initials: A
authors.lastname: Croft
authors.forename: H
authors.initials: H
authors.lastname: Rizos
authors.forename: T M
authors.initials: TM
authors.lastname: Becker
authors.forename: F
authors.initials: F
authors.lastname: Yang
authors.forename: H
authors.initials: H
authors.lastname: Liu
authors.forename: R F
authors.initials: RF
authors.lastname: Thorne
authors.forename: P
authors.initials: P
authors.lastname: Hersey
authors.forename: X D
authors.initials: XD
authors.lastname: Zhang
mesh_terms: D019943:Amino Acid Substitution; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D045744:Cell Line, Tumor; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008545:Melanoma / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D012326:RNA Splicing; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D007211:Indoles; D008565:Membrane Proteins; D009687:Nuclear Proteins; C528407:PLX 4720; D010750:Phosphoproteins; D020033:Protein Isoforms; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; C489470:SRSF6 protein, human; D013449:Sulfonamides; D000068103:Serine-Arginine Splicing Factors; D048493:Proto-Oncogene Proteins B-raf