title: Melanoma Differentiation-associated Gene 7/IL-24 Exerts Cytotoxic Effects by Altering the Alternative Splicing of Bcl-x Pre-mRNA via the SRC/PKCδ Signaling Axis.
abstract: Melanoma differentiation-associated gene 7 (MDA-7/IL-24) exhibits cytotoxic effects on tumor cells while sparing untransformed cells, and Bcl-x(L) is reported to efficiently block the induction of cell death by MDA-7/IL-24. The expression of Bcl-x(L) is regulated at the level of RNA splicing via alternative 5' splice site selection within exon 2 to produce either the pro-apoptotic Bcl-x(s) or the anti-apoptotic Bcl-x(L). Our laboratory previously reported that Bcl-x RNA splicing is dysregulated in a large percentage of human non-small cell lung cancer (NSCLC) tumors. Therefore, we investigated whether the alternative RNA splicing of Bcl-x pre-mRNA was modulated by MDA-7/IL-24, which would suggest that specific NSCLC tumors are valid targets for this cytokine therapy. Adenovirus-delivered MDA-7/IL-24 (Ad.mda-7) reduced the viability of NSCLC cells of varying oncogenotypes, which was preceded by a decrease in the ratio of Bcl-x(L)/Bcl-x(s) mRNA and Bcl-x(L) protein expression. Importantly, both the expression of Bcl-x(L) and the loss of cell viability were "rescued" in Ad.mda-7-treated cells incubated with Bcl-x(s) siRNA. In addition, NSCLC cells ectopically expressing Bcl-x(s) exhibited significantly reduced Bcl-x(L) expression, which was again restored by Bcl-x(s) siRNA, suggesting the existence of a novel mechanism by which Bcl-x(s) mRNA restrains the expression of Bcl-x(L). In additional mechanistic studies, inhibition of SRC and PKCδ completely ablated the ability of MDA-7/IL-24 to reduce the Bcl-x(L)/(s) mRNA ratio and cell viability. These findings show that Bcl-x(s) expression is an important mediator of MDA-7/IL-24-induced cytotoxicity requiring the SRC/PKCδ signaling axis in NSCLC cells.
authors: From the Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia 23249.|the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614.
authors: Brian A
authors: BA
authors: Shapiro
authors: the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614.
authors: Ngoc T
authors: NT
authors: Vu
authors: From the Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia 23249.
authors: Michael D
authors: MD
authors: Shultz
authors: the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614.
authors: Jacqueline C
authors: JC
authors: Shultz
authors: the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614.
authors: Jennifer A
authors: JA
authors: Mietla
authors: the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614.
authors: Mazen M
authors: MM
authors: Gouda
authors: the Department of Neurosurgery, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614.
authors: Adly
authors: A
authors: Yacoub
authors: the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614.|the Virginia Commonwealth University Institute of Molecular Medicine, Richmond, Virginia 23298.|the Virginia Commonwealth University Massey Cancer Center, Richmond, Virginia 23298, and.
authors: Paul
authors: P
authors: Dent
authors: the Virginia Commonwealth University Institute of Molecular Medicine, Richmond, Virginia 23298, paul.fisher@vcuhealth.org.|the Virginia Commonwealth University Massey Cancer Center, Richmond, Virginia 23298, and.|the Department of Human and Molecular Genetics, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298.
authors: Paul B
authors: PB
authors: Fisher
authors: the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614, margaret.park@vcuhealth.org.|the Virginia Commonwealth University Massey Cancer Center, Richmond, Virginia 23298, and.
authors: Margaret A
authors: MA
authors: Park
authors: From the Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia 23249, charles.chalfant@vcuhealth.org.|the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614.|the Virginia Commonwealth University Institute of Molecular Medicine, Richmond, Virginia 23298.|the Virginia Commonwealth University Massey Cancer Center, Richmond, Virginia 23298, and.|the Virginia Commonwealth University Johnson Center for Critical Care and Pulmonary Research, Richmond, Virginia 23298.
authors: Charles E
authors: CE
authors: Chalfant
mesh_terms: D000072283:A549 Cells; D017398:Alternative Splicing; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007378:Interleukins / Q000235:genetics / Q000378:metabolism*; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000235:genetics / Q000378:metabolism*; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism*; D000099180:Interleukin-24
chemical_list: D007378:Interleukins; D051745:Protein Kinase C-delta; D016392:Proto-Oncogene Proteins pp60(c-src); D012333:RNA, Messenger; D012334:RNA, Neoplasm; D051020:bcl-X Protein; D000099180:Interleukin-24; C494811:BCL2L1 protein, human; C497258:PRKCD protein, human
keywords: MDA-7/IL-24, Bcl-x; RNA splicing; alternative splicing; apoptosis; cell death; cell signaling; non-small cell lung cancer; signal transduction