title: Alternatively spliced isoforms of IL-32 differentially influence cell death pathways in cancer cell lines.
abstract: Alternative splicing is a biological mechanism that enables the synthesis of several isoforms with different or even opposite functions. This process must be tightly regulated to prevent unwanted isoform expression favoring pathological processes. Some isoforms of interleukin 32 (IL-32) are reported to be more potent in inducing inflammation, however the role in cell death remains to be investigated. This study demonstrates that IL-32γ and IL-32β can induce caspase-8-dependent cell death whereas this was not observed for IL-32α. Overexpression of IL-32β or IL-32γ but not IL-32α, resulted in enhanced expression of the survival cytokine IL-8. Furthermore, restoring the IL-8 signaling pathway by overexpressing CXCR1 in HEK293 cells, rescued IL-32β but not IL-32γ-induced cell death. Interestingly, IL-32γ was able to downregulate CXCR1 and thereby induce cell death. Subsequent studies into the role of IL-32 in thyroid cancer (TC) revealed that several IL-32 isoforms, IL-8, and CXCR1 are expressed in TC cell lines and specimens. Remarkably, TC cell lines were found to produce high concentrations of IL-8, indicating an important role for IL-8 in the survival-signaling pathway in these cells. Intriguingly, a significant correlation between the IL-8 receptor CXCR1 and IL-32γ was observed in TC specimens, while this was not observed for the other IL-32 splice variants. Blocking IL-32 alternative splicing by Isoginkgetin resulted in predominant expression of IL-32γ splice variants and cell death in TC cell lines. All together, modulation of IL-32 alternative splicing could represent a novel strategy for the treatment of malignancies, in particular thyroid cancer.
authors.affiliation: Department of Internal Medicine.
authors.forename: Bas
authors.initials: B
authors.lastname: Heinhuis
authors.affiliation: Department of Internal Medicine.|Division of Endocrinology, Radboudumc, Nijmegen 6500 HB, The Netherlands.
authors.forename: Theo S
authors.initials: TS
authors.lastname: Plantinga
authors.affiliation: Department of Internal Medicine.|Department of Pathology, Kilimanjaro Christian Medical Centre, Moshi 3010, United Republic of Tanzania.
authors.forename: George
authors.initials: G
authors.lastname: Semango
authors.affiliation: Department of Pathology, Radboudumc, Nijmegen 6500 HB, The Netherlands.|Department of Pathology, Maastricht University Medical Centre, Maastricht 6229 HX, The Netherlands and.
authors.forename: Benno
authors.initials: B
authors.lastname: Küsters
authors.affiliation: Department of Internal Medicine.
authors.forename: Mihai G
authors.initials: MG
authors.lastname: Netea
authors.affiliation: Department of Internal Medicine.|Department of Medicine, University of Colorado Denver, Aurora, CO 80045, USA.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Dinarello
authors.affiliation: Department of Internal Medicine.
authors.forename: Jan W A
authors.initials: JWA
authors.lastname: Smit
authors.affiliation: Department of Internal Medicine.|Division of Endocrinology, Radboudumc, Nijmegen 6500 HB, The Netherlands.
authors.forename: Romana T
authors.initials: RT
authors.lastname: Netea-Maier
authors.affiliation: Department of Internal Medicine.
authors.forename: Leo A B
authors.initials: LAB
authors.lastname: Joosten
mesh_terms: D017398:Alternative Splicing; D015153:Blotting, Western; D053181:Caspase 8 / Q000378:metabolism; D016923:Cell Death; D045744:Cell Line, Tumor; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D007378:Interleukins / Q000235:genetics* / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics*; D013964:Thyroid Neoplasms / Q000235:genetics*; D014162:Transfection
chemical_list: C508606:CXCL8 protein, human; C496971:IL32 protein, human; D016209:Interleukin-8; D007378:Interleukins; D020033:Protein Isoforms; C505530:CASP8 protein, human; D053181:Caspase 8