title: Microtubule disruption and tumor suppression by mitogen-activated protein kinase phosphatase 4.
abstract: The extracellular signal-regulated kinase (Erk) is one of the downstream effectors of the Ras pathway whose activation is essential for the proliferation and survival of cancer cells. Erk activation is negatively regulated by mitogen-activated protein kinase (MAPK) phosphatases (MKP), which are generally up-regulated by Erk activation, thus forming a feedback loop for regulation of Erk activity. In searching for early alterations in the Ras pathway in epidermal carcinogenesis, we identified MKP4, a cytosolic MKP with specificity to not only Erk, but also, to a lesser extent, c-jun-NH(2)-kinase and p38. MKP4 is down-regulated at initiation and lost at malignant conversion in a clonal model of epidermal carcinogenesis that lacks Ras mutation. The loss of MKP4 was associated with squamous cell carcinoma (SCC) but not benign papilloma clonal lineages and with independently induced SCC relative to benign tumors in mouse skin. Reconstitution of MKP4 expression in malignant tumor cells leads to cell death and tumor suppression. Unlike Erk inhibition that blocks cell cycle entry, MKP4 reconstitution resulted in G(2)-M associated cell death and microtubule disruption. Thus, microtubule disruption by MKP4 provides a novel mechanism for tumor suppression by a cytosolic MKP and implies a novel therapeutic strategy through combined MAPK inhibitions that mimic the function of MKP4.
authors.affiliation: Department of Dermatology, Oregon Health and Science University, Portland, Oregon 97239, USA. liuy@ohsu.edu
authors.forename: Yuangang
authors.initials: Y
authors.lastname: Liu
authors.forename: James
authors.initials: J
authors.lastname: Lagowski
authors.forename: Aaron
authors.initials: A
authors.lastname: Sundholm
authors.forename: Alexandra
authors.initials: A
authors.lastname: Sundberg
authors.forename: Molly
authors.initials: M
authors.lastname: Kulesz-Martin
mesh_terms: D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000378:metabolism; D045744:Cell Line, Tumor; D003600:Cytosol / Q000378:metabolism; D054637:Dual-Specificity Phosphatases / Q000378:metabolism / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D054639:Mitogen-Activated Protein Kinase Phosphatases / Q000378:metabolism / Q000502:physiology*; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology*; D010212:Papilloma / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D048051:p38 Mitogen-Activated Protein Kinases; D054639:Mitogen-Activated Protein Kinase Phosphatases; C104821:DUSP9 protein, human; D054637:Dual-Specificity Phosphatases; C484491:Dusp9 protein, mouse