title: Claudin-1 overexpression in melanoma is regulated by PKC and contributes to melanoma cell motility.
abstract: Serial analysis of gene expression followed by pathway analysis implicated the tight junction protein claudin-1 (CLDN1) in melanoma progression. Tight junction proteins regulate the paracellular transport of molecules, but staining of a tissue microarray revealed that claudin-1 was overexpressed in melanoma, and aberrantly expressed in the cytoplasm of malignant cells, suggesting a role other than transport. Indeed, melanoma cells in culture demonstrate no tight junction function. It has been shown that protein kinase C (PKC) can affect expression of claudin-1 in rat choroid plexus cells, and we observed a correlation between levels of activated PKC and claudin expression in our melanoma cells. To determine if PKC could affect the expression of CLDN1 in human melanoma, cells lacking endogenous claudin-1 were treated with 200 nM phorbol myristic acid (PMA). PKC activation by PMA caused an increase in CLDN1 transcription in 30 min, and an increase in claudin-1 protein by 12 h. Inhibition of PKC signaling in cells with high claudin-1 expression resulted in decreased claudin-1 expression. CLDN1 appears to contribute to melanoma cell invasion, as transient transfection of melanoma cells with CLDN1 increased metalloproteinase 2 (MMP-2) secretion and activation, and subsequently, motility of melanoma cells as demonstrated by wound-healing assays. Conversely, knockdown of CLDN1 by siRNA resulted in the inhibition of motility, as well as decreases in MMP-2 secretion and activation. These data implicate claudin-1 in melanoma progression.
authors.affiliation: Laboratory of Immunology, Gerontology Research Center, National Institute on Aging, Baltimore, MD, USA.
authors.forename: P D
authors.initials: PD
authors.lastname: Leotlela
authors.forename: M S
authors.initials: MS
authors.lastname: Wade
authors.forename: P H
authors.initials: PH
authors.lastname: Duray
authors.forename: M J
authors.initials: MJ
authors.lastname: Rhode
authors.forename: H F
authors.initials: HF
authors.lastname: Brown
authors.forename: D T
authors.initials: DT
authors.lastname: Rosenthal
authors.forename: S K
authors.initials: SK
authors.lastname: Dissanayake
authors.forename: R
authors.initials: R
authors.lastname: Earley
authors.forename: F E
authors.initials: FE
authors.lastname: Indig
authors.forename: B J
authors.initials: BJ
authors.lastname: Nickoloff
authors.forename: D D
authors.initials: DD
authors.lastname: Taub
authors.forename: O P
authors.initials: OP
authors.lastname: Kallioniemi
authors.forename: P
authors.initials: P
authors.lastname: Meltzer
authors.forename: P J
authors.initials: PJ
authors.lastname: Morin
authors.forename: A T
authors.initials: AT
authors.lastname: Weeraratna
mesh_terms: D015153:Blotting, Western; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology*; D062445:Claudin-1; D005455:Fluorescent Antibody Technique; D006801:Humans; D007150:Immunohistochemistry; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D008545:Melanoma / Q000378:metabolism / Q000473:pathology*; D008565:Membrane Proteins / Q000378:metabolism*; D018613:Microscopy, Confocal; D009361:Neoplasm Invasiveness / Q000503:physiopathology*; D011493:Protein Kinase C / Q000378:metabolism*; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
chemical_list: C568108:CLDN1 protein, human; D062445:Claudin-1; C568114:Cldn1 protein, rat; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D011493:Protein Kinase C; D020778:Matrix Metalloproteinase 2