title: Atypical localization of membrane type 1-matrix metalloproteinase in the nucleus is associated with aggressive features of hepatocellular carcinoma.
abstract: Membrane type 1-matrix metalloproteinase (MT1-MMP) is a versatile proteinase and recent studies indicated it could be internalized. Our earlier study found that it is overexpressed in hepatocellular carcinoma (HCC) and could promote intrahepatic metastasis. The present study was conducted to examine its subcellular localization and its clinicopathological significance in HCC after curative partial hepatectomy. Localization of MT1-MMP in 101 pairs of HCCs and their adjacent liver tissues, and 8 normal liver tissues was examined by the immunohistochemical method. MT1-MMP protein was localized at membrane and cytoplasm of hepatocytes in the normal and tumor adjacent liver tissues. In contrast, the HCCs were highly heterogeneous with variable degrees of membrane, cytoplasmic, and even nuclear staining. Interestingly, patients with presence of nuclear MT1-MMP were associated with poor overall survival (log-rank test, P=0.043) and large tumor size (>5 cm) (Fisher's exact test, P=0.031). Subcellular distribution was further demonstrated by Western blotting and immunofluorescence with Hep3B stable transfectant overexpressing MT1-MMP. Western blot analyses of subcellular fractions confirmed a differential partitioning of various post-translationally modified MT1-MMP in these fractions. Different antibodies corroborated the presence of MT1-MMP in the nuclear fraction. Concomitant nuclear presence of MMP2 with MT1-MMP further indicated its potential involvement in the nuclear functions. MT1-MMP co-localized with caveolin-1 at the perinuclear region, suggesting nuclear translocation of MT1-MMP via caveolae-mediated endocytosis. In summary, the association of nuclear MT1-MMP with aggressive tumor features including poor prognosis and large tumor expands its functional repertoire and further indicates a new functional role of MMPs within nuclei of tumor cells.
authors.affiliation: Department of Surgery, Centre for the Study of Liver Disease, The University of Hong Kong, Pokfulam, Hong Kong, China.
authors.forename: Ying Chi
authors.initials: YC
authors.lastname: Ip
authors.forename: Siu Tim
authors.initials: ST
authors.lastname: Cheung
authors.forename: Sheung Tat
authors.initials: ST
authors.lastname: Fan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000201:enzymology* / Q000473:pathology; D051242:Caveolin 1 / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000201:enzymology*; D003593:Cytoplasm / Q000378:metabolism; D018450:Disease Progression; D005260:Female; D005455:Fluorescent Antibody Technique; D005500:Follow-Up Studies; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008113:Liver Neoplasms / Q000201:enzymology* / Q000473:pathology; D008297:Male; D053511:Matrix Metalloproteinase 14 / Q000378:metabolism*; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D009364:Neoplasm Recurrence, Local / Q000473:pathology; D011379:Prognosis; D011446:Prospective Studies; D021381:Protein Transport; D015996:Survival Rate
chemical_list: D051242:Caveolin 1; D020778:Matrix Metalloproteinase 2; C507086:MMP14 protein, human; D053511:Matrix Metalloproteinase 14