Altered subcellular localization and low frequency of mutations of ING1 in human brain tumors.
OBJECTIVE
Clinical and experimental evidence suggest that the p33ING1b candidate tumor suppressor functionally cooperates with p53 in controlling biochemical and biological functions. Because p53 is frequently mutated in brain tumors and the ING1 locus maps to a site of which the loss is associated with gliomas, we analyzed the mutation and expression profiles of ING1B in human brain tumors. Here we present the first report of ING1 expression and mutation analyses in human brain tumor samples and malignant glioma cell lines.


METHODS
Expression and mutation analyses of ING1B together with subcellular localization studies of ING1 proteins were performed on 29 brain tumor specimens and 6 human glioma cell lines.


RESULTS
A single point mutation (3.5%) was detected in the 29 brain tumor specimens analyzed. This missense mutation occurred in a sequence reported previously to confer nuclear translocation properties to p33ING1b. Interestingly, overexpression and subcellular mislocalization of p33ING1b were observed in all 29 of the brain tumor specimens and some glioma cell lines. In tumor samples, ING1 proteins aberrantly localized to the cytoplasm, and to a lesser extent, to the nucleus of glioma cells.


CONCLUSIONS
Our data indicate that although mutations of ING1 seem to be infrequent in human brain tumors, deregulated expression and mislocalization of ING1 proteins, particularly the p33ING1b isoform, are common events in gliomas and glioblastomas.
Vieyra
Diego
D
Department of Medical Biochemistry and Southern Alberta Cancer Research Center, The University of Calgary, Calgary, Alberta, Canada.
Senger
Donna L
DL
Toyama
Tatsuya
T
Muzik
Huong
H
Brasher
Penny M A
PM
Johnston
Randal N
RN
Riabowol
Karl
K
Forsyth
Peter A
PA
Toyam
Tatsuya
T
D001254:Astrocytoma / Q000378:metabolism; D001932:Brain Neoplasms / Q000235:genetics*; D018797:Cell Cycle Proteins; D002467:Cell Nucleus; D004273:DNA, Neoplasm / Q000235:genetics; D004268:DNA-Binding Proteins; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D005910:Glioma / Q000235:genetics*; D006131:Growth Inhibitors / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007124:Immunoenzyme Techniques; D000076023:Inhibitor of Growth Protein 1; D047908:Intracellular Signaling Peptides and Proteins; D020125:Mutation, Missense / Q000235:genetics*; D009687:Nuclear Proteins; D018807:Polymorphism, Single-Stranded Conformational; D020033:Protein Isoforms; D021381:Protein Transport; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013347:Subcellular Fractions; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D006131:Growth Inhibitors; C501503:ING1 protein, human; D000076023:Inhibitor of Growth Protein 1; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D020033:Protein Isoforms; D011506:Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D025521:Tumor Suppressor Proteins