ADAM12 is selectively overexpressed in human glioblastomas and is associated with glioblastoma cell proliferation and shedding of heparin-binding epidermal growth factor.
ADAMs (a disintegrin and metalloproteinases) are multifunctional molecules involved in cell-cell fusion, cell adhesion, membrane protein shedding, and proteolysis. In the present study, we examined the mRNA expression of 13 different ADAM species with putative metalloproteinase activity in human astrocytic tumors, nonneoplastic brain tissues, and other intracranial tumors by reverse transcriptase-polymerase chain reaction, and found that prototype membrane-anchored ADAM12 (ADAM12m) is predominantly expressed in glioblastomas. Real-time quantitative polymerase chain reaction indicated that the expression level of ADAM12m is remarkably at least 5.7-fold higher in glioblastomas (n = 16) than in nonneoplastic brain tissues (n = 6), low grade (n = 7) and anaplastic astrocytic tumors (n = 9) (P < 0.05 for each group), and intracranial neurinomas (n = 5) (P < 0.01). In situ hybridization showed that glioblastoma cells are responsible for the gene expression. By immunohistochemistry, ADAM12m was predominantly immunolocalized on the cell membranes of glioblastoma cells. Immunoblotting analysis demonstrated that ADAM12m is expressed as an activated N-glycosylated form of approximately 90 kd in glioblastoma tissues. There was a direct correlation between the mRNA expression levels of ADAM12m and proliferative activity (MIB1-positive cell index) of gliomas (r = 0.791, P < 0.0001; n = 32). Protein bands consistent with the soluble form of heparin-binding epidermal growth factor, a substrate of ADAM12m, were observed by immunoblotting in glioblastoma samples with the ADAM12m expression, and inhibited by treatment with ADAM inhibitor of the glioblastomas. These data demonstrate for the first time that among the 13 different ADAM species, ADAM12m is highly expressed in human glioblastomas, and suggest the possibility that ADAM12m plays a role in the prominent proliferation of the glioblastomas through shedding of heparin-binding epidermal growth factor.
Kodama
Takahide
T
Department of Pathology, School of Medicine, Keio University. 35 Shinanomachi, Shinjuku-ku, Tokyo 160-0016, Japan.
Ikeda
Eiji
E
Okada
Aiko
A
Ohtsuka
Takashi
T
Shimoda
Masayuki
M
Shiomi
Takayuki
T
Yoshida
Kazunari
K
Nakada
Mitsutoshi
M
Ohuchi
Eiko
E
Okada
Yasunori
Y
D051722:ADAM Proteins; D000072199:ADAM12 Protein; D001921:Brain / Q000473:pathology; D001932:Brain Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation; D017931:DNA Primers / Q000494:pharmacology; D004815:Epidermal Growth Factor; D005909:Glioblastoma / Q000378:metabolism*; D006031:Glycosylation; D006493:Heparin / Q000378:metabolism*; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D017403:In Situ Hybridization; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000502:physiology; D008666:Metalloendopeptidases / Q000096:biosynthesis* / Q000502:physiology; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
D017931:DNA Primers; C587883:HBEGF protein, human; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D004815:Epidermal Growth Factor; D006493:Heparin; D051722:ADAM Proteins; D000072199:ADAM12 Protein; C000606480:ADAM12 protein, human; D008666:Metalloendopeptidases