Distinct expression pattern of claudin-6, a primitive phenotypic tight junction molecule, in germ cell tumours and visceral carcinomas.
OBJECTIVE
This study aimed to clarify claudin-6 expression patterns in cancers.


RESULTS
We surveyed claudin-6 expression by immunohistochemistry using tissue microarray in 860 tumours, including germ cell tumours and major carcinomas. Claudin-6 was expressed consistently in germ cell tumours (28 of 28, 100%), whereas only 64 (8%) of 832 non-germ cell tumours demonstrated claudin-6 expression. Further immunohistochemical study in full tissue sections demonstrated diffuse claudin-6 staining in all seminomas (n=14), embryonal carcinomas (n=10), yolk sac tumours (n=12) and mononuclear trophoblastic cells of choriocarcinomas (n=3), and focal staining in immature epithelial components of immature teratomas (n=6). Additionally, because alpha-fetoprotein (AFP)-producing gastric adenocarcinomas and pulmonary high-grade fetal adenocarcinomas were among the claudin-6 expressing non-germ cell tumours in the microarray studies, we predicted that claudin-6 may be a biomarker for them and studied additional tumours in full sections, which showed claudin-6 expression in AFP-producing gastric adenocarcinomas (18 of 20, 90%) and pulmonary high-grade fetal adenocarcinomas (four of five, 80%). Only one of 11 hepatoblastomas demonstrated focal claudin-6 staining.


CONCLUSIONS
This study demonstrated that claudin-6 is a novel diagnostic marker for primitive germ cell tumours and is also expressed frequently in some cancers with a primitive phenotype.
Department of Pathology and Diagnostic Pathology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
Tetsuo
T
Ushiku
Aya
A
Shinozaki-Ushiku
Daichi
D
Maeda
Shigeki
S
Morita
Masashi
M
Fukayama
D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D014408:Biomarkers, Tumor / Q000378:metabolism; D018236:Carcinoma, Embryonal / Q000378:metabolism / Q000473:pathology; D057167:Claudins / Q000378:metabolism*; D018240:Endodermal Sinus Tumor / Q000378:metabolism / Q000473:pathology; D005260:Female; D005333:Fetus / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism* / Q000473:pathology; D008297:Male; D009373:Neoplasms, Germ Cell and Embryonal / Q000378:metabolism* / Q000473:pathology; D010641:Phenotype; D018239:Seminoma / Q000378:metabolism / Q000473:pathology; D013274:Stomach Neoplasms / Q000378:metabolism* / Q000473:pathology; D013736:Testicular Neoplasms / Q000378:metabolism / Q000473:pathology; D019108:Tight Junctions / Q000473:pathology*; D000509:alpha-Fetoproteins / Q000378:metabolism
D014408:Biomarkers, Tumor; D057167:Claudins; D000509:alpha-Fetoproteins; C122101:claudin 6