High prevalence of decreased expression of KAI1 metastasis suppressor in human oral carcinogenesis.
OBJECTIVE
KAI1 was originally identified in prostate cancer as a metastasis suppressor gene. Recent studies have shown a frequent down-regulation of KAI1 expression in many tumor types, whereas mutation or hypermethylation of the gene is infrequent. The aim of the present study was to examine whether loss of KAI1 expression that might be caused by genetic or epigenetic alterations could contribute to oral carcinogenesis.


METHODS
We analyzed mutational and methylation status of the KAI1 gene and both the mRNA and protein level in a series of oral tumors [28 precancerous lesions, 101 primary oral squamous cell carcinomas (OSCCs), and 30 metastatic OSCCs] and OSCC-derived cell lines. We also examined p53 protein expression, which has been reported to be a candidate activator for the KAI1 gene.


RESULTS
With the exception of three microsatellite instabilities in the KAI1 gene, we found no mutations in the coding sequence of the KAI1 gene, no loss of heterozygosity, and no hypermethylation of the KAI1 promoter region in all samples investigated. By immunohistochemistry, however, high frequencies of KAI1 down-regulation were evident not only in the metastatic OSCCs [29 of 30 (97%)] but also in the primary OSCCs [83 of 101 (82%)] and in the precancerous lesions [13 of 28 (46%)]. There was a significant relationship between down-regulation of KAI1 protein expression and primary tumors associated with lymph node metastases (P = 0.0115), whereas there was no statistical correlation between p53 status and KAI1 expression. Taken together, reverse transcription-PCR data were consistent with the protein expression status in 16 patients from whom mRNA was available.


CONCLUSIONS
Our data suggest that whereas loss of KAI1 protein expression is associated with primary tumors with lymph node metastases, the down-regulation of KAI1 is an early event in the progression of human oral cancer. The down-regulation of KAI1 is not associated with either mutation, allelic loss, methylation of the promoter, or p53 regulation.
Uzawa
Katsuhiro
K
Department of Clinical Molecular Biology, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan.
Ono
Kanae
K
Suzuki
Hiroyoshi
H
Tanaka
Chihaya
C
Yakushiji
Takashi
T
Yamamoto
Nobuharu
N
Yokoe
Hidetaka
H
Tanzawa
Hideki
H
D000368:Aged; D000483:Alleles; D015703:Antigens, CD; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002880:Chromosomes, Human, Pair 11 / Q000235:genetics; D019175:DNA Methylation; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000235:genetics; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004848:Epithelium / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007124:Immunoenzyme Techniques; D051861:Kangai-1 Protein; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism*; D008875:Middle Aged; D009062:Mouth Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D009362:Neoplasm Metastasis / Q000235:genetics*; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
D015703:Antigens, CD; C497688:CD82 protein, human; D004273:DNA, Neoplasm; D004791:Enzyme Inhibitors; D051861:Kangai-1 Protein; D008562:Membrane Glycoproteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D000077209:Decitabine; D015254:DNA Modification Methylases; D001374:Azacitidine