Demethylation of the synuclein gamma gene CpG island in primary gastric cancers and gastric cancer cell lines.
OBJECTIVE
Whereas synuclein gamma (SNCG) gene expression is usually highly tissue-specific and restricted to the nervous system, SNCG is expressed in advanced-stage breast and ovarian cancers. When overexpressed, SNCG stimulates cancer cell proliferation and metastasis. It is thought that the molecular mechanism of CpG island demethylation may underlie aberrant SNCG expression. To determine whether aberrant SNCG expression and demethylation play a role in gastric carcinogenesis, we examined the expression and methylation status of SNCG in primary gastric cancers, gastric cancer cell lines, and non-neoplastic gastric mucosal tissues.


METHODS
Ten gastric cancer cell lines, 105 primary gastric cancers, and 10 non-neoplastic gastric mucosal tissues were examined. SNCG expression and methylation status were examined by reverse transcription-PCR and bisulfite-single-strand conformational polymorphism followed by direct sequencing, respectively. The relationship between SNCG methylation status and various clinicopathological factors of the primary gastric cancers was then analyzed.


RESULTS
SNCG mRNA expression was observed in 5 of 10 cell lines. Analysis of cell lines positive for SNCG expression revealed that most of the SNCG CpGs were demethylated. SNCG mRNA was not expressed in the 10 non-neoplastic gastric mucosal tissues, although several CpGs were demethylated. Of the 105 primary gastric cancers, 40 (38.1%) showed apparent SNCG demethylation, similar to the result obtained using cell lines. SNCG demethylation was more frequent in primary gastric cancers positive for lymph node metastasis (51%; 26 of 51) than in cancers without lymph node involvement (26%; 14 of 54; P < 0.05), and also more common in stage II-IV (48%; 27 of 56) than in stage I (27%; 13 of 49) cancers (P < 0.05).


CONCLUSIONS
Aberrant SNCG gene expression can occur via CpG island demethylation, and tends to occur during the more progressive stages of gastric carcinogenesis.
Yanagawa
Naoki
N
Department of Pathology, Yamagata University School of Medicine, Yamagata, Japan.
Tamura
Gen
G
Honda
Teiichiro
T
Endoh
Makoto
M
Nishizuka
Satoshi
S
Motoyama
Teiichi
T
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002455:Cell Division; D045744:Cell Line, Tumor; D018899:CpG Islands; D019175:DNA Methylation; D018076:DNA, Complementary / Q000378:metabolism; D000077209:Decitabine; D018450:Disease Progression; D005091:Exons; D005260:Female; D005753:Gastric Mucosa / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics*; D018807:Polymorphism, Single-Stranded Conformational; D011379:Prognosis; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000235:genetics*; D013447:Sulfites / Q000494:pharmacology; D051843:Synucleins; D013997:Time Factors
D018076:DNA, Complementary; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D013447:Sulfites; D051843:Synucleins; D000077209:Decitabine; D001374:Azacitidine; C009279:sodium bisulfite