Hypermethylation of the TSLC1/IGSF4 promoter is associated with tobacco smoking and a poor prognosis in primary nonsmall cell lung carcinoma.
BACKGROUND
The tumor suppressor gene TSLC1/IGSF4 on chromosomal region 11q23 is frequently inactivated by promoter methylation in various cancers, including nonsmall cell lung carcinoma (NSCLC). Several studies have demonstrated that the hypermethylation of the CpG islands of genes, including tumor suppressors, is associated with exposure to tobacco smoke. The purpose of this study was to investigate the possible association of TSLC1/IGSF4 methylation with tobacco smoking as well as with the clinical characteristics of tumors using a large number of primary NSCLC.


METHODS
The promoter methylation of TSLC1/IGSF4 was analyzed in 103 primary NSCLC. TSLC1/IGSF4 expression was examined by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry, whereas its methylation status was determined by bisulfite single-strand conformation polymorphism (SSCP) coupled with bisulfite sequencing.


RESULTS
The TSLC1/IGSF4 promoter was methylated in 45 (44%) of 103 primary NSCLC. Methylation was observed in all histologic subtypes of NSCLC, including adenocarcinoma (29 of 68, 43%), squamous cell carcinoma (14 of 26, 54%), adenosquamous carcinoma (1 of 2, 50%), and large cell carcinoma (1 of 7, 14%). The incidence of methylation in tumors was significantly higher in male patients than in female patients (P = .027). The TSLC1/IGSF4 methylation was preferentially observed in heavy smokers (smoking index > or = 800) (P = .0054). Furthermore, in smokers the methylation was significantly associated with pack-years smoked (P = .034) and cigarettes per day (P = .021). The TSLC1/IGSF4 methylation was also significantly associated with a shorter disease-free survival (P = .049), providing an independent prognostic factor (P = .038) in adenocarcinoma patients.


CONCLUSIONS
TSLC1/IGSF4 methylation is associated with tobacco smoking and could be an indicator of poor prognosis.
Kikuchi
Shinji
S
Tumor Suppression and Functional Genomics Project, National Cancer Center Research Institute, Tokyo, Japan.
Yamada
Daisuke
D
Fukami
Takeshi
T
Maruyama
Tomoko
T
Ito
Akihiko
A
Asamura
Hisao
H
Matsuno
Yoshihiro
Y
Onizuka
Masataka
M
Murakami
Yoshinori
Y
D000368:Aged; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics*; D000075982:Cell Adhesion Molecule-1; D015815:Cell Adhesion Molecules; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation; D018572:Disease-Free Survival; D005260:Female; D016147:Genes, Tumor Suppressor; D006801:Humans; D007136:Immunoglobulins / Q000235:genetics*; D008175:Lung Neoplasms / Q000235:genetics*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D018807:Polymorphism, Single-Stranded Conformational; D011379:Prognosis; D011401:Promoter Regions, Genetic; D012907:Smoking / Q000009:adverse effects / Q000235:genetics*; D025521:Tumor Suppressor Proteins / Q000235:genetics*
C403514:CADM1 protein, human; D000075982:Cell Adhesion Molecule-1; D015815:Cell Adhesion Molecules; D007136:Immunoglobulins; D008565:Membrane Proteins; D025521:Tumor Suppressor Proteins