Defective expression of transforming growth factor beta receptor type II is associated with CpG methylated promoter in primary non-small cell lung cancer.
OBJECTIVE
Reduced expression of the transforming growth factor beta receptor type II (TGF beta RII), a key inhibitor of epithelial cell growth and tumor suppressor gene, was reported frequently in many types of tumors including non-small cell lung cancer (NSCLC). This study explored the significance of the TGF beta RII gene in NSCLC carcinogenesis.


METHODS
With 43 independent pairs of tumor and paracarcinoma tissue samples from patients with primary NSCLC, we carried out PCR-denaturing gradient gel electrophoresis screening for DNA variants over the coding sequence of the TGF beta RII gene, immunohistochemical assay of TGF beta RII expression, methylation-specific PCR analysis, and semiquantitative reverse transcription-PCR.


RESULTS
The PCR-denaturing gradient gel electrophoresis did not detect variation in the whole coding sequence of the TGF beta RII gene, but the immunohistochemistry experiment revealed reduced or lost expression of the gene in 44% (19 of 43) of the tumor samples. The methylation analysis on the 19 pairs detected the frequent occurrence of methylated TGF beta RII promoter in tumor tissues, whereas most of the paracarcinoma tissues were free of methylation. The reduced TGF beta RII expression was highly significantly associated with the methylation event (P < 10(-4)). The reverse transcription-PCR analysis demonstrated a clear agreement between reduced TGF beta RII expression and decreased mRNA level of the gene in the tumor tissue samples.


CONCLUSIONS
TGF beta RII plays an important role as a tumor suppressor in NSCLC carcinogenesis. The defective expression may serve as one of most important molecular mechanisms in explaining progression of the disease. In particular, aberrant 5' CpG methylation of the gene has explained the down-regulation of the gene at a transcriptional level.
Zhang
Hong-Tao
HT
Laboratory of Population and Quantitative Genetics, Institute of Genetics, The State Key Laboratory of Genetic Engineering, Morgan-Tan International Center for Life Sciences, Fudan University, Shanghai, People's Republic of China.
Chen
Xiao-Feng
XF
Wang
Ming-Hua
MH
Wang
Jiu-Cun
JC
Qi
Qing-Yuan
QY
Zhang
Rong-Mei
RM
Xu
Wei-Qing
WQ
Fei
Qing-Yan
QY
Wang
Fei
F
Cheng
Qi-Qun
QQ
Chen
Feng
F
Zhu
Cheng-Song
CS
Tao
Shi-Heng
SH
Luo
Zewei
Z
D000328:Adult; D000368:Aged; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics* / Q000378:metabolism; D018899:CpG Islands; D004247:DNA / Q000737:chemistry; D019175:DNA Methylation; D004252:DNA Mutational Analysis; D015536:Down-Regulation; D005091:Exons; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger / Q000378:metabolism; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000096:biosynthesis* / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
D012333:RNA, Messenger; D018125:Receptors, Transforming Growth Factor beta; D004247:DNA; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II