TY - JOUR
T1 - The expression of DNA methyltransferases and methyl-CpG-binding proteins is not associated with the methylation status of p14ARF p16INK4a and RASSF1A in human lung cancer cell lines
AU - Sato, Mitsuo
AU - Horio, Yoshitsugu
AU - Sekido, Yoshitaka
AU - Minna, John D.
AU - Shimokata, Kaoru
AU - Hasegawa, Yoshinori
N1 - Funding Information:
The authors thank Dr Chaubert for giving us technical advice for bisulfite genomic sequencing, and Keiko Shimamoto for her technical assistance. This work was supported in part by a Grant-in-Aid from Japan Society for Promotion of Science (to Y Sekido), a grant from Kanae Foundation for Life & Socio-medical Science, (to Y Sekido), grants NCI P50 CA70907 and CA71618 (to JD Minna) and a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology (to Y Hasegawa).
PY - 2002
Y1 - 2002
N2 - Promoter hypermethylation is an important means for the transcriptional repression of a number of cancerassociated genes. However, the underlying mechanism of this aberration in cancer remains unclear. Here, we examined 5′ CpG island methylation status and expression of the p14ARF p16INK4a and RASSF1A tumor suppressor genes, and investigated the relationship of these factors with the mRNA expression of DNA methyltransferases (DNMTs) and/or methyl-CpG-binding proteins (MBPs) in 30 lung cancer cell lines including 12 small cell lung cancers (SCLCs) and 18 non-small cell lung cancers (NSCLCs). When β-actin was used as an internal control, the mRNA expression of three DNMTs (DNMT1, DNMT3A, and DNMT3B) and five MBPs (MBD1, MBD2, MBD3, MBD4, and MeCP2) was upregulated in SCLC, while only that of DNMT1, DNMT3B and MBD3 was upregulated in NSCLC, compared with normal lung tissues. However, when normalized using proliferating cell nuclear antigen (PCNA) as an internal control, these differences disappeared or diminished; there was even a significant reduction in the expression ratios of DNMT1, MBD2 and MeCP2 in SCLC and DNMT1, MBD2 and MBD4 in NSCLC. Furthermore, although significant correlations between PCNA expression and mRNA expression levels of the three DNMTs and four of the MBPs (excluding MeCP2) were observed, there was no obvious correlation between promoter hypermethylation of these tumor suppressor genes and the expression level of any of the DNMTs or MBPs. Our results suggest that upregulation of DNMTs and MBPs probably reflects an increased cell proliferation in human lung cancers and that there are likely to exist gene-specific mechanisms for epigenetic gene silencing.
AB - Promoter hypermethylation is an important means for the transcriptional repression of a number of cancerassociated genes. However, the underlying mechanism of this aberration in cancer remains unclear. Here, we examined 5′ CpG island methylation status and expression of the p14ARF p16INK4a and RASSF1A tumor suppressor genes, and investigated the relationship of these factors with the mRNA expression of DNA methyltransferases (DNMTs) and/or methyl-CpG-binding proteins (MBPs) in 30 lung cancer cell lines including 12 small cell lung cancers (SCLCs) and 18 non-small cell lung cancers (NSCLCs). When β-actin was used as an internal control, the mRNA expression of three DNMTs (DNMT1, DNMT3A, and DNMT3B) and five MBPs (MBD1, MBD2, MBD3, MBD4, and MeCP2) was upregulated in SCLC, while only that of DNMT1, DNMT3B and MBD3 was upregulated in NSCLC, compared with normal lung tissues. However, when normalized using proliferating cell nuclear antigen (PCNA) as an internal control, these differences disappeared or diminished; there was even a significant reduction in the expression ratios of DNMT1, MBD2 and MeCP2 in SCLC and DNMT1, MBD2 and MBD4 in NSCLC. Furthermore, although significant correlations between PCNA expression and mRNA expression levels of the three DNMTs and four of the MBPs (excluding MeCP2) were observed, there was no obvious correlation between promoter hypermethylation of these tumor suppressor genes and the expression level of any of the DNMTs or MBPs. Our results suggest that upregulation of DNMTs and MBPs probably reflects an increased cell proliferation in human lung cancers and that there are likely to exist gene-specific mechanisms for epigenetic gene silencing.
KW - DNA methylation
KW - DNA methyltransferase
KW - Epigenetic modification
KW - Lung cancer
KW - Methyl-CpG-binding protein
KW - Tumor suppressor gene
UR - http://www.scopus.com/inward/record.url?scp=0037130479&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0037130479&partnerID=8YFLogxK
U2 - 10.1038/sj.onc.1205581
DO - 10.1038/sj.onc.1205581
M3 - Article
C2 - 12101420
AN - SCOPUS:0037130479
SN - 0950-9232
VL - 21
SP - 4822
EP - 4829
JO - Oncogene
JF - Oncogene
IS - 31
ER -