REGULAR ARTICLES Cell Research (2004); 14(3): 217-226
Epigenetic modification regulates both expression
of tumor-associated genes and cell cycle progressing in human colon cancer
cell lines: Colo-320 and SW1116
Jing Yuan FANG, Ying Xuan CHEN, Juan
LU, Rong LU, Li YANG, Hong Yin ZHU, Wei Qi GU, Lun
Gen LU
Shanghai Institute of Digestive Disease, Renji Hospital
Shanghai Second
Medical University,
Shanghai 200001, China.
Received,
Oct 15, 2003 Revised, Apr 17, 2004
Accepted, Apr 20, 2004
The aim of this study is to assess the effects of DNA methylation and histone acetylation, alone or in combination, on the expression of
several tumor-associated genes and cell cycle progression in two established
human colon cancer cell lines: Colo-320 and SW1116. Treatments with 5-aza-2¡¯-deoxycytidine (5-aza-dC) and trichostatin A, alone or in combination, were applied respectively.
The methylation status of the CDKN2A promoter was determined by methylation-specific PCR, and the acetylated status of the
histones associated with the p21WAF1 and
CDKN2A genes was examined by chromatin immunoprecipitation. The expression of the CDKN2A, p21WAF1, p53, p73,
APC, c-myc, c-Ki-ras and survivin genes
was detected by real-time RT-PCR and RT-PCR. The cell cycle profile was
established by flow cytometry.
We found that along with the demethylation
of the CDKN2A gene
promoter in both cell lines induced by 5-aza-dC alone or in combination
with TSA, the expression of both CDKN2A
and APC genes increased. The treatment of TSA or sodium butyrate
up-regulated the transcription of p21WAF1 significantly
by inducing the acetylation of histones
H4 and H3, but failed to alter the acetylation
level of CDKN2A-associated
histones. No changes in transcription of p53, p73, c-myc,
c-Ki-ras and survivin
genes were observed. In addition, TSA or sodium butyrate was shown to
arrest cells at the G1 phase. However, 5-aza-dC was not able
to affect the cell cycle progression. In conclusion, regulation
by epigenetic modification of the transcription of tumor-associated genes
and the cell cycle progression in both human colon cancer cell lines Colo-320
and SW1116 is gene-specific.
Keywords: human colon cancer cell
lines, tumor-associated genes, DNA methylation,
histone acetylation, cell
cycle.
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