Page 125 - D. Cancer biology

Aberrant hypomethylation mediated-PARP4 overexpression induces
cisplatin resistance of ovarian cancer
Jung-Hyuck Ahn
Department of Biochemistry, College of Medicine, Ewha Womans University

BACKGROUND AIM
Although cisplatin is one of the most effective chemotherapeutic To identify epigenetically regulated genes directly associated
agents for ovarian cancer, the emergence of chemoresistance is a with ovarian cancer cisplatin resistance, we compared the
major challenge to successful therapy. Recent studies suggest that expression and methylation profiles of cisplatin-sensitive and -
anticancer drug resistance, including cisplatin resistance, can be resistant human ovarian cancer cell lines.
mediated by aberrant DNA methylation. In particular, aberrant
promoter hypermethylation and subsequent gene silencing can affect
sensitivity to cisplatin by inactivating genes that are critical for
response to the drug.
METHODS

(n=2 to 4/group). During surgery, the reduction of cerebral blood flow was monitored by using Laser Doppler Flowmetry secured
To identify epigenetically regulated genes directly associated with ovarian cancer
Table 1. Cytotoxicity of
cisplatin resistance, we measured the response of 11 human ovarian cancer cell cisplatin against 11
lines to cisplatin and classified them into three groups based on cytotoxicity: ovarian cell lines
sensitive, intermediate, and resistant. We compared expression and methylation
profiles of cisplatin-sensitive and -resistant human ovarian cancer cell lines and
identified the key genes for cisplatin drug response.

RESULTS

PA-1
A2780
(p = 0.0010)
**
** (p = 0.0078) Resistant 10 8 Sensitive Resistant Figure TOV112D M U 2.5 2.0 *** *** 2. Figure 3.
120
***
***
Relative expression (Fold change) 1.5 1.0 0.5 Relative expression (Fold change) 6 4 2 Neuroprotective effects Identification of
**
2.0
Table 1. Clinical characteristics of
Relative expression(Fold change)
Con
Aza
Sensitive
Methylation (%)
80
patients with ovarian cancer who
***
1.5
1.0
40
were sensitive or resistant to
0.5
primary chemotherapy
0.0
0
-
TOV-112D
PA-1
-
+
-
A2780
+
+
0.0
5-aza treatment
PA-1 TOV-21G TOV-112D Caov-3 A2780 OVCAR-3 OV-90 SK-OV-3 0 PA-1 TOV-21G TOV-112D Caov-3 A2780 OVCAR-3 OV-90 SK-OV-3 by downregulation of Abca1 mRNA as a
Figure 3. PARP4 mRNA expression is up-
regulated following demethylation in cisplatin-
Figure 1. PARP4 expression is up-regulated miR-33-5p and miR- target for miR-33-
in cisplatin-resistant cell lines. PARP4 mRNA sensitive cell lines. Eight ovarian cancer cell lines
treated
were
expression was determined by gene 135b-5p. with 5-aza-2’-deoxycytidine. 5p and miR-135b-
expression microarray and RT-qPCR in eight Methylation status of a specific promoter CpG
ovarian cancer cell lines. Error bars represent site was measured by pyrosequencing analysis 5p.
standard deviation (SD) of triplicate and PARP4 mRNA expression was measured by
measurements. Statistical analyses were RT-qPCR.
performed using a t-test.
2.
Figure ** (p = 0.0015) Figure 2. A CpG Figure 2.
Neuroprotective effects Neuroprotective effects
1.0
Resistant
Sensitive
site is hypomethy-
0.8
lated within the
Methylation (% )
by downregulation promoter by downregulation of
of
0.6
PARP4
0.4
in
miR-33-5p and cisplatin-
miR-
0.2
resistant cell lines.
0.0 miR-33-5p and miR-
SK-OV-3
OVCAR-3
PA-1
TOV-112D
OV-90
Caov-3
TOV-21G
A2780
135b-5p. Figure 2. A CpG site is Figure 4. The specific PARP4 promoter CpG is
hypomethylated within the PARP4 hypomethylated in patients with chemo-resistant
The DNA methylation status of CpG sites
ovarian cancer.
promoter in cisplatin-resistant cell 135b-5p. Receiver operating characteristic
within the PARP4 promoter region was
lines. The DNA methylation status of curves shows the discrimination of chemo-resistant
quantified
the
Illumina
using
patients from chemo-sensitive patients based on
CpG sites within the PARP4 promoter DNA methylation status at the specific promoter
HumanMethylation 450 BeadChip in eight
region was quantified using the Illumina CpG site of PARP4 *DFE: Disease-free interval following
ovarian cancer cell lines.
completion of chemotherapy (month)
CONCLUSION REFERENCES ACKNOWLEDGEMENTS
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ABCA1
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