Reviewer's report
Title:Correlation between the methylation of SULF2 and WRN promoter and the
irinotecan chemosensitivity in gastric cancer
Version: 3Date:16 June 2013
Reviewer: Gyeong Hoon Kang
Reviewer's report:
The authors analyzed 102 gastric cancer tissue samples for their methylation
status in SULF2 and WRN and correlated with drug sensitivity using histoculture
drug response assay. Specific comments are as follows.
Major compulsatory revisions
1. The authors did not perform the MethyLight technology which utilizes an
oligonucleotide probe with fluorescence reporter dye and quencher dye. The
authors performed SYBR Green methylation-specific PCR (MSP) but did not
quantify SULF2 and WRN methylation levels. The authors should have
performed quantitative analysis of WRN or SULF2 methylation, using MethyLight,
pyrosequencing, or COBRA. MSP is inconsistent in detection of low level of
methylation and the presence of methylation by MSP does not tell us whether
50% of tumor DNA alleles are methylated or 0.1% of tumor DNA alleles are
methylated. With 0.1% methylation, we cannot expect methylation-associated
inactivation of gene expression in all tumor cells.
2. The authors demonstrated that there was an increase in the inhibition rate in
association with SULF2 methylation or both SULF2 and WRN methylation.
However, it cannot be excluded that the increased response may not be specific
to CPT-11. Thus, the authors should perform HDRA with other chemotherapeutic
drugs, e.g. 5-FU or oxaliplatin.
Minor Essential Revisions
1. It cannot be accepted that gastric cancer has an overall 5 year survival of 10%
(the first paragraph of “Introdcution” section). If this corresponds to China, please
provide references.
2. And it might be not true that gastric cancer is the fourth most common cancer
in Japan (the first paragraph of “Introdcution” section).
Discretionary Revisions
1. It would be better if the authors perform RT-PCR for SULF2 and WRN and
correlate expression of the gene with methylation status.
2. Please add a brief, general description of the study subjects at the beginning
of the results section: Distribution of sex, age and tumor location (antral, body,
upper third), etc.
3. “#2 test was used to assess the association between methylation and patient
characteristics” should be moved from “Results” section to “Data analysis”
paragraph.
4. It would be better for the authors to provide percentage values after number of
cases in parenthesis throughout Table 1.
5. The authors should give percentage values of the inhibition rates for SULF2
and WRN methylation and unmethylation groups.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Acceptable
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Declaration of competing interests:
I declare that I have no competing interests.
Reviewer's report
Title:Correlation between the methylation of SULF2 and WRN promoter and the
irinotecan chemosensitivity in gastric cancer
Version: 3Date:16 June 2013
Reviewer: Gyeong Hoon Kang
Reviewer's report:
The authors analyzed 102 gastric cancer tissue samples for their methylation
status in SULF2 and WRN and correlated with drug sensitivity using histoculture
drug response assay. Specific comments are as follows.
Major compulsatory revisions
1. The authors did not perform the MethyLight technology which utilizes an
oligonucleotide probe with fluorescence reporter dye and quencher dye. The
authors performed SYBR Green methylation-specific PCR (MSP) but did not
quantify SULF2 and WRN methylation levels. The authors should have
performed quantitative analysis of WRN or SULF2 methylation, using MethyLight,
pyrosequencing, or COBRA. MSP is inconsistent in detection of low level of
methylation and the presence of methylation by MSP does not tell us whether
50% of tumor DNA alleles are methylated or 0.1% of tumor DNA alleles are
methylated. With 0.1% methylation, we cannot expect methylation-associated
inactivation of gene expression in all tumor cells.
2. The authors demonstrated that there was an increase in the inhibition rate in
association with SULF2 methylation or both SULF2 and WRN methylation.
However, it cannot be excluded that the increased response may not be specific
to CPT-11. Thus, the authors should perform HDRA with other chemotherapeutic
drugs, e.g. 5-FU or oxaliplatin.
Minor Essential Revisions
1. It cannot be accepted that gastric cancer has an overall 5 year survival of 10%
(the first paragraph of “Introdcution” section). If this corresponds to China, please
provide references.
2. And it might be not true that gastric cancer is the fourth most common cancer
in Japan (the first paragraph of “Introdcution” section).
Discretionary Revisions
1. It would be better if the authors perform RT-PCR for SULF2 and WRN and
correlate expression of the gene with methylation status.
2. Please add a brief, general description of the study subjects at the beginning
of the results section: Distribution of sex, age and tumor location (antral, body,
upper third), etc.
3. “#2 test was used to assess the association between methylation and patient
characteristics” should be moved from “Results” section to “Data analysis”
paragraph.
4. It would be better for the authors to provide percentage values after number of
cases in parenthesis throughout Table 1.
5. The authors should give percentage values of the inhibition rates for SULF2
and WRN methylation and unmethylation groups.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Acceptable
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Declaration of competing interests:
I declare that I have no competing interests.
Please review this paper.
user
Reviewer's report
Title:Correlation between the methylation of SULF2 and WRN promoter and the
irinotecan chemosensitivity in gastric cancer
Version: 3Date:16 June 2013
Reviewer: Gyeong Hoon Kang
Reviewer's report:
The authors analyzed 102 gastric cancer tissue samples for their methylation
status in SULF2 and WRN and correlated with drug sensitivity using histoculture
drug response assay. Specific comments are as follows.
Major compulsatory revisions
1. The authors did not perform the MethyLight technology which utilizes an
oligonucleotide probe with fluorescence reporter dye and quencher dye. The
authors performed SYBR Green methylation-specific PCR (MSP) but did not
quantify SULF2 and WRN methylation levels. The authors should have
performed quantitative analysis of WRN or SULF2 methylation, using MethyLight,
pyrosequencing, or COBRA. MSP is inconsistent in detection of low level of
methylation and the presence of methylation by MSP does not tell us whether
50% of tumor DNA alleles are methylated or 0.1% of tumor DNA alleles are
methylated. With 0.1% methylation, we cannot expect methylation-associated
inactivation of gene expression in all tumor cells.
2. The authors demonstrated that there was an increase in the inhibition rate in
association with SULF2 methylation or both SULF2 and WRN methylation.
However, it cannot be excluded that the increased response may not be specific
to CPT-11. Thus, the authors should perform HDRA with other chemotherapeutic
drugs, e.g. 5-FU or oxaliplatin.
Minor Essential Revisions
1. It cannot be accepted that gastric cancer has an overall 5 year survival of 10%
(the first paragraph of “Introdcution” section). If this corresponds to China, please
provide references.
2. And it might be not true that gastric cancer is the fourth most common cancer
in Japan (the first paragraph of “Introdcution” section).
Discretionary Revisions
1. It would be better if the authors perform RT-PCR for SULF2 and WRN and
correlate expression of the gene with methylation status.
2. Please add a brief, general description of the study subjects at the beginning
of the results section: Distribution of sex, age and tumor location (antral, body,
upper third), etc.
3. “#2 test was used to assess the association between methylation and patient
characteristics” should be moved from “Results” section to “Data analysis”
paragraph.
4. It would be better for the authors to provide percentage values after number of
cases in parenthesis throughout Table 1.
5. The authors should give percentage values of the inhibition rates for SULF2
and WRN methylation and unmethylation groups.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Acceptable
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Declaration of competing interests:
I declare that I have no competing interests.
assistant