Review for 10.1186/s12876-015-0379-y (2015)

Reviewer's report
Title:Histone deacetylase (HDAC)-1, -2, -4 and -6 expression in human
pancreatic adenocarcinoma: associations with clinicopathological parameters,
tumor proliferative capacity and patients' survival
Version:2Date:17 August 2015
Reviewer: Phoebe Phillips
Reviewer's report:
Summary of Findings:
The authors investigated expression of class I (HDAC-1,-2) and class II
(HDAC-4,-6) histone deactylases (HDACs) in pancreatic ductal adenocarcinoma
patient specimens (no prior chemotherapeutic treatment). HDACs were detected
by immunohistochemistry, and specimens histologically scored for staining
frequency and intensity. The authors observed significant correlations between:
1) Higher HDAC-1 expression and increased tumour cell proliferation marker
staining; 2) Higher HDAC-4 expression and reduced organ metastases; 3) Higher
HDAC-6 expression and earlier histological stage; and 4) Higher expression of
HDAC-1 and HDAC-6 correlated with increased overall survival.
Significance:
This is the first study to examine HDACs -2, -4, and -6 protein expression in
human pancreatic cancer specimens. There is one prior study which examined
HDAC-1 in pancreatic cancer specimens (Wang et al, Oncol Rep, 2009), which
concluded opposite findings to this study i.e. high expression of HDAC-1
correlated with reduced patient survival.
The clinical significance of the present findings is unclear. An unanswered
question is why would we want to inhibit HDAC with HDAC inhibitors when the
findings of this paper showed that increased HDAC expression improved survival
of pancreatic cancer patients (also see major revisions)?
The study could have been strengthened with an investigation of how HDAC
expression influences chemotherapy response in pancreatic cancer patients.
Minor Essential Revisions:
1. Line 81-83: ‘moreover, chemotherapy, such as 5FU or gemcitabine, is not
potentially capable of contributing to significant survival benefit’. Please rewrite
including specific comment on the current standard of care and exactly what the
survival advantages are.
2. Were the pancreatic cancer sections TMA’s or individual slides? Please add
this detail to the methods section. Could the authors please provide higher
quality resolution for the immunohistochemistry figures for Figure 1?
3. Line 210, Page 9: please add reference to Table 1.
4. Figure 1 shows example immunohistochemistry images for each HDAC, which
appear to show varied localization depending on the HDAC sub-type. Did
sub-cellular localization in pancreatic cancer cells vary with tumour
stage/metastatic spread for any of the HDACs studied? Can the authors please
explain the importance of cellular localization with known function of HDACs in
the discussion?
5. Please provide Ki67 representative image in Figure 1.
6. Could the authors please provide isotype controls for all immunohistochemistry
experiments? Please include in results figure.
7. Page 9, Line 225: “…increased the absence of organ metastases” should read
…reduced organ metastases.
8. Page 12, Line 278: “…HDACIs concern the up-regulation..” should read
“…HDACIs concerns the upregulation…”.
9. Page 12, Line 280: missing reference for altered regulation of pro/anti
apoptotic proteins.
10. Spell out ‘Ki-protein statement’ in tables – i.e. measure of proliferative
capacity and also p<0.05 = significance.
11. The image quality for the survival curves (Figure 2) is very poor. Labels are
particularly poor resolution.
12. Page 13: The term “entities” is unclear.
13. Page 14, Lines 331-32: “at well-tolerated by patients, dosages” should read:
….at doses well-tolerated by patients.
14. Discussion, Page 12, Line 295-296: Remove HDAC-2 and correlation with
overall survival - it was not statistically significant.
15. Add a full stop Page 13 Line 319 after …survival [24].
16. The language used in the results section is very repetitive; consider
re-working to enhance the readers experience.
Major Compulsory Revisions:
1. How do authors explain that patients with high HDAC-1 expression lived
longer, but had increased tumour proliferative capacity? Discussion needs to be
amended.
2. Statistics: Several result statements (Results section) are not adequately
supported by the data. Statements such as ‘borderline more frequently observed’
but ‘at a non-significant level’ need to be re-written. Things which are not
statistically significant should be surmised as being no different from the
comparison group. For example: Page 10, Lines 228-232 and Page 10 lines
242-247.
3. Can authors clarify how specific HDAC inhibitors are for each of the HDACs
analyzed in this study? Please add details to the discussion.
4. The authors comment that the discrepancy between their findings and
previous work on HDAC1 in pancreatic cancer, may be due to sample size. This
argument is weak considering there are only 15 extra samples in this study. Are
there any other possible explanations e.g. different demographic? The authors
also mention differences in antibodies as a potential cause. How was the
antibody in this study validated?
5. Why inhibit HDACs with HDAC inhibitors when the findings of this paper
showed that increased HDAC expression improved survival of pancreatic cancer
patients? The discussion on this is not adequately supported by the data
provided.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Needs some language corrections before being
published
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
I declare that I have no competing interests