Review for 10.1186/1471-230X-14-67 (2014)

Reviewer's report
Title:Deregulated Expression of Circadian Clock Genes in Gastric Cancers
Version:1Date:20 October 2013
Reviewer: Pasquale Innominato
Reviewer's report:
Reviewer's report
• Major Compulsory Revisions
1- English language should be revised throughout the whole text.
2- Figure 1 and Table 2 show exactly the same results, constituting redundant
information.
3- Figure 2 shows an example of IHC results of a single patient, but neither in the
text nor in any figure or table the global results of clock genes protein expression
are reported. Moreover, it seems that only Per2 has positive staining in both
cases, whereas the other clock proteins seem not to be detected. The Authors
should report their findings concerning clock protein expression.
4-In both the introduction and the discussion there is no described link between
the first part about early diagnosis of gastric cancer and the second part about
circadian rhythms.
5-The Authors should discuss more in depth the meaning and possible
implications of their main findings. In particular, why per2 is overexpressed in
tumor cells as compared to gastric mucosa, whereas in the other tumors studies
(by them or others) per2 is usually downregulated in cancer? As for cry1, could a
noon (about the reported time of surgical sampling) higher expression of this
gene possibly mean a disregulated clock machinery in more advanced stages of
gastric cancer? The Authors ought to better discuss this finding in the context of
studies in human healthy oral mucosa, other kind of cancers and experimental
data in advanced cancers in mice.
• Minor Essential Revisions
1- References could be updated (eg, #2, cancer statistics for 2005).
2-Despite the rather small sample size, analysis for evaluating the prognostic
value of clock gene expression could include a Cox proportional hazard model.
Indeed, the cutoff at 2 and 5 years could be considered somewhat arbitrary,
given the heterogeneity in the stages of gastric cancer patients enrolled in this
study.
3-The Authors might want to detail how tumor and nearby gastric mucosa were
obtained (same surgical sample or two different ones). This would reassure the
reader about the lack of contamination of tumor cells in the mucosa sample, and
the presence of a large majority of neoplastic cells within the tumor sample.
4- Reference 13 is about skin cancer, not breast.
5-As correctly pointed out by the Authors, it might be interesting to explore the
differences between patient with and without HP infection: had they this
information about their cohort?
6- The Authors might want to provide details about the quality controls of their
qRT-PCR (did they check for the specificity of their findings with, for example,
evaluation of the right size of the expected amplicons and sufficiently low
threshold cycle for each gene?).
• Discretionary Revisions
1-The Authors ought to consider the global clock genes expression patterns
within each individual patient to explore the possible associations with pertinent
clinical outcomes alongside the analysis of each single gene separately. The fact
of having studied simultaneously 8 clock genes constitutes a strength of the
study that, in my opinion, has not been sufficiently exploited.
2-CCG usually stands for “clock-controlled genes”, and this might induce the
reader in error; the Authors might want to use another acronym for clock genes
(eg, just CG).
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Not suitable for publication unless extensively edited
Statistical review: No, the manuscript does not need to be seen by a statistician.
Declaration of competing interests:
I declare I have no competing interests