Review for 10.1186/1471-230X-10-9 (2010)

Reviewer's report
Title:Prostaglandin E2-induced colonic secretion in patients with colorectal
neoplasia
Version: 1Date:8 July 2009
Reviewer: Jens Leipziger
Reviewer's report:
This study uses a previously developed micro Ussing chamber to investigate
prostanoid dependent electrogenic ion transport in human biopsy tissue from
control persons and from patients suffering form colonic cancer disease. Short
circuit current increases are induced with theophylline, forskolin and different EP
receptor agonists. No difference was observed in these experiments. The
blockers of ion secretion bumetanide and ouabain neither showed differential
effects. A very small effect became visible when treating the tissue with
indomethacin in which healthy tissue from tumor patients apparently showed a
larger inhibitory effect. This greater inhibition in tumor patient tissue is not
reflected in greater resting SCC value.
The context of the question of this study is very interesting as it may indicate that
colonic tumor patient may have non-diseased colonic tissue that is functionally
altered in the direction of more secretion.
Major compulsory revision:
The effect in the indomethacin series is very small. The patient collective of 18
cancer patients is likely very heterogeneous with respect to all thinkable
parameters (age, sex, medications, location of primary tumor, genetic
background, etc.). It is therefore possible that unknown confounders could have
come to matter here. I fear that a rigorous evaluation by a statistician will
challenge this finding. It is suggested to consult your statistician to ascertain that
the correct testing was performed.
The “Introduction” is very short. The referee took notice of two very nice recent
papers (PNAS 2009 106:9409-13, Lancet 2009, 373:1301-9) which could be
worked into this part. The PNAS paper offers an intriguing new perspective of
COX2 inhibition and adenoma formation in a mouse model.
You differentiate between CRC and CRN. Reason?
Your conductance values of around 90 mS/cm2 are very high. These values
does not carry any significant information because of the edge leakiness with
only 1 mm Ussing chamber aperture. I would mention this issue as a technical
note into the “Methods” section and leave out these data from the “Abstract” and
the “Results” part. It is fully appreciated that this short-coming can not be solved
in this method.
Not a single original trace is shown. This should be included to see the quality of
the original data and would allow the evaluation of the time course of the effects.
Page 10: the scoring system is not fully understood. If understood correctly, the
biopsies for functional measurements and those to see the overview anatomy are
not the same. As specimen quality probably is a random process also related to
the actual procedure of taking the biopsy this correlation does not really make
sense. However, if you correlate the anatomy of your measured tissue with is
anatomical appearance after the experiment this could make sense.
Fig. 5. It does not really make much sense to show this figure. It just shows a
normal piece of colonic mucosa. It is should be convincing to state something like
“normal tissue anatomy was observed in control and patient tissue, (data not
shown).”
Page 11, line 4: Do you mean blood levels of PGE2?
Page 11, second paragraph: You should include the PNAS 2009 106:9409-13
paper to discuss the mechanism of PGE2 and CRN.
Page 11, second paragraph: You say: “It is this control and particularly the
COX-2 enzyme activity that appears to be altered by or be the cause of CRN and
CRC… “
In my knowledge the causal link of COX-2 activity an tumorigenesis is not
established. You should be more defensive.
Page 12: It is not understood why the indomethacin series showed a significant
difference while the resting currents do not. I find your discussion of this issue not
fully sufficient.
Fig. 1 is very complex and not well explained in this text. It is also believed that
the epithelial cells themselves are an important source of PGE2. It seems
appropriate to strive for congruence of the content in fig. 1 and what is found in
the text.
Level of interest: An article of importance in its field
Quality of written English: Needs some language corrections before being
published
Statistical review: Yes, but I do not feel adequately qualified to assess the
statistics.
Declaration of competing interests:
I declare that I have no competing interests.