Dicer and miRNA in relation to clinicopathological variables in colorectal cancer patients.

Abstract

Dicer is aberrantly expressed in several types of cancers. Applying real-time PCR, we detected the expression of Dicer mRNA in normal mucosa (n = 162), primary colorectal cancer (CRC) (n = 162) and liver metastasis (n = 37), and analysed the relationship between Dicer expression and clinicopathological features. We also correlated the expression of Dicer mRNA to the miRNA expression of miR-141, miR-200a, miR-200b, mir-200c and miR-429 in liver metastases.
RT-PCR and qPCR were used to analyse the Dicer expression in normal mucosa, primary tumour and liver metastasis by using the High Capacity cDNA Reverse Transcription Kit and TaqMan™® Gene Expression assays for Dicer and GAPDH. RT-PCR and qPCR were used to detect miRNA expression in liver metastases by utilizing TaqMan® MicroRNA Reverse Transcription Kit and TaqMan® miRNA Assays. Statistical analyses were performed with STATISTICA.
Dicer expression in rectal cancer (3.146 ± 0.953) was higher than in colon cancer (2.703 ± 1.204, P = 0.018). Furthermore the Dicer expression was increased in primary tumours (3.146 ± 0.952) in comparison to that in normal mucosa from rectal cancer patients (2.816 ± 1.009, P = 0.034) but this is not evident in colon cancer patients. Dicer expression in liver metastases was decreased in comparison to that of either normal mucosa or primary tumour in both colon and rectal cancers (P < 0.05). Patients with a high Dicer expression in normal mucosa had a worse prognosis compared to those with a low Dicer expression, independently of gender, age, tumour site, stage and differentiation (P < 0.001, RR 3.682, 95% CI 1.749 - 7.750). In liver metastases, Dicer was positively related to miR-141 (R = 0.419, P = 0.015).
Dicer is up-regulated in the early development of rectal cancers. An increased expression of Dicer mRNA in normal mucosa from CRC patients is significantly related to poor survival independently of gender, age, tumour site, stage and differentiation.

Full text

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RESEARCH ARTICLE Open Access
Dicer and miRNA in relation to clinicopathological
variables in colorectal cancer patients
Johannes Stratmann1, Chao-Jie Wang2, Sebastian Gnosa2, Åsa Wallin2, David Hinselwood2, Xiao-Feng Sun2and
Hong Zhang1*
Abstract
Background: Dicer is aberrantly expressed in several types of cancers. Applying real-time PCR, we detected the
expression of Dicer mRNA in normal mucosa (n = 162), primary colorectal cancer (CRC) (n = 162) and liver
metastasis (n = 37), and analysed the relationship between Dicer expression and clinicopathological features. We
also correlated the expression of Dicer mRNA to the miRNA expression of miR-141, miR-200a, miR-200b, mir-200c
and miR-429 in liver metastases.
Methods: RT-PCR and qPCR were used to analyse the Dicer expression in normal mucosa, primary tumour and
liver metastasis by using the High Capacity cDNA Reverse Transcription Kit and TaqMan™®Gene Expression assays
for Dicer and GAPDH. RT-PCR and qPCR were used to detect miRNA expression in liver metastases by utilizing
TaqMan®MicroRNA Reverse Transcription Kit and TaqMan®miRNA Assays. Statistical analyses were performed with
STATISTICA.
Results: Dicer expression in rectal cancer (3.146 ± 0.953) was higher than in colon cancer (2.703 ± 1.204, P =
0.018). Furthermore the Dicer expression was increased in primary tumours (3.146 ± 0.952) in comparison to that in
normal mucosa from rectal cancer patients (2.816 ± 1.009, P = 0.034) but this is not evident in colon cancer
patients. Dicer expression in liver metastases was decreased in comparison to that of either normal mucosa or
primary tumour in both colon and rectal cancers (P < 0.05). Patients with a high Dicer expression in normal
mucosa had a worse prognosis compared to those with a low Dicer expression, independently of gender, age,
tumour site, stage and differentiation (P < 0.001, RR 3.682, 95% CI 1.749 - 7.750). In liver metastases, Dicer was
positively related to miR-141 (R = 0.419, P = 0.015).
Conclusion: Dicer is up-regulated in the early development of rectal cancers. An increased expression of Dicer
mRNA in normal mucosa from CRC patients is significantly related to poor survival independently of gender, age,
tumour site, stage and differentiation.
Keywords: CRC, Dicer, miRNAs, Prognosis, qPCR
Background
CRC is one of the world’s leading cancer diseases and
third leading cause of cancer death world-wide [1]. Only
about 5-10% of the CRC cases arise on a defined heredi-
tary background due to two main diseases, familial ade-
nomatous polyposis (APC) and hereditary nonpolyposis
colorectal cancer [2]. Most of the cases seem to occur
sporadically without a hereditary background, and are
related to environmental factors (e.g., red meat, high-fat
diet, inadequate intake of fibre, obesity, sedentary life-
style, diabetes mellitus, smoking, high consumption of
alcohol) [3] and also to inflammatory bowel diseases
[4,5].
Recently it has been speculated that microRNAs (miR-
NAs) play a major role in cancer development [6].
MicroRNAs are small non-coding RNAs with a length
of approximately 22 nucleotides. These are known to
work as switches for genes and their correlated proteins,
have hundreds of targets in tumour suppressor or onco-
gene pathways [6] and are often referred to as
* Correspondence: hong.zhang@his.se
1Division of Biomedicine, Systems Biology Research Centre, School of Life
Sciences, Skövde University, SE-541 28, Skövde, Sweden
Full list of author information is available at the end of the article
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© 2011 Stratmann et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.

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“oncomirs” [7]. More specifically the miRNAs of the
miR-200 family have been shown to control epithelial to
mesenchymal transition (EMT) by down-regulating the
expression of the Zeb factors and controlling the meta-
static ability of cancer cells [8].
One of the key enzymes in the miRNA generating
process, Dicer [9], is a protein with a size of 219 kDa
[10] and consists of two RNase III domains, RNase IIIa
and RNase IIIb, which are responsible for the biogenesis
of short interfering RNAs and miRNAs [11]. Dicer is
located in the cytoplasm and associates there with
miRNA precursors, the pre-miRNAs, resulting in clea-
vage to mature ~22 nucleotide miRNA-miRNA
duplexes. Translational repression or degradation of
mRNA occurs when miRNA binds to the RNA induced
silencing complex [12].
Studies on non-small cell lung carcinoma (NSCLC)
show that Dicer protein is down-regulated in areas of
invasion and advanced carcinomas [13], and further-
more that reduced mRNA expression is significantly
associated with poor patient survival [14]. Similar results
are obtained in studies on Dicer mRNA in breast can-
cers [15], as well as in ovarian cancer patients where
Dicer mRNA was shown to be decreased in ovarian can-
cers in comparison to benign and normal samples [16],
furthermore, low Dicer protein expression is signifi-
cantly associated with advanced tumour stages and with
decreased survival [12]. In contrast, another study on
ovarian cancer patients showed that Dicer mRNA and
protein expression are significantly up-regulated in can-
cers, and increased Dicer is related to reduced disease-
free survival [17]. A study on prostate cancers exhibits
up-regulated Dicer in 81% of prostate cancers, and
increased Dicer expression is related to advanced stages
[18]. Recently, a study on CRC cancer also shows that
high Dicer expression is related to poor patient survival
[19]. These studies show that there are differentiated
patterns and roles of Dicer expression in different types
of tumours.
Major aims of our study were to determine the Dicer
mRNA level in the normal mucosa and primary
tumours from CRC patients as well as liver metastases
from independent CRC patients. Further, we examined
whether the Dicer mRNA level in these different tissues
was related to the patient survival as well as to other
clinicopathological variables. Dicer is directly connected
with miRNAs [9], who’s up- or down regulations are
strongly associated with the development of CRC [20],
while a study in mice revealed that certain miRNAs can
be generated independent from Dicer and require cata-
lysis by the Argonaute protein [21]. More specifically, it
was shown that high expression of miR-200c in CRC
patients was significantly associated with poor patient
survival [22]. Therefore, we decided to analyse the
miRNAs of the miR-200 family, miR-141, miR-200a,
miR-200b, miR-200c and miR-429 in liver metastases
since it is known that the members of the miR-200
family are functional linked to EMT, and may be
involved in facilitating the metastatic behaviour of can-
cer cells [23]. Furthermore we examined the relationship
of Dicer to the miRNA level in order to have an insight
into their interaction. We report here, for the first time,
that an increased Dicer mRNA level in normal mucosa
from CRC patients is associated with a worse survival.
Dicer is up-regulated in rectal cancers in comparison to
colon cancers. Furthermore we found a correlation
between Dicer and miR-141 expression in liver
metastases.
Methods
Patients
The patient material included primary tumour, the corre-
sponding normal mucosa and liver metastases collected
at Linköping University Hospital between 1980 and 2009.
Primary tumour and the corresponding normal mucosa
(taken from uninvolved morphologically normal colorec-
tal tissues) were obtained from 162 patients with primary
CRC, whereas liver metastases were collected from 37
independent CRC patients. For each primary tumour
patient, the primary tumour and the corresponding nor-
mal mucosa for comparison were collected. Median age
of the CRC patients was 74 years (ranging from 35 to 94
years). Thirty-two out of 108 reported CRC patients were
pre-treated with either pre-chemotherapy or pre-radio-
therapy. Median age of the patients with liver metastases
was 65 years (ranging from 37 years to 86 years).
Twenty-six patients with liver metastases underwent pre-
surgical chemotherapy. All specimens were flash-frozen
in liquid nitrogen and then stored at -80°C. According to
the histological diagnose criteria of the World Health
Organization; all samples were examined by the patholo-
gists at the Department of Pathology in Linköping Uni-
versity to confirm their histopathological type, TNM
stage and metastasis. The survival analyses were based on
overall survival.
RNA extraction and RT-PCR
Total RNA was extracted from nitrogen flash frozen tis-
sue using the TRizol reagent (Sigma-Aldrich, St. Louis,
MO) and RNeasy Kit (75144, QIAGEN, Venlo, NL)
according to the manufacturer’s instructions. The con-
centration and integrity of RNA were measured with the
Agilent 2100 Bioanalyzer (Agilent Technologies, Santa
Clara, CA). For the RT-PCR the High Capacity cDNA
Reverse Transcription Kit (Applied Biosystems, Foster
City, CA) was utilized. 10 μL total RNA was reverse
transcribed using MultiScribe™ Reverse Transcriptase
according to the manufacturer’s instructions, without an
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RNase inhibitor in a final volume of 20 μL. The pro-
gram is the following: 25°C 10 min, 37°C 120 min, 85°C
5 min.
For miRNA analysis, total RNA inclusive of the small
RNA fraction was extracted by using the mirVana
miRNA Isolation Kit (Ambion Inc.; Austin TX), accord-
ing to the manufacturers’ protocol. For the RT-PCR the
TaqMan®MicroRNA Reverse Transcription Kit was
used according to the manufacturer’s protocol. The pro-
gram was the following: 16°C 30 min, 42°C 30 min, 85°
C 5 min.
qPCR
The relative expression levels of Dicer were determined
by qPCR with TaqMan™®Gene Expression Fast Master
Mix in Applied Biosystems 7900HT Fast Real-Time
PCR System and normalised to GAPDH. Primers and
hydrolysis probes were TaqMan™®Gene Expression
assays on demand for Dicer (Hs00229023_m1*) and
GAPDH (4352934E) (Applied Biosystems). All the sam-
ples were performed in triplicates. The PCR amplifica-
tion program was the following: 95°C 20 sec, 40 cycles
of 95°C 1 sec and 60°C 20 sec. In addition, ddH2O as
the non-template control was analysed for every plate.
qPCR on miRNAs was performed according to the
manual from a recent miRNA study [24] with TaqMan®
Universal PCR Master Mix II and TaqMan miRNA
Assays for mature miRNAs (Applied Biosystems) for
hsa-mir-141 (Assay ID; 000463), -200a (Assay ID;
000502), -200b (Assay ID; 002251), -200c (Assay ID;
002300) and -429 (Assay ID; 001024). All samples were
analysed in triplicates and RNU48 (Assay ID; 001006 )
was used as a reference gene. We followed the manual
provided by Applied Biosystems (Amplification Effi-
ciency of TaqMan®Gene Expression Assays) to work
on the samples, namely, for each gene of interest and
reference gene the amplification efficiency was directly
determined by the slope on the SDS-program provided
by Applied Biosystems. The slope must be ≤ -3, 321 to
get amplification efficiencies ≤ 100%. The calculation
was done with the formula
E = 10
?−1
slope
?
- 1 where E =
amplification efficiency. For each real-time-PCR run, the
slope was adjusted for each sample in order to assure
that the amplification efficiencies were similar for each
gene and each run. The data obtained from the qPCR
was analysed by the ΔΔCt-method. The Dicer expres-
sion level was divided at a cut-off point of 75%, to dis-
tinguish between a low and high expression.
Statistical Analysis
For all statistical analyses the program STATISTICA
(StatSoft, Tulsa, OK) was utilized. The values for the
mRNA level from the real-time PCR were transformed
to log2values and the data were normally distributed.
Student’s t-test was used to examine the differences in
Dicer mRNA levels between the samples. Student’s t-
test or one-way ANOVA method was applied to analyse
the relationships with clinicopathological variables.
Kaplan-Meier method was used to calculate survival
curves. Cox’s Proportional Hazard Model was used to
estimate the relationship between mRNA expression
value and patients survival in univariate and multivariate
analyses. Pearson correlation was used to analyse the
relationship between Dicer and miRNAs. P-values of
less than 0.05 were considered statistically significant.
Results
Dicer mRNA level in normal mucosa, primary tumour and
liver metastasis
The mRNA level of Dicer between primary CRCs (2.863
± 1.137) and the corresponding normal mucosa (2.851 ±
1.040) from 162 CRC patients did not show a significant
difference (P = 0.835), while Dicer mRNA in liver
metastasis (1.839 ± 1.148) was obviously lower than that
in either the normal mucosa or the primary tumour (P
< 0.0001, Figure 1A).
Further analyses on Dicer expression were done in
comparison to the tumour site. In the colon (Figure 1B),
Dicer was still not significantly different between normal
mucosa (2.870 ± 1.066) and primary tumour (2.702 ±
1.204, P = 0.250) while the Dicer mRNA expression in
liver metastases (2.081 ± 1.207) was significantly
decreased in comparison to that in either normal
mucosa (P = 0.003) or primary tumours (P = 0.034). In
the rectum (Figure 1C), Dicer level in primary tumours
(3.146 ± 0.952) was significantly increased compared to
that in normal mucosa (2.816 ± 1.009, P = 0.034). Dicer
in liver metastases (1.499 ± 0.999) was decreased in
comparison to either the normal mucosa (P < 0.0001)
or the primary tumour (P < 0.0001).
Dicer mRNA level in relation to patient survival and other
clinicopathological variables
We first focused on the mRNA level of Dicer in normal
mucosa and found that a high level of Dicer in normal
mucosa was related to poor survival (P = 0.011, Figure
2). Even in multivariate analysis including gender, age,
tumour site, stage and differentiation, the relationship
between Dicer and survival still remained significant (P
= 0.0006, RR 3.682, 95% CI 1.749 - 7.750, Table 1). We
also examined the survival significance of Dicer expres-
sion level in normal mucosa in a multivariate model
including gender, age and tumour site (Table 1), as well
as stage (non-lymph node metastasis vs. metastasis) and
histologicaltype(non-mucinousvs.mucinous
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Figure 1 The mRNA level of Dicer in normal mucosa, primary tumour and liver metastasis. (A) Dicer mRNA level in normal mucosa,
primary tumour and liver metastasis from colorectal cancer patients. (B) Dicer mRNA level in normal mucosa, primary tumour and liver
metastasis from colon cancer patients. (C) Dicer mRNA level in normal mucosa, primary tumour and liver metastasis from rectal cancer patients.
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carcinoma), the increased Dicer level was still signifi-
cantly related to poor survival (P = 0.002, RR 3.447, 95%
CI 1.588 - 7.481). There were no significant relation-
ships between Dicer expression in normal mucosa and
other clinicopathological variables including gender, age,
tumour site, stage, differentiation and histological type
(P > 0.05, data not shown).
We then examined the Dicer mRNA level in primary
tumours in relation to clinicopathological variables.
There was no significant relationship between Dicer and
survival in primary tumours. Focus on the tumour site
showed that Dicer was significantly higher in rectal can-
cer (3.146 ± 0.953) than in colon cancer (2.703 ± 1.204,
P = 0.018, Figure 3). There was no further significant
relationship of Dicer to the other clinicopathological
variables (P > 0.05, data not shown).
Finally, we examined Dicer in liver metastases in
relation to clinicopathological variables. Liver metasta-
sis samples were separated according to the size of the
largest metastasis. It seems that the Dicer expression
in smaller sized tumours (≤ 42.5 mm) was higher
(2.068 ± 1.294) than in larger sized tumours (> 42.5
mm) (1.423 ± 0.622, P = 0.104). Patients with no
metastases to other organs than the liver, showed a
higher value of Dicer expression (1.948 ± 1.138) com-
pared to distant metastases (1.447 ± 0.891) although
the difference was not statistically significant (P =
0.158). When the patients were separated based on
other clinicopathological variables including gender,
age, the number of liver metastases, pre-chemotherapy,
local recurrence and the time period for occurrence of
liver metastases after primary tumour diagnosis, no
significant relationship to Dicer expression was
observed (P > 0.05, data not shown).
Dicer mRNA in relation to miRNA expression in liver
metastasis
Correlation studies between Dicer and miR-141, miR-
200a, miR-200b, miR-200c, miR-429 expression in liver
metastases revealed a positive correlation between Dicer
mRNA and miR-141 expression (Pearson correlation
coefficient, R = 0.419, P = 0.015, Table 2). There was
also a positive trend between Dicer mRNA and miR-429
(R = 0.312, P = 0.077, Table 2). There was no significant
relationship between Dicer level and the other miRNAs
(P > 0.05, Table 2).
Figure 2 A high level of Dicer in normal mucosa was connected to poor patient survival.
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Discussion
In the present study, we examined Dicer mRNA level in
the matched normal mucosa and primary tumour from
162 CRC patients and 37 liver metastases. We found a
significant increase of Dicer mRNA expression in pri-
mary tumour from rectal cancer patients in comparison
to that in the normal mucosa but there was no such evi-
dence in colon cancer patients, suggesting that Dicer
may play a different role in the development of rectal
cancer from its role in colon cancer. This assumption
led to a direct comparison of the Dicer mRNA level in
primary tumours from rectal and colon cancer, which
proved that the Dicer mRNA level was significantly up-
regulated in rectal cancer compared to colon cancer,
indicating that Dicer was differently regulated in the
Table 1 Multivariate analysis of the Dicer mRNA in
normal mucosa, gender, age, tumour site, stage and
differentiation in relation to patient survival
Variablesn Hazard Ratio95% CIP
Dicer mRNA
Low
High
Gender
Male
Female
0.0006
106
37
1.000
3.682
-
1.749 - 7.750
0.462
91
52
1.000
0.744
-
0.337 - 1.639
Age (years)
≤ 72
> 72
Tumour site
Colon
Rectum
Stage
I
II
III
IV
Differentiation
Better
Worse
0.052
60
83
1.000
2.082
-
0.993 - 4.363
0.072
88
55
1.000
0.478
-
0.214 - 1.069
< 0.0001
20
75
33
15
1.000
0.903
3.651
16.726
-
0.189 - 4.317
0.793 - 16.803
3.335 - 83.871
0.415
103
40
1.000
1.398
-
0.625 - 3.130
Figure 3 Dicer expression in rectal cancer was higher than that in colon cancer.
Table 2 Correlations between Dicer mRNA level and the
miRNA expression in liver metastases
miRNAR*P
miR-141
miR-200a
miR-200b
miR-200c
miR-429
0.419
0.239
0.110
- 0.132
0.312
0.015
0.180
0.543
0.463
0.077
*Pearson correlation coefficient
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two sites. In earlier studies where CRC was divided into
different sub-types according to the site where the can-
cer occurred, it was shown that different types of this
cancer exhibited their own specific genetic features like
microsatellite instability in proximal colon cancer
whereas distal colon cancers showed chromosome
instability [25]. Even though rectal cancer is similar to
colon cancer it exhibits its own specific features, for
instance, up-regulated nuclear b-catenin [26], as well as
a higher level of Cox-2 than in colon cancer [27]. K-ras
mutations are more common in colon cancer than in
rectal cancer, the number of mutations in colon
tumours is higher than in rectal tumours, and the muta-
tional pattern restricted to the APC gene is more fre-
quent in rectal than colon cancer [28]. Therefore our
results may provide further support that CRC could be
differentiated into two different diseases, colon cancer
and rectal cancer.
Comparison of the Dicer mRNA level in liver metas-
tases to that in normal mucosa and primary tumours
from colon and rectal cancer exhibited a significant
decrease of Dicer mRNA level in liver metastases. Simi-
lar results were obtained in breast cancer, where Dicer
was decreased in metastases due to inhibition by specific
miRNAs [9]. Our assumption gets further support from
two studies in ovarian cancer patients, which indicated
that a reduced Dicer mRNA level is associated with
advanced tumour stage [12,16]. Similar results were
seen in 67 NSCLCs, where a reduced Dicer expression
level was found in poorly differentiated tumours [14].
Interestingly, in the present study, higher Dicer
expression in normal mucosa was related to a worse
survival independently of gender, age, tumour site, stage
and differentiation. Dicer up-regulation was found in
prostate cancer, where an increased Dicer level was sig-
nificantly associated with aggressive cancer features.
This up-regulation in prostate cancer was suggested to
be induced by a genomic instability at chromosome 14
(14q32) due to amplification [18]. It is known that nor-
mal mucosa, which is assumed to be uninvolved during
cancer formation and apparently normal at the morpho-
logical level, shows abnormal gene regulation in com-
parison to normal mucosa from non-cancer patients
[29]. Dicer involvement in early cancer development has
been reported in lung cancer, where precursor lesions of
lung adenocarcinoma i.e. adenomatous hyperplasia,
showed Dicer over-expression [13]. These findings
would lead to the conclusion that the higher Dicer
mRNA level in normal mucosa has a certain role in
early cancer formation.
Examination of Dicer mRNA level in liver metastases
in association with clinicopathological variables was not
statistically relevant in the tested variables (largest
tumour diameter, distant metastasis excluding the liver,
gender, age, number of liver metastasis, pre-chemother-
apy, local recurrence and period of time until occur-
rence of liver metastasis after primary tumour
diagnosis). This finding was also reported in breast can-
cer patients where low or high Dicer mRNA levels were
not significantly associated with metastases or patient
outcome [9]. Nonetheless, it seemed that metastases
with a larger size showed a lower Dicer mRNA level
than metastases with a smaller size. Far distant metas-
tases excluding liver metastases showed a lower Dicer
expression than those in the liver. These results suggest
that a low Dicer mRNA level in metastases might be
involved in facilitating the metastatic spread for distant
metastases as was presumed in breast cancer [15].
Our miRNA correlation study showed that the Dicer
mRNA level was positively associated with miR-141 in
liver metastasis samples. The miR-141 is known to be
mainly involved in activation of epithelial differentiation
in breast, pancreatic and CRC. A decreased miR-141
level promotes the drift into metastatic behaviour of
cancer cells, due to repression of miR-141 by ZEB1 [30].
However our results, showing four out of five tested
miRNAs were not correlated to Dicer support the fact
that more factors are involved in the aberrant levels of
miRNAs during cancer progression.
How a decreased Dicer level was associated with the
change from primary to metastatic tumour in CRC, as
well as in relation to miRNAs and clinicopathological
variables, needs to be confirmed in a larger cohort of
patients. Our miRNA study in liver metastasis was a
pilot study to gain first insights into how miRNA regula-
tion might be connected to Dicer in liver metastasis
from CRC patients. Since the liver metastases were inde-
pendent from the matched normal and primary cancer
tissue, the results of comparison of the Dicer expression
in liver metastasis with primary tumour/normal mucosa
was a weakness. In addition analysis of global tumour
RNA levels may miss subtleties of tissue expression that
are crucial for tumour behaviour. The expression of
mRNA in a tissue fragment may not necessarily equate
with the mRNA expression by the tumour.
Conclusion
Dicer is up-regulated in the earlier development of rec-
tal cancers, and the increased Dicer expression in nor-
mal mucosa is an independent prognostic factor in CRC
patients. These findings strengthen the role of Dicer in
making early diagnosis, evaluating survival and planning
therapy of CRC patients.
Acknowledgements
This study was supported by grants by from Swedish Cancer Foundation,
Swedish Research Council and the Health Research Council in the South-
East of Sweden.
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Author details
1Division of Biomedicine, Systems Biology Research Centre, School of Life
Sciences, Skövde University, SE-541 28, Skövde, Sweden.2Division of
Oncology, Department of Clinical and Experimental Medicine, Faculty of
Health Sciences, Linköping University, SE-581 85, Linköping, Sweden.
Authors’ contributions
JS carried out the main experiments and drafted the manuscript. CJW
participated in the project design, valuable discussion and statistical analysis.
SG participated in the real-time PCR experimental procedure with primary
colorectal cancer and liver metastasis samples. ÅW did the experiment on
liver metastases. DH revised and helped in drafting the manuscript. XFS and
HZ conceived of the study, participated in the design and helped drafting
the manuscript. All authors read and approved the final manuscript.
Competing interests
The authors declare that they have no competing interests.
Received: 16 March 2011 Accepted: 10 August 2011
Published: 10 August 2011
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Pre-publication history
The pre-publication history for this paper can be accessed here:
http://www.biomedcentral.com/1471-2407/11/345/prepub
doi:10.1186/1471-2407-11-345
Cite this article as: Stratmann et al.: Dicer and miRNA in relation to
clinicopathological variables in colorectal cancer patients. BMC Cancer
2011 11:345.
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