1. What study design was used? (200 words minimum)
2. How did the study design limit the findings of the article? (100 words minimum)
3. Could a better study design be selected? Why or Why not? (200 words minimum)
4. What other design that can selected that is effective? (200 words minimum)
Please see attached file. Thank you
Differential MIR-21 Expression in Plasma From Mesenteric
Versus Peripheral Veins
An Observational Study of Disease-free Survival in Surgically Resected Colon
Cancer Patients
Mariano Monzo, MD, PhD, Francisco Martı´nez-Rodenas, MD, PhD, Isabel Moreno, MD, PhD,
Alfons Navarro, PhD, Sandra Santasusagna, MS, Ismael Macias, MD, Carmen Mun˜oz, MS,
Rut Tejero, PhD, and Raquel Herna´ndez, MD
Abstract: Findings on the role of plasma miR-21 expression in
colorectal cancer are contradictory. Before reaching a peripheral vein
(PV), microRNAs released by the tumor are dispersed throughout the
body. We hypothesized that blood drawn from the mesenteric vein
(MV) near the site of the primary tumor could provide more homogeneous information than blood drawn from the PV.
We have analyzed miR-21 expression in matched samples of tumor
tissue, normal tissue, MV plasma, and PV plasma in 57 surgically
resected patients with colon cancer and correlated our findings with
clinical characteristics and disease-free survival (DFS).
miR-21 expression was higher in MV than PV plasma (P ¼ 0.014)
and in tumor than in normal tissue (P < 0.001). Patients with high levels
of miR-21 in MV plasma had shorter DFS (P ¼ 0.05) than those with
low levels, and those with high levels in both MV and PV plasma had
shorter DFS than all other patients (P ¼ 0.01).
Our findings suggest that the primary tumor in colon cancer releases
high concentrations of miR-21 in the MV but that these concentrations
are later diluted in the circulatory system. MV expression of miR-21
may be a stronger prognostic marker than PV expression.
(Medicine 94(1):e145)
Abbreviations: CRC = colorectal cancer, CT = computed
tomography, DFS = disease-free survival, miRNA = microRNA,
MV = mesenteric vein, PV = peripheral vein.
INTRODUCTION
Colorectal cancer (CRC) is the third most common type of
cancer and the second cause of cancer death worldwide.1
The main prognostic factor for relapse and survival in CRC is
disease stage, and patients with stage III disease have a higher
risk of relapse than those with stage II. Surgery is the standard
treatment for stage I to III, and adjuvant treatment has been
shown to be effective in stage III but less so in stage II.2
Prognostic and predictive biomarkers can provide a useful tool
for selecting treatment and improving outcome in these patients.
The analysis of biomarkers in the plasma or serum of CRC
patients is a noninvasive yet effective way to determine prognosis, detect occult tumors, and monitor treatment.
MicroRNAs (miRNAs), noncoding RNAs that play a key
role in the regulation of mRNA expression, are promising
diagnostic and prognostic biomarkers in several cancers.3
Numerous studies have shown that miRNAs are aberrantly
expressed during tumor development and can act either as
oncogenes or tumor suppressors.4,5 The specific mechanism
whereby tumor cells release miRNAs into the blood is not
completely understood. Recent studies have shown that exosomes and microvesicles can act as miRNA transporters,6–8
whereas other studies have found that miRNAs circulate freely
in blood by binding to the AGO-2 protein complex, which
prevents the digestion of RNase in plasma.9
miR-21 was the first tumor-related miRNA to be identified, detected in the serum of a patient with B-cell lymphoma.10
Since then, miR-21 has been widely studied in tumor, plasma,
and serum samples, both in CRC and in other tumors, where it
controls carcinogenesis by targeting different genes, including
TPM1,11 PDCD4,12,13 PTEN,14 and BTG2.15 In hepatocellular
carcinoma16 and non–small-cell lung cancer,17 plasma and
serum levels of miR-21 have been identified as reliable biomarkers for both diagnosis and prognosis. In addition, postoperative levels of miR-21 were lower than baseline levels in
both gastric cancer18 and squamous cell carcinoma of the
esophagus.19
In CRC, some studies have identified miR-21 in serum20,21
or plasma22,23 as a useful diagnostic and prognostic biomarker.
However, in other studies, miR-21 expression was not detected
in the peripheral blood of CRC patients, although other miRNAs, including miR-17–3- miR-92,24 miR-29a,25 miR92a,26
and miR-221,27 were identified as circulating tumor biomarkers. These contradictory findings may be due to various
causes, including differences in patient characteristics, internal
controls, and cutoff values. Importantly, all previous studies of
circulating miR-21 in CRC have consistently obtained circulating miRNAs from an area far from the primary tumor, generally
from a peripheral vein (PV) located in the forearm. However,
Editor: Maria Kapritsou.
Received: June 18, 2014; revised and accepted: September 5, 2014.
From the Molecular Oncology and Embryology Laboratory, Human
Anatomy Unit, School of Medicine, University of Barcelona, IDIBAPS,
Barcelona (MM, AN, SS, IM, CM, RT); Department of Medical Oncology
and Surgery, Hospital Municipal de Badalona, Badalona, Spain (FM-R, IM,
RH).
Correspondence: Mariano Monzo, Department of Human Anatomy and
Embryology, School of Medicine, University of Barcelona, Casanovas
143, 08036 Barcelona, Spain (e-mail: [email protected]).
This study was partially supported by a grant from SDCSC (Servei de
Donacio´ del Cos a la Cie`ncia). RT is recipient of an APIF (Ajuts de
Personal Investigador Predoctoral en Formacio´) grant from the Universitat de Barcelona. Neither of these funding bodies had a role in the
design and conduct of the study; collection, management, analysis, and
interpretation of the data; preparation, review, or approval of the manuscript; or decision to submit the manuscript for publication.
The authors have no conflicts of interest to disclose.
Copyright # 2015 Wolters Kluwer Health, Inc. All rights reserved.
This is an open access article distributed under the Creative Commons
Attribution-NonCommercial-NoDerivatives License 4.0, where it is
permissible to download, share and reproduce the work in any medium,
provided it is properly cited. The work cannot be changed in any way or
used commercially.
ISSN: 0025-7974
DOI: 10.1097/MD.0000000000000145
Medicine Volume 94, Number 1, January 2015 www.md-journal.com | 1
before reaching the PV of the forearm, the miRNAs released
by the tumor are diluted and dispersed in other parts of the
body, which may explain the inconsistency between miRNA
expression levels in the tumor itself and those detected in
peripheral blood.
In CRC, venous return occurs through the superior mesenteric vein (MV) if the tumor is located in the right colon, through
the inferior MV if the tumor is located in the left colon, and
through the iliac veins if the tumor is located in the middle or
lower third rectum. Therefore, we can hypothesize that in colon
cancer, blood samples drawn from the MV near the site of the
primary tumor can provide more homogeneous and effective
information than blood drawn from the PV of the forearm. To
test this hypothesis, we have analyzed miR-21 expression in
paired samples of tumor tissue, normal tissue, plasma obtained
by blood drawn from the MV, and plasma obtained by blood
drawn from the PV in 57 surgically resected patients with colon
cancer and correlated our findings with the clinical characteristics and disease-free survival (DFS) of these patients.
METHODS
Eligibility and Patient Evaluation
From August 2009 to August 2013, samples were obtained
from 57 patients with stage I to IV colon cancer who underwent
surgical resection at the Municipal Hospital of Badalona.
Approval for the study was obtained from the institutional
review board of the hospital, and signed informed consent
was obtained from all patients and controls in accordance with
the Declaration of Helsinki.
All 57 patients underwent a complete history and physical
examination including routine hematological and biochemical
analyses, chest radiographs, and computed tomography (CT) of
the thorax and abdomen. Target lesions detected by abdominal
ultrasound were also assessed by CT or magnetic resonance
imaging.
Samples
For all 57 patients, we obtained tumor tissue, paired normal
tissue, MV blood, and PV blood. Normal tissue was obtained
from the area of the colon farthest from the tumor. Both tumor
and normal tissue samples were analyzed and confirmed by a
pathologist and frozen at 808C for further use.
On the day of surgery, 5 mL of blood was drawn from the
PV and stored in heparinized tubes. During surgery, with
vascular ligation before tumor resection, an additional 5 mL
of blood was drawn from either the superior or the inferior MV,
according to the anatomic location of the tumor. Blood samples
from 18 healthy individuals (young male athletes) were
obtained from the blood bank of the Hospital Clinic for use
as controls. All blood samples were centrifuged at 5000g during
5 min, and plasma was centrifuged at 10,000g during 10 minutes
at 48C to eliminate remaining cells. Plasma samples were frozen
at 808C for further use.
RNA Extraction and miRNA Quantification
Total RNA was extracted from fresh tumor and paired
normal tissue and from PV plasma and paired MV plasma
using miRNeasy Mini Kit (Qiagen, Valencia, CA, USA)
according to the manufacturer’s protocol. miRNA detection
was performed using commercial assays (TaqMan MicroRNA
assays, Life Technologies, Grand Island, NY, USA) for
miR-21, in the 7500 Sequence Detection System (Life
Technologies). The appropriate negative controls (nontemplate control) were also run in each reaction. All reactions
were performed in duplicate. Relative quantification was
calculated using the formula 2DDCt. Normalization was performed with miR-191.
Statistical Analyses
Differences between 2 groups were calculated using the
Mann–Whitney U test or the Kruskal–Wallis test as appropriate. miR-21 expression levels were dichotomized according
to the fixed threshold method using the maxstat package of R to
determine the optimal cutoff that best discriminated between
different groups of patients for DFS. Fifty-two patients were
evaluable for DFS; the 5 stage IV patients in whom only the
primary tumor—but not the metastasis—was removed were not
included in the analysis of DFS. DFS was calculated from the
date of surgery to the date of death, relapse, or last follow-up.
The univariate analysis of DFS was performed with the
Kaplan–Meier method and compared using the log-rank test.
All statistical analyses were performed with SPSS 14.0 (SPSS
Inc, Chicago, IL) and R 2.6.0 Software (Vienna, AU). Statistical
significance was set at P 0.05.
RESULTS
miR-21 Expression in Plasma and Tissue
Median miR-21 expression (fold change) was 0.2874 in
MV plasma, 0.1805 in PV plasma, and 0.0201 in plasma from
healthy controls. Median miR-21 expression in tumor and
normal tissue was 0.3907 and 0.1733, respectively. miR-21
expression was significantly higher in MV plasma compared
with PV plasma (P ¼ 0.005) (Figure 1A). miR-21 expression
was also significantly higher in tumor than in normal tissue
(P < 0.001) (Figure 1A).
Patient Characteristics and miR-21 Expression
Table 1 shows the clinicopathologic characteristics of the
57 patients included in the study. Median age was 70 years.
Thirty-four patients were males and 23 females. At diagnosis,
35 patients were having stage I to II of cancer, 15 stage III, and
7 stage IV. All patients underwent surgical resection; in 2 of
the 7 stage IV patients, both the primary tumor and the metastasis were removed. Twenty-eight patients received adjuvant
therapy with fluoropyrimidines.
MV miR-21 levels correlated positively with tumor size
(P ¼ 0.04) and showed a trend toward correlation with carcinoma embryonic antigen levels (P ¼ 0.08). Among patients
with stage I to II disease, miR-21 levels were higher in MV
plasma than in PV plasma (P¼ 0.001), whereas no significant
differences were observed among patients with stage III to IV
disease (Figure 1B). A highly significant association was
observed between MV miR-21 levels and the anatomic location
of the tumor (P¼ 0.003), whereas the association with PV
miR-21 levels was less significant (P¼ 0.01) (Table 1,
Figure 1C).
miR-21 Expression and Metastases
Of the 13 patients who developed metastases during the
course of the disease, 8 had metastases in areas drained by the
MV of the colon: 4 peritoneal metastases, 2 liver metastases,
and 2 anastomotic. Of these 8 patients, 7 had higher miR-21
expression levels in MV plasma than in PV plasma (P ¼ 0.02)
(Table 2, Figure 1D).
Monzo et al Medicine Volume 94, Number 1, January 2015
2 | www.md-journal.com Copyright # 2015 Wolters Kluwer Health, Inc. All rights reserved.
miR-21 Expression and DFS
Fifty-two patients were evaluable for DFS. Median DFS
was not reached among the 8 patients with low levels of miR-21
in MV plasma, compared with 32.2 months (95% confidence
interval [CI] 27.9–37.5) for the 44 patients with high levels of
miR-21 (P ¼ 0.05; Figure 2A). Median DFS was 38.1 months
(95% CI 32.1–44.2) for the 24 patients with low levels of PV
miR-21 and 30.1 months (95% CI 23.5–36.7) for the 28 patients
with high levels (P ¼ 0.07; Figure 2B).
To further evaluate whether the levels of miR-21 in both
MV and PV plasma could have a combinatory effect on DFS,
we classified patients in 3 groups: those with high miR-21 levels
in both MV and PV plasma, those with low levels in both MV
and PV plasma, and those with other combinations of miR-21
levels. Median DFS for the 8 patients with low MV and PV
miR-21 was not reached, compared with 29.1 months (95% CI
22.2–35.9) for the 26 patients with high MV and PV miR-21
and 31.2 months (95% CI 24.9–37.5) for the remaining 18
patients (P ¼ 0.03; Figure 2C). Based on these findings, we then
compared DFS in the 26 patients with high miR-21 expression
in both MV and PV plasma with all other patients. Median DFS
was 29.1 months (95% CI 22.2–35.9) for these 26 patients
versus 40 months (95% CI 34.8–45.2) for the remaining
patients (P ¼ 0.01; Figure 2D).
DISCUSSION
The main cause of death in patients with solid tumors is the
development of metastases. The analysis of plasma and serum
from cancer patients can help identify reliable biomarkers to
predict relapse and metastasis in these patients. Recent findings
suggest that the primary tumor can release proteins and miRNAs into the blood, which will organize a microenvironment
known as a premetastatic niche in an area far from the primary
tumor. This premetastatic niche will then provide support for
the nesting and growth of metastatic tumor cells.28,29 Logically,
the veins that are nearest the primary tumor would be most
likely to contain the greatest concentration of these proteins
and miRNAs.
The present study shows that miR-21 expression levels are
significantly higher in MV plasma than in PV plasma. This
finding suggests that the primary tumor in colon cancer releases
high concentrations of miR-21 in the MV, but that these
concentrations are later diluted in the circulatory system. This
would explain why in other studies, only approximately 30% of
–1
–1.0
–0.5
0.0
0.5
1.0
1.5
2.0
0
1
2
3
Plasma miR-21 expression
Plasma miR-21 expression
C
PV
MV
N
T
I/II PV
I/II MV
III PV
III MV
IV PV
IV MV
P = 0.009
P = 0.001
P = 0.44
P < 0.001 P = 0.90
P = 0.005
P = 0.06
miR-21 miR-21
–1.0
–0.5
0.0
0.5
1.0
1.5
2.0
Plasma miR-21 expression
AC-PV
AC-MV
TC-PV
TC-MV
DC-PV
DC-MV
SC-PV
SC-MV
PV
MV
P = 0.003 P = 0.01
MV PV
–0.5
0.0
0.5
1.0
1.5
2.0
Plasma miR-21 expression
P = 0.02
miR-21 miR-21
A B
D D
FIGURE 1. miR-21 expression levels (fold change) in plasma and tumor. (A) In plasma from healthy C and from the PV and MV of colon
cancer patients and in matched T and N tissue samples from the same patients. (B) In plasma from the PV and MV of colon cancer patients
classified by disease stage. (C) In plasma from the PV and MV of colon cancer patients classified by the anatomic location of the tumor. (D)
In plasma from the PV and MV in 8 patients who developed locoregional metastases. AC ¼ ascending colon, C ¼ controls, DC¼ descenddescending colon, MV ¼ mesenteric vein, N ¼ normal, PV ¼ peripheral vein, SC ¼ sigmoid colon, T ¼ tumor; TC ¼ transverse colon.
Medicine Volume 94, Number 1, January 2015 MIR-21 Expression in Plasma From Mesenteric Versus Peripheral Veins
Copyright # 2015 Wolters Kluwer Health, Inc. All rights reserved. www.md-journal.com | 3
TABLE 1. Patient Characteristics
Characteristics N (%), N ¼ 57
P value for Association With miR-21 Expression
Plasma From Mesenteric Vein Plasma From Peripheral Vein
Sex 0.5 0.05
Male 34 (60)
Female 23 (40)
Median age, y 70 0.5 0.2
CEA levels
5 38 (67) 0.08 0.4
>5 19 (33)
C 19.9 levels
37 50 (88) 0.1 0.09
>37 7 (12)
Tumor location
Ascending colon 17 (30)
Transverse colon 8 (14) 0.003 0.02
Descending colon 7 (12)
Sigmoid colon 25 (44)
Tumor size, cm
>5 14 (24) 0.05 0.2
5 42 (74)
unknown 1 (2)
Histological type
Well differentiated 50 (88) 0.5 0.3
Poorly differentiated 7 (12)
Preexistent polyp
Absent 44 (77) 0.5 0.2
Present 13 (23)
Perilymphatic invasion
Absent 52 (91)
Present 4 (7) 0.1 0.1
unknown 1 (2)
TNM stage
I–II 35 (62) 0.8 0.6
III 15 (26)
IV 7 (12)
Adjuvant treatment
Fluoropyrimidines 28 (50) 0.8 0.8
Palliative 5 (8)
None 24 (42)
CEA ¼ carcinoma embryonic antigen, TNM ¼ tumor, nodule, metastasis.
TABLE 2. Characteristics of 8 Patients Who Developed Locoregional Metastases
Patient
miR-21 Expression in
PV Plasma
miR-21 Expression in
MV Plasma
Disease
Stage
Tumor
location
Type of
Metastasis
1 0.180685 0.027026 IIIC Sigmoid colon Anastomotic leakage
2 0.186873 0.036793 IIIB Sigmoid colon Liver
3 0.073384 0.108137 IIIC Sigmoid colon Peritoneal
4 0.112819 0.149980 IIA Ascending colon Anastomotic leakage
5 0.117168 0.462750 IIB Transverse colon Peritoneal
6 0.197543 0.511818 IIIC Transverse colon Liver
7 0.180384 0.759566 IIIC Transverse colon Peritoneal
8 0.625005 1.499196 IIB Transverse colon Peritoneal
MV ¼mesenteric vein, PV¼ peripheral vein.
Monzo et al Medicine Volume 94, Number 1, January 2015
4 | www.md-journal.com Copyright # 2015 Wolters Kluwer Health, Inc. All rights reserved.
miRNAs detected in PV plasma or serum mirrored those found
in the primary tumor.30
Furthermore, miR-21 levels in MV plasma showed a trend
toward correlation with CEA5 levels. In fact, previous studies
have shown that in patients with CRC, CEA5 levels are higher
in the MV than in the PV.31,32 A previous study with a large
cohort of patients20 found a correlation between tumor size and
miR-21 expression in PV plasma; our findings are similar, but
we observed this correlation only in MV plasma. We also found
an association between the anatomic location of the tumor and
miR-21 expression levels in both MV and PV plasma, although
miR-21 expression was higher in MV than in PV plasma. In
addition, recent studies in CRC patients have observed circulating tumor cells in blood obtained from MVs and from hepatic
veins.33 Taken together with these previous results, our findings
indicate that veins near the tumor are the best source of
biomarkers.
Similar to our findings, previous studies found no association between miR-21 expression and tumor stage, which may
have been due to the use of different internal controls in these
studies.21 However, among patients with stage I to II disease, we
did observe a significant overexpression of miR-21 in MV
plasma compared with PV plasma, which would confirm
previous reports20,21 that miR-21 is overexpressed in the early
stages of tumor development.
At 4 years of follow-up, patients with high miR-21 levels
in MV plasma had a significantly worse prognosis than those
with low levels; in contrast, no differences were observed
according to miR-21 levels in PV plasma, which suggests that
miR-21 is more easily detected in MV than in PV plasma.
Interestingly, however, patients with high miR-21 expression in
both MV and PV plasma had a significantly shorter DFS than
those with low levels in either MV or PV plasma. We can
speculate that whether initial MV and PV levels are high; PV
levels that remain high throughout follow-up may well be used
to identify patients with a high risk of relapse.
Interestingly, the 8 patients who relapsed and developed
metastases in areas drained by the MV of the colon—the liver
and intestines—had higher levels of MV miR-21 than PV miR21. In contrast, metastases in areas not drained by the MV of the
colon—such as the lung—were not associated with miR-21
expression levels. In fact, miR-21 has been associated with
hepatocellular tumors in several studies, which have shown that
miR-21 targets several genes—such as MAP2K3,34 PDCD4,35
1.0
0.8
0.6
0.4
0.2
0.0
0 10 20 30 40
Probability
DFS (months)
miR-21 levels in MV
Low P = 0.05 High
Number at risk
Low
High
8
44
7
35
5
22
4
11
3
3
1.0
0.8
0.6
0.4
0.2
0.0
0 10 20 30 40
Probability
DFS (months)
miR-21 levels in PV
Low P = 0.07 High
Number at risk
Low
High
24
28
19
23
17
10
8
7
3
3
1.0
0.8
0.6
0.4
0.2
0.0
0 10 20 30 40
Probability
DFS (months)
PV & MV miR-21 levels
P = 0.03
Number at risk
Both low
Other comb
Both high
8 7 5 4
4
7
3
3
18 14 13
9
0
1.0
0.8
0.6
0.4
0.2
0.0
0 10 20 30 40
Probability
DFS (months)
PV & MV miR-21 levels
P = 0.01
Number at risk
Other comb
Both high
Other comb
Both high
Other comb 26 21
21 8 3
26 21 26 3 18
9 7
A B
C D Both high
Both low
FIGURE 2. DFS according to miR-21 levels (fold change). (A) DFS according to miR-21 expression in plasma from theMV. (B) DFS
according to miR-21 expression in plasma from thePV. (C) DFS in patients with high miR-21 expression in both MV and PV plasma
compared with those with low expression in both the MV and the PV and those with other combinations. (D) DFS in patients with high
miR-21 expression in both MV and PV plasma compared with all other patients. DFS ¼ disease-free survival, MV¼ mesenteric vein,
PV ¼ peripheral vein.
Medicine Volume 94, Number 1, January 2015 MIR-21 Expression in Plasma From Mesenteric Versus Peripheral Veins
Copyright # 2015 Wolters Kluwer Health, Inc. All rights reserved. www.md-journal.com | 5
and PTEN36—leading to the development of hepatocellular
carcinomas. In a large cohort of patients with hepatocellular
carcinomas, array analysis identified a panel of 7 miRNAs
(miR-122, miR-192, miR-21, miR-223, miR-26a, miR-27a, and
miR-801), wherein miR-21 expression levels were able to
distinguish patients from healthy controls.37
It has recently been reported that miRNAs released by the
primary tumor can play a key role in preparing the premetastatic
niche.38,39 miR-21 and miR-29a are released by tumor cells
through exosomes, which bind to the Toll-like receptors of
immune cells. The activation of the Toll-like receptors leads to
the release of tumor necrosis factor-a and interleukin-6, which
in turn prepare the extracellular environment for tumor growth
and dissemination.40 Our findings suggest that the miRNAs
released in the MV may be retained in areas near the primary
tumor (liver and intestines), where they could work to build the
premetastatic niche. To validate these findings, however,
further research on other miRNAs associated with colon cancer
should compare expression levels in MV and PV plasma and
examine the potential association between MV plasma expression and locoregional metastases. The findings of the present
study will hopefully act as a springboard to strengthen collaboration among surgeons, medical oncologists, and molecular
biologists with the aim of improving outcome in colon
cancer patients.
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