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304 Current Genomics, 2015, 16, 304-311
miR-15b and miR-21 as Circulating Biomarkers for Diagnosis of Glioma
Pietro Ivo D’Urso1,#, Oscar Fernando D’Urso2,#, Cosimo Damiano Gianfreda3, Valeria Mezzolla4,*,
Carlo Storelli2 and Santo Marsigliante2
1Department of Neurosurgery, King’s College Hospital, London, UK; 2Department of Biological and
Environmental Sciences and Technologies (DISTEBA), Salento University, Lecce 73100, Italy;
3Neurosurgery Operative Unit, “V. Fazzi” Hospital 73100 Lecce, Italy; 4Institute of Sciences of Food
Productions, National Research Council, ISPA-CNR, Via Lecce-Monteroni, 73100 Lecce, Italy
Abstract: Malignant gliomas are lethal primary intracranial tumors. To date, little information on the
role of deregulated genes in gliomas have been identified. As the involvement of miRNAs in the carcino-
genesis is well known, we carried out a pilot study to identify, as potential biomarkers, differentially ex-
pressed microRNAs in blood samples of patients affected by glioma. We studied the miRNAs’ expres-
sion, by means of microarray and Real-Time PCR, in 30 blood samples from glioma patients and in 82
blood samples of patients suffering from: (a) various neurological disorders (n=30), (b) primary B-lymphoma of the Central
Nervous System (PCNSL, n=36) and (c) secondary brain metastases (n=16). By quantitative real time reverse-transcriptase
polymerase chain reaction (qRT-PCR), we identified significantly increased levels of two candidate biomarkers, miR-15b and
miR-21, in blood of patients affected by gliomas. ROC analysis of miR-15b biomarker levels allowed to differentiate patients
with tumour from patients without glioma. Furthermore, combined expression analyses of miR15b and miR-21 distinguished
between patients with and without glioma (90% sensitivity and 100% specificity). In addition, a decrement in the expression
levels of miR-16 characterized glioblastomas compared to low grade and anaplastic gliomas. In conclusion, this pilot study
suggest that it’s possible to identify the disease state by meaning miR-15b and miR-21 markers in blood, while miR-16 can
be used to distinguish glioblastoma from other grade gliomas. They can potentially be used as biomarkers for non-invasive
diagnosis of gliomas; further studies are mandatory to confirm our preliminary findings.
Keywords: Biomarkers, Blood, Diagnosis, Glioma, Microarrays, miRNAs.
INTRODUCTION
Glioma is the most common primary Central Nervous
System (CNS) tumour, including about 50% of primary
brain cancers in adults. They origin ate from the neuroepithe-
lial glial cells and th e main malignancy of these tumors is
linked to their diffusely infiltrative growth pattern, strong
angiogenesis and an intrinsic resistance to chemotherapy and
radiotherapy. These aspects make gliomas extremely diffi-
cult to treat. Although new therapeutic care and supportive
strategies, the median survival of glioblastoma multiforme
has not significantly changed over the past decade, being
remaining limited to 12–15 months [1]. Even if with the cur-
rent neuroradiological imaging a high degree of detection
due to suspected presence can be reached, the gold standard
for the diagnosis remains the histology. miRNAs are small
noncoding RNA that can contribute to tumour pathogenesis
and progression, as suggested by their different levels of
expression in normal tissues and cancers [2-4]. A large por-
tion of overexpressed miRNAs was identified in many hu-
man solid tumours, such as colon, breast, prostate, lung,
stomach and pancreatic cancers, but also in many circulating
*Address correspondence to this author at the Institute of Sciences of Food
Productions, National Research Council, ISPA-CNR, Via Lecce-Monteroni,
73100 Lecce, Italy; Tel: 0832.422609; Fax: 0832.422620;
E-mail: valeria.mezzolla@ispa.cnr.it
#These authors contributed equally.
body fluids. In blood, circulating miRNAs are abundant,
very stable and a fraction of circulating miRNAs, due to en-
capsulation in an envelop made by proteins and/or lipids, is
resistant to plasma RNAses. Furthermore, miRNAs detected
in circulating body fluids are relatively stable, highly acces-
sible, not invasive and these are important prerequisites for
reliable clinical biomarkers [5, 6]. Circulating miRNAs in
the blood of tumour patients can be released during tissue
injury or by active delivery and could play the same impor-
tant role as miRNAs in tissues. However, the mechanisms of
delivery and biological function of extracellular miRNAs
remain unknown [7]. The microRNA content of cancer cell-
derived exosomes is correlated to the microRNA level in the
primary tumor in ovarian and lung cancer. miRNAs have
been identified in exosomes and microvesicles derived from
several tissues [6], such as human and mouse mast cells [8],
glioblastoma tumors [9], plasma [10], saliva [11] and urine
[12]. For example, miR-150 biomarker, involved in the ex-
pression of c-Myb gene, is secreted in microvesicles from
human blood cells or cultured THP-1 cells and taken up by
HMEC-1 microvascular endothelial cells [13]. It has been
demonstrated with several techniques that different tumour
types have distinct intracellular miRNA profiles [14-18] and
specific expression profiles can distinguish different clinical
pathways, as for primary from secondary glioblastoma types
[19]. In some cases, the detection of circulating miRNAs has
been linked to occasional lysis of blood cells during sample
1875-5488/15 $58.00+.00 ©2015 Bentham Science Publishers
Identification of microRNAs in the Blood for the Diagnosis of Glioma Current Genomics, 2015, Vol. 16, No. 5 305
preparation [2]. To date, literature data report few circulating
miRNAs useful for the detection and risk stratification of
gliomas, as serum miR-128, whose expression decreased in
glioma preoperative serum compared with normal controls
and meningioma serum samples; furthermore, low miR-128
levels in serum and tissue were significantly correlated with
high pathological grade [20]. In order to early detect sys-
temic cancer, to predict tumor progression or to check the
response to therapy, it was evaluated using of cancer-derived
circulating DNA [21-24], as miRNAs in cerebrospinal fluid
samples from patients with glioma [25]. The involvement of
miRNAs in the carcinogenesis is well known and the possi-
bility to detect their levels in blood samples is appealing for
early diagnosis and for monitoring patients. For that reason,
we carried out a pilot study with the aim of identify in blood
samples of patients affected by glioma differentially ex-
pressed microRNAs as potential novel glioma biomarkers.
PATIENTS AND METHODS
Serum Samples and Clinical Information
In this study, a total of 112 plasma samples were ana-
lyzed, 30 plasma samples of patients with glioma, 30 from
patients with various neurological pathologies, 36 from pa-
tients with PCNSL and 16 from individuals with brain me-
tastases or leptomeningeal secondary involvement originated
from various tumours. RNA was extracted from sera pre-
pared by centrifugation starting from 10 ml of whole blood,
obtained at the time of surgical treatment. All whole blood
and serum samples were used with the consent of the pa-
tients.
RNA Extraction, Reverse-Transcription and qRT-PCR
Total RNA was extracted using TRIZOLTM reagent (Invi-
trogen) and microRNA was isolated using a PureLink™
miRNA Isolation Kit (Invitrogen), following manufacturer’s
instructions. The RNA concentration was determined by
NanoDrop ND-3300 spectrophotometer and TaqMan
miRNA assays (Applied Biosystems) quantified miRNA
levels [26]. Briefly, 10 L cointaining total RNA was used in
reverse-transcription reactions (16°C for 30 min, 42°C for 30
min, 85°C for 5 min, followed by 4°C). Real-time PCR was
carried out using a 7500 Real-Time PCR System, with fol-
lowing cycling conditions: 95°C for 10 min, 40 cycles of 15
s at 95°C and 60 s at 60°C. The 7500 SDS system software
(version 1.2.3; Applied Biosystems) was used to transform
fluorescent data of each sample, run in duplicate, into cycle
threshold (Ct) measurements. Mean Ct values and standard
deviations were calculated for total miRNAs and the amount
of target miRNA was normalized respect to the amount of
miR-24, selected from several control miRNAs, as follow-
ing: Ct = CtmiR - CtmiR- 24. Relative Expression Lev-
els (REL) were reported as 2- Ct.
Microarray Fabrication, miRNA Extraction, Labelling
and Hybridisation
The epoxy microscope glass slides (Sigma), activated
with glycidyloxipropyltrimethoxysilane (GOPTS), immobi-
lise amino-modified oligonucleotide DNA. A 340 custom
oligo-array was built with DNA probe complementary to a
corresponding full length of 340 mature miRNAs and com-
prised positive and negative control probes. More informa-
tions about microarray protocols can be found at the Gene
Expression Omnibus (GEO) at the National Centre for Bio-
technology Information (NCBI). Total RNA was extracted
from blood/sera using TRIZOLTM reagent (Invitrogen) and
miRNA was isolated using a PureLink™ miRNA Isolation
Kit (Invitrogen). microRNAs were tagged and hybridized by
NCode™ miRNA Labeling System (Invitrogen), according
to manufacturer’s instructions, and then placed on the mi-
croarray slides; each miRNA sample was tagged with Alexa
Fluor® 5, while the universal reference RNA was labelled
using Alexa Fluor® 3. Each array was subsequently washed
and analyzed using an Affymetrix 428 array Scanner.
Statistics
The statistical analysis was performed using SPSS (ver-
sion 19; SPSS) and GraphPad Prism (version 5.0, GraphPad
Software). The 2-tailed Mann-Whitney U tests and Kruskal-
Wallis tests with Dunn’s multiple comparison were applied
for groupwise comparisons of clinical and biological data’s
distributions. Results were statistically significative for
P<0.05.
RESULTS
Patients
In this study, we analyzed 112 plasma samples derived
from 53 male and 59 female patients; the age was 18–75
years (mean 51 years). In all patients with glial tumour, the
histopathologic diagnosis was established by brain biopsy.
There were 6 patients with anaplastic astrocytoma (WHO
grade III), 8 patients with low-grade astrocytoma (World
Health Organization [WHO] grade II) and 16 patients with
glioblastoma (WHO grade IV). Primary treating physicians
by means of a questionnaire gave preliminary informations.
The median interval between cancer and serum sampling
was 1 month for both astrocytic and oligodendroglial can-
cers, but the wide range considers the presence of patients
with long follow-up times. In 4 patients in the astrocytic
group, blood samples were obtained more than one year after
surgery and in 5 patients with oligodendroglial cancers, more
than two years after tissue sampling. All serum samples were
achieved after surgery and prior to radiotherapy in 60% of
the patients. Eighteen of 30 serum samples derived from
patients affected by glioma were analyzed by microarray,
while all the samples were analyzed by qRT-PCR. Similarly,
18 of the 30 serum samples derived from patients affected by
various neurological disorders (control group) were studied
by microarray, while all the samples were analyzed by
means of qRT-PCR.
The microarray gene expression profile was performed
comparing the serum derived from 18 patients affected by
glioma against the serum of 18 patients with various neuro-
logical disorders in order to find differentially expressed
microRNA.
In order to validate the microarray expression profile data
we have studied the expression levels of the four differen-
tially expressed microRNAs in a larger cohort of patients
composed by 30 patients affected by glioma (18 of which
306 Current Genomics, 2015, Vol. 16, No. 5 D’Urso et al.
were already analyzed by microarray), 30 control patients
affected by vairous neurological disorders (18 of which were
already analyzed by microarray), 30 patients affected by
PCNSL and 16 patients affected by metastases.
Differential Expression of miRNAs in Glioma - Gene Ex-
pression Profiling
The expression profile of 340 mammalian microRNAs
was monitored by DNA microarrays using plasma samples
from 18 patients with glioma and plasma from 18 patients
suffering from various neurological disorders (“control”
group). To avoid low expression genes, only microRNAs
with a Signal value greater than 100 were selected and miR-
NAs with a signal to noise ratio greater than 2.5 were chosen
for further studies. Afterwards, microRNAs showing differ-
ent level of expression between glioma and “control” serum
were independently filtered by a parametric Student's t test,
assuming equal variances, p-value cut-off of 0.01 and multi-
ple testing corrections (Benjamini and Hochberg False Dis-
covery Rate). Using these restrictions, we selected four mi-
croRNAs which clearly present a differential expression be-
tween glioma and control group: miR-16, miR-15b miR-21
and miR-155. Using Smooth correlation coefficients, all
samples were analized by average linkage clustering, on the
basis of similarity of expression patterns over the detected
genes. This yielded two major clusters, one performing the
glioma group and the other the control group, as expected
(Fig. 1).
Diagnostic Analysis of miR-15b and miR-21 Levels in
Plasma by qRT-PCR
The four microarray-selected miRNAs were quantified
by TaqMan qRT-PCR in a set of serum samples derived
from 30 patients affected by glioma (18 of which are the
same serum samples used in for microarray gene expression
profile) and from 30 “control” patients affected by miscella-
neous neurologic disorders (18 of which are the same serum
samples used in for microarray gene expression profile).
As expected miR-15b and miR-21 were significantly
increased (early Ct values) in serum samples derived from
patients affected by glioma. Conversely, miR-16 showed
significantly decreased levels in patients with glioma; low
levels of miR-24 were measured in all samples (Table 1). As
other classes of small RNAs, such as the snoRNA RNU6B,
are not useful for the normalization as they are unstable in
serum, it’s important to find small housekeeping microR-
NAs. In this study, miR-24 was proposed for normalisation
and showed to be applicable to the analysis of these types of
tumors. MiRNA expression levels in individual plasma
specimens were therefore reported as RELs. A remarkably
increased mean REL miR-15b and a decreased expression of
miR-16 was demonstrated in plasma samples from patients
with glioma (Fig. 2).
By ROC curves of miR-15b, we observed evident separa-
tions between the glioma patients group and those without
tumour, with an area under the curve (AUC) of 1 (for a re-
view on ROC and AUC plots see Zweig et al. 1993) [27].
Corresponding to this analysis, a cut off plasma REL with
the highest accuracy for miR-15b was determined to be 4
with 100% sensitivity and specificity (Fig. 2). By combined
REL of miR-15b with REL of miR-21 and by a diagnostic
tree, we increased the specificity of discrimination of glioma
from other diseases (Fig. 3). For miR-21, a REL of 4 was
used to distinguish glioma from PCNSL and brain metasta-
ses while a REL of 1,74 was selected to distinguish glioma
from “control” samples.
Fig. (1). Cluster analysis. Tree generated by a cluster analysis performed on 36 blood samples. MiRNAs expression profile shows a clear
separation of 18 patients with glioma from 18 patients suffering various neurological disorders.
Identification of microRNAs in the Blood for the Diagnosis of Glioma Current Genomics, 2015, Vol. 16, No. 5 307
Table 1. miRNA expression in blood samples from patients with glioma, compared with control patients.
Patients with GliomaaControl Patientsb p valuee
CtcSDd Ctc SDd
miR-15b 31,79378 0,960109 34,7718 0,84934 <0,01
miR-16 28,58248 1,168615 27,55171 0,550783 0,02
miR-21 31,30626 0,989405 32,4941 0,550783 <0,01
miR-155 34,03455 0,5547 34,00748 0,554491 0,03
miR-24 29,46907 0,280595 29,49652 0,290466 0,01
a n=30
b Patients with miscellaneous neurological disorder
cData are means of CT values
dStandard deviation
eThe value is for comparison of miRNA expression among
patients with glioma and control patients and was calculated using
the Mann-Whitney test
Fig. (2). Relative expression levels of miR-15b, miR-16 and miR-21 in blood samples from patients with glioma, PCNSL and control patients.
Scatter plots of expression levels of miR-15b (2.a), miR-21 (2.b) and miR-16 (2.c) in blood samples from patients with glioma, miscellaneous
CNS disorders, PCNSL and brain or leptomeningeal metastases. Relative Expression Levels (REL) was normalized to expression levels of
biomarker miR24 (y-axis); median REL values were represent by black horizontal lines. (2.d) The area under the curve (AUC) of 1 were
yielded by blood relative expression of miR-15b as a single biomarker.
308 Current Genomics, 2015, Vol. 16, No. 5 D’Urso et al.
Fig. (3). miRNA diagnostic tree - REL values lower than 4 for
miR-21 selected a first subgroup made of 30 gliomas together with
30 control and 2 PCNSL patients. Internal to this group, using an-
other REL range for miR-21 (values between 1.74 and 4) a group
made of all gliomas together with 2 PCNSL patients is selected. A
further classification is shown using REL values for miR-15b
higher than 4, in order to finally select the 30 glioma only.
Between the three miRNAs iden tified miR-16 only was
able to discriminate between the different grades of gliomas,
as its expression in the plasma were decreased significantly
in glioblastoma (WHO IV) (Fig. 4). By ROC curves of miR-
16, an evident separation was observed between glioblas-
toma (WHO IV) group and those of other grades (WHO II
and III), with an AUC of 0.98. In this analysis, a cut off
plasma REL with highest accuracy for miR-16 was 0.33 with
0.98% sensitivity and 98% specificity (Fig. 4). The only
false-negative results were observed for two patients with
anaplastic astrocytoma diagnosis (WHO grade III).
DISCUSSION
In the present study, we demonstrated that in patients
affected by glioma an altered extracellular produc-
tion/excretion of miR-15b, miR-16, miR-21 and miR-155
can be detected in peripheral blood samples, providing evi-
dence that microRNAs circulating in plasma may be used as
biomarkers for the detection and grading of gliomas. These 4
deregulated miRNAs were quantified by qRT-PCR. In
plasma samples collected from subjects with glioma, miR-
15b levels were significantly increased compared with pa-
tients affected by miscellaneous neurologic disorders,
PCNSL or brain metastases and AUC had value 1 in ROC
analyses; these results are in agreement with those reported
by several other authors, who reported high miR-15b expres-
sion levels in the cerebrospinal fluid (CSF) derived from
patients with glioma and in glioma tissues [25, 28, 29]. MiR-
15b, involved in tumour carcinogenesis by regulating cell
cycle progression, has a significant diagnostic value for
glioma. Interestingly the biomarker miR-15b, inducing cell
cycle arrest in G1 phase by targeting Cyclin E1 (CCNE1)
and regulating the cell cycle by G1 to S phase transition, may
function as a tumor suppressor, as suggested by Xia et al.
[28]. By microRNA microarray, miRNA expression levels
compared between normal and glioma tissues in Chinese
patients were significantly deregulated in glioma samples, as
observed for miR-15b, -34a, -146b and -200a; miR-15b was
down-regulated also in chronic lymphocytic leukemia and in
gastric tumour, modulating multidrug resistance by targeting
BCL2 [29, 30].
Fig. (4). Relative expression levels of miR-16 in blood samples
from patients with glioma WHO II, glioma WHO III, glioma WHO
IV, control patients, patients with PCNSL and patients with metas-
tases. Scatter plots of expression levels of miR16 in blood samples
collected from patients with various grade glioma, miscellaneous
CNS disorders, PCNSL and brain or leptomeningeal metastases.
Relative Expression Levels (REL) was normalized to the expres-
sion levels of biomarker miR24 (y-axis); median REL values were
represent by black horizontal lines.
To increase the discriminatory diagnostic value, we also
combined miR-15b and miR-21 expression analyses. Thus,
combined analysis of these biomarkers demonstrated that
miRNA blood levels accurately distinguished patients with
glioma, PCNSL and brain metastases or leptomeningeal car-
cinoma. For miR-15b, a cut off plasma REL with the highest
accuracy was 4, instead for miR-21 a REL of 4 was used to
distinguish glioma from PCNSL and brain metastases while
a REL of 1.74 was selected to distinguish glioma from “con-
trol” samples. More precisely, the REL of these two miR-
NAs have proved to be of great importance since they have
allowed to discriminate between patients with glioma and all
the other (specifically, REL values lower than 4 for miR-21
selected all 30 gliomas together with 30 control and 2
PCNSL). Internal to this group, has been possible to use an-
other REL values for miR-21 (values between 1.74 and 4) to
select again a group made of all gliomas together with 2
PCNSL patients. An additional classification has been done
using REL values for miR-15b higher than 4, to finally select
the 30 glioma only (Fig. 3). MiR-15b, the most abundant
microRNA in blood samples, showed an 8-fold higher ex-
pression levels in patients with glioma. MiR-21, which was
also overexpressed in the cerebrospinal fluid samples from
patients with glioma, is one of the most consistently ex-
pressed microRNA in cancer originating from other tissues.
It functions as an oncogene in glioma, preventing apoptosis.
Identification of microRNAs in the Blood for the Diagnosis of Glioma Current Genomics, 2015, Vol. 16, No. 5 309
Several pathways are predicted targets for miR-21, such as
the tumor suppressor gene p53 pathway, the transforming
growth factor and the mitochondrial apoptosis pathways.
Furthermore, studies have shown that tropomyosin 1 could
be down-regulated by miR-21. Other predicted targets in-
clude programmed cell death gene 4 (PDCD4), the phospha-
tase and tensin homolog tumor suppressor and reversion-
inducing cysteine-rich precursor with Kazal motifs [31, 34].
Noteworthy, glioblastomas expressed significantly higher
levels of miR-15b and miR-21 than anaplastic astrocytomas,
while there was no significant association between expres-
sion levels of these markers and survival among patients with
glioma [29]. Consistently with Baraniskin [25], we observed
no association between miR-15b and miR-21 expression
levels and the survival among patients with tumour or the
glioma grading. On the other hand, a correlation was found
between glioma grading and the expression levels of miR-
16. A decreased expression levels of biomarker miR-16
characterize the glioblastoma (WHO IV) in respect to lo w
grade and anaplastic glioma. These data are in accordance
with that of Baraniskin et al., who demonstrated that mi-
croRNAs circulating in the cerebrospinal fluid (CSF) can be
used as biomarkers for glioma detection [26]. MiR-16, that
forms a cluster with miR-15a at chromosome position
13q14, functions by targeting many oncogenes, as BCL2,
MCL1, CCND1, WNT3A and these miRNAs are down-
regulated in chronic lymphocytic lymphoma (CLL), prostate
carcinoma and pituitary adenomas [32, 33].
Can cer-secreted microRNAs are important intermediaries
in cancer-host crosstalk and they are investigated for their
potential use as prognostic and predictive biomarkers. miR-
21 and miR15b may represent an therapeutic target to con-
trol multiple steps of pathogenesis; for example, the inhibi-
tion of miR-21 in glioblastoma cells increased apoptosis,
while in cultured hepatocellular carcinoma cells significantly
led to decrease of tumor cell proliferation, migration and
invasion [31]. After transfection with anti-miR-21, reduced
cellular invasion were observed in a colorectal, breast and
prostate cancers cells; moreover, when anti-miR-21 was
transfected in metastatic breast cancer cells, the number of
lung metastases was significantly decreased [31]. The de-
crease of the expression levels of miR-15b and miR-200b
underlines the mechanisms of epithelial-mesenchymal transi-
tion induced by chemotherapy and it might serve as thera-
peutic targets to reverse chemotherapy resistance in tongue
tumours. Low levels of miR-200b and miR-15b were ex-
pressed in patients with lymph node metastasis or che-
motherapeutic resistance, indicating that tumor progression
was associated with miR-200b and miR-15b downregulated
levels [35]. Also other microRNAs are investigated for their
potential prognostic use. In the breast tumour, miR-105
characteristically was expressed and secreted by metastatic
breast cancer cells, as it was a potent regulator of migration
targeting the tight junction protein ZO-1. The overexpression
of miR-105 in non-metastatic cancer cells induced metastasis
and vascular permeability in distant organs, whereas these
effects were alleviated in highly metastatic tumors when
miR-105 was inhibited [36]. miR-139-5p is identified as a
prognostic marker for the aggressive forms of breast tumour;
bioinformatic analysis reveales a predicted disruption to the
TGF, Wnt, Rho and MAPK/PI3K signaling cascades, im-
plying a potential regulated role in the cellular invasion and
migration [37]. Metastatic endothelial recruitment, angio-
genesis and colonization were suppressed by miR-126,
through coordinate targeting of pro-angiogenic genes. Ex-
tracellular (exosome-like) vesicles are involved in cell-to-
cell communication; breast cancer cells released membrane
vesicles into extracellular medium containing potential on-
cogenic molecules, such as proteins and miRNAs, that could
transmit signals to non-malignant cells and implicate tumor
progression and metastasis [38].
MiRNA take part in a wide range of biological processes,
as immune response, cellular proliferation and apoptosis.
Several works evaluate host-pathogen interaction, focused
on viral and bacterial infections. Virus express many mi-
croRNAs in infected cells to modulate the levels of both vi-
ral and cellular mRNAs, thereby influencing viral replication
and pathogenesis; less is known about the bacterial infec-
tions and the effect of bacterial pathogens on host miRNA
expression. In the plant infection, for example, up-regulation
of miR-393a induced by Pseudomonas syringae in Arabi-
dopsis thaliana contributes to the resistance of the plant
against the bacterial pathogen; as bacterial defense mecha-
nism, conversely, P. syringae secretes in to the host cell ef-
fector proteins that suppress transcription or activity of host
microRNAs [39].
In the mammalian infection, the analysis of circulating
miRNAs in the serum of individuals infected with Mycobac-
terium tuberculosis identified 59 up-regulated miRNAs and
33 down-regulated. It has been shown that T-cells can trans-
fer miRNAs to antigen-presenting cells via exosomes, sug-
gesting that intercellular miRNA transfer may contribu te to
coordinate and fine-tune gene expression during the immune
response [39]. Human monocytes stimulated with bacterial
wall component lipopolysaccharide (LPS), furthermore, up-
regulated miR-132, miR-146a/b and miR-155 targeting
mRNAs of genes downstream of Toll-like receptor 4
(TLR4), to protect host cells from an excessive TLR4 re-
sponse [40, 41]. In the gut mucosa homeostasis, comparative
analysis of miRNA expression of germ-free mice and mice
colonized with the microbiota from pathogen-free mice iden-
tified 9 miRNAs differentially expressed: miR-298 (ileum)
and miR-128, miR-200c, miR-665, microR-465c-5p, miR-
342-5p, miR-466d-3p, miR-466d- 5p and miR-68 (colon).
Dulmasso et al. concluded that host microRNA expression is
modulated by microbiota and it in turn regulates host gene
expression [42].
This study is based on a limited number of miRNAs,
considering that the total number of known microRNAs has
triplicated in recent years; thus, further studies are required
to better understand which are the target of these miRNAs
and in which molecular pathways are involved.
CONCLUSION
In this work, considering the high diagnostic value of
combined miR-15b, miR-21 and miR-16 analyses, we pre-
sent a set of circulating miRNA that characterize glioma. In
accordance with Baraniskin study in CSF samples, the avail-
ability of these miRNA may facilitate the diagnosis and
clinical management of this tumour type. As cancer-secreted
microRNAs are emerging mediators of cancer-host crosstalk,
310 Current Genomics, 2015, Vol. 16, No. 5 D’Urso et al.
they may be used as indicators of early disease detection and
recurrence prediction after surgery. These results provide an
evident rationale for quantification in prospective trials of
microRNAs in plasma for diagnostic and prognostic pur-
poses in brain tumors.
CONFLICT OF INTEREST
The author(s) confirm that this article content has no con-
flict of interest.
ACKNOWLEDGEMENTS
Declared none.
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Received on: March 20, 2015 Revised on: April 16, 2015 Accepted on: April 20, 2015
