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R E V I E W Open Access
MicroRNAs: an emerging science in cancer
epigenetics
Rishabh Kala
1
, Gregory W Peek
1
, Tabitha M Hardy
1
and Trygve O Tollefsbol
1,2,3,4,5*
Abstract
MicroRNAs (miRNAs) are remarkable molecules that appear to have a fundamental role in the biology of the cell.
They constitute a class of non-protein encoding RNA molecules which have now emerged as key players in
regulating the activity of mRNA. miRNAs are small RNAmolecules around 22 nucleotides in length, which affect the
activity of specific mRNA, directly degrading it and/or preventing its translation into protein. The science of miRNAs
holds them as candidate biomarkers for the early detection and management of cancer. There is also considerable
excitement for the use of miRNAs as a novel class of therapeutic targets and as a new class of therapeutic agents
for the treatment of cancers. From a clinical perspective, miRNAs can induce a number of effects and may have a
diverse application in biomedical research. This review highlights the general mode of action of miRNAs, their
biogenesis, the effect of diet on miRNA expression and the impact of miRNAs on cancer epigenetics and drug
resistance in various cancers. Further we also provide emphasis on bioinformatics software which can be used to
determine potential targets of miRNAs.
Keywords: miRNA, Biogenesis, Diet, Cancer epigenetics, Bioinformatics software
Introduction
MicroRNAs (miRNAs) are a group of endogenous small
and noncoding RNAs that are approximately 18–25
nucleotides in length that play a critical role in the regu-
lation of gene expression. In the past decade, the
biological functions and biogenesis of miRNAs have
become popular topics for biomedical research. As
expected, miRNA expression is highly correlated with
human diseases, such as cancer and other aging associ-
ated diseases. miRNAs may function not only as onco-
genes but also as tumor suppressors, further implicating
their roles as therapeutic targets. Moreover, miRNAs can
be used as biomarker or prognostic signature molecules
for determining the likely outcome of certain diseases
such as cancer. The importance of these small non-
coding RNA molecules in predicting the outcome of
various cancers has been highlighted. Previous study on
human patients emphasizes the substantial role of this
relatively newly identified class of RNA molecules as
diagnostic and prognostic biomarkers in cancers [1].
miRNA biogenesis and its mode of action
The miRNAs undergo a relatively complicated biogen-
esis (Figure 1) that starts with their synthesis as long pri-
mary transcripts (pri-miRNA) by RNA polymerase II [2].
This long primary transcript is then further cleaved by
Drosha, an RNase III nuclear enzyme which liberates
a ~ 60-to 70-nucleotide stem loop intermediate known
as the miRNA precursor (pre-miRNAs) [3,4]. Because
of the self-complementarity within the RNA molecule,
this precursor molecule forms a characteristic hairpin
double-strand. The pre-miRNAs are transported from
the nucleus to the cytoplasm by Exportin-5, and are fur-
ther processed by Dicer, a second RNase III enzyme [5].
The role of Dicer is to cleave pre-miRNA molecules to
produce 22 basepair dsRNA molecules. One strand
(the active, or “guide”strand) is then loaded into the
RNA-induced silencing complex (RISC), while the
inactive strand, also called a “passenger”strand, is re-
moved and degraded. Through sequence-specific inter-
actions between the mature miRNAs and mRNA, the
* Correspondence: trygve@uab.edu
1
Department of Biology, University of Alabama Birmingham, 1300 University
Boulevard, Birmingham, AL 35294, USA
2
Center for Aging, University of Alabama Birmingham, 1530 3rd Avenue
South, Birmingham, AL 35294, USA
Full list of author information is available at the end of the article
JOURNAL OF
CLINICAL BIOINFORMATICS
© 2013 Kala 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.
Kala et al. Journal of Clinical Bioinformatics 2013, 3:6
http://www.jclinbioinformatics.com/content/3/1/6
ribonucleoprotein complex is positioned on either of the
two untranslated regions (UTR) of their targets [5-8].
RISC is composed of the transactivation-responsive
RNA binding protein (TRBP) and Argonaute (Argo),
the catalytic component of RISC complex. The guide
strand can then recognize the complementary sequence
of mRNA via its association with RISC. miRNA target
recognition involves base-pairing between nucleotides
2–7 (the seed) of the 5
0
end of the miRNAs and a 6, 7 or
8 nucleotide sequence of the mRNA 3
0
UTR, with
additional less absolute requirements [9,10]. These
include (1) the fidelity of seed base-pairing to short 3
0
UTR motifs, (2) high A and U content in the nucleotides
surrounding the seed-binding motif, (3) location of the
3
0
UTR binding site at least 15 nucleotides past the stop
codon, (4) seed-binding motif avoidance of any location
near the center of a long 3
0
UTR, and (5) seed-binding
motif location close to supplemental UTR pairing with
miRNA nucleotides 13–16 [9]. Although it is known that
a single species of miRNA can affect the expression
levels of many genes, it is not yet clear how the specifi-
city of this function of miRNAs is regulated. These non-
coding RNA molecules are evolutionarily conserved and
can be located in the introns or exons of genes, or in the
sequence between genes (intergenic sequence) and are
assumed to be involved in development, cell differenti-
ation, metabolic pathways, signal transduction, prolifera-
tion, and apoptosis [6].
During the process of biogenesis there are a host of
mechanisms that govern the transcription and post-
transcriptional regulation of the miRNAs. The discovery
of these mechanisms has enhanced our understanding of
miRNA deregulation in a variety of disease states, in-
cluding cancer, although much work remains for a more
complete understanding of miRNA-mediated regulation
of gene expression and downstream effects. Examples in-
volve regulatory proteins Dicer and Drosha, with down-
regulation of Dicer and Drosha believed to affect miRNA
expression level and increase risk in neuroblastoma tu-
mors. In fact, an important study has shown that in vitro
knockdown of Dicer and Drosha promoted the growth
of neuroblastoma cell lines [11].
miRNAs have emerged as new targets in biomedical
studies because of their effects on a number of biological
phenomena with reported impact on various diseases
including ageassociated diseases such as cancer. In light
of miRNA involvement in cancer-associated genomic
alterations, high-throughput technologies for assessing
miRNAs have been developed to study the global miRNA
expression patterns in cancer called the miRNAome
(Table 1). With the onset of next-generation sequencing,
therepertoireofexperimentallyverifiedmaturemiRNA
has rapidly expanded [12,13]. Current methodology, as
well as an extensive miRNA database, is presented or iden-
tified by miRBase, available at http://microrna.sanger.ac.
uk/ or http://www.mirbase.org/. It is maintained by the
University of Manchester and can be searched by acces-
sion number, name, keyword, chromosome location, tissue
expression, sequence, homologous sequence or PubMed
ID. miRBase is updated frequently with the recently
described version miRBase 16 containing over 17,000
miRNA sequences from over 140 species updated in
August 2012 (miRBase 19) to over 25,000 mature se-
quences [13].
Useful software for determining miRNA targets has
now begun to proliferate [14-16]. Software of particular
interest is miRanda, available at http://microrna.org or
via miRBase (miRBase Targets) [15,17,18]. miRanda uses
data from the genomic database Ensembl, available at
http://www.ensembl.org/ [17,19], which allows a user to
determine the target genes of a specific miRNA, the
miRNAs for which a specific gene is a target and the ex-
pression profile of a specific miRNA [15]. miRanda ac-
commodates the identification of both conserved and
Figure 1 miRNA biogenesis. miRNAs undergo a relatively
complicated biogenesis starting from a precursor molecule called
miRNA, which is further processed by enzymes Drosha and Dicer, to
produce a mature/active miRNA molecule.
Kala et al. Journal of Clinical Bioinformatics 2013, 3:6 Page 2 of 8
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nonconserved target sites which can be individually eval-
uated by the support vector regression (SVR) algorithm
for degree and rank of capacity for gene down-
regulation [20]. The mirSVR algorithm was designed for
ranking the level of down-regulation associated with
miRandadesignated target sites according to miRNA
transfection and inhibition experiments [9,20]. The
mirSVR scores, which simulate down-regulation predic-
tions, were found to be especially valuable for recogniz-
ing gene down-regulation by multiple miRNAs, and they
are provided on the miRanda website [20].
The database miR2Disease provides extensive inven-
tory and documentation of involvement of miRNA dys-
regulation in human disease and is available at http://
www.miR2Disease.org [21]. As of the March 2011 up-
date, miR2Disease provided comprehensive documenta-
tion of miRNA dysregulation of 349 miRNAs associated
with 163 diseases including age-associated disease like
cancer [21]. Access is provided by search via specific
miRNA, disease name (and associated tissue) or experi-
mentally validated target gene (from TarBase). Detailed
analysis is provided by links to referenced literature.
The database TransmiR, available at http://cmbi.bjmu.
edu.cn/transmir, documents miRNA regulation by tran-
scription factors and thus provides a critical link to
origins of gene dysregulation by miRNA and any conse-
quent disease etiology [22]. As of the March 2012 up-
date, TransmiR documents 201 transcription factors and
209 miRNAs from 16 organisms [22]. It can be assessed
by combinations of transcription factor name, miRNA
name, species, regulation type (activate or repress) and/
or PubMedID. Links are provided to NCBI gene and
protein data along with associated literature and net-
works of transcription factors and their target miRNA
genes are included [22].
miRTarBase at http://miRTarBase.mbc.nctu.edu.tw/
is an extensive database of experimentally confirmed
miRNA-target interactions. These interactions are ex-
perimentally validated using Western blot, knockdown
or reporter gene analysis [23]. The miRTarBase database
released in October 2011 included 669 miRNAs and
2553 target genes of 14 species [23]. The networks of
mature miRNA and gene targets appear to be suitable
for potential integration with protein-protein interaction
networks as well as network data derived from
TransmiR [22,23].
miRNAs and cancer epigenetics
miRNAs are emerging as a new class of molecules whose
deregulation may ultimately contribute to cancer forma-
tion. They also likely cooperate with the other classic
oncogenes and/or down-regulate tumor suppressor
genes in cancer cells to drive the behavior of the tumors.
Although many miRNAs have been shown to be
deregulated in cancers, the set of miRNAs that actually
play a pathogenic role in cancer has not yet been clearly
determined. Additional changes in the expression level
of miRNAs in cancer cell lines can directly regulate cer-
tain fundamental behaviors of cancer cells, such as pro-
liferation and apoptosis [24]. Many of the miRNAs
deregulated in cancers have been shown to have a direct
impact on tumor suppression and their metastasis.
Table 1 Databases and software used in miRNA analysis
Database or software Principal applications Additional features Search by
miRBase
(http://microrna.sanger.ac.uk/ or
http://www.mirbase.org/)
miRNA target
identification
Links to databases and software,
such as miRanda
Accession number,
name, keyword tissue,
sequence PubMed ID
miRanda
(http://microrna.org)
Identification of target genes
or targeting miRNA. miRNA
expression profile and
distinguish conserved
and non-canonical sites
Support vector regression
(SVR) algorithm to determine
level of gene down-regulation.
miRNA, target gene
TarBase
(http://microrna.gr/)
miRNA target identification miRNA
miR2Disease
(http://www.miR2Disease.org)
Associate human
diseases with specific
miRNA dysregulation
Uses TarBase Specific miRNA,
disease name, tissue
or target gene
TransmiR
(http://cmbi.bjmu.edu.cn/transmir)
Identify transcription
factors that regulate
specific miRNA
Links to NCBI gene and
protein data and literature
Transcription factor names,
miRNA name, species,
regulation type, literature
miRTarBase
(http://miRTarBase.mbc.nctu.edu.tw/)
Document experimentally confirmed miRNA-
target interactions
Provides method of
interaction confirmation,
information on mature
miRNA and precursor,
expression profile, gene
target network
Species, miRNA,
target gene combination
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These non-coding classes of RNA can serve as useful
biomarkers and may greatly improve clinical manage-
ment by better defining appropriate treatment options
for patients [5].
In addition to their role in tumor suppression or tumor
promotion, miRNAs have also been identified as master
regulators of key genes implicated in mechanisms of
chemoresistance. There are two main mechanisms which
are thought to be the key players in chemoresistance: one
is genetic and the other is epigenetic. Although evidence
regarding genetic changes following chemotherapeutic
treatment is limited, numerous studies have demonstrated
significant epigenetic alterations in drug-resistant cancer
cells [25,26]. In addition to these well-studied mechanisms
of cancer drug resistance, there have been recent studies
that link cancer drug resistance with the alteration of
miRNAs expression [27].
Epigenetics is the study of heritable changes in gene
expression caused by mechanisms other than changes in
the underlying DNA sequences, which might affect vari-
ous cellular phenomena like cell signaling, proliferation,
apoptosis. Epigenetic processes are commonly thought
to favor cell survival and tumor progression. Examples
of epigenetic changes are DNA methylation and histone
modifications, both of which serve to regulate gene ex-
pression without altering the underlying DNA sequence
[28,29]. In order for DNA to undergo methylation and
histone modifications, epigenetic modifying enzymes
such as DNA methyltransferases (DNMTs), histone dea-
cetylases (HDACs), histone acetylases (HAT) and his-
tone demethylases (HDMs) are required. Interestingly,
these miRNAs can control the expression of various
epigenetic-modifying enzymes which are involved in car-
cinogenic processes [30,31]. There are a number of stud-
ies highlighting this connection. One such study was
performed by Lujambio et al. in 2008 which showed that
hypermethylation of miR-148 resulted in its down-
regulation because of positive feedback that exists to
reinforce the overexpression of DNMTs in breast cancer
cells which resulted in breast tumor growth and metas-
tasis. Furthermore, the reactivation of miR-148 upon
treatment with a DNA demethylating agent was associ-
ated with reduced tumor growth and inhibition of
metastasis [32]. Another study involved comparison be-
tween normal lung cell and cancerous cells and reported
an expressional difference of miRNA in both the cell
types [33]. The miRNA-29 family (miRNA-29a,-29b,-
29c), which is down-regulated in cancers, was shown to
have some interesting complementarity with the 30UTR
of DNA methyltransferase (DNMT)3A and 3B both of
which are known de novo methyltransferases. Further in-
vestigation determined whether miR-29s could target
DNMT3A and 3B expression by restoration of miR-29s.
It was found that the enforced expression of miR-29s in
lung cancer cell lines restored normal patterns of DNA
methylation and induced re-expression of methylation-
silenced tumor suppressor genes, thus affecting cancer
growth [33].
miRNAs are implicated in several cellular responses to
drug exposure, including, but not limited to, drug in-
flux/efflux, cell cycle arrest, DNA repair, and apoptosis,
all of which mediate cancer cell survival and tumor pro-
gression. There have been a number of miRNAs which
are reported to be involved in breast cancer drug resist-
ance, one of which is miR-101, which targets EZH2,
the enzyme responsible for trimethylating histone H3
lysine 27 to establish a repressive chromatin state.
miRNA upregulation has been linked to tamoxifen and
fulvestrant resistance [34,35]. Crosstalk may occur be-
tween certain classes of miRNAs such as miR-101,miR-
206,andmiR-221/222, which translationally repress the
estrogen receptor alpha (ERα) and could also be respon-
sible for the decreased sensitivity to anti-estrogen drugs
[27,34,35]. Further, on comparing ERα-negative breast
cancer cells lines such as MDA-MB 468, HS578T and
MDAMD-231 with ERα-positive cell lines such as MCF-
7, T47D and MDA-MB 361, there was an expressional
difference in miR-221 and miR-222. Further analysis
revealed that knockdown of these two marker miRNAs
partially restored ERαprotein expression in ERαprotein-
negative/ mRNA-positive cells, thus making them a poten-
tial biomarker for prognostic as well as therapeutic
purposes [27]. These findings indicate a role for miRNAs
in regulating estrogen receptor and drug resistance. Fur-
thermore, since a number of miRNAs can target DNA
and histone-modifying enzymes, they are likely to affect
gene expression on a much broader scope.
The roles of miRNAs in cancers have been extensively
investigated in the past few years. Recently, the connec-
tion of miRNA and tumor suppressor networks was elu-
cidated. p53, a wellknown tumor suppressor, regulates
diverse physical responses to many cancer-related stress
signals, which may affect cell proliferation, cell death,
DNA repair, and angiogenesis. Thus far results obtained
are mixed. In some studies, p53 was found to affect
miRNA expression and in other studies miRNAs were
found to play a crucial role in p53-mediated tumor sup-
pression [36]. A wide array of miRNAs were found to be
affected by the expression level of this key tumor sup-
pressor gene, including in colon cancer were p53 may
have a direct role in miRNA expression [37]. In another
study, 470 miRNAs were analyzed using microarray and
12 of these were found to be significantly affected by
p53 [38]. Moreover, it has been found that miR-34a af-
fects the pathway that mediates cellular aging and limits
longevity, by mitigating SIRT1 expression and p53-
related apoptosis, stability and activity [39]. SIRT1, a
mammalian homologue of yeast silent information
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regulatory Sir2, with an enzymatic activity of nicotina-
mide adenine dinucleotide (NAD+)-dependent histone
deacetylases, is a class III histone deacetylase. miR-34a is
a tumor suppressor gene that is an evolutionarily con-
served miRNA, with a single, recognizable orthologue in
several invertebrate species [36]. miR-34a functions as a
tumor suppressor, in part, through a SIRT1-p53 pathway.
This miRNA inhibits SIRT1 expression through a miR-
34a-binding site within the 30UTR of SIRT1. In support
of this concept, it was discovered that miRNA did not
affect the SIRT1 RNA transcription but it did affect the
translation of SIRT1 RNA by acting on the 30response
element of SIRT-1 [39,40]. Xu et al. [40] reported an
effort to use softwares such as miRnada, TargetScan, and
Pic Tar, which could help in target prediction for miR-22
and miR-34a. Moreover, knockdown of miR-34a func-
tion by antisense oligonucleotides attenuates the acetyl-
ation of p53. miR-34a may have other targets besides
SIRT1 that can regulate cell survival. Thus, SIRT1 may
be one of several distinct targets of miR-34a that con-
tribute to its ability to promote apoptosis.
Recently, a study was performed with 5-fluorouracil
(5-FU)-resistant human colorectal cancer DLD-1 cells
and with parental DLD-1 cells [41]. In that study the
level of miR-34a was observed to be low in the drug re-
sistant cell line but it was found to be high in parental
cells after treatment. Moreover with respect to SIRT-1
expression, miR-34a was observed to be upregulated in
resistant cells. Further activation of miR-34a resulted in
inhibition of growth with a decrease in Sirt1 expression.
These findings suggest that miR-34a targeting the Sirt1
genes could negatively regulate, at least in part, the re-
sistance to 5-FU in human colorectal cancer DLD-1 cells
[41].
The miR-200 family is a crucial modulator of epithelial
to mesenchymal transition (EMT), which is a normal
embryological process involved in various adult patholo-
gies including cancer metastasis and tumorigenicity. The
miR-200 family is down-regulated and exhibits tumor
suppressive properties in renal, prostate, breast, bladder,
pancreatic, and gastric cancers. It is a key regulator of
the epithelial phenotype and is involved in EMT pro-
cesses in breast cancer. There have been a crosslinking
reported between Class III histone deacetylase SIRT1,a
proposed oncogene in breast cancer, and miR-200. With
overexpressed SIRT1 an overexpression of EMT was
observed due to a positive feedback loop between epige-
netically silenced miR-200 and SIRT1. Further restor-
ation of miR-200 or the knockdown of SIRT1 prevented
transformation of normal mammary epithelial cells as
evidenced by decreased breast cancer metastasis. Finally,
it was observed that SIRT1 overexpression is associated
with decreased miR-200a in breast cancer patient sam-
ples, indicating that miR-200a may be a potential tumor
suppression target in breast cancer metastasis [42]. Sev-
eral other class of miRNAs have also been associated
with 30UTR of SIRT1, such as miR-34a,miR-132, and
miR-199a and this association is tissue specific and re-
sults in downregualtion of SIRT1 expression in colon,
adipocyte, and cardiac tissues, respectively [39,43]. An-
other study using gastric cancer cell in a mouse model,
showed overexpression of miR-499 resulted in decreased
expression of SIRT1 which resulted in 60% growth inhib-
ition when compared with control. This was further
shown using FACS analysis and β-Gal activity assays.
Importantly, qPCR analysis also showed a loss of miR-
499 expression in human clinical gastric tumor when
compared with normal tissue [44]. Moreover, SIRT-1
protein level was found to be higher in mouse embry-
onic stem cells when compared with mouse differenti-
ated tissues. Certain classes of miRNAs such as miR-9,
miR-181a,miR-181b,miR-204,miR-199b,miR-135,
post-transcriptionally downregulate SIRT1 levels in dif-
ferentiated tissues [45]. Further, in support of a tumor
suppressor role of miRNAs, a study was performed on
T24 bladder cancer cells in which cells were treated with
a DNA demethylating agent and HDAC inhibitors,
which resulted in a decrease in DNA methylation and
an increase in histone activation around the promoter
region of the miR-127 gene. This ultimately lead to
increased expression of miR-127 and tumor inhibition
[46].
Table 2 The effects of miRNA on target molecules
Target molecule in cancer miRNA involved Effects on target molecule
SIRT1/HDAC III miR-34a, miR-22, miR-499, miR-200,
mi-9, miR-181a, miR-181b, miR-204,
miR-199b, miR-135
Down-regulated
p53 miR-34a Upregulated
EMT miR-200 Down-regulated
DNMT miR-148, miR-29a, miR-29b, miR-29c Overexpression of DNMTs
EZH2 histone lysine methyltransferase miR-101 Upregulated and causes drug resistance in breast cancer
ER expression miR-101, miR-206, miR-221/222 Down-regulated
p21 miR-34a Upregulated
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miRNA modification by diet
Growing evidence suggests that bioactive dietary compo-
nents impact epigenetic processes and are often involved
with the reactivation of tumor suppressor genes, activa-
tion of cell survival proteins, and induction of cellular
apoptosis in many types of cancer [47-49]. Recent evi-
dence suggests that bioactive dietary components can also
target various oncogenic or tumor suppressive miRNAs to
alter the gene expression profile in cancer prevention
[50-52]. Genistein, an isoflavone isolated from soybeans,
has been reported to have both preventive and therapeutic
effects on carcinogenesis and many other diseases [50].
One of the studies performed on ovarian cancer cells,
which compared treated and non-treated cells, found that
there were a total of 53 miRNAs which were differentially
expressed in the cancer cells. Further, upon analyzing
gene expression data using real time PCR, both ER-
αand ER-βwere observed to be induced in genistein-
treated cells, which can correlate with the expression
changes of these 53 miRNAs, hence revealing a significant
reduction in migration and invasion of ovarian cancer
cells. Another investigation used dietary genistein for
treatment of uveal melanoma cells and found a time-and
dose-dependent inhibition which might be due to inhib-
ition of miR-27a [51].
Curcumin (diferuloylmethane), a naturally occurring
flavinoid derived from the rhizome of Curcuma longa,
has been reported to alter the expression of miRNAs.
One such study performed by Sun et. al. found an
upregulation of miRNA-22 and down-regulation of
miRNA-199a in a pancreatic cancer cell line and a simi-
lar study was performed using curcumin in a breast
cancer cell line which showed an upregulation of
miRNA-15a and miRNA-16 using real time PCR analysis
[53].
Epigallocatechin-3-gallate (EGCG) is a major compo-
nent of green tea and is thought to exert its anticancer
effects by epigenetic mechanisms [54]. Studies have
shown that EGCG can inhibit epigenetic enzyme activity
and thus can modulate apoptosis, the cell cycle and cell
proliferation. Recently EGCG is also found to modulate
miRNA expression. To further confirm this notion, a
study was performed using hepatocellular carcinoma
cells and it was found that there is an increase in miR-16
expression which resulted in apoptosis [55].
Conclusion
miRNAs, a small group of noncoding RNAs, are drawing
more attention than ever and are thought to be a new
category of tumor suppressors or mediators of signal
transduction. Further studies are needed to understand
the interactions and regulatory mechanisms between
miRNAs and their target molecules. Therefore, it will be
important to clarify how the miRNA/SIRT1/p53/DNMT
regulatory network is controlled in humans in future re-
search (Table 2). Recent studies have suggested that
miRNAs may act as tumor suppressors by regulating
various cellular phenomenona like apoptosis, cellular
movement, metastasis and cell proliferation. The regula-
tory loop between SIRT1 and miRNA might provide new
opportunities for therapeutic tissue-specific regulation
and cancer inhibition. However, the mechanism by
which miRNA regulation occurs is still unclear. Besides
the involvement of miRNA in cancer, miRNAs may also
influenced the aging process and provide a new avenue
for potential targets in aging biology. miRNAs are
also investigated as early plasma biomarkers and are
expected to be more sensitive when compared with
current biomarkers. From a clinical perspective, miRNAs
can induce diverse effects but care must be exercised
when extrapolating findings from in vitro to in vivo.
Despite difficulties to overcome, the value of miRNAs in
clinical applications is projected to be monumental.
Abbreviations
miRNA: Micro RNA; DNMT: DNA methyltransferases; HDAC: Histone
deacetylases; HAT: Histone acetylases; SIRT: Silence information regulatory;
UTR: Un-translated region; RISC: RNA-induced silencing complex;
MESC: Mouse embryonic stem cells; SVR: Support vector regression;
NAD: Nicotinamide adenine dinucleotide; FACS: Fluorescence activated cell
sorter; EMT: Epithelial to mesenchymal transition; EGCG: Epigallocatechin-3-
gallate; PCR: Polymerase chain reaction; 5-FU: 5-fluorouracil; ER: Estrogen
receptor.
Competing interests
No potential competing interests were disclosed.
Authors’contributions
Primary author: RK; Author of bioinformatics section: GWP; Edited the
manuscript: TMH and TOT. All authors read and approved the final
manuscript
Acknowledgements
This work was supported in part by grants from NCI (R01 CA129425), the
American Institute for Cancer Research and a UAB CAS Interdisciplinary
Award. Funding for RK and GWP was provided by the UAB Department of
Biology; Funding for TMH was provided by NIH NIGMS 5K12GM088010 Noe
(PI).
Author details
1
Department of Biology, University of Alabama Birmingham, 1300 University
Boulevard, Birmingham, AL 35294, USA.
2
Center for Aging, University of
Alabama Birmingham, 1530 3rd Avenue South, Birmingham, AL 35294, USA.
3
Comprehensive Cancer Center, University of Alabama Birmingham, 1802 6th
Avenue South, Birmingham, AL 35294, USA.
4
Nutrition Obesity Research
Center, University ofs Alabama Birmingham, 1675 University Boulevard,
Birmingham, AL 35294, USA.
5
Comprehensive Diabetes Center, University of
Alabama Birmingham, 1825 University Boulevard, Birmingham, AL 35294,
USA.
Received: 30 December 2012 Accepted: 4 February 2013
Published: 16 March 2013
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doi:10.1186/2043-9113-3-6
Cite this article as: Kala et al.:MicroRNAs: an emerging science in cancer
epigenetics. Journal of Clinical Bioinformatics 2013 3:6.
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