Identification of Long stress-induced non-coding transcripts that have altered
expression in cancer☆
Jessica M. Silvaa,b,⁎, Damon S. Pereza, Jay R. Pritchetta, Meredith L. Hallinga, Hui Tangc, David I. Smitha
aDivision of Experimental Pathology, Department of Laboratory Medicine and Pathology, Mayo Clinic and Foundation, 200 First Street, S.W., Rochester, MN 55905, USA
bDepartment of Biochemistry and Molecular Biology, Mayo Clinic and Foundation, 200 First Street, S.W., Rochester, MN 55905, USA
cDivision of Biomedical statistics and informatics, Department of Health Sciences Research, Mayo Clinic and Foundation, 200 First Street, S.W., Rochester, MN 55905, USA
a b s t r a c t a r t i c l ei n f o
Received 4 December 2009
Accepted 24 February 2010
Available online 7 March 2010
Long non-coding transcripts
Entire genome analysis
It has recently become clear that the transcriptional output of the human genome is far more abundant than
previously anticipated, with the vast majority of transcripts not coding for protein. Utilizing whole-genome
tiling arrays, we analyzed the transcription across the entire genome in both normal human bronchial
epithelial cells (NHBE) and NHBE cells exposed to the tobacco carcinogen NNK. Our efforts focused on the
characterization of non-coding transcripts that were greater than 300 nucleotides in length and whose
expression was increased in response to NNK. We identified 12 Long Stress-Induced Non-coding Transcripts
that we term LSINCTs. Northern blot analysis revealed that these transcripts were larger than predicted from
the tiling array data. Quantitative real-time RT-PCR performed across a panel of normal cell lines indicates
that these transcripts are more abundantly expressed in rapidly growing tissues or in tissues that are more
prone to cellular stress. These transcripts that have increased expression after exposure to NNK also had
increased expression in a number of lung cancer cell lines and also in many breast cancer cell lines.
Collectively, our results identified a new class of long stress responsive non-coding transcripts, LSINCTs,
which have increased expression in response to DNA damage induced by NNK. LSINCTs interestingly also
have increased expression in a number of cancer-derived cell lines, indicating that the expression is
increased in both, correlating cellular stress and cancer.
© 2010 Elsevier Inc. All rights reserved.
The three gigabase pair human genome contains approximately
20,000 genes which themselves produce over one million proteins.
However, less than 2% of the genome directly encodes proteins .
Recently new technologies, including whole-genome tiling arrays,
have revealed that the majority of the genome is transcriptionally
active and that the number of non-coding transcripts vastly exceeds
the number of protein-coding transcripts [2–7].
The most abundantly expressed non-coding transcripts include
the RNA components of the ribosome and the transfer RNAs, both of
which are involved in translating coding transcripts into proteins. A
second group of important non-coding transcripts are the microRNAs
(miRNAs), which are much smaller (∼20-25 nucleotides) and
perform many critical functions. The miRNAs function to regulate
gene expression through binding to multiple transcripts that contain
sequences homologous to the “core” sequence within each miRNA .
Several miRNAs (e.g. those derived from the miR-15a-16-1 and
miR17-92 clusters) have also been correlated with carcinogenesis,
acting as either tumor suppressor miRNAs or oncogenic miRNAs
. Other small non-coding RNAs (ncRNAs) include the piwiRNAs and
the snoRNAs. piwiRNAs regulate gene expression through mRNA
degradation and translational repression . snoRNAs are involved
in post-transcriptional hypermodification of rRNA. snoU5 has also
been found to be a candidate tumor suppressor in prostate cancer
There are also considerably larger non-coding transcripts that play
important functional roles within the cell. Perhaps the best known long
ncRNA transcript is the human XIST/TSIX transcript, which is involved
in chromatin remodeling events associated with X-chromosome
inactivation and dosage compensation in eukaryotes. Copies of this
8 kb transcript are responsible for coating the inactive X chromosome.
Two adjacent long ncRNAs that have been identified are tncRNA
(NEAT1) and MALAT1 (NEAT2). Both have been demonstrated to play
Genomics 95 (2010) 355–362
☆ "Sequence data from this article have been deposited with the DDBJ/EMBL/
GenBank Data Libraries under Accession Numbers: GU228573, GU228574, GU228575,
GU228576, GU228577, GU228578, GU228579, GU228580, GU228581, GU228582,
GU228583, GU228584, for LSINCT1 to LSINCT12 respectively."
⁎ Corresponding author.DivisionofExperimentalPathology, DepartmentofLaboratory
55905. Fax: +1 507 266 5193.
E-mail addresses: firstname.lastname@example.org (J.M. Silva),
email@example.com (D.S. Perez), firstname.lastname@example.org
(J.R. Pritchett), email@example.com (M.L. Halling), firstname.lastname@example.org (H. Tang),
email@example.com (D.I. Smith).
0888-7543/$ – see front matter © 2010 Elsevier Inc. All rights reserved.
Contents lists available at ScienceDirect
journal homepage: www.elsevier.com/locate/ygeno
roles in cancer development. tncRNA (trophoblast derived non-coding
RNA) is a 4.5 kb transcript associated with the suppression of the MHC
class II antigen promoter in T cells thus, suppressing the display of fetal
histocompatibility antigens to allow fetal evasion of the maternal
immune system . In addition, tncRNA has also been found to have
increased expression in HELA cells. MALAT1 is an 8 kb ncRNA that is
over-expressed in a variety of different cancers and is a marker for
metastasis in early stage non-small cell lung cancer patients .
Another long ncRNA HOTAIR is produced within one cluster of HOX
genes and is responsible for regulating another HOX gene cluster on a
different chromosome . Thus, the functions of the long ncRNAs are
diverse and there is increasing evidence that many are important
ncRNAs may modulate several cellular stress responses . For
instance, Adapt33 ncRNA is a stress-responsive transcript that is
induced under conditions of a cytoprotective "adaptive response” and
has been shown to be a stress-inducible riboregulator . Another,
small ncRNA, DsrA, stimulates translation of the RpoS stress response
factor in Escherichia coli by base-pairing with the 5' leader of the RpoS
mRNA and opening a stem-loop that represses translation initiation
. Recently, Ben Amor et al. conducted a genome-wide bioinfor-
matic analysis and identified 76 long non-protein-coding RNAs
(npcRNA) involved in Arabidopsis differentiation and stress responses
. In humans, the expression of the ncRNAs PRINS (Psoriasis
susceptibility-related RNA Gene Induced by Stress) was induced by
ultraviolet-B irradiation, viral infection (herpes simplex virus), and
translational inhibition .
We were interested in identifying human non-coding transcripts
that are both long and induced upon cellular stress. Our interest in
stress-responsive transcripts is because of the known association
betweencellularstressand cancer.Weperformed whole-genome tiling
array experiments using RNA prepared from Normal Human Bronchial
Epithelial cells (NHBE cells) exposed to NNK (4-(methylnitrosamino)-
1-(3-pyridyl)-1-butanone), a potent tobacco carcinogen. NNK is one of
the most carcinogenic tobacco-specific nitrosamines. Picomolar con-
centrations of NNK can be detected in body fluids and tissues of cancer
patients and tobacco products [21,22]. NNK is an organ-selective lung
carcinogen in laboratory animals  and is formed from nicotine
during tobacco processing and smoking. NNK is metabolically activated
by the cytochrome P450 enzymes (predominately CYP2A6 and
CYP2A13) to intermediates that methylate and pyridyloxobutylate
DNA, resulting in DNA adduct formation, single strand breaks, and
increased levels of 8-oxodeoxyguanosine in the DNA . The cellular
stress NNK elicits has been shown in vivo and in vitro dysregulating
various genes affecting viability, cell movement, cell cycle, and cell
proliferation [25–28]. Lung cancers induced by NNK are primarily
promote tumor growth and metastasis in mouse models of lung cancer
. It has also been shown to induce several other cancers including
nasal, oral cavity, liver, pancreas, and cervix[31,32]. Interestingly,
NNK has been utilized to induce cancer in human breast epithelial
incidence and/or multiplicity in human HRAS proto-oncogene trans-
genic (Hras128) rats .
We hypothesize that long stress-induced non-coding transcripts
are encoded in the genome and that they are not only involved in the
response to cellular stress, but also have altered expression in cancer
derived cells. Our tiling array data has identified a unique group of
long stress-induced non-coding transcripts, which we term LSINCTs.
These LSINCTs accumulate to higher levels in NNK-induced cells, and
are more abundantly expressed in normal human tissues that are
more proliferative. In addition, LSINCTs have increasedexpression in a
number of lung cancer-derived cell lines and are also over-expressed
in many breast cancers. These results support the concept that the
expression of these non-coding transcripts is correlated with cellular
stress and carcinogenesis.
Materials and Methods
Cell Lines, Cell Culture and Chemical Treatment
All cell lines were grown in 5% CO2 at 37 °C incubator. HMEC,
HCC1500, and HCC1569 cells were purchased from Lonza (Basel,
Switzerland). Cryopreserved NHBE cells were purchased from Cambrex
Bio Science (Walkerville, MD) and grown in defined BEBM medium
(Cambrex) with supplements at manufacturer-suggested concentra-
tions. All lung cancer cell lines were purchased from ATCC (Manassas,
Virginia) and grown in ATCC RPMI-1640 medium containing 10% fetal
bovine serum (FBS). T47D, BT474, HCC1500, HCC1569, and UACC893
were grown in ATCC RPMI-1640 medium containing 10% fetal bovine
serum (FBS). MCF7, MCF10A, MDA157, and MDA435 were grown in
Gibco DMEM with L-glutamine and 10% FBS. The MDA468 cell line was
cultured in L15 medium with L-glutamine and 10% FBS.
NNK-induced cells were prepared by treating NHBE and MCF7 cells
with 200 µM NNK (4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone)
(Toronto Research Chemicals) prepared in dimethyl sulfoxide for
24 hours. We measured a strong induction of three DNA damage
genes; GADD45, CYP2A6,and CYP2A13 asanindication of DNA damage
response to determine optimal concentration of NNK [32,34].
RNA and RNA isolation
Human normal total RNA was purchased from Applied Biosystems
Inc. (Austin, TX) and served as a control when analyzing LSINCTs
expression across a panel of cancer specimens.
Total RNA was isolated from cells or tissues using the Qiagen
RNAeasy Plus Mini Kit (Valencia, CA) and Gentra Systems Versagene
Total RNA Cell Kit (Minneapolis, MN) according to the manufacturer's
Whole-genome tiling array design
The GeneChip®Human 35 bp Tiling Array 1.0R Set (Affymetrix)
design is based on the human genome version 34 according to NCBI
genome.ucsc.edu/) and repeat masked. Probes are roughly at a 35 bp
resolution (center-to-center spacing of consecutive 25-mers), subject
only to requirements of synthesis and probe quality. Arrays were
subdivided according to genome location into 14 separate microarrays.
Each probe pair is formed by a perfectly-matched 25-mer (PM), iden-
tical to the genome sequence at the selected position, and a mismatch
(MM) probe that differs from PM at the central base. This tiling array
design contained 41 804 probe pairs representing 1 364 427 919 (91%)
nucleotides of the repeat masked (http://www.repeatmasker.org/)
human genome sequence that could be grouped into windows con-
taining at least 5 probes.
Tiling array experimental procedure
Analysis was performed at the Microarray Core Facility at Mayo
Clinic (Rochester, MN). Briefly, total RNA was isolated from NHBE
cultured in T-150 flasks in triplicate using Gentra Systems Versagene
Total RNA Cell Kit (Minneapolis, MN), including DNase treatment. To
focus on longer transcripts, total RNA was isolated using a column
withlowaffinityforRNAslessthan 80 nt. RNAqualitywasassessedby
ultraviolet spectrophotometry. Agilent traces were then obtained for
The GeneChip®WT Double-Stranded DNA Terminal Labeling Kit
and GeneChip®WT Amplified Double-Stranded cDNA Synthesis Kit
from Affymetrix (Santa Clara, CA) was used. This protocol entails first
and second strand cDNA synthesis using random hexamers, RNA
removal and cDNA purification, a quality control cDNA step, a cDNA
fragmentation step, TdT labeling, prehybridization of the chips, and
J.M. Silva et al. / Genomics 95 (2010) 355–362
the final hybridization of the labeled cDNA onto the GeneChip®Human
a total of four chips, as suggested by the protocol. Each tiling array chip
was completed in triplicate (i.e., three complete 14 chip sets were
hybridized and scanned for both control NHBE and NHBE exposed
Each array was scanned using the Affymetrix GeneChip®300 G7
scanner. The GeneChip®Operating Software (GCOS) automatically
generated four files required for data analysis, including the CEL file.
The raw CEL files were used in our data analysis. Using Integrated
Genome Browser (IGB) from Affymetrix and the UCSC Human
Genome Browser, we were able to visualize the raw and normalized
hybridization signals from different data sets, together with annota-
tion information from public and private data banks.
Northern Blot analysis
Probes were created as PCR products (300 bp) based on LSINCT-
specific primers, designed using the Primer3 program (http://biotools.
Supplemental data. PCR products were extracted from 2% low-melting
point agarose gels and purified using the QIAquick Gel Extraction Kit
(Qiagen). Probes were then labeled with [±P32]-labeled deoxynucleo-
tide triphosphates usingtheMegaprimeDNA LabelingSystemskitfrom
Amersham Biosciences (Piscataway, NJ). Formaldehyde 1% agarose gels
were loaded with 5-20 µg total RNA, which was transferred onto
Nitrocellulose Membrane (Bio-Rad) overnight and then fixed to the
membrane by UV-crosslinking (Stratalinker, Stratagene). Membranes
were hybridized at 42° with labeled probes overnight using ULTRAhyb
Ultrasensitive hybridization buffer (Ambion) in a rotating incubator.
Membranes were washed in buffers and were exposed to CL-X Posure
Film (Thermo Scientific) for 1 to 3 days.
Quantitative Real-Time RT-PCR
Primers for LSINCTs were designed using Primer3 (Supp Table 7b).
cDNA was synthesized using the Thermoscript RT-PCR System from
Invitrogen using 2 µg of total RNA and random primers. cDNA
quantitation was then performed with specific primers using the
SYBR green method (ABI 7900HT Fast Real-time PCR system). Primers
were optimized for qPCR with β-actin as a control gene and then with
the transcript region of interest. When the optimal primer concen-
tration produced a linear response to input cDNA concentration, RNA
samples were analyzed in triplicate for each tested transcript. To
normalize the expression levels (Δ CT), the threshold cycle (CT) for
each transcript was subtracted from the CTof the more abundantly-
expressed control gene (β-actin). Transcripts displaying consistently
altered expression levels consistently in each of the triplicate exper-
iments were included for statistical analysis comparing normal versus
cancer samples from breast and cells induced with NNK treatment.
Stressed or cancer samples that displayed a 2-fold difference in expres-
sion compared to appropriate controls underwent further analysis to
determine statistical significance.
Affymetrix provided two software programs for initial data
analysis, Tiling Analysis Software (TAS) and Integrated Genome
Browser (IGB). Tiling Analysis Software v1.1 User Guide (Affymetrix)
was consulted. Briefly, the analyses provided within the TAS
application included analyzing feature intensity data stored in CEL
files to produce signal and p-values for each genomic position,
computation of genomic intervals based on those computed signal
and p-values, and computation of summary statistics and visualiza-
tions for assessing the quality of the array data. The results of this
analysis were imported into applications such as IGB or the UCSC
Human Genome Browser. With IGB, annotation variations were com-
pared in different data sets. IGB combined in one viewer its own
experimentalor computational results,common referenceinformation,
and access to public and private data banks.
LSINCT Selection using Model-Based Analysis of Tiling Arrays (MAT)
The peak-finding algorithm, MAT, was used to analyze tiling array
data. Raw CEL files were first normalized across all replicates using
quantile normalization , then the differential expression between
NNK and NHBE cells was studied using MAT . Using a stringent
threshold of FDR rate equal to zero, the process identified nearly 1000
significantly differentially expressed genomic intervals. The length of
these intervals ranges from 307 nt to 6680 nt (average 1017 nt).
University of California Santa Cruz Genome Bioinformatics Browser
UCSC Homo sapiens genome browser gateway March 2006 (NCBI
Build 36.1) was used to analyze the LSINCT regions. BED files created
withIGBwere used tolocatepotentialLSINCTsthroughoutthegenome.
Sequence coordinates from the BED files were imported into the UCSC
browser where these regions underwent additional investigation in
order to confirm that these sequences are indeed non-coding. This
analysisincludedseveral of the UCSCbrowser fields. Transcriptanalysis
any RefSeq Genes, and no known mRNA homology.
Whole genome tiling array of RNA from NHBE and NHBE-NNK induced
A tiling array experiment was performed to obtain an unbiased
view of transcription changes across the entire genome in NHBE cells
exposed to NNK compared to unexposed NHBE cells. Initial experi-
mentsdeterminedoptimal NNKconcentrations for inductionof a DNA
damage response (data not shown). NHBE cells were exposed to
different NNK concentrations for a 24 hour period and the expression
of threegenes: GADD45,CYP2A6,andCYP2A13were measured. These
are genes known to be induced in response to DNA damage . We
found that 200 µM NNK produced strong induction of these. It should
be noted that this inducing NNK concentration is extremely high
relative to the picomolar concentrations of NNK that are detected in
the blood of humans who smoke cigarettes however, in vitro studies
in bronchial epithelial cells confirm this concentration to be optimal
for metabolizing NNK [32,34].
To identify NHBE NNK-induced Transcriptionally Active Regions
(NNK- TARs), we utilized the Tiling Analysis Software (TAS) and
Integrated Genome Browser (IGB). We analyzed NHBE NNK-TARs as
compared with transcripts found from non-treated NHBE cells based
on a p-value of b0.01 using TAS. We analyzed the NNK-TARs by TAS/
IGB and Model-Based Analysis of Tiling Arrays (MAT) to identify
candidate NNK-TARs for further investigation. A number of the NNK-
TARs were identified with both methods, but there were many NNK-
TARs that were only identified with one of the two methods. In total,
over 231, 305 NNK-TARs were identified with their lengths ranging
from 100 nt to greater than 3000 nt. This analysis was further char-
acterized by identifying NNK-induced TARs (119 305) or NNK-
decreased TARs (112 000). In this study we focused our efforts on the
identification of TARs which were induced by NNK. In order to identify
the longer non-coding transcripts and to intentionally exclude short
non-codingRNAsincludingsomepre-miRNAs; we excludedtranscripts
smallerthan 300 nts,therebyidentifying 1 305 longNNK-induced TARs
J.M. Silva et al. / Genomics 95 (2010) 355–362
Identification of long stress-induced non-coding transcripts (LSINCTs)
Long Stress-Induced Non-Coding Transcripts (LSINCTs) were
selected from the 1 305 long NNK-induced TARs using IGB, the
University of California Santa Cruz Genome Browser (UCSC) March
2006 version, as well as the Ensembl Browser (refer to Methods
section). Utilizing these browsers, the long NNK-induced TARs
underwent additional investigation in order to confirm that these
sequences are indeed long and contained non-coding potential. This
analysis included size, verifying a lack of significant open reading
frames, the absence of repeats, and no homology to any RefSeq Genes
or any potential mRNAs.
Utilizing the UCSC Genome browser (Supp Fig. 2 lower panel
showing LSINCT5), we are able to identify a group of 12 LSINCTs that
satisfied these criteria and these have been termed LSINCT 1-12. Two
of the identified LSINCTs, LSINCT2 and LSINCT5, are shown in Fig. 2.
The 12 LSINCTs selected for analysis have predicted lengths
ranging from 300-800 nt based on the hybridization pattern to
adjacent oligonucleotide tiling array probes. One LSINCT (LSINCT10)
was located in intron 3 of the SDC5 gene, while the remainder of
LSINCTs are located within intergenic regions of the genome (Supp
Table 1). In addition to these 12 LSINCTs, our selection criteria also
recovered two previously characterized long non-coding transcripts,
tncRNA and MALAT1 (Supp. Fig. 3).
LSINCTs are longer than expected from the tiling array data
We analyzed the full size of the LSINCTs by utilizing Northern Blots.
tiling array data (Supp Table 1). This result is unexpected however not
surprising as the threshold value for IGB identified only transcripts
which contain a p-value of less than one. As seen in LSINCT10 (Supp
Fig. 1. Whole genome tiling array was conducted using RNA isolated from NHBE cells treated with NNK. 231,305 NNK-TARs, were identified with lengths ranging from 100 nt to
greater than 3000 nt. Further analysis identified 119 305 NNK-induced TARs. 1 305 NNK-induced TARs were then identified by excluding only TARs longer than 300 nts. Utilizing
criteria for non-coding RNAs identified 12 Long Stress-Induced Non-Coding Transcripts, LSINCTs.
Fig. 2. Tiling array data analyzed with the Integrated Genome Browser for LSINCT2 (Panel A) and LSINCT5 (Panel B) showing location. Top panels exhibiting difference of LSINCT
signal (vertical bars) with significant p value (white horizontal bar) in NHBE NNK-induced cells. Lower panels exhibit LSINCTs with a decreased signal in untreated NHBE cells (black
bars) compared to an increased signal in NHBE cells exposed to NNK (striped bars).
J.M. Silva et al. / Genomics 95 (2010) 355–362
instead of multiple smaller ones, which may be seen with some of the
other LSINCTs as well. For example, LSINCT2 has a RNA transcript of
∼3.5 kb as compared to an expected size of 311 nt based on tiling array
data. (Fig. 3)
In addition, we alsoused the Northern Blotsto validatethat each of
the LSINCTs did indeed have increased expression after exposure of
cells to NNK as seen in LSINCT2 and LSINCT5 (Fig. 3) which was also
validatedbyqPCR(Fig.5A).This furthervalidatedthetilingarray data.
Similar results were seen for the other 11 LSINCTs.
LSINCT location relative to genes
The LSINCTs analyzed here are located throughout the intergenic
and intragenic regions of the genome. We analyzed the upstream or
downstream genes nearest to each LSINCT. As indicated in Supple-
mentalTable 2, thereare several significant genes adjacentto LSINCTs,
including Epidermal Growth Factor Receptor (EGFR), HOXC4, and
InsulinGrowthFactorBindingProtein4 (IGFBP4)adjacentto LSINCT1,
LSINCT2, and LSINCT6, respectively. LSINCT RNA transcripts range
from 3.5 kb to 4 kb in length, suggesting that several of these non-
coding transcripts could be part of the transcriptional units of the
closest associated genes. The close proximity of several of these
LSINCTs to the closest adjacent genes suggested that these transcripts
could be part of the transcriptional output from that gene. In order to
rule this out we created PCR primers within each of these LSINCTs and
multiple primers withindifferentregions of the closest adjacentgenes
but could not amplify products with these primer pairs utilizing cDNA
made from NHBE-NNK induced RNA. This suggests that these LSINCTs
are not part of the major transcript arising from these adjacent genes
(data not shown).
LSINCTs are induced by stress
In order to further validate that the expression of the LSINCTs is
induced by stress, random primed cDNA made from NHBE cells and
NHBE cells exposed to NNK was analyzed for the expression of each
LSINCT using quantitative real time RT-PCR (qPCR). LSINCTs 1-12
displayed an average of 2 to 4-fold greater expression in NHBE cells
after NNK treatment (Fig. 5A). We also studied the expression of
LSINCTs in NNK-induced MCF7 cells (Fig. 5B). The expression of
LSINCTs 2, 4, 5, 6, and 9 was increased by NNK, expression of LSINCTs
1, 8, and 12 was decreased, and there was no change in the expression
of LSINCTs 10 or 11. These data indicate that there are differences in
LSINCT inducibility in various tissue-derived cell lines.
LSINCT Expression in a panel of normal human tissues
In addition to examining the expression of LSINCTs in NNK-induced
cells, we monitored LSINCT expression in ten normal tissues (Supp
spleen. We found the LSINCTs to have lower expression in other normal
tissues including liver, brain, ovary, kidney, gall bladder, cervix, and
expressed in proliferative stress-responsive normal tissues whereas
LSINCT expression in a panel of lung and breast cancer cell lines
in proliferative stress-responsive normal tissue, led us to examine the
correlation of LSINCTs in carcinogenesis. As NNK is one of the most
carcinogenic tobacco-specific nitrosamines and has been shown to
induce lung cancer , we firstchosetoexamineLSINCT expression in
a lung cancer cell line panel (Supp Table 4). We found that all LSINCTs
contained at least a 2-fold overexpression in at least one of the lung
cancer cell lines (Fig. 6A). The cell line that showed the greatest
increases in expression of the largest number of LSINCTs was NCI-1437.
NNK treatment has been previously shown to induce breast
carcinogenesis and has also been used to identify O6-Methylguanine
DNA adducts in maternal rats mammary glands [32,38]. In order to
identify if our newly discovered NNK-induced LSINCTs also have an
Fig. 3. Northern Blots for (A) LSINCT2 and LSINCT5 expression in NHBE and NHBE NNK-
induced cells showing length ∼3.5 kb and increased expression in NNK-induced cells.
(B) LSINCT2 (∼3.5 kb) and LSINCT6 (∼4 kb) expression in MCF7 and MCF7 NNK-
induced cells. LSINCTs show higher expression in MCF7 cells compared to MCF7-NNK-
induced cells analyzed to actin.
Fig. 4. LSINCT expression ina panel of normal tissues. LSINCTs contain higherexpressionin normal tissues that are localizedin stress environments.Experiments wererepeated three
times in triplicate.
J.M. Silva et al. / Genomics 95 (2010) 355–362
in a breast cancer cell line panel derived from both primary and
increased expression in at least several of the breast cancer cell lines
two of the breast cancer cell lines: HCC1500 and HCC1569 (Fig. 6B). In
addition to qPCR analysis we also compared LSINCT expression in
MCF7 with or without NNK treatment by Northern Blot (Fig. 3B).
LSINCT2 and LSINCT6 were expressed higher in the breast cancer cell
line MCF7 when exposed to NNK demonstrating that here is indeed
higher expression of LSINCTs under stressful conditions.
Fig. 7 shows that LSINCT2 and LSINCT5 were overexpressed in
most breast cancer cell lines (6 of 7) with LSINCT5 showing significant
overexpression in all breast cancer cell lines. This is not seen in the
lung cancer panel as LSINCT2 has overexpression in half of the cell
lines whereas LSINCT5 does not have significant overexpression in
any lung cancer cell lines. These data indicate altered cancer
expression of the LSINCTs and show a correlation of LSINCTs with
The discovery that the majority of the human genome is transcrip-
tionally active has resulted in a number of studies aimed at
characterizing the large number of non-coding transcripts produced
across the genome. While most of the current work has focused on the
identification of novel smaller ncRNAs suchasthe miRNAs, a number of
considerably larger non-coding transcripts have been identified. A
number of these have been characterized and many of them have been
found to be important cellular regulators. Several of these have been
found to be stress responsive and associated with cancer.
We therefore utilized a unique genome-wide search for long stress-
induced non-coding transcripts. NHBE cells were exposed to high
concentrations of NNK, a carcinogen produced in cigarette smoke, and
transcripts were compared to untreated cells by hybridization to an
Affymetrix whole-genome tiling array. Utilizing a stringent selection
process we have now identified 12 Long Stress-Induced Non-Coding
Transcripts. In addition, our screen identified two previously known
adjacent long non-coding transcripts, tncRNA and MALAT1. These long
ncRNAs are recognized as important regulators in various cancers. Our
analysis also identifies these two transcripts as stress-responsive non-
Currently, there is a growing number of long regulatory ncRNAs
associated with stress and cancer. These ncRNAs include well-known
XIST and HOTAIR (Hox transcript antisense RNA) [15,39]. There is evi-
to regulate gene expression patterns through epigenetic effects. It is
unknown whether the LSINCTs we identified are included in this class of
long regulatory ncRNAs. Other regulatory ncRNAs associated with stress
and cancer include the 2 kb transcribed antisense to beta-secretase-1
(BACE1-AS) gene. BACE1-AS has been found to regulate BACE1 in
when induced by various cellular stressors.[40,41] Another important
long ncRNA associated with prostate cancer is the 1.6 kb long prostate
tissue-specific and prostate cancer-associated ncRNA PCGEM1 (Prostate
Cancer Gene Expression Marker 1). Fu et. al has recently identified
overexpression of PCGEM1 in a LNCAP model that led to inhibition of
apoptosis by the induction of doxorubicin. This list does not entirely
cover all long ncRNAs , however our data raises the possibility that
LSINCT expression also plays a role in cellular stress and carcinogenesis.
We used both qPCR and Northern Blot analysis to show that the 12
showed the 12 LSINCTs to be considerably larger in size than expected
from the tiling array results with each transcript being between 2 and
4 kb in length. This could be caused by two reasons. The first is that
there was an arbitrary cut-off for significant signals and if several
larger transcript into multiple smaller ones. In addition, since there is
repeat masking in the tiling array design there are instances where
thatwouldresult in thefalse impressionthatonelargertranscriptwas
actually several smaller transcripts. In addition to examining LSINCT
expression in normal lung cells following exposure to NNK, we also
Fig. 5. (A) LSINCT1-LSINCT12 expression in NHBE cells (white bars), and NHBE cells treated with NNK (black bars). (B) LSINCT1-LSINCT12 expression in MCF7 cells (white bars) and
MCF7 cells induced with NNK (black bars). Experiments were repeated three times and done in triplicates.
J.M. Silva et al. / Genomics 95 (2010) 355–362
cell lines following a similar exposure to NNK, as NNK has been shown
to be associated with breast carcinogenesis.
These data revealed that, although LSINCTs expression could be
detected in each of the tissues tested, expression was higher in
proliferative or stress-responsive tissues (spleen and colon). In contrast
We also measured the expression of the LSINCTs in a panel of lung
cancer cell lines ascompared to thenormal cell lineNHBE. This analysis
cancer cell lines we utilized were non-small cell lung cancer
adenocarcinomas with the exception of NCI-358, which is a bronch-
ioalveolar carcinoma cell line. Although NNK has been shown to
primarily induce lung adenocarcinomas, we are the first to show the
expression of our NNK-induced transcripts in a bronchioalveolar cell
line, indicating that NNK may also promote these types of cancers.
NNK's ability to transform immortalized breast cells and promote
tumorgenesis in breast tumor models led us to examine LSINCT expres-
sion in breast cancer cell lines. This revealed that each of the LSINCTs
to normal breast epithelial cell line (HMEC) and immortalized MCF10
cells. Further analysis indicates some LSINCT overexpression in the
breast cell lines that are HER2- and TP53+ (Supplemental Table 6).
Further analysis of the LSINCTs which were over-expressed in the
breast cancer panel has allowed us to fully characterize several
LSINCTs in detail. For instance, we have validated the larger transcript
of LSINCT5 by RNA Amplification of cDNA Ends (RACE) to corroborate
the Northern Blots, showing it is indeed a 2.5 kb transcript. In this
process, we have also found LSINCT5 to be polyadenylated and
transcribed in trans. It also has increased expression in several other
cancers including cancers of the cervix and ovary.
Our preliminary studies have therefore identified a group of long
stress-responsive non-coding transcripts. It should be realized that
there are probably many more stress responsive transcripts through-
out the genome as we have utilized a very stringent screen which may
have ruled out a number of viable non-coding transcripts and
examined only those induced by NNK. We also identified a similar
number of non-coding transcripts that had decreased expression after
exposure to NNK. We are currently characterizing several of the
LSINCTs in more detail to determine the precise role that they play in
cellular stress and in cancer development.
JS carried out the analysis of identifying non-coding transcripts and
tiling array and helped draft manuscript. JP conducted qPCR experi-
ments. MH conducted qPCR experiments. HTparticipated in design and
analysis of tiling array. DS conceived of thestudy, participated in design
of tiling array, supervised all individuals, and helped draft manuscript.
All authors read and approved the final manuscript.
Fig. 7. LSINCT2 (panel A) and LSINCT5 (panel B) fold expression difference in a panel of
lung cancer cell lines and a panel of breast cancer cell lines.
Fig. 6. Panel of lung cancer cell lines (A) and breast cancer cell lines (B) showing the
number of LSINCTs with more than 2 fold increase expression as compared to NHBE or
HMEC cells. Experiments were repeated two times and done in triplicate.
J.M. Silva et al. / Genomics 95 (2010) 355–362
Conflict of interest statement Download full-text
The authors declare no conflict of interest.
We acknowledge the Mayo Clinic Microarray Core Facility for
assistance with tiling array experiments. We would like to thank Louis
Maher III, Ph.D. for revisions and comments on this manuscript. This
work was funded by the Mayo Foundation and the Department of
Defense Breast Cancer Program for funding this as a Concept Award
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