Salivary Biomarker
Salivary Biomarker
Salivary Biomarker
http://genomemedicine.com/content/4/5/82
REVIEW
Abstract
The use of saliva as a diagnostic sample provides a
non-invasive, cost-ecient method of sample collection
for disease screening without the need for highly
trained professionals. Saliva collection is far more
practical and safe compared with invasive methods of
sample collection, because of the infection risk from
contaminated needles during, for example, blood
sampling. Furthermore, the use of saliva could increase
the availability of accurate diagnostics for remote and
impoverished regions. However, the development of
salivary diagnostics has required technical innovation
to allow stabilization and detection of analytes in the
complex molecular mixture that is saliva. The recent
development of cost-effective room temperature
analyte stabilization methods, nucleic acid preamplification techniques and direct saliva transcriptomic
analysis have allowed accurate detection and
quantification of transcripts found in saliva. Novel protein
stabilization methods have also facilitated improved
proteomic analyses. Although candidate biomarkers
have been discovered using epigenetic, transcriptomic,
proteomic and metabolomic approaches, transcriptomic
analyses have so far achieved the most progress
in terms of sensitivity and specificity, and progress
towards clinical implementation. Here, we review recent
developments in salivary diagnostics that have been
accomplished using genomic, transcriptomic, proteomic
and metabolomic approaches.
Saliva: a biospecimen for non-invasive and
accurate disease detection
The discovery that saliva contains molecular profiles that
reflect systemic diseases has opened the doors to a new
noninvasive diagnostic methodology: salivary diagnostics.
*Correspondence: dtww@ucla.edu; nicolai@bonne.no
School of Dentistry and Dental Research Institute, University of California Los
Angeles, 650 Charles Young Drive, CHS 73-032, Los Angeles, California, USA
2010 BioMed Central Ltd
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Table 1. Promising oral, and head and neck cancer salivary biomarkers discovered using epigenomics, transcriptomics,
proteomics and metabolomics
Approach
Markers
Sensitivity/
specificity (%)/AUC
Epigenomics
NR
34.1/91.8/0.63
24.0/97.1/0.61
KIF1A, EDNRB
77.4/93.1/NR
EDNRB
65/51/0.61
77/83/NR
69/96/NR
62/100/NR
HOXA9, NID2
50/90/0.77
91/91/0.95
71/89/0.81
79/77/0.86
80/77/0.85
64/86/0.78
87/56/0.75
miR-200a
NR/NR/0.65
miR-125a
NR/NR/0.62
miR-31
80/68/0.82
90/83/0.93
IL-8
86/97/0.98
Combination
of proteomic/
transcriptomics
0.89/0.78/0.86,
0.67/0.96/0.85,
0.82/0.84/0.88 for
OSCC total/T1-T2/T3T4 respectively
Metabolomics
86.5/82.4/0.89
Transcriptomics
Proteomics
Discovery by CE-TOF-MS-based metabolomics [7] Taurine, piperidine and a peak at 120.0801 m/z
NR/NR/0.87
AUC, area under curve; CE-TOF-MS, capillary electrophoresis time-of-flight mass spectrometry; ELISA, enzyme-linked immunosorbent assay; HNSCC, head and
neck squamous cell carcinoma; LC, liquid chromatography; MS, mass spectrometry; NR, not reported; OSCC, oral squamous cell carcinoma; Q-MSP, quantitative
methylation-sensitive PCR; qPCR, quantitative PCR; qRT-PCR, quantitative reverse transcription PCR; RT-preamp-qPCR, reverse transcription preamplification
quantitative PCR; ULC/Q-TOF-MS, ultraperformance liquid chromatography coupled with quadruple/time-of-flight mass spectrometry; C4 RP-LC, C4 reversed-phase
liquid chromatography.
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Table 2. Promising salivary biomarkers for other diseases discovered using transcriptomics, proteomics and
metabolomics
Approach
Markers
Sensitivity/
specificity (%)/AUC
Transcriptomics
90.0/95.0/0.97
93.75/82.8/0.93
MIP-1
94/92.7/0.94
IL-6, IL-8
Proteomics
88.5/92.3/0.9
Combination
proteomic/
transcriptomic
approaches
83/97/92% accuracy
Metabolomics
NR/NR/0.99
NR
NR/NR/0.97
94/81/86% accuracy
Protein: CA6
AUC, area under curve; CE-TOF-MS, capillary electrophoresis time-of-flight mass spectrometry; ELISA, enzyme-linked immunosorbent assay; HR, high responder;
LC-MS-MS, liquid chromatography-tandem mass spectrometry; LR, low responder; NR, not reported; qRT-PCR, quantitative reverse transcription PCR; RT-PCR, reverse
transcription PCR; SERS, surface-enhanced Raman spectroscopy; 2D-DIGE, two-dimensional difference gel electrophoresis.
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Exosomes
Exosomes might be involved in transport of systemic biomarkers to saliva or transport of effectors of salivary gland transcriptional
machinery from blood to the salivary glands. These membrane bound microvesicles of 30 to 100 nm in diameter and endocytic origin [91]
are secreted by many cell types in diseased and non-diseased states. Exosomes contain protein, RNA and DNA, and have been found in
most body fluids, including saliva [92-95]. Using in vitro methods, studies have shown that exosomes secreted from one cell can be taken
up by other cells and can influence the receiving cells transcriptional signature [92,96,97]. Intercellular communication via exosomes can
also occur between normal cells and cancer cells and between cancer cells and distant sites. This has been suggested as a mechanism
by which cancer cells prepare distant sites for receiving metastatic cells [98,99]. Exosomes protect their contents from enzymatic
degradation, suggesting a role in intercellular transport of molecules [6,97,100]. Similarities between serum and saliva biomarker profiles
and the co-existence of exosomes in saliva and serum [101] also suggest the involvement of exosomes in transport of salivary biomarkers.
Furthermore, a recent in vitro investigation showed that tumor-derived exosomes can interact with salivary gland cells and activate their
transcriptional machinery [102].
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Salivary diagnostics
Early-stage disease detection is imperative for successful
therapy for most cancers, and the ability to quickly
identify suspicious lesions will also greatly reduce
hospital burdens. In the future, salivary diagnostics is
expected to facilitate rapid, easily accessible and noninvasive clinical diagnosis, thus allowing more cases of
disease to be detected at early stages and decreasing
mortality caused by oral and systemic cancers, and
infectious diseases.
Oral disease detection
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General population
Breast cancer
Monitor
Oral cancer
Concluding remarks
The use of saliva as a diagnostic specimen avoids the
pain, anxiety and infection risk associated with tradi
tional methods of specimen collection, such as blood
sampling or tissue biopsy. Saliva sampling also facilitates
the collection of multiple subsequent samples for disease
monitoring. Processing and analysis of saliva is also much
easier than blood and other samples. Unlike blood, saliva
does not clot and salivary analytes are very stable.
Analytes must be cost efficiently and easily stabilized for
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doi:10.1186/gm383
Cite this article as: Bonne NJ, Wong DTW: Salivary biomarker development
using genomic, proteomic and metabolomic approaches. Genome Medicine
2012, 4:82.