Circulating microRNAs as blood-based markers for patients with primary and metastatic breast cancer

Identification of circulating microRNA signatures for breast cancer detection

PURPOSE

There is a quest for novel noninvasive diagnostic markers for the detection of breast cancer. The goal of this study is to identify circulating microRNA (miRNA) signatures using a cohort of Asian Chinese patients with breast cancer, and to compare miRNA profiles between tumor and serum samples.

EXPERIMENTAL DESIGN

miRNA from paired breast cancer tumors, normal tissue, and serum samples derived from 32 patients were comprehensively profiled using microarrays or locked nucleic acid real-time PCR panels. Serum samples from healthy individuals (n = 22) were also used as normal controls. Significant serum miRNAs, identified by logistic regression, were validated in an independent set of serum samples from patients (n = 132) and healthy controls (n = 101).

RESULTS

The 20 most significant miRNAs differentially expressed in breast cancer tumors included miRNA (miR)-21, miR-10b, and miR-145, previously shown to be dysregulated in breast cancer. Only 7 miRNAs were overexpressed in both tumors and serum, suggesting that miRNAs may be released into the serum selectively. Interestingly, 16 of the 20 most significant miRNAs differentially expressed in serum samples were novel. MiR-1, miR-92a, miR-133a, and miR-133b were identified as the most important diagnostic markers, and were successfully validated; receiver operating characteristic curves derived from combinations of these miRNAs exhibited areas under the curves of 0.90 to 0.91.

CONCLUSION

The clinical use of miRNA signatures as a noninvasive diagnostic strategy is promising, but should be further validated for different subtypes of breast cancers.

Cancer diagnosis and prognosis decoded by blood-based circulating microRNA signatures

In the recent years, circulating microRNAs (miRNAs) have garnered a lot of attention and interest in the field of disease biomarkers. With characteristics such as high stability, low cost, possibility of repeated sampling and minimal invasiveness, circulating miRNAs are ideal for development into diagnostic tests. There have been many studies reported on the potential of circulating miRNAs as early detection, prognostic, and predictive biomarkers in cancer. Here, we have reviewed the application of plasma and serum miRNAs as biomarkers for cancer focusing on epithelial carcinomas [prostate, breast, lung, colorectal, and gastric cancer (GC)] and hematological malignancies (leukemia and lymphoma). We have also addressed the common challenges that need to be overcome to achieve a successful bench to bedside transition.

Deregulated serum concentrations of circulating cell-free microRNAs miR-17, miR-34a, miR-155, and miR-373 in human breast cancer development and progression

BACKGROUND

MicroRNAs (miRs) are small, noncoding RNAs that target genes involved in tumor development and progression. In the current study, we investigated the use of circulating miR concentrations as biomarkers in the serum of breast cancer patients.

METHODS

We analyzed serum samples from 120 patients with primary breast cancer after surgery and before chemotherapy (M0, classified into 3 subgroups of 40 patients with progesterone/estrogen-positive, HER2-positive, and triple-negative cancer), 32 patients with overt metastasis (M1), and 40 healthy women. Using quantitative TaqMan MicroRNA PCR, we measured the relative concentrations of 6 circulating microRNAs (miR-10b, -17, -34a, -93, -155, and -373) known to be relevant for tumor development and progression. The data were correlated with clinicopathologic risk factors, with particular reference to HER2 and hormone receptor status of the primary tumor and the presence of metastases.

RESULTS

The relative serum concentrations of circulating miR-34a [P = 0.013, area under the curve (AUC) 0.636], miR-93 (P = 0.001, AUC 0.699), and miR-373 (P = 0.0001, AUC 0.879) were significantly different between M0 breast cancer patients and healthy women, whereas miR-17 (P = 0.002, AUC 0.679) and miR-155 (P = 0.0001, AUC 0.781) were differently expressed between M0 and M1 patients. Increased concentrations of miR-373 were associated with negative HER2 status of the primary tumor (P = 0.0001). Deregulated concentrations of miR-17 (P = 0.019) and miR-34a (P = 0.029) were detected in patients with progesterone/estrogen receptor-positive and -negative status, respectively.

CONCLUSIONS

Our findings indicate that serum concentrations of deregulated microRNAs may be linked to a particular biology of breast carcinomas favoring progression and metastatic spread.

Hide and seek: tell-tale signs of breast cancer lurking in the blood

Breast cancer treatment is improving due to the introduction of new drugs, guided by molecular testing of the primary tumour for mutations/oncogenic drivers (e.g. HER2 gene amplification). However, tumour tissue is not always available for molecular analysis, intra-tumoural heterogeneity is common and the "cancer genome" is known to evolve with time, particularly following treatment as resistance develops. After resection, those patients with only residual micrometastases are likely to be cured but those with radiologically detectable overt disease are not. Thus, the discovery of blood test(s) that could (1) alert clinicians to early primary or recurrent disease and (2) monitor response to treatment could impact significantly on mortality. Towards this, we and others have focused on molecular profiling of circulating nucleic acids isolated from plasma, both cell-free DNA (cfDNA) and microRNAs, and the relationship of these to circulating tumour cells (CTCs). This review considers the utility of each as circulating biomarkers in breast cancer with particular emphasis on the bioinformatic tools available to support molecular profiling.

Methylated DNA and microRNA in body fluids as biomarkers for cancer detection

Epigenetic alterations including DNA methylation and microRNAs (miRNAs) play important roles in the initiation and progression of human cancers. As the extensively studied epigenetic changes in tumors, DNA methylation and miRNAs are the most potential epigenetic biomarkers for cancer diagnosis. After the identification of circulating cell-free nuclear acids, increasing evidence demonstrated great potential of cell-free epigenetic biomarkers in the blood or other body fluids for cancer detection.

MicroRNAs activate natural killer cells through Toll-like receptor signaling

MicroRNAs (miRNAs) bind to complementary sequences of target mRNAs, resulting in translational repression or target degradation and thus gene silencing. miRNAs are abundant in circulating blood, yet it is not known whether, as a class of regulatory molecules, they interact with human natural killer (NK) cells. Here we found that the treatment of human NK cells with several mature miRNAs in the presence of a low concentration of interleukin-12 induced CD69 expression, interferon-γ production, and degranulation marker CD107a expression. In vivo, infusion of several miRNAs alone in murine peripheral blood also resulted in comparable NK-cell activation, but not T-cell activation. Furthermore, miRNA administration significantly protected mice from tumor development in an NK cell-dependent manner. Mechanistically, we found that miRNA stimulation led to downstream activation of nuclear factor κB (NF-κB), an effect that was blunted by a block in Toll-like receptor 1(TLR1) signaling and attenuated in lymphoma patients. Knockdown of TLR1 resulted in less activation by miRNAs. Collectively, we show that miRNAs have a capacity to selectively activate innate immune effector cells that is, at least in part, via the TLR1-NF-κB signaling pathway. This may be important in the normal host defense against infection and/or malignant transformation.

Dampening enthusiasm for circulating microRNA in breast cancer

Genome-wide platforms for high-throughput profiling of circulating miRNA (oligoarray or miR-Seq) offer enormous promise for agnostic discovery of circulating miRNA biomarkers as a pathway for development in breast cancer detection. By harmonizing data from 15 previous reports, we found widespread inconsistencies across prior studies. Whether this arises from differences in study design, such as sample source or profiling platform, is unclear. As a reproducibility experiment, we generated a genome-wide plasma miRNA dataset using the Illumina oligoarray and compared this to a publically available dataset generated using an identical sample size, substrate and profiling platform. Samples from 20 breast cancer patients, 20 mammography-screened controls, as well as 20 breast cancer patients after surgical resection and 10 female lung or colorectal cancer patients were included. After filtering for miRNAs derived from blood cells, and for low abundance miRNAs (non-detectable in over 10% of samples), a set of 522 plasma miRNAs remained, of which 46 were found to be differentially expressed between breast cancer patients and healthy controls (p<0.05), of which only 3 normalized to baseline levels in post-resection cases and were unique to breast cancer vs. lung or colorectal cancer (miR-708*, miR-92b* and miR-568, none previously reported). We were unable to demonstrate reproducibility by various measures between the two datasets. This finding, along with widespread inconsistencies across prior studies, highlight the need for better understanding of factors influencing circulating miRNA levels as prerequisites to progress in this area of translational research.

Non-Coding RNAs: Functional Aspects and Diagnostic Utility in Oncology

Noncoding RNAs (ncRNAs) have been found to have roles in a large variety of biological processes. Recent studies indicate that ncRNAs are far more abundant and important than initially imagined, holding great promise for use in diagnostic, prognostic, and therapeutic applications. Within ncRNAs, microRNAs (miRNAs) are the most widely studied and characterized. They have been implicated in initiation and progression of a variety of human malignancies, including major pathologies such as cancers, arthritis, neurodegenerative disorders, and cardiovascular diseases. Their surprising stability in serum and other bodily fluids led to their rapid ascent as a novel class of biomarkers. For example, several properties of stable miRNAs, and perhaps other classes of ncRNAs, make them good candidate biomarkers for early cancer detection and for determining which preneoplastic lesions are likely to progress to cancer. Of particular interest is the identification of biomarker signatures, which may include traditional protein-based biomarkers, to improve risk assessment, detection, and prognosis. Here, we offer a comprehensive review of the ncRNA biomarker literature and discuss state-of-the-art technologies for their detection. Furthermore, we address the challenges present in miRNA detection and quantification, and outline future perspectives for development of next-generation biodetection assays employing multicolor alternating-laser excitation (ALEX) fluorescence spectroscopy.

The significance and robustness of a plasma free amino acid (PFAA) profile-based multiplex function for detecting lung cancer

Background

We have recently reported on the changes in plasma free amino acid (PFAA) profiles in lung cancer patients and the efficacy of a PFAA-based, multivariate discrimination index for the early detection of lung cancer. In this study, we aimed to verify the usefulness and robustness of PFAA profiling for detecting lung cancer using new test samples.

Methods

Plasma samples were collected from 171 lung cancer patients and 3849 controls without apparent cancer. PFAA levels were measured by high-performance liquid chromatography (HPLC)–electrospray ionization (ESI)–mass spectrometry (MS).

Results

High reproducibility was observed for both the change in the PFAA profiles in the lung cancer patients and the discriminating performance for lung cancer patients compared to previously reported results. Furthermore, multivariate discriminating functions obtained in previous studies clearly distinguished the lung cancer patients from the controls based on the area under the receiver-operator characteristics curve (AUC of ROC = 0.731 ~ 0.806), strongly suggesting the robustness of the methodology for clinical use. Moreover, the results suggested that the combinatorial use of this classifier and tumor markers improves the clinical performance of tumor markers.

Conclusions

These findings suggest that PFAA profiling, which involves a relatively simple plasma assay and imposes a low physical burden on subjects, has great potential for improving early detection of lung cancer.

MicroRNA and Epigenetics: Diagnostic and Therapeutic Opportunities

MicroRNAs (miRNAs) are a large family of post-transcriptional regulators of gene expression that control cellular and developmental processes by targeting messenger RNAs (mRNA). These small non-coding RNAs (ncRNAs) are aberrantly expressed in cancer, and are known to contribute to tumorigenesis and disease progression. Therapeutic strategies based on modulating miRNAs activity are emerging due to the ability of these ncRNAs to influence cellular behavior. MiRNA levels predict disease prognosis and overall patient survival, and reconstituting their basal levels has been proven to inhibit tumor growth and metastasis. Different delivery mechanisms have been tested in vivo, however many challenges need to be overcome before their utilization in the clinic. Moreover, it has been found that circulating miRNAs in body fluids have the potential to reshape cancer diagnosis and prognosis by functioning as biomarkers and indicators of progression and metastasis. These miRNAs as biofluids-based biomarkers provide an alternative strategy for early diagnosis and treatment of cancer patients.

Circulating microRNAs as specific biomarkers for breast cancer detection

BACKGROUND

We previously showed microRNAs (miRNAs) in plasma are potential biomarkers for colorectal cancer detection. Here, we aimed to develop specific blood-based miRNA assay for breast cancer detection.

METHODOLOGY/PRINCIPAL FINDINGS

TaqMan-based miRNA profiling was performed in tumor, adjacent non-tumor, corresponding plasma from breast cancer patients, and plasma from matched healthy controls. All putative markers identified were verified in a training set of breast cancer patients. Selected markers were validated in a case-control cohort of 170 breast cancer patients, 100 controls, and 95 other types of cancers and then blindly validated in an independent set of 70 breast cancer patients and 50 healthy controls. Profiling results showed 8 miRNAs were concordantly up-regulated and 1 miRNA was concordantly down-regulated in both plasma and tumor tissue of breast cancer patients. Of the 8 up-regulated miRNAs, only 3 were significantly elevated (p<0.0001) before surgery and reduced after surgery in the training set. Results from the validation cohort showed that a combination of miR-145 and miR-451 was the best biomarker (p<0.0001) in discriminating breast cancer from healthy controls and all other types of cancers. In the blind validation, these plasma markers yielded Receiver Operating Characteristic (ROC) curve area of 0.931. The positive predictive value was 88% and the negative predictive value was 92%. Altered levels of these miRNAs in plasma have been detected not only in advanced stages but also early stages of tumors. The positive predictive value for ductal carcinoma in situ (DCIS) cases was 96%.

CONCLUSIONS

These results suggested that these circulating miRNAs could be a potential specific biomarker for breast cancer screening.

Circulating nucleic acids as biomarkers in breast cancer

During tumor development, tumor cells release their nucleic acids into the blood circulation. This process occurs by apoptotic and necrotic cell deaths along with active cell secretion, resulting in high levels of circulating DNA, mRNA, and microRNA in the blood of patients with breast cancer. As circulating cell-free tumor nucleic acids may reflect the characteristics of the primary tumor and even of micrometastatic cells, they may be excellent blood biomarkers for screening breast cancer. Assays that allow the repetitive monitoring of patients by using blood samples as liquid biopsy may be efficient in assessing cancer progression in patients whose tumor tissue is not available. This review evaluates the recent data on the potential use of circulating cell-free nucleic acids as biomarkers for breast cancer.

Isolation of circulating microRNA associated with RNA-binding protein

Circulating microRNAs (miRNAs) have been recently detected in extracellular body fluids and proved themselves as promising biomarkers for a broad spectrum of diseases. The techniques to isolate, detect, and characterize extracellular miRNAs vary significantly from report to report. In this chapter we describe a consistent, efficient and highly reproducible protocol for isolation and detection of microvesicles-free circulating miRNA from human blood plasma or cell culture media. Furthermore, since exosomes-free circulating miRNAs are associated with Argonaut proteins (the same proteins to which miRNAs are bound inside the cell), we provide a protocol for immunoprecipitation of AGO2 associated miRNAs.

Identification of prostate cancer-associated microRNAs in circulation using a mouse model of disease

MicroRNAs (miRNAs) derived from the cell-free fractions of blood are emerging as useful noninvasive markers of cancer. However, many tumors display significant molecular heterogeneity, which is likely to be reflected in the circulating miRNA fingerprints associated with that pathology. One strategy to minimize such heterogeneity is to employ genetically engineered mouse models of human cancer. Here, we describe a method to profile miRNAs in the serum of a mouse model of prostate cancer, TRansgenic Adenocarcinoma of Mouse Prostate (TRAMP), and discuss practical considerations for translating these potential biomarkers into a clinical setting.

The level of circulating miRNA-10b and miRNA-373 in detecting lymph node metastasis of breast cancer: potential biomarkers

MicroRNAs (miRNAs) are a class of small noncoding RNAs whose expression changes are associated with cancer development and invasion. We hypothesized that miR-10b and miR-373, which are increased in lymphatic metastatic tissues, could be directly assayed in the plasma and used to detect the lymph node status of breast cancer patients. Between November 2009 and January 2012, 35 breast ductal carcinoma patients with lymph node metastasis (N patients), 25 ductal carcinoma patients without lymph node metastasis (N(0) patients), and ten healthy female donors were enrolled in the study. Circulating miR-10b and miR-373 were determined in preoperative plasma samples by reverse transcription quantitative real-time PCR assay. In preliminary tests, the plasma levels of circulating miR-10b and miR-373 were found to be significantly higher in ten breast cancer patients with lymph node metastasis compared to ten N(0) patients and ten normal donors (P < 0.01). On validation analysis, the median value level of miR-10b in the 35 N patients was 4.44-fold (P < 0.01) increased, and miR-373 was 4.38-fold (P < 0.01) increased in comparison to the 25 N(0) patients. MiR-10b was used for differentiation of N patients from N(0) patients; the odds ratio was 2.19, and the value of the area under the receiver-operating curve (AUC) was 0.80, with sensitivity of 71 % and specificity of 72 %. For miR-373, the odds ratio was 2.62, and the AUC was 0.84, with sensitivity of 68 % and specificity of 89 %. A combination of the two circulating miRNAs further enhanced the sensitivity to 72 % and the specificity to 94.3 %. Our data suggest that circulating miRNA-10b and miRNA-373 are potential biomarkers for detecting the lymph node status of breast cancer.

MicroRNAs as potential biomarkers in human solid tumors

MicroRNAs (miRNAs) regulate the expression of approximately 30% of protein-coding genes. Functions of miRNAs are essential to maintain a steady state of cellular machinery. Dysregulations of miRNAs play pivotal roles in the initiation and progression of malignancies. Abnormal miRNA expressions have been found in a variety of human solid tumors. Furthermore, extracellular miRNAs could circulate in body fluids, and hence show great promise for refining diagnosis and prognosis of cancer. Here we review the progress of analysis of microRNAs as a potential approach for diagnosis and prognosis of solid cancer. We will also discuss obstacles in developing miRNAs as circulating biomarkers.

Identification of circulating microRNAs as diagnostic biomarkers for use in multiple myeloma

Background:

Multiple myeloma is a plasma cell disorder that is characterised by clonal proliferation of malignant plasma cells in the bone marrow, monoclonal paraprotein in the blood or urine and associated organ dysfunction. It accounts for approximately 1% of cancers and 13% of haematological cancers. Myeloma arises from an asymptomatic proliferation of monoclonal plasma cells termed monoclonal gammopathy of undetermined significance (MGUS).

Methods:

MicroRNA expression profiling of serum samples was performed on three patient groups as well as normal controls. Validation of the nine microRNAs detected as promising biomarkers was carried out using TaqMan quantitative reverse transcription PCR. MicroRNA levels in serum were normalised using standard curves to determine the numbers of microRNAs per μl of serum.

Results:

Three serum microRNAs, miR-720, miR-1308 and miR-1246, were found to have potential as diagnostic biomarkers in myeloma. Use of miR-720 and miR-1308 together provides a powerful diagnostic tool for distinguishing normal healthy controls, as well as patients with unrelated illnesses, from pre-cancerous myeloma and myeloma patients. In addition, the combination of miR-1246 and miR-1308 can distinguish MGUS from myeloma patients.

Conclusion:

We have developed a biomarker signature using microRNAs extracted from serum, which has potential as a diagnostic and prognostic tool for multiple myeloma.

Circulating microRNAs in exosomes indicate hepatocyte injury and inflammation in alcoholic, drug-induced, and inflammatory liver diseases

MicroRNAs are fine tuners of diverse biological responses and are expressed in various cell types of the liver. Here we hypothesized that circulating microRNAs (miRNAs) may serve as biomarkers of liver damage and inflammation. We studied miRNA-122, which is abundant in hepatocytes, and miR-155, -146a, and -125b, which regulate inflammation in immune cells in mouse models of alcoholic liver disease (ALD), drug (acetaminophen, APAP)-induced liver injury (DILI), and Toll-like receptor (TLR) 9+4 ligand-induced inflammatory cell-mediated liver damage. We found that serum/plasma miR-122 correlated with alanine aminotransferase (ALT) increases in the liver damage caused by alcohol, APAP, and TLR9 (CpG)+4 (LPS) ligands. MiR-155, a regulator of inflammation, was increased in serum/plasma in alcoholic and inflammatory liver injury. Alcohol failed to increase serum miR-122 in TLR4-deficient and p47phox-deficient mice that were protected from ALD. We found the most robust increase in plasma miR-122 in DILI and it correlated with the highest ALT levels. Consistent with the massive inflammatory cell infiltration in the liver, plasma miR-155 and miR-146a were significantly elevated after CpG+LPS administration. We show for the first time that, depending on the type of liver injury, circulating miRNAs are associated either with the exosome-rich or protein-rich compartments. In ALD and in inflammatory liver injury, serum/plasma miR-122 and miR-155 were predominantly associated with the exosome-rich fraction, whereas in DILI/APAP injury these miRNAs were present in the protein-rich fraction.

CONCLUSION

Our results suggest that circulating miRNAs may serve as biomarkers to differentiate between hepatocyte injury and inflammation and the exosome versus protein association of miRNAs may provide further specificity to mechanisms of liver pathology.

Cell-free Circulating miRNA Biomarkers in Cancer

Considerable attention and an enormous amount of resources have been dedicated to cancer biomarker discovery and validation. However, there are still a limited number of useful biomarkers available for clinical use. An ideal biomarker should be easily assayed with minimally invasive medical procedures but possess high sensitivity and specificity. Commonly used circulating biomarkers are proteins in serum, most of which require labor-intensive analysis hindered by low sensitivity in early tumor detection. Since the deregulation of microRNA (miRNA) is associated with cancer development and progression, profiling of circulating miRNAs has been used in a number of studies to identify novel minimally invasive miRNA biomarkers. In this review, we discuss the origin of the circulating cell-free miRNAs and their carriers in blood. We summarize the clinical use and function of potentially promising miRNA biomarkers in a variety of different cancers, along with their downstream target genes in tumor initiation and development. Additionally, we analyze some technical challenges in applying miRNA biomarkers to clinical practice.

Serum microRNA-155 as a potential biomarker to track disease in breast cancer

Background

One major impediment to improving the management of breast cancer is the current lack of tumor marker with sufficient sensitivity and specificity. A growing body of evidence implicates the diagnostic potential of circulating miRNAs in cancer detection. MiR-155 plays an important role in the pathogenesis of breast cancer. However, the level of circulating miR-155 and its clinical relevance are not well established. The objective of the current study was to learn more about serum miR-155 in patients with breast cancer.

Methodology/Principal Findings

Using quantitative reverse transcription polymerase chain reaction (RT-qPCR), we demonstrated that serum miR-155 had significant increased levels in breast cancer patients (n = 103) compared with healthy subjects (n = 55) (p<0.001), which had a mean fold change of 2.94. Receiver operating characteristic (ROC) analysis revealed that miR-155 had considerable diagnostic accuracy, yielding an ROC-AUC (the areas under the ROC curve) of 0.801 (sensitivity 65.0%, specificity 81.8%). In addition, sera from a subset of breast cancer patients (n = 29) were collected after surgery and after four cycles of chemotherapy to evaluate the effects of clinical treatment on serum levels of candidate miRNAs. Surprisingly, a decreased level of serum miR-155 was found; whereas the concentrations of carbohydrate antigen 15-3 (CA15-3), carcinoembryonic antigen (CEA) and tissue polypeptide specific antigen (TPS) did not show this trend. Our results revealed that 79% patients showed response or stable disease after therapy had declined levels of serum miR-155.

Conclusions/Significance

Our results suggest that serum miR-155 is a potential biomarker to discriminate breast cancer patients from healthy subjects. For the first time, we demonstrated a declined trend of miR-155 after surgery and chemotherapy, which raises the possibility to use it as an indicator for treatment response.

Potential role of blood microRNAs as non-invasive biomarkers for early detection of asymptomatic coronary atherosclerosis in obese children with metabolic syndrome

The pandemic of the childhood obesity represent a major public health problem all over the world. This leads to detection of many health conditions that were previously considered an adulthood diseases. The rise in the prevalence of the obesity and overweight among children means that the world will face an explosion in the prevalence of the metabolic syndrome (MS), which increases the risk of atherosclerotic disease and death in adulthood. The atherosclerotic process has proved to develop silently for decades during childhood and adolescence before the cardiovascular complications such as myocardial infarction and stroke occur. This means that obese children especially with MS could have heart attacks and suffer from heart disease in an age when they should be very healthy, but most of these data either derived from autopsy findings or studies that confirmed the presence of peripheral atherosclerosis. Very early detection of coronary atherosclerosis in obese children with metabolic syndrome through a non invasive method will be of great importance, allowing for early therapeutic intervention. The discovery of microRNAs (miRNAs) is considered a major scientific breakthrough in the last years; recent studies have suggested a potentially important role of miRNAs in the control of diversity aspects of cardiac functions in health and disease including coronary atherosclerosis. Moreover, circulating miRNAs profiles recently used as a non-invasive biomarker for diagnosis of multiple cardiovascular diseases. The identification of distinct circulating miRNA profiles may impact the development of specific miRNAs as biomarkers in pediatric cardiovascular diseases. Therefore, we postulate that some of these circulating miRNAs may be a potential biomarker for early non-invasive diagnosis of coronary atherosclerosis in very early asymptomatic stage in obese children with metabolic syndrome, giving an excellent chance to fight against the first killer in the adult population in childhood period.

Circulating microRNAs: new biomarkers in diagnosis, prognosis and treatment of cancer (review)

MicroRNAs (miRNAs) are small non-coding, endogenous, single-stranded RNAs. MiRNAs have been implicated in different areas such as the immune response, neural development, DNA repair, apoptosis, oxidative stress response and cancer. However, while the majority of miRNAs are found intracellularly, a significant number of miRNAs have been observed outside of cells, including various body fluids. Circulating miRNAs function as 'extracellular communication RNAs' that play an important role in cell proliferation and differentiation. MiRNA regulation is essential to many cellular processes, and escape from this regulatory network seems to be a common characteristic of several disease processes and malignant transformation. The interest in circulating miRNAs reflects in fact their central role in regulation of gene expression and the implication of miRNA-specific aberrant expression in the pathogenesis of cancer, cardiac, metabolic, neurologic, immune-related diseases as well as others. In our review we aimed to summarize the data related to the action of cellular miRNAs on the onset of various diseases, thus bringing together some of the latest information available on the role of circulating miRNAs. Additionally, the role of circulating miRNAs could be particularly relevant in the context of neoplastic diseases. At least 79 miRNAs have been reported as plasma or serum miRNA biomarkers of solid and hematologic tumors. Circulating miRNA profiling could improve the diagnosis of cancer, and could predict outcome for cancer patients, while the profiling of alterations in circulating miRNA that may signal a predisposition to cancer, could also be a therapeutic target in these patients.

Circulating microRNAs in cancer: diagnostic and prognostic significance

The involvement of microRNAs (miRs) in numerous pathological conditions is well established. In many kinds of cancer cells and animal models, various miRs have been shown to act as oncogenes or tumor suppressors. Recently, it was found that circulating miRs can be detected, and may be associated, with the clinicopathological features and prognosis of cancers, thus, providing potential novel diagnostic and prognostic markers for malignancies in humans. This review aims to address these issues based on recently published literature.

Circulating microRNA-92a and microRNA-21 as novel minimally invasive biomarkers for primary breast cancer

PURPOSE

MicroRNAs (miRNAs) play an essential role in breast malignant tumor development and progression. The development of clinically validated biomarkers for primary breast cancer (BC) has remained an insurmountable task despite other advances in the field of cancer molecular biology. The objective of this study is to investigate the differential expression of miRNAs and the potential of circulating microRNAs as novel primary breast cancer biomarkers.

METHODS

Our analyses were performed on 48 tissue and 100 serum samples of patients with primary BC and a set of 20 control samples of healthy women, respectively. The relative expression of ten candidate miRNAs (miR-106b, miR-125b, miR-17, miR-185, miR-21, miR-558, miR-625, miR-665, miR-92a, and miR-93) from the results of four bioinformatics approaches and literature curation was measured by real-time quantitative reverse transcription PCR (qRT-PCR).

RESULTS

The level of miR-92a was significantly lower, while miR-21 was higher, as previous reports, in tissue and serum samples of BC than that of healthy controls (p < 0.001). Logistic regression and receiver operating characteristic curve analyses revealed the significant and independent value (p < 0.001) of the miR-92a and miR-21 expression quantification in serums. Moreover, the comparison with the clinicopathologic data of the BC patients showed that decreased levels of miR-92a and increased levels of miR-21 were associated with tumor size and a positive lymph node status (p < 0.001).

CONCLUSIONS

These findings suggest that many miRNAs expressions are altered in BC, whose expression profiling may provide a useful clue for the pathophysiological research. Circulating miR-92a has potential use as novel breast cancer biomarker, which is comparable to miR-21.

MicroRNAs in common human diseases

MicroRNAs (miRNAs) are a class of short non-coding RNA molecules that have attracted tremendous attention from the biological and biomedical research communities over the past decade. With over 1900 miRNAs discovered in humans to date, many of them have already been implicated in common human disorders. Facilitated by high-throughput genomics and bioinformatics in conjunction with traditional molecular biology techniques and animal models, miRNA research is now positioned to make the transition from laboratories to clinics to deliver profound benefits to public health. Herein, we overview the progress of miRNA research related to human diseases, as well as the potential for miRNA to becoming the next generation of diagnostics and therapeutics.

Circulating microRNAs in plasma as early detection markers for breast cancer

In recent years, circulating miRNAs have attracted a great deal of attention as promising novel markers for various diseases. Here, we investigated their potential to serve as minimally invasive, early detection markers for breast cancer in blood plasma. We profiled miRNAs extracted from the plasma of early stage breast cancer patients (taken at the time-point of diagnosis) and healthy control individuals using TaqMan low-density arrays (TLDA). Selected candidates identified in the initial screen were further validated in an extended study cohort of 207 individuals including 127 sporadic breast cancer cases and 80 healthy controls via RT-qPCR. Four miRNAs (miR-148b, miR-376c, miR-409-3p and miR-801) were shown to be significantly upregulated in the plasma of breast cancer patients. ROC curve analysis showed that the combination of only three miRNAs (miR-148b, miR-409-3p and miR-801) had an equal discriminatory power between breast cancer cases and healthy controls as all four miRNAs together (AUC = 0.69). In conclusion, the identified miRNAs might be of potential use in the development of a multimarker blood-based test to complement and improve early detection of breast cancer. Such a multimarker blood test might for instance provide a prescreening tool, especially for younger women, to facilitate decisions about which individuals to recommend for further diagnostic tests.

Circulating miRNAs as surrogate markers for circulating tumor cells and prognostic markers in metastatic breast cancer

PURPOSE

The use of circulating tumor cells (CTC) as a prognostic marker in metastatic breast cancer (MBC) has been well established. However, their efficacy and accuracy are still under scrutiny mainly because of methods of their enrichment and identification. We hypothesized that circulating miRNAs can predict the CTC status of patients with MBC, and tested for the same. Furthermore, we aimed at establishing a panel of circulating miRNAs capable of differentiating MBC cases from healthy controls.

EXPERIMENTAL DESIGN

Circulating miRNAs from plasma of CTC-positive and CTC-negative patients with MBC, and healthy controls, were profiled by TaqMan Human MicroRNA arrays. Candidates from the initial screen were validated in an extended cohort of 269 individuals (61 CTC-positive, 72 CTC-negative, 60 CTC-low MBC cases, and 76 controls).

RESULTS

CTC-positive had significantly higher levels of miR-141, miR-200a, miR-200b, miR-200c, miR-203, miR-210, miR-375, and miR-801 than CTC-negative MBC and controls (P < 0.00001), whereas miR-768-3p was present in lower amounts in MBC cases (P < 0.05). miR-200b was singled out as the best marker for distinguishing CTC-positive from CTC-negative patients (AUC 0.88). We identified combinations of miRNAs for differentiating MBC cases from controls (AUC 0.95 for CTC-positive; AUC 0.78 for CTC-negative). Combinations of miRNAs and miR-200b alone were found to be promising prognostic marker for progression-free and overall survival.

CONCLUSION

This is the first study to document the capacity of circulating miRNAs to indicate CTC status and their potential as prognostic markers in patients with MBC.

Breast cancer and microRNAs: therapeutic impact

Despite advances in detection and therapies, breast cancer is still the leading cause of cancer death in women worldwide. The etiology of this neoplasm is complex, and both genetic and environmental factors contribute to the complicate scenario. Gene profiling studies have been extensively used over the last decades as a powerful tool to define the signature of different cancers and to predict outcome and response to therapies. More recently, a new class of small (19-25 nucleotides) non-coding RNAs, microRNAs (miRs or miRNAs) has been linked to several human diseases, included cancer. MicroRNAs are involved in temporal and tissue-specific eukaryotic gene regulation,(1) either by translational inhibition or exonucleolytic mRNA decay, targeted through imperfect complementarity between the microRNA and the 3' untranslated region (3'UTR) of the mRNA.(2) Since their ability to potentially target any human mRNA, it is likely that microRNAs are involved in almost every biological process, including cell cycle regulation, cell growth, apoptosis, cell differentiation and stress response.(3) The involvement of microRNAs in the biology of human cancer is supported by an increasing body of experimental evidence, that has gradually switched from profiling studies, as the first breast cancer specific signature reported in 2005 by our group(4) describing an aberrant microRNA expression in different tumor types, to biological demonstrations of the causal role of these small molecules in the tumorigenic process, and the possible implications as biomarkers or therapeutic tools.(5) These more recent studies have widely demonstrated that microRNAs can modulate oncogenic or tumor suppressor pathways, and that, at the same time, their expression can be regulated by oncogenes or tumor suppressor genes. The possibility to modulate microRNA expression both in vitro and in vivo by developing synthetic pre-microRNA molecules or antisense oligonucletides has at the same time provided a powerful tool to a deeper comprehension of the molecular mechanisms regulated by these molecules, and suggested the intriguing and promising perspective of a possible use in therapy. Here we review our current knowledge about the involvement of microRNAs in cancer, focusing particularly on breast cancer, and their potential as diagnostic, prognostic and therapeutic tools.

Peripheral blood microRNAs: A novel tool for diagnosing disease?

Peripheral blood microRNAs (miRNAs) are endogenous, noncoding small RNAs present in blood. Because of their size, abundance, tissue specificity, and relative stability in peripheral circulation, they offer great promise of becoming a novel noninvasive biomarker. However, the mechanism by which they are secreted, their biological function, and the reason for the existence of extracellular miRNAs are largely unclear. This article describes advances in the study of the mechanism of origin and biological function of extracellular miRNAs along with approaches adopted by research and questions that remain. This work also discusses the potential for peripheral blood miRNAs to serve as a diagnostic tool.

Circulating microRNAs: macro-utility as markers of prostate cancer?

The realization that microRNAs (miRNAs) are frequently deregulated in malignancy has had a major impact on cancer research. In particular, the recent finding that highly stable forms of miRNAs can be accurately measured in body fluids, including blood, has generated considerable excitement. Here, we discuss the potential of blood-based circulating miRNAs as diagnostic, prognostic, and predictive biomarkers of prostate cancer. We also describe practical considerations that may influence identification and/or measurement of miRNA biomarkers in the circulation. Finally, evidence is prevented for the emerging concept that circulating miRNAs are actively released by their cells of origin and can modulate gene expression at distal sites. These mobile miRNAs, which we term 'hormomirs' because of their hormone-like characteristics, could act as local or long-range signals to maintain normal homeostasis or influence the development and progression of diseases such as cancer.

Systemic mirnas as potential biomarkers for malignancy

MiRNAs are a class of short, endogenous, single-stranded RNA molecules that play a role in the regulation of gene expression. They have been shown to modulate a number of cellular processes including cell differentiation, growth and apoptosis and as a result have been implicated in carcinogenesis. They are detectable in tumour tissue, and altered expression levels have been identified in various cancer types. Of interest, miRNAs have recently been detected and identified to be dysregulated in the circulation of patients with breast cancer. The fact that a minimally invasive test can distinguish the presence or absence of disease illustrates the immense potential these molecules hold as predictive markers. This review serves to identify those systemic miRNAs that are upregulated or downregulated in malignancy and how treatment impacts on their circulating levels. In addition, this review questions the source of these small molecules in the bloodstream and how they may possibly play a role in the future detection of cancer as either prognostic or predictive markers.

Circulating microRNA profiles reflect the presence of breast tumours but not the profiles of microRNAs within the tumours

BACKGROUND

Extra-cellular microRNAs have been identified within blood and their profiles reflect various pathologies; therefore they have potential as disease biomarkers. Our aim was to investigate how circulating microRNA profiles change during cancer treatment. Our hypothesis was that tumour-related profiles are lost after tumour resection and therefore that comparison of profiles before and after surgery would allow identification of biomarker microRNAs. We aimed to examine whether these microRNAs were directly derived from tumours, and whether longitudinal expression monitoring could provide recurrence diagnoses.

METHODS

Plasma was obtained from ten breast cancer patients before and at two time-points after resection. Tumour tissue was also obtained. Quantitative PCR were used to determine levels of 367 miRNAs. Relative expressions were determined after normalisation to miR-16, as is typical in the field, or to the mean microRNA level.

RESULTS

210 microRNAs were detected in at least one plasma sample. Using miR-16 normalisation, we found few consistent changes in circulating microRNAs after resection, and statistical analyses indicated that this normalisation was not justifiable. However, using data normalised to mean microRNA expression we found a significant bias for levels of individual circulating microRNAs to be reduced after resection. Potential biomarker microRNAs were identified, including let-7b, let-7g and miR-18b, with higher levels associated with tumours. These microRNAs were over-represented within the more highly expressed microRNAs in matched tumours, suggesting that circulating populations are tumour-derived in part. Longitudinal monitoring did not allow early recurrence detection.

CONCLUSIONS

We concluded that specific circulating microRNAs may act as breast cancer biomarkers but methodological issues are critical.

Low levels of cell-free circulating miR-361-3p and miR-625* as blood-based markers for discriminating malignant from benign lung tumors

The high mortality rate of lung cancer patients is mainly due to the late stage at which lung cancer is diagnosed. For effective cancer prevention programs and early diagnosis, better blood-based markers are needed. Hence, blood-based microarray profiling of microRNA (miR) expression was performed in preoperative serum of 21 non-small cell lung cancer (NSCLC) patients and 11 healthy individuals by microfluid biochips containing 1158 different miRs. Two out of the 30 most dysregulated miRs were further validated in serum of 97 NSCLC patients, 20 patients with benign lung diseases and 30 healthy individuals by TaqMan MicroRNA Assays. Microarray profiling showed that miR-361-3p and miR-625* were significantly down-regulated in serum of lung cancer patients. Their further evaluation by quantitative RT-PCR showed that the levels of miR-361-3p and miR-625* were lower in NSCLC than in benign disease (p = 0.0001) and healthy individuals (p = 0.0001, p = 0.0005, respectively). Moreover, the levels of miR-625* were significantly lower in patients with large cell lung cancer (LCLC, p = 0.014) and smoking patients (p = 0.030) than in patients with adenocarcinoma and non-smoking patients, respectively. A rise in the levels of both miRs was observed in the postoperative samples compared with the preoperative levels (p = 0.0001). Functional analyses showed that Smad2 and TGFß1 are not dysregulated by miR-361-3p and miR-625* in the lung cell line A549, respectively. Our present pilot study suggests that miR-361-3p and miR-625* might have a protective influence on the development of NSCLC, and the quantitative assessment of these miRs in blood serum might have diagnostic potential to detect NSCLC, in particular in smokers.

Small RNAs have a large impact: circulating microRNAs as biomarkers for human diseases

The highly conserved RNAs, microRNAs (miRNAs), are a class of small single stranded noncoding RNAs that function through translational repression of specific target mRNAs. miRNAs exhibit a wide range of involvement regulating gene expressions. miRNA expression dysregulated in cancer cells and damaged tissues from different diseases implicates a functional role of miRNAs in the disease development. More recently miRNAs have been detected in cell-free serum, and these circulating miRNAs can distinguish diseased individuals from healthy controls. The noninvasive nature of circulating miRNA collection and their sensitivity and specificity in diseases has encouraged a pursuit of miRNA biomarker research. As a result, approximately 100 circulating miRNAs have been identified as biomarkers for different diseases, and the number is growing. Here we review recently reported circulating miRNA biomarkers and discuss their values and challenges for the disease biomarkers.

miRNA expression profiling for identification of potential breast cancer biomarkers

To identify micro RNA (miRNA) biomarker candidates for early detection of breast cancer and detection of minimal residual breast cancer, we performed miRNA expression profiling in pooled RNA samples from breast tumors, and from bone marrow mononuclear cells, peripheral blood mononuclear cells and plasma from healthy controls. We found substantially higher levels of five miRNAs in the breast tumors compared to the normal samples. However, validation of these miRNA levels, and seven other candidates selected from the literature, in individual samples from healthy controls and patients with non-metastatic breast cancer did not suggest further examination of their biomarker potential.

Complementary strand microRNAs mediate acquisition of metastatic potential in colonic adenocarcinoma

BACKGROUND

Altered expression of specific microRNAs (miRNA) is known to occur during colorectal carcinogenesis. However, little is known about the genome-wide alterations in miRNA expression during the neoplastic progression of primary colorectal cancers.

METHODS

Using a miRNA array platform, we evaluated the expression of 668 miRNA in primary colonic adenocarcinomas. Biological functions of selected miRNA were evaluated with in vitro invasion assays.

RESULTS

RNA was extracted for miRNA analysis from 65 primary colon cancers. We identified a seven-miRNA expression signature that differentiated stage I and stage IV primary colon cancers. We then demonstrated this signature was able to discriminate between stage II and III primary colon cancers. Six differentially expressed miRNA were downregulated in association with the development of metastases, and all 7 miRNA were complementary strand miRNA. We transfected HCT-116, a highly invasive colon cancer cell line, with corresponding downregulated miRNA and demonstrated that overexpression of three miRNA (miR200c*, miR143*, and miR424*) significantly abrogated invasive potential.

CONCLUSION

We have identified a seven-miRNA signature that is associated with metastatic potential in the primary tumor. Forced overexpression of three downregulated miRNA resulted in attenuation of in vitro invasion, suggesting direct tumor suppressive function and further supporting the biological importance of complementary strand miRNA.

Circulating microRNAs in cancer: origin, function and application

MicroRNAs (miRNAs) are a class of small non-coding RNAs that regulate gene expression at the posttranscriptional level. The dysregulation of miRNAs has been linked to a series of diseases, including various types of cancer. Since their discovery in the circulation of cancer patients, there has been a steady increase in the study of circulating miRNAs as stable, non-invasive biomarkers. However, the origin and function of circulating miRNAs has not been systematically elucidated. In this review, we summarize the discovery of circulating miRNAs and their potential as biomarkers. We further emphasize their possible origin and function. Finally, we discuss the application and existing questions surrounding circulating miRNAs in cancer diagnostics. Although several challenges remain to be concerned, circulating miRNAs could be useful, non-invasive biomarkers for cancer diagnosis.

miRNAs in breast cancer: ready for real time?

Over the past decade, major advances in our comprehension of breast cancer biology have led to improved diagnostic and prognostic techniques and the development of novel targeted therapies. However, the efficacy of new treatments remains limited by a combination of drug toxicity, resistance and persisting insufficiencies in our understanding of tumor-signaling pathways; furthermore, the reliability of identified biomarkers is contentious. Following their recent discovery, miRNAs have been established as critical regulators of gene expression, and their putative roles as oncogenes and tumor-suppressor genes has provided a potential new dimension to our clinical approach to breast cancer diagnosis and treatment. Their role as biomarkers and therapeutic targets is appealing; however, several barriers have limited our ability to translate this potential into a clinical reality. This review focuses on the currently accepted roles of miRNAs in breast cancer pathogenesis, and highlights the clinical challenges and breakthroughs in this field to date.

Circulating miR-378 and miR-451 in serum are potential biomarkers for renal cell carcinoma

Background

There is no standard serum biomarker used for diagnosis or early detection of recurrence for renal cell carcinoma (RCC) patients. MicroRNAs (miRNAs) are abundant and highly stable in blood serum, and have been recently described as powerful circulating biomarkers in a wide range of solid cancers. Our aim was to identify miRNA signature that can distinguish the blood serum of RCC patients and matched healthy controls and validate identified miRNAs as potential biomarkers for RCC.

Methods

In the screening phase of the study, blood serum of 15 RCC patients and 12 matched healthy controls were analyzed by use of the TaqMan Low-Density Arrays enabling parallel identification of expression levels of 667 miRNAs through qRT-PCR-based approach. In the validation phase, identified miRNAs were further evaluated on the independent group of 90 RCC patients and 35 matched healthy controls by use of individual qRT-PCR assays and statistically evaluated.

Results

We identified 30 miRNAs differentially expressed between serum of RCC patients and healthy controls: 19 miRNAs were up-regulated and 11 miRNAs were down-regulated in RCC patients. MiR-378, miR-451 and miR-150 were further evaluated in the independent group of patients, and two of them were successfully validated: levels of miR-378 were increased (p = 0.0003, AUC = 0.71), miR-451 levels were decreased (p < 0.0001, AUC = 0.77) in serum of RCC patients. Combination of miR-378 and miR-451 enable identification of RCC serum with the sensitivity of 81%, specificity 83% and AUC = 0.86.

Conclusions

Circulating miRNAs in serum are promising biomarkers in RCC.

De novo sequencing of circulating miRNAs identifies novel markers predicting clinical outcome of locally advanced breast cancer

Background

MicroRNAs (miRNAs) have been recently detected in the circulation of cancer patients, where they are associated with clinical parameters. Discovery profiling of circulating small RNAs has not been reported in breast cancer (BC), and was carried out in this study to identify blood-based small RNA markers of BC clinical outcome.

Methods

The pre-treatment sera of 42 stage II-III locally advanced and inflammatory BC patients who received neoadjuvant chemotherapy (NCT) followed by surgical tumor resection were analyzed for marker identification by deep sequencing all circulating small RNAs. An independent validation cohort of 26 stage II-III BC patients was used to assess the power of identified miRNA markers.

Results

More than 800 miRNA species were detected in the circulation, and observed patterns showed association with histopathological profiles of BC. Groups of circulating miRNAs differentially associated with ER/PR/HER2 status and inflammatory BC were identified. The relative levels of selected miRNAs measured by PCR showed consistency with their abundance determined by deep sequencing. Two circulating miRNAs, miR-375 and miR-122, exhibited strong correlations with clinical outcomes, including NCT response and relapse with metastatic disease. In the validation cohort, higher levels of circulating miR-122 specifically predicted metastatic recurrence in stage II-III BC patients.

Conclusions

Our study indicates that certain miRNAs can serve as potential blood-based biomarkers for NCT response, and that miR-122 prevalence in the circulation predicts BC metastasis in early-stage patients. These results may allow optimized chemotherapy treatments and preventive anti-metastasis interventions in future clinical applications.

miR-200b is involved in intestinal fibrosis of Crohn's disease

Intestinal fibrosis is one of the major serious complications of Crohn’s disease (CD). However, there are no effective antifibrotic drugs to treat intestinal fibrosis in CD. Therefore, it is important to understand the pathogenesis of fibrosis in CD. It has been reported that members of the miR-200 family are essential in the regulation of renal fibrogenesis. In this study, we analyzed the function of miR-200a and miR-200b in intestinal fibrosis, which was induced by transforming growth factor β1 (TGF-β1) in vitro. Furthermore, we detected the expression of miR-200a and miR-200b in CD specimens, which were divided into groups of fibrosis and no-fibrosis. The results of this study showed that administration of miR-200b could partially protect intestinal epithelial cells from fibrogenesis in vitro. Furthermore, we found that miR-200b was overexpressed in the serum of the fibrosis group. The results suggest that miR-200b has potential value for diagnostic and therapeutic applications for CD patients with fibrosis complications.

Circulating micro-RNAs as potential blood-based markers for early stage breast cancer detection

Introduction

MicroRNAs (miRNAs, miRs) are a class of small, non-coding RNA molecules with relevance as regulators of gene expression thereby affecting crucial processes in cancer development. MiRNAs offer great potential as biomarkers for cancer detection due to their remarkable stability in blood and their characteristic expression in many different diseases. We investigated whether microarray-based miRNA profiling on whole blood could discriminate between early stage breast cancer patients and healthy controls.

Methods

We performed microarray-based miRNA profiling on whole blood of 48 early stage breast cancer patients at diagnosis along with 57 healthy individuals as controls. This was followed by a real-time semi-quantitative Polymerase Chain Reaction (RT-qPCR) validation in a separate cohort of 24 early stage breast cancer patients from a breast cancer screening unit and 24 age matched controls using two differentially expressed miRNAs (miR-202, miR-718).

Results

Using the significance level of p<0.05, we found that 59 miRNAs were differentially expressed in whole blood of early stage breast cancer patients compared to healthy controls. 13 significantly up-regulated miRNAs and 46 significantly down-regulated miRNAs in our microarray panel of 1100 miRNAs and miRNA star sequences could be detected. A set of 240 miRNAs that was evaluated by radial basis function kernel support vector machines and 10-fold cross validation yielded a specificity of 78.8%, and a sensitivity of 92.5%, as well as an accuracy of 85.6%. Two miRNAs were validated by RT-qPCR in an independent cohort. The relative fold changes of the RT-qPCR validation were in line with the microarray data for both miRNAs, and statistically significant differences in miRNA-expression were found for miR-202.

Conclusions

MiRNA profiling in whole blood has potential as a novel method for early stage breast cancer detection, but there are still challenges that need to be addressed to establish these new biomarkers in clinical use.

Circulating microRNAs as noninvasive biomarkers in breast cancer

MicroRNAs (miRNAs) are master regulators of gene expression. By degrading or blocking translation of messenger RNA targets, these non-coding RNAs can modulate the expression of more than half the protein-coding genes in mammalian genomes. MiRNAs play important regulatory roles in a variety of cellular functions and in several diseases, including cancer. Aberrant miRNA expression has been well characterized in cancer, with implications for progression and prognosis. Recently, the discovery of miRNAs in body fluids, such as serum and plasma, opens up the possibility of using them as noninvasive biomarkers of disease and therapy response. In this chapter, we discuss the use of circulating miRNAs as biomarkers of disease and therapy response and as diagnostic and prognostic markers in breast cancer. We also discuss the main issues related to establishing circulating miRNAs as biomarkers in cancer.

Multiplex molecular analysis of CTCs

Beyond enumeration, CTC characterization is expected to help guide therapeutic selection for personalized care of cancer patients. Different approaches may be used to simultaneously identify multiple CTC-specific markers for biological characterization; yet awareness of associated pitfalls is also important. We have focused this chapter on molecular profiling of CTCs following enrichment. We describe the MagSweeper technology that was specifically developed to isolate live and highly purified CTCs for pooled or single cell or pooled cell molecular analyses or for CTC growth in vitro or in vivo. However, most of what is discussed will apply to any multiplex analysis of CTCs, irrespective of the enrichment method.

MicroRNA expression characterizes oligometastasis(es)

BACKGROUND

Cancer staging and treatment presumes a division into localized or metastatic disease. We proposed an intermediate state defined by ≤ 5 cumulative metastasis(es), termed oligometastases. In contrast to widespread polymetastases, oligometastatic patients may benefit from metastasis-directed local treatments. However, many patients who initially present with oligometastases progress to polymetastases. Predictors of progression could improve patient selection for metastasis-directed therapy.

METHODS

Here, we identified patterns of microRNA expression of tumor samples from oligometastatic patients treated with high-dose radiotherapy.

RESULTS

Patients who failed to develop polymetastases are characterized by unique prioritized features of a microRNA classifier that includes the microRNA-200 family. We created an oligometastatic-polymetastatic xenograft model in which the patient-derived microRNAs discriminated between the two metastatic outcomes. MicroRNA-200c enhancement in an oligometastatic cell line resulted in polymetastatic progression.

CONCLUSIONS

These results demonstrate a biological basis for oligometastases and a potential for using microRNA expression to identify patients most likely to remain oligometastatic after metastasis-directed treatment.

microRNAs as markers of survival and chemoresistance in pancreatic ductal adenocarcinoma

microRNAs (miRs) are a recently recognized class of noncoding short RNAs, 17-25 nucleotides in length, that play a role in post-transcriptional gene regulation by translational repression and/or mRNA degradation. Various miRs have been highlighted in pancreatic cancer development and metastasis, and as potential clinical diagnostic/prognostic biomarkers. Recently, studies have indicated that miRs are responsible for resistance to chemotherapeutic agents. The miR-10b has been identified as a 'metastamiR' in various tumor types, notably breast cancer, but data surrounding its relevance in pancreatic ductal adenocarcinoma has been sparse. The evaluated article presents data indicating that miR-10b is upregulated in pancreatic ductal adenocarcinoma and can be used as a diagnostic marker in endoscopic ultrasound-guided fine-needle aspiration biopsies of suspicious pancreatic lesions. In addition, miR-10b may be able to guide neoadjuvant gemcitabine-based chemoradiotherapy and predict metastatic-free survival and overall survival.

Micro-RNAs as diagnostic or prognostic markers in human epithelial malignancies

Micro-RNAs (miRs) are important regulators of mRNA and protein expression; the ability of miR expression profilings to distinguish different cancer types and classify their sub-types has been well-described. They also represent a novel biological entity with potential value as tumour biomarkers, which can improve diagnosis, prognosis, and monitoring of treatment response for human cancers. This endeavour has been greatly facilitated by the stability of miRs in formalin-fixed paraffin-embedded (FFPE) tissues, and their detection in circulation. This review will summarize some of the key dysregulated miRs described to date in human epithelial malignancies, and their potential value as molecular bio-markers in FFPE tissues and blood samples. There remain many challenges in this domain, however, with the evolution of different platforms, the complexities of normalizing miR profiling data, and the importance of evaluating sufficiently-powered training and validation cohorts. Nonetheless, well-conducted miR profiling studies should contribute important insights into the molecular aberrations driving human cancer development and progression.