Plasma microRNA panel for minimally invasive detection of breast cancer

Plasma DNA integrity as a biomarker for primary and metastatic breast cancer and potential marker for early diagnosis

Circulating or cell-free DNA (cfDNA) has been evaluated as a biomarker in many cancers including breast cancer. In particular, integrity of cfDNA has been shown to be altered in cancers. We have estimated the biomarker potential of cfDNA in primary (PBC) and metastatic breast cancer (MBC). cfDNA integrity (cfDI) and concentration were determined in plasma of 383 individuals, including 82 PBC and 201 MBC cases, as well as 100 healthy controls, by measuring ALU and LINE1 repetitive DNA elements using quantitative PCR. The MBC patient group was further sub-divided into patients with detectable circulating tumour cells (CTCpos-MBC, n = 100) and those without (CTCneg-MBC, n = 101). A hierarchical decrease in cfDI and increase in cfDNA concentration from healthy controls to PBC and further onto MBC patients were observed. Investigation of cfDNA in media of cell lines was in concordance with these results. Combination of cfDI and cfDNA concentration could differentiate PBC cases from controls (area under the curve, AUC = 0.75), MBC cases from controls (AUC = 0.81 for CTCneg-MBC, AUC = 0.93 for CTCpos-MBC), and CTCneg-MBC from CTCpos-MBC cases (AUC = 0.83). cfDI additionally demonstrated a positive correlation to progression-free (HR of 0.46 for ALU, P = 0.0025) and overall survival (HR of 0.15 for ALU and 0.20 for LINE1, P < 0.0001) in MBC, and had lower prediction error than CTC status. Our findings show that reduced cfDI and increased cfDNA concentration can serve as diagnostic markers for PBC and MBC, and cfDI as a prognostic marker for MBC, thereby making them attractive candidates for blood-based multi-marker assays.

Micro-RNAs as clinical biomarkers and therapeutic targets in breast cancer: Quo vadis?

Breast cancer (BC) is the most frequent type of non skin cancer among women and a major leading cause of cancer-related deaths in Western countries. It is substantial to discover novel biomarkers with diagnostic, prognostic or predictive usefulness as well as therapeutic value for BC. Micro-RNAs (miRNAs) belong to a novel class of endogenous interfering RNAs that play a crucial role in post transcriptional gene silencing through mRNA targeting and, thus, are involved in many biological processes encompassing apoptosis, cell-cycle control, cell proliferation, DNA repair, immunity, metabolism, stress, aging, etc. MiRNAs exert their action mainly in a tumor suppressive or oncogenic manner. The specific aberrant expression patterns of miRNAs in BC that are detected with the use of high-throughput technologies reflect their key role in cancer initiation, progression, migration, invasion and metastasis. The detection of circulating extracellular miRNAs in plasma of BC patients may provide novel, non-invasive biomarkers in favor of BC diagnosis and prognosis and, at the same time, accumulating evidence has underscored the possible contribution of miRNAs as valuable biomarkers to predict response to chemotherapy or radiotherapy. Data from in vitro and in vivo studies on BC have revealed promising therapeutic approaches via miRNA delivery and miRNA inhibition. The purpose of this review is to explore the ontological role of miRNAs in BC etiopathogenesis as well as to highlight their potential, not only as non-invasive circulating biomarkers with diagnostic and prognostic significance, but also as treatment response predictors and therapeutic targets aiding BC management.

Methodological challenges in utilizing miRNAs as circulating biomarkers

MicroRNAs (miRNAs) have emerged as important regulators in the post-transcriptional control of gene expression. The discovery of their presence not only in tissues but also in extratissular fluids, including blood, urine and cerebro-spinal fluid, together with their changes in expression in various pathological conditions, has implicated these extracellular miRNAs as informative biomarkers of disease. However, exploiting miRNAs in this capacity requires methodological rigour. Here, we report several key procedural aspects of miRNA isolation from plasma and serum, as exemplified by research in cardiovascular and pulmonary diseases. We also highlight the advantages and disadvantages of various profiling methods to determine the expression levels of plasma- and serum-derived miRNAs. Attention to such methodological details is critical, as circulating miRNAs become diagnostic tools for various human diseases.