Circulating Micro-RNAs as Potential Blood-Based Markers for Early Stage Breast Cancer Detection

Michael G Schrauder,Laura Kahmann,Swetlana Richter,Matthias W Beckmann,Sebastian M Jud,Peter A Fasching,Mayada R Bani,Arndt Hartmann,Rüdiger Schulz-Wendtland,Christian R Loehberg,Evelyn Wenkel,Christian M Bayer,Claudia Rauh,Michael P Lux,Alexander Hein,Reiner Strick,Boris R Adamietz,Pamela L Strissel

doi:10.1371/journal.pone.0029770

Abstract

IntroductionMicroRNAs (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.MethodsWe 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).ResultsUsing 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.ConclusionsMiRNA 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.

Highlights

MicroRNAs are a class of small, non-coding RNA molecules with relevance as regulators of gene expression thereby affecting crucial processes in cancer development
Characterization of study population In total, 153 whole blood samples of early stage Breast cancer (BC) patients and healthy control individuals were analyzed in this study
All BC cases were histologically confirmed as early stage invasive ductal carcinoma of the breast with a tumor size ranging between 0.15 and 4.0 cm

Summary

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. Whereas most studies focus on the improvement of prognosis by improving the therapies, one of the most promising approaches is to detect the cancer in an early stage. MicroRNAs (miRNAs, miRs) are a novel class of endogenous, non-coding, single-stranded RNAs, first described in 1993 by Lee et al in C. elegans [2]. These small regulatory RNA molecules (approximately 22 nucleotides long) post-transcriptionally inhibit gene expression by either degrading or blocking translation of messenger RNA (mRNA) targets [3]. Depending on the degree of concordance between the miRNA sequence and the mRNA the negative regulatory effect on the target mRNAs can vary from weak repression of protein translation to complete cleavage of the mRNA [8]

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