Circulating microRNAs: promising breast cancer Biomarkers

We read with interest the recent article by Roth and colleagues [1] reporting the fi ndings of altered tumorspecifi c microRNAs (miRNAs) in sera of breast cancer patients.Th is report further substantiates emerging data suggesting that blood-based miRNAs have immense potential as novel non-invasive cancer biomarkers.However, we have several concerns regarding the authors' study.Roth and colleagues claim this article to be the fi rst evidence that circulating miRNAs have potential as breast cancer biomarkers, yet refer to previous reports of similar fi ndings [2,3].Th is aside, other claims in the study are unsubstantiated.Firstly, the fi nding that total RNA levels were signifi cantly higher in M0 patients compared to controls and M1 breast cancer patients most likely refl ects the quality of RNA extraction techniques and is not clinically relevant.We have previously demonstrated that total RNA levels diff er signifi cantly depending on the RNA isolation method and starting blood medium [2].Th e authors have not adequately discussed their fi nding that patients with metastatic disease had signifi cantly lower total RNA levels compared to M0 patients; if their claim that total RNA concentration indicated tumour progression held truth, then one would expect a sequential increase in total RNA concentration from controls, to M0 and M1 patients.Th e four candidate miRNAs (miR-10b, miR-34a, miR-141, and miR-155) selected by Roth and colleagues for analysis is contentious.Evidence demonstrating consis tent diff erential expression of this miRNA panel in breast tumours, and functionality in breast tumour genesis and progression, is lacking.Given that currently 1,212 mature human miRNAs have been identifi ed (miRBase, release 16 September 2010 [4]), and others