MicroRNAs (
miRNAs) are emerging as novel
biomarkers for diagnosis and treatment of various
cancers, including
breast cancer. Because the value of
biomarkers primarily depends on whether they are quantifiable, great effort has been taken to develop assays for sensitive and accurate quantification of
miRNAs. However, most of current assays have high nonspecific amplification effect, which limits quantification accuracy. In this study, we circumvented copying of
nucleic acid sequence and developed a signal amplification strategy based on a novel
DNA-
peptide dendrimer (DPD) probe coupled with mass spectrometry. The DPD probe RP8-MAP4-DNA contained three functional domains, including substrate
peptides containing eight reporter
peptides and tryptic cleavage sites,
peptide dendrimer scaffold and
DNA complementary to target
miRNA. The probe was first hybridized with the target
miRNA (i.e., miR-21) that was biotinylated and attached to
streptavidin agarose in advance. After
trypsin digestion, the reporter
peptide was liberated and quantified using LC-MS/MS. The signal intensity was approximately 8 fold greater than that without signal amplification. Finally, the developed assay was applied for the quantitative analysis of miR-21 in 3 human breast cell lines and 102 matched pairs of breast tissue samples. The miR-21 expression in tissue was also evaluated depend on histopathological features, molecular subtypes and prognosis of
breast cancer. The result demonstrated that combination of DPD probe and mass spectrometry is a promising strategy for quantification of
miRNAs and illustration of their
biomarker potential, especially those at low abundance.