Single-Molecule High-Confidence Detection of miRNA Cancer Biomarkers PROJECT SUMMARY/ ABSTRACT The ultimate goal of this proposal is to develop a technology platform for high confidence and robust single molecule analysis of miRNA biomarkers in cancer samples through simultaneous detection of miRNAs, in under an hour. Although miRNAs are short, they regulate essentially all cellular pathways relevant to human health and disease, including cancer. After being exported from cells, the cell-free circulating miRNAs are found to be relatively more stable than other nucleic acids, making them of high interest as clinical cancer biomarkers. Current methods for miRNA analysis, including PCR assays, face challenges due to inherent inconsistencies in day-to-day and lab-to-lab results in addition to false negatives and positives. We have recently developed a unique fluorescence resonance energy transfer (FRET)-based single molecule dynamic sensor to enable high confidence and ultrasensitive detection of an unlabeled DNA as well as miRNA targets and demonstrated that the sensing platform works in serum and fully discriminates targets from point mutant controls. Using total internal reflection fluorescence microscopy, we demonstrated that the sensor exhibits a static FRET level in the absence of a target. However, in the presence of the target, the sensor forms a four- way junction and hence undergoes a dynamic switching between a low- and a high-FRET state, a feature that enables high-confidence detection of the target. We demonstrated these features initially using a p53 tumor suppressor gene and later a miRNA associated with the triple-negative breast cancer (TNBC), both in buffer and in spiked-in samples using 10% serum. In this proposal, we will focus on the development and testing of this platform for high-confidence detection through multiplexed analysis of miRNAs in non-clinical as well as minimally processed cancer samples. In Aim 1, we will design and characterize a sensing platform for the detection of DNA sequences in one sample. In Aim 2, we will characterize and validate the detection platform for simultaneous detection of miRNAs specific to TNBC. We will also establish a speedy detection of TNBC miRNAs using a microfluidic device with parallel channels. In Aim 3, we will identify the abundant miRNAs in tumor tissues and serum samples of TNBC-carrying patient-derived xenograft (PDX) mice via miRNA sequencing and apply our single-molecule multiplexed platform to detect those TNBC miRNAs in serum samples from the PDX mice. Our proposed approach offers a number of important innovations including i) a generic platform for error-free detection of miRNAs, ii) ultimate sensitivity via single-molecule detection, iii) simultaneous detection of multiple biomarkers in the same sample - allowing high-confidence detection, and iv) target labeling and amplification are not required. Therefore, this multiplexed platform has the potential to be a transformative technology in the early diagnosis of cancer. By providing detection sensitivity and confidence that meets or exceeds state-of-the-art clinical analyzers, the proposed approach could bring new initiatives in clinical diagnosis, cancer assessment, and individualized cancer treatments.

PROJECT NARRATIVE Micro-RNAs (miRNAs) are promising biomarkers for cancer staging, diagnosis, prognosis, and therapeutics, however, their clinical applications are greatly limited by the inconsistent results among studies and lack of high-confidence detection methodologies. We will develop and optimize a single-molecule detection platform for simultaneous detection of endogenous miRNAs in cancer samples and develop a microfluidic chip to enable a speedy analysis of multiple samples in under 1 hour. While the detection platform is generic to miRNA biomarkers of different cancers, we will test our platform with a set of diverse preclinical triple-negative breast cancer (TNBC) samples from TNBC-carrying patient-derived xenograft (PDX) mice.