Abstract LB-341: Circulating exosomal microRNAs as promising early biomarkers of neoadjuvant chemotherapy response in breast cancer
Authors: Todorova Valentina K. , Byrum Stephanie , Gies Allen , Makhoul Issam 
Published: September 2020

Abstract
Objective: Early prediction of patient response to chemotherapy can facilitate opportunities to avoid inefficient treatment and related toxicity. Cancer cells secrete a large amount of exosomes that contain various molecular constituents reflecting the originating tumor. This study aimed to examine whether circulating exosomal microRNA profile can predict the pathological complete response (pCR) to neoadjuvant chemotherapy in breast cancer patients. Method: Plasma exosomal microRNAs of 20 breast cancer patients treated with adriamycin/cyclophosphamide (60/600 mg/m2 of body surface area) neoadjuvant chemotherapy were extracted prior to and after the first chemotherapy cycle. The pathological response was classified into pCR and non-pCR by histopathological analysis after breast surgery. Exosomal miRNAs were extracted from plasma and analyzed by next generation sequencing (NGS) using Illumina high-throughput RNA sequencing technology. Sequence data were converted to FASTQ files and analyzed using CLC Genomics Workbench version 12.02 (Qiagen). Unique molecular identifiers (UMIs) were extracted and grouped into unique search sequences according to exact sequence of the small RNA sequence and the UMI. Reads were then mapped to MiRNA database miRbase v22 and quantified using the QIAseq miRNA Quantification workflow, which utilizes the RNA-seq Analysis tools in CLC Genomics Workbench (version 12.0.2). The unmapped reads from the quantifying step were then extracted and mapped to human genome GRCh38 using annotation hg38. Samples were analyzed for differential expression using the exact test in the CLC Genomics Workbench suite of Transcriptomics tools. Analysis included Principal Component Analysis, Unsupervised Clustering and Heat Maps, Empirical analysis of gene expression, and volcano plots of the expression difference between groups. miRNAs with post-treatment versus pre-treatment fold change (FC) &gt; 1.5 and false discovery rate (FDR) adjusted p-value &lt;0.05 were considered significant. Results: The histopathological assessment after the surgery identified pCR in 6 patients and non-pCR in 14 patients. The results from the miRNA-Seq analysis showed has-miR-141-3p was significantly down-regulated (FC&gt;2, FDR=0.0003) in the group of patients with pCR, while 3 miRNAs (hsa-miR-34a-5p, hsa-miR-183-5p, and hsa-miR-182-5p) were significantly upregulated in the group of patients with non-pCR (FC&gt;1.5, FDR&lt;0.05). Conclusions: These new findings suggest the potential role of exosomal miR-141-3p, hsa-miR-34a-5p, hsa-miR-183-5p, and hsa-miR-182-5p as biomarkers for early prediction of pCR to neoadjuvant chemotherapy of breast cancer. The results from this study built a foundation for future research on the role of miRNAs in the response to neoadjuvant chemotherapy.
Citation Format: Valentina K. Todorova, Stephanie Byrum, Allen Gies, Issam Makhoul. Circulating exosomal microRNAs as promising early biomarkers of neoadjuvant chemotherapy response in breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-341.