Abstract 5409: Deep sequencing of circulating microRNAs in rectal cancer patients undergoing neoadjuvant chemoradiotherapy

Abstract

Abstract Introduction: Rectal cancer accounts for approximately one third of all colorectal cancers (CRC), which belong among leading causes of cancer deaths worldwide. Standard treatment for locally advanced rectal cancer (cT3/4 and/or cN+) includes neoadjuvant chemoradiotherapy (CHRT) with fluoropyrimidines followed by radical surgical resection. MicroRNAs (miRNAs) are small non-coding RNAs playing significant roles in the pathogenesis of many cancers including rectal cancer. MiRNAs could present the new predictive biomarkers of response to CHRT in rectal cancer patients. Materials and Methods: In prospective one-center study, 48 patients diagnosed with rectal cancer who underwent neoadjuvant chemoradiotherapy followed by surgical treatment were included. Blood plasma samples were collected before the neoadjuvant chemoradiotherapy (in 24 cases) and after the therapy at the time of clinical restaging (in 48 cases). Total RNA was isolated from 72 blood plasma samples of 48 patients. cDNA libraries were prepared using CleanTaq Small RNA Library Prep Kit (TriLink BioTechnologies). The final sequencing analyses were performed by Next 500/550 High Output v2 Kit - 75 cycles using the NextSeq 500 instrument (both Illumina). For miRNA mapping and analysis, an online tool Chimira was used. Obtained data were statistically evaluated using the Bioconductor edgeR and DESeq2 package. Results: When miRNA profiles of samples collected before and after therapy were compared, 10 miRNAs showed higher levels and of 2 miRNAs lower levels in pre-treatment specimens (P<0.05). Samples collected at the time of clinical restaging were divided into groups accordingly to tumor regression grade (Dworak score) evaluated after surgical resection of the tumor. Pre-treatment miRNA profiles of patients from CHRT responsive group (Dworak 3+4) and non-responsive group (Dworak 1+2) were compared and 4 miRNAs were upregulated and 4 miRNAs were downregulated in patients with good response to CHRT. Finally, samples collected after the therapy, at the time of clinical restaging, were divided into groups accordingly to the nodal metastatic involvement and 10 miRNAs were identified to be significantly deregulated between groups (P<0.025). Conclusion: Our findings suggest that circulating miRNAs could serve as potential predictive biomarkers of the response to neoadjuvant CHRT in rectal cancer. This work was supported by Ministry of Health of the Czech Republic, grant nr.15-33158A, 15-34553A, 15-31627A, 15-34678A, 16-31314A, 16-31765A and by grant of Czech Grant Agency nr. 16-18257S. Citation Format: Tana Machackova, Dominika Brchnelova, Zdenek Kala, Vladimir Prochazka, Tomas Grolich, Lukas Fiala, Beata Hemmelova, Jaroslav Juracek, Marek Vecera, Jiri Sana, Natalia Gablo, Parwez Ahmad, Marek Svoboda, Ondrej Slaby. Deep sequencing of circulating microRNAs in rectal cancer patients undergoing neoadjuvant chemoradiotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5409.