The Prognostic Role of microRNAs 142-5p, 182-3p, and 99a-3p in Locally Advanced Rectal Cancer Patients

Background/Aim: MicroRNAs (miRNAs) are likely to play a significant role in predicting rectal cancer response to chemoradiation therapy and overall cancer prognosis, offering insights that complement other biological tumor markers. This study aimed to conduct miRNA profiling in rectal cancer tissues in patients with good (GR) and bad response (BR) to neoadjuvant chemoradiation therapy (nCRT), followed by the selection of clinically relevant miRNAs. The relationship between selected miRNAs and subsequent disease outcomes and survival prognosis was assessed. Patients and Methods: Forty patients with locally advanced rectal cancer who received nCRT followed by surgical treatment at the Pauls Stradiņš Clinical University Hospital during the period from 2016 to 2021 were included in the study. Two study groups were created, GR and BR, according to the Dworak tumor regression grading (TRG) system. The identification of 752 miRNAs was conducted in rectal cancer tissues according to the protocol of miRCURY LNA miRNA miRNome PCR Panels. Six up‑regulated miRNAs were deemed as clinically significant and subsequently validated in both the BR and GR groups. Results: MiR‑142‑5p, miR‑182‑3p, and miR‑99a‑3p exhibited statistical significance in the validation procedure. The results showed that BR to nCRT, lower expression of miRNA‑142‑5p and miR‑99a‑3p, and higher expression of miR‑ 182‑3p were associated with a trend toward worse local recurrence‑free survival, distant metastases‑free survival, and overall survival.