miRNAs targeting RAS and their clinical relevance in resected pancreatic adenocarcinoma (PC): Results from a prospective study

e16314 Background: Pancreatic adenocarcinoma (PC) is one of the big killers with a 5-year disease-free survival (DFS) rate of 19-26% after resection despite adjuvant treatments. KRAS mutations have been reported in approximately 90% of PC cases and, beyond KRAS activation by gene mutations, several miRNAs directly targeting KRAS have been reported to be simultaneously downregulated, strengthening the already activated RAS signaling. In addition, the interplay between miRNAs and RAS includes downstream miRNA effectors whose role needs to be elucidated. The aim of this study was to evaluate the expression of candidate miRNAs strictly related to KRAS expression in order to elucidate the prognostic value. Methods: In this single-center observational prospective study we included patients with pathologically confirmed PC, who underwent radical surgery and were referred to the Clinical Oncology Unit, Careggi University Hospital, Florence (Italy), between 2015 and 2022. Total RNA was extracted from FFPE sections, retro-transcribed and the resulting cDNA was then used for qPCR analysis. Results: Among 44 patients included in the study, 34.1% were male and 65.9% female (median age 75 years). The majority of cases had the primary tumor located at the head of the pancreas (65.9%) and the pathological stage was pT1-2 in 45.5%, pT3 in 54.5%, pN0 in 22.7%, pN+ in 77.3%. Overall, 63.6% of patients received adjuvant chemotherapy and 69.0% experienced disease recurrence. Twenty-three specimens were adequate for miRNA analysis. A different expression of the three target miRNAs between PC and healthy tissue was observed: miR-155 was overexpressed and miR-206 downregulated in PC, while miR-143 had a similar expression in both tissues. miR-143 overexpression was associated with nodal involvement (pN+) at the pathological examination (p = 0.029). Among clinicopathological features, pN+ was associated with shorter DFS (p = 0.009) and overall survival (OS) (p = 0.021) compared to pN0. A trend toward inferior DFS was observed for higher expression of miR-206 (p = 0.095) and miR-143 (p = 0.092). Among patients receiving a first-line treatment for advanced disease, miR-155 was overexpressed in responders vs non-responders (p = 0.048). Conclusions: miRNA expression is involved in tumorigenesis and metastatic spread in PC. A comprehensive analysis of the miRNA-RAS interplay deserves to be further investigated as a predictor of clinical outcome, especially for miR-143 overexpression which was associated with lymphatic spread and, consequently, poor prognosis.