MiR-17-5p Regulates Malignant Biological Behavior Of Pancreatic Ductal Adenocarcinoma

Objective Pancreatic ductal adenocarcinoma(PDAC)is a malignant tumor that originates from the ductal epithelium of the pancreas.Lack of specific biological markers and symptoms makes pancreatic ductal adenocarcinoma difficult to diagnose at an early stage.As a result,the majority of the patients(more than 80%)are already at the advanced stage at the time of diagnosis and cannot be operated.The prognosis of PDAC is very poor.The life expectancy is usually less than 6 months and the five-year survival rate is about 9%.Advances in therapies have been slow.PDAC often exhibits malignant biological behaviors:rapid cell proliferation,prone to recurrence,metastasis and resistance to chemotherapeutic drugs.Therefore,it is critical to find the underlying mechanism that leads to the malignant biological behavior of pancreatic ductal adenocarcinoma.With the rapid and continuous progress in the field of epigenetics,the involvement of epigenetic factors,such as DNA methylation,histone modification and non-coding RNA has been reported in the research of pancreatic ductal adenocarcinoma,suggesting that epigenetic mechanisms play an important role in the development of pancreatic ductal adenocarcinoma.The purpose of this research is to study the mechanism of miR-17-5p in promoting the malignant biological behavior of pancreatic ductal adenocarcinoma and provide potential novel targets for the treatment of pancreatic ductal adenocarcinoma as well as new molecular markers.Methods1.Malignant biological phenotypes were tested using cell transfection technology,gene editing technology,CCK-8 cell viability test,clone formation experiment,tumor xenograft assay and flow cytometry experiment to detect whether miR-17-5p,a member of miR-17-92 cluster,can affect the oncological characteristics of the pancreatic ductal adenocarcinoma.2.Using immunohistochemistry analysis to detect cell proliferation markers in tumor xenograft.3.Detection of miR-17-5p expression in the tumor tissue of patients with pancreatic ductal adenocarcinoma and adjacent normal tissue.Explore the potential relevance and significance of miR-17-5p in clinical diagnosis and treatment.4.Predict the target genes of miR-17-5p through bioinformatics analysis and identify the target genes of miR-17-5p and validate the binding sites on target genes through luciferase reporter assays.5.Chromatin immunoprecipitation(Ch IP)experiments to determine the molecular biological mechanism of the malignant biological phenotype of pancreatic ductal adenocarcinoma cells by miR-17-5p.Results1.The miR-17-92 gene cluster family member miR-17-5p can promote tumor cell proliferation and accelerate cell cycle progression in pancreatic ductal adenocarcinoma cell lines and tumor xenograft of pancreatic ductal adenocarcinoma cells.2.miR-17-5p can inhibit the expression of retinoblastoma-like protein 2(RBL2)and alter cell cycle profiles via directly targeting the 3‘ untranslated region of RBL2.3.RBL2 binds to E2 F transcription factor 4(E2F4)and inhibits the expression of E2 F transcription factor target genes thereby suppressing the proliferation of PDAC cells.Mi R-17-5p can disrupt RBL2/E2F4-repressing complexes.