Expression And Clinical Significance Of MicroRNA-135a-5p In Pancreatic Cancer

BackgroundPancreatic cancer,one of the most lethal malignant tumors with the worst prognosis,is characterized by difficulty of being diagnosed at early stage and high degree of malignancy.About 80%of patients have been in locally advanced stage or discovered with distant metastasis at the time of diagnosis,without any chance of radical resection.Moreover,patients who can receive surgery will have a high risk of recurrence or metastasis.The lower surgical resection rate and high recurrence rate of pancreatic cancer leads to the fact that chemotherapy has been one of the main methods for the treatment of pancreatic cancer.At present,gemcitabine is the first-line drug for chemotherapy,but about 80%of patients can be resistant to gemcitabine,which leads to tumor recurrence.Therefore,chemotherapy resistance is one of the key factors affecting the prognosis and survival of patients with pancreatic cancer.Numerous studies have shown that microRNAs play an important role in the recurrence,metastasis and chemoresistance of many malignant tumors.At present,domestic and foreign scholars screen drag-related microRNAs based on drug-resistant cell lines or cell line-derived xenograft（CDTX）models,which can not be the embodiment of the real chemotherapy sensitivity of tumor.This means limited clinical conversion value of relevant microRNAs study results.The method of patient-derived tumor xenograft（PDTX）model overcomes the above disadvantages while retaining the characteristies of primary tumors and maintaining stability throughout each passage.Up to now there have been no reports on the use of PDTX models to screen for chemoresistance-related microRNAs in pancreatic cancer-Therefore,in this study,the PDTX mouse model of pancreatic cancer established in our previous study was utilized to screen out gemcitabine-resistant microRNAs,and the clinical value of microRNA was evaluated by analyzing the relationship between microRNAs and clinicopathological parameters.Objective1.To utilize PDTX mouse model to screen out thoes micorRNAs relevant to gemcitabine-resistance in pancreatic cancer;2.To predict the target gene of microRNA.3.To detect the difference in the expression level of mi microRNA in pancreatic cancer tissues and adjacent normal tissues,and to evaluate its clinical value by investigating the corrlation between microRNA expression,both clinical and pathological parameters and the prognosis of patients with pancreatic cancer.Methods1.Pharmacodynamic tests was carried out in pancreatic cancer PDTX mouse model to screen for gemcitabine resistance-related microRNAs;2.Bioinformatics methods were used to predict possible targets of microRNA associated with gemcitabine resistance in pancreatic cancer;3.RNA in situ hybridization was used to detect the expression of microRNA in pancreatic cancer tissues and paracancerous tissues.The chi-square test was used to analyze the correlation between the expression of microRNA and clinicopathological parameters.Univariate and multivariate survival analyses were used to assess the value of microRNA in predicting the prognosis of pancreatic cancer.Results1.The expression level of miR-135a-5p in the gemcitabine resistant group was significantly higher than that in the sensitive group;2.One of the potential targets for miR-135a-5p predicted by bioinformatics methods and literature is FAK or PTK2.3.The expression level of miR-135a-5p was higher in AsPC-1 cell line,and lowest in PANC-1,based on the PCR results for the four cell lines of AsPC-1,BxPC₃,MiaPaCa-2and PANC-1.4.Compared with adjacent normal tissues,miR-135a-5p is highly expressed in pancreatic ductal adenocarcinoma tissue;miR-135a-5p expression is an independent risk factor predicting poor prognosis in patients with pancreatic cancer,and its high expression is associated with poor prognosis in patients with pancreatic cancer and postoperative gemcitabine chemotherapy.Conclusions1.MiR-135a-5p may be associated with gemcitabine resistance in pancreatic cancer;2.One of the potential targets of miR-135a-5p is FAK;3.The expression level of miR-135a-5p was higher in AsPC-1 cell line and the lowest in PANC-1 cell line;4.The expression level of miR-135a-5p was significantly correlated with the clinical prognosis of patients with pancreatic cancer and patients receiving postoperative chemotherapy with gemcitabine.