Expression Of Long Non-coding RNA MIR31HG In Pancreatic Cancer And Its Correlation With Drug Resistance

BackgroundPancreatic cancer(PC)is an extremely malignant tumor of digestive tract and the incidence of PC has increased worldwide over recent years.The mortality rate is high,PC is the 4th leading cause of mortality resulted from malignant tumors in the United States,and the prognosis is poor,its 5-year survival rate is less than 8%.According to the National Cancer Center of China,the incidence and mortality of PC in China ranked 9th and 6th in malignant tumors,respectively,in 2015.Interdisciplinary diagnosis and treatment play a fundamental role in treating patients with pancreatic cancer.Radical surgery is still the only effective way to cure pancreatic cancer.Yet,merely 15 to 20 percent of the patients with pancreatic cancer are eligible for surgery.Presently,neoadjuvant therapy prior to a main treatment is an advocated course of treatment.Chemotherapy is an important treatment for neoadjuvant therapy,postoperative pancreatic cancer,and advanced pancreatic cancer.Chemotherapy resistance has posed a significant challenge to the curative effect of chemotherapy on treating pancreatic cancer,which justifies the pressing need of understanding the biological mechanism of pancreatic cancer resistance to chemotherapy at a molecular level.Long non-coding RNAs(Lnc RNAs)are a type of RNA that does not encode proteins and generally has over 200 nucleotides.Latest studies discover that Lnc RNAs play a critical role in the regulation of X-chromosome silencing,proto-oncogene activation,transcriptional interference,and gene imprinting.There are studies pointing out that in liver cancer,prostatic cancer,lung cancer,and other cancerous cases,a large number of Lnc RNAs are abnormally expressed,making them function as a key regulator in cancer progression.Previous studies reported that Lnc RNAs regulate chemotherapy sensitivity and resistance in gastric cancer,mammary cancer,lung cancer,and liver cancer;also,the expression profile of some Lnc RNA in tumors is closely related to the change of drug resistance.Lnc RNA MIR31 HG is located on 9p21.3,with 2166 bps in size.It has been found that MIR31 HG is abnormally expressed in non-small cell lung cancer,breast cancer,bladder cancer,and colorectal cancer,and involved in cancer progression.However,the underlying mechanisms regarding the expression and regulation of MIR31 HG in pancreatic cancer remain unclear.Further research is required to investigate the correlation of MIR31 HG expression with drug resistance in pancreatic cancer.ObjectiveTo investigate the abnormal expression of Lnc RNA in pancreatic cancer;Study the expression of Lnc RNA MIR31 HG in pancreatic cancer and its relationship with clinicopathological data;Observe the effect of interfering MIR31 HG expression on the proliferation and migration of pancreatic cancer;Investigate the role of MIR31 HG in drug resistance of pancreatic cancer and its possible molecular mechanism,and to provide a new target for targeted intervention of pancreatic cancer.Methods1.Gene chips of six pairs of pancreatic cancer tissue and paraneoplastic tissue were detected to identify Lnc RNAs of differential expression and locate the target Lnc RNA.2.RNAs were extracted from specimens of pancreatic cancer tissue and pancreatic cancer cell lines for quantitative fluorescence PCR to examine the expression of MIR31 HG.Statistical analysis was carried out based on the MIR31 HG expression of the specimens and the clinical and pathological characteristics of the patients with pancreatic cancer.3.Synthesized Si RNA was prepared while the expression of MIR31 HG was downregulated.Following this,CCK-8 and Transwell assays were conducted to assess the effect of MIR31 HG expression down-regulation on the proliferation and migration abilities of pancreatic cancer cells.4.Detected the effect of down-regulated MIR31 HG expression on IC50 of 5-fu in pancreatic cancer cells.Observed the pancreatic cancer cell survival after Interference the MIR31 HG expression under the treatment of same concentration of 5-FU.5.Discussed the impact of down-regulation of MIR31 HG expression on C-myc expression by Western-blot.Results1.Totally 26,561 Lnc RNAs and 28,695 protein-coding genes were detected on gene microarray.In the selected 6 pairs of tissues,1587 Lnc RNAs with FC>2 times and P<0.05 were found,of which 903 were up-regulated and 684 down-regulated.2.The expression of MIR31 HG in PC tissues was higher than that of the adjacent tissues and the expression of MIR31 HG in PC cell lines As PC-1?PANC-1?Capan-1?Capan-2?SW1990 were significantly higher than that of the normal pancreatic ductal epithelial cell HPDE6c-7.3.the expression of MIR31 HG varied among PC patients in different tumor sizes,with a higher expression present in those having greater than 3 cm in diameter(P = 0.015);the MIR31 HG expression in the cases of metastasis was higher than that without metastasis(P = 0.031);based on the AJCC staging system,stage III-IV patients MIR31 HG expression was higher than those in stage 0-II patients(P = 0.011);the patients having lower degree of differentiation group,indicated a higher level of MIR31 HG expression(P = 0.011);the patients having a higher level of Ca19-9 presented MIR31 HG expression higher than those having a lower level of Ca19-9(P = 0.026);4.Down-regulation of MIR31 HG expression impaired the migration and proliferation abilities of pancreatic cancer cells.5.The IC50 in PANC-1 and As PC-1 cells of the MIR31 HG down-regulated group was significantly lower than that of the NC group;When treated with 5-FU at the same concentration,PANC-1 and As PC-1 of down-regulated MIR31 HG expression reported lower cell survival rates;6.The C-myc protein expression took a shift to a lower level as the MIR31 HG expression in PANC-1 and As PC-1 was down-regulated.ConclusionsThis study provides evidence that some Lnc RNAs are abnormally expressed in pancreatic cancer.Lnc RNA MIR31 HG is highly expressed in pancreatic cancer tissue and pancreatic cancer cells,which is associated with the tumor size,metastasis,clinical staging,and the degree of differentiation.Also,the Lnc RNA may function as a cancer-promoting gene.Down-regulation of MIR31 HG expression is an effective method to inhibit the migration and proliferation of pancreatic cancer cells,improve the sensitivity of pancreatic cancer cells to 5-FU and lower the drug resistance to 5-FU.MIR31 HG controls the proliferation,migration,and drug resistance of pancreatic cancer cells by regulating C-myc expression.MIR31 HG is a promising molecular target for lower drug resistance in pancreatic cancer.Provide a new direction for the diagnosis and treatment of pancreatic cancer.