Investigation of the correlation between non-coding RNAs and BRD4 expression in gastric cancer as the diagnostic targets

Abstract

Despite the advances in cancer treatment and diagnosis, stomach cancer is still considered one of the most common and deadly cancers in the world. The high death rate in stomach cancer is mostly caused by the poor prognosis of patients and the lack of effective treatments. Therefore, identifying new and effective therapeutic and diagnostic targets for this malignancy is a necessity. BRD4, which plays a role in regulating the positive expression of various genes by forming enhancer sequences by binding to acetylated histones, has been shown to have an oncogenic role in most cancers, especially gastric cancer. Therefore, the identification of the molecular pathways involved in the regulation of the expression of this gene can lead to the identification of valuable molecular targets for the treatment and diagnosis of gastric cancer. Non-protein coding RNAs, including microRNAs and lncRNAs, play a significant role in such regulatory pathways by interacting with each other. Therefore, in this study, the effort was to identify non-coding RNAs with therapeutic and diagnostic value for gastric cancer through the regulation of BRD4 expression. Methods: First, by using bioinformatics methods and using Cancer Regulome and miRmap software, microRNAs that had the ability to target BRD4 were identified as candidate microRNAs. Then, the expression of BRD4 gene and candidate microRNAs in samples related to TCGA-STAD dataset was evaluated to determine their possible role in gastric cancer. Also, using TCGA samples and ROC curve analysis, the biomarker power of these genes was evaluated. Then laboratory samples of gastric cancer including 25 primary gastric cancer tissue samples and 25 adjacent healthy tissue samples were prepared. The RNA content of the samples was extracted and after cDNA synthesis, the expression of the BRD4 gene and candidate microRNA and the relationship between their expression in the laboratory samples were evaluated. Also, using informatic studies, lncRNAs were identified as having the ability to regulate the expression of BRD4 by regulating the expression of the candidate microRNA. Results: The results obtained from informatics data indicated a negative relationship between the expression of miR-26a-3p and BRD4 and the ability of this microRNA to target the BRD4 gene. Also, the results of the TCGA-STAD data set analysis showed a decrease in the expression of this microRNA and an increase in the expression of BRD4 in gastric cancer samples and the biomarker value of their expression changes. Decreased expression of miR-26a-2p, increased expression of BRD4 and negative correlation between their expression in laboratory samples of gastric cancer were also confirmed. Informatics studies also showed that the expression of lncRNAs DLG5-AS1 and JMJD1C-AS1 had a significant negative relationship with the expression of miR-26a-3p. Also, the expression of these two lncRNAs had a positive and significant relationship with BRD4 expression in TCGA-STAD samples, which indicated their role in miR-26a-3p/BRD4 regulatory pathway.