MicroRNA‑608 promotes apoptosis via BRD4 downregulation in pancreatic ductal adenocarcinoma

Abstract

The prognosis of pancreatic ductal adenocarcinoma (PDAC) remains poor even among patients with the same Tumor-Node-Metastasis stage. Thus, it is necessary to identify biomarkers that can accurately predict outcomes. There is accumulating evidence suggesting that microRNA (miR) expression influences overall survival (OS) time in patients with PDAC, via the regulation of tumor suppressor genes and oncogene expression. Specifically, miR-608 expression is hypothesized to regulate PDAC progression via the downregulation of bromodomain-containing protein 4 (BRD4) expression and the promotion of cell apoptosis. The present study aimed to investigate this theory. Thus, whole genome expression microarray analysis was performed on three patient samples with OS time >30 months, and compared with three samples with <12 months, in order to identify differentially expressed miRNAs (DEMs), via EdgeR analysis. A total of 591 DEMs were identified that exhibited a fold change >1, including 390 upregulated and 201 downregulated genes. Subsequently, 10 DEMs were identified using quantitative PCR in a different population of 68 tissues, collected from patients with PDAC. Notably, a high level of miRNA-608 expression was associated with longer OS times (P<0.05). Bioinformatics analysis was then performed to predict the molecular mechanism underlying the regulation of cell apoptosis by miRNA-608, and a dual-luciferase assay determined that overexpression of mimics in the Panc-1 and Bxpc-3 pancreatic cancer cell lines increased levels of apoptosis compared with the control. Additionally, high miRNA-608 expression decreased the protein level of BRD4. A luciferase reporting assay was used to elucidate whether miRNA-608 may directly inhibit the expression of BRD4 by binding to the 3'-untranslated region of its mRNA in the same cell lines. A subsequent rescue experiment indicated that the upregulation of BRD4 may reverse the apoptosis-promoting effect induced by miRNA-608. In summary, the present study revealed that miRNA-608 promotes apoptosis in PDAC via the negative regulation of BRD4. The results of the present study provide a theoretical basis that may improve the prediction of prognosis in patients with PDAC, and also indicate an opportunity to develop individualized treatment and investigate novel therapeutics that target these mechanisms.

Bromodomain-containing protein 4 silencing by microRNA-765 produces anti-ovarian cancer cell activity

“…Zheng et al, reported that expression of miR-4651 silenced BRD4 to inhibit non-small cell lung cancer (NSCLC) cell growth and proliferation [ 28 ]. Li et al, found that miR-608 induced pancreatic ductal adenocarcinoma cell apoptosis by silencing BRD4 [ 29 ]. Similarly, BRD4-targeting miR-608 inhibited HCC cell proliferation [ 30 ].…”

Biological Functions and Molecular Mechanisms of MiR-608 in Cancer

“…Interestingly, in pancreatic cancer, miR-608 is downregulated, and miR-608 can target ribonucleotide reductase M1 (RRM1) and cytidine deaminase (CDA) and control gemcitabine resistance ( 32 ). miR-608 also promotes PDAC cell apoptosis and prolongs PDAC patient OS by binding BRD4 ( 86 , 87 ) and AKT serine/threonine kinase 2 (AKT2). Therefore, miR-608 has the potential to act as a new diagnostic and prognostic marker and even a treatment target for pancreatic cancer.…”

“…Li et al. ( 86 ) revealed that miR-608 can decrease the level of BRD4 and facilitate cell apoptosis. However, in PDAC, miR-608 is usually significantly reduced.…”

“…Moreover, the roles of the BLACAT1/miR-608/SOX12 axis in osteosarcoma (29), HOXD4-AS1/miR-608/FZD4 axis(30) in ovarian cancer, and lncRNA NORAD/miR-608/STAT3 (31) axis in melanoma indicate that miR-608 could be an ideal therapeutic target. Li et al(86) revealed that miR-608 can decrease the level of BRD4 and facilitate cell apoptosis. However, in PDAC, miR-608 is usually significantly reduced.…”

“…However, in PDAC, miR-608 is usually significantly reduced. A strategy to overexpress miR-608 utilizing gene editing technology or targeted therapy could significantly improve the prognosis for PDAC(86). Zhang et al(33) also elucidated that miR-608 can obviously alleviate the progression of prostate cancer.…”