EGR1 interacts with DNMT3L to inhibit the transcription of miR-195 and plays an anti-apoptotic role in the development of gastric cancer.

Yang Yang,Fang Li,Liying Liu,Ruifang Sun,Su’E Chang,Fei Wu,Jing Zhang,Lumin Wang,Yulong Li,Xiaofei Wang,Chen Huang

doi:10.1111/jcmm.14597

Abstract

EGR1 regulates the expression of its downstream target genes and may exert different biological effects in different tumours. We found that the expression of EGR1 was increased in gastric cancer (GC), and silencing the expression of EGR1 promoted the apoptosis of GC cells. Moreover, overexpression of EGR1 repressed the apoptosis of GC cells. Bioinformatics analysis showed that EGR1 had binding sites at the upstream promoter region of miR‐195; ChIP assays were applied to determine EGR1 occupancy of the miR‐195 promoter. The RT‐PCR results showed that EGR1 suppressed the expression of miR‐195. The mechanism by which EGR1 acts as a transcriptional repressor is still unclear. Bioinformatics analysis showed that EGR1 may interact with DNMT3L. We confirmed that EGR1 and DNMT3L formed a complex, and EGR1 was an important player in the transcriptional control of miR‐195. Overexpression of miR‐195 inhibited proliferation and promoted apoptosis in GC cells. We found a well‐matched miR‐195 binding site at the AKT3 3′‐UTR. Double luciferase reporter assays showed that AKT3 was a target of miR‐195, and silencing AKT3 repressed cell proliferation and promoted apoptosis. Our results indicated EGR1 may interact with DNMT3L to inhibit the miR‐195‐AKT3 axis and regulate the GC cell apoptosis.

Highlights

Gastric cancer (GC) is one of the most common tumours worldwide
3.2 | Silencing the expression of miR‐195 could promote proliferation and repress apoptosis in GC cells quantitative reverse transcription polymerase chain reaction (qRT‐PCR) was performed to detect the transfection efficiency of miR‐195 inhibitor in SGC‐7901 and BGC‐823 cells, and the results showed that the expression of miR‐195 was decreased in cells transfected with miR‐195‐inhibitor compared with cells transfected with inhibitor‐control (Figure 2A)
The miRNAs are abnormally expressed in many malignant tumours in humans. miR‐195 is a member of the miRNA family, and it is located on chromosome 17 and involved in colorectal cancer,[19] cervical cancer,[20] prostate cancer,[21] gastric cancer,[22] liver cancer[23] and many others

Summary

| INTRODUCTION

Gastric cancer (GC) is one of the most common tumours worldwide. The number of newly diagnosed gastric cancer cases in China is about 679 100 per year, accounting for 15.8% of all new cancer cases. The development of gastric cancer involves many factors such as the activation of oncogenes, inactivation of tumour suppressor genes, epigenetic regulation and abnormal expression of transcription factors. Transcription factors play key roles in cancer cell proliferation, apoptosis, invasion and metastasis by regulating downstream target genes. EGR1 as a member of early growth response (EGR) family that regulates the expression of its downstream target genes and plays a key role in cell growth, proliferation, apoptosis, migration, invasion and other physiological processes. In breast cancer,[6] bladder cancer[7] and lung cancer,[8] it acts as tumour suppressor gene, while in gastric cancer it promotes migration and invasion of gastric cancer cells,[9] suggesting that EGR1 may play the role of an oncogene in gastric cancer.

| MATERIALS AND METHODS

Findings

| DISCUSSION