Circular RNA hsa_circ_0004872 inhibits gastric cancer progression via the miR-224/Smad4/ADAR1 successive regulatory circuit

Abstract

Background Emerging evidence has shown that circular RNAs (circRNAs) play a crucial regulatory role in the occurrence and development of cancer. Exploring the roles and mechanisms of circRNAs in tumorigenesis and progression may help to identify new diagnostic markers and therapeutic targets. In the present study, we investigated the role and regulatory mechanism of hsa_circ_0004872 in gastric cancer (GC). Methods qRT-PCR was used to determine the expression of hsa_circ_0004872 in GC tissues and cells. EdU, CCK-8, transwell and scratch wound healing assays were used to assess the role of hsa_circ_0004872 in GC cell proliferation, invasion and migration, respectively. Subcutaneous and tail vein tumor injections in nude mice were used to assess the role of hsa_circ_0004872 in vivo. RIP assay, biotin-coupled probe pull-down assay, FISH and luciferase reporter assay were performed to confirm the relationship between hsa_circ_0004872 and the identified miRNA. ChIP assay, luciferase reporter assay and western blot were used to determine the direct binding of Smad4 to the promoter of the ADAR1 gene. Results In this study, we found that hsa_circ_0004872 was dramatically downregulated in GC tissues compared with adjacent noncancerous tissues. The expression level of hsa_circ_0004872 was associated with tumor size and local lymph node metastasis. Enforced expression of hsa_circ_0004872 inhibited the proliferation, invasion and migration of GC cells, whereas knockdown of hsa_circ_0004872 had the opposite effects. Nude mice experiments showed that ectopic expression of hsa_circ_0004872 dramatically inhibited tumor growth and metastasis in vivo. Moreover, we demonstrated that hsa_circ_0004872 acted as a “molecular sponge” for miR-224 to upregulate the expression of the miR-224 downstream targets p21 and Smad4. Importantly, we found that the RNA-editing enzyme ADAR1 inhibited hsa_circ_0004872 expression and further led to the upregulation of miR-224. Smad4, the downstream target of miR-224, could further affect hsa_circ_0004872 levels by directly binding to the promoter region of ADAR1 to inhibit ADAR1 expression. Conclusions Our findings showed that hsa_circ_0004872 acted as a tumor suppressor in GC by forming a negative regulatory loop consisting of hsa_circ_0004872/miR-224/Smad4/ADAR1. Thus, hsa_circ_0004872 may serve as a potential biomarker and therapeutic target for GC.

CircASXL1 knockdown represses the progression of colorectal cancer by downregulating GRIK3 expression by sponging miR-1205

“…The migration and invasion of SW480 and SW620 cells were assessed using transwell chamber without or with Matrigel (Corning, New York, Madison, USA), respectively, as previously described [ 29 ]. Shortly, cells were suspended in serum-free DMEM (Biosun), and added into the upper chamber.…”

“…And the mutant plasmids of circASXL1 and GRIK3 (MUT-circASXL1 and MUT-GRIK3 3′UTR) were established in the same manner. Constructed plasmids were transfected into SW480 and SW620 cells using Lipofectamine 2000 (Invitrogen) according to the published reference [ 29 ]. The binding relationship was demonstrated by detecting luciferase activity using a Dual-Lucy Assay Kit (Solarbio) with Ranilla Luciferase activity as a reference.…”

Mechanisms Regulating Abnormal Circular RNA Biogenesis in Cancer

“…ADAR1 overexpression is also one of the reasons for the down-regulation of hsa_circ_0004872 expression in gastric cancer tissues. Has_circ_0004872 acts as a "miRNA sponge" to inhibit the proliferation, invasion, and migration of gastric cancer cells, and can serve as a diagnostic and prognostic marker for gastric cancer patients [62]. In pancreatic ductal adenocarcinoma (PDAC), circNEIL3 plays a role of oncogene and promotes the progression and metastasis of PDAC.…”

Circ_0007841 accelerates ovarian cancer development through facilitating MEX3C expression by restraining miR-151-3p activity

“…For instance, circSEC31A contributes to lung cancer proliferation and invasion through inhibiting miR-376a [ 8 ]. Hsa_circ_0004872 is a tumor suppressor to repress gastric cancer cell proliferation and migration [ 9 ]. In addition, circSEMA5A overexpression enhances bladder cancer cell proliferation and migration via facilitating ENO1 expression [ 10 ].…”