Silencing of circRNA circ_0001666 Represses EMT in Pancreatic Cancer Through Upregulating miR-1251 and Downregulating SOX4

Abstract

BackgroundPancreatic cancer (PC) is an aggressive malignancy and has a poor prognosis. Although emerging research has revealed that circular RNAs (circRNAs) are crucial modulators that control tumor development and metastasis, their functional involvement in PC has not been well characterized. Here, we examined whether and how circRNA circ_0001666 governs epithelial-mesenchymal transition (EMT) in PC.MethodsWe investigated the effects of circ_0001666 on EMT and PC cell invasion by gain- and loss-of-function assays. We also explored the mechanisms underlying the functions of circ_0001666 in PC cells.ResultsWe found that circ_0001666 is highly expressed in PC tissues and PC cell lines. Patients with high circ_0001666 expression had shorter survival times. In vitro and in vivo experiments have demonstrated that upregulation of circ_0001666 facilitates PC cell proliferation, EMT and invasiveness, whereas knockdown of circ_0001666 exhibits opposite functions. Moreover, circ_0001666 is able to bind to miR-1251, thus increasing the expression of SOX4, which is a direct downstream effector of miR-1251. The oncogenic effects of circ_0001666 on EMT and PC cell invasion were rescued by miR-1251 overexpression.ConclusionsThese results suggested that circ_0001666 acts as an oncogenic circRNA to promote EMT and invasion of PC cells through sponging miR-1251, and indicated that circ_0001666 could be explored as a potential therapeutic target for PC.

Knockdown of long noncoding RNA HUMT inhibits the proliferation and metastasis by regulating miR-455-5p/LRP4 axis in hepatocellular carcinoma

“…Next, the magnetic beads were incubated with proteinase K buffer for 30 min. Finally, the enrichment of HUMT, miR-455-5p, and LRP4 in purified RNAs was examined by qRT-PCR [ 41 ].…”

Mechanism underlying circRNA dysregulation in the TME of digestive system cancer

“…Given the highly metastatic nature of pancreatic cancer cells, distant metastasis, especially lymphatic metastasis, occurs in the early stage of pancreatic cancer. Relevant studies have shown that high expression of circ0074298, circCCT3, and circ0001666 in pancreatic cancer is closely related to lymph node metastasis (93)(94)(95), while low expression of circNFIB1 and circ0092367 is related to advanced TNM stage, lymph node metastasis, and overall survival (96,97). High expression of circZNF91 promotes chemotherapy resistance in pancreatic cancer cells and is inversely proportional to overall survival (98).…”

“…Similarly, Zhang et al demonstrated that overexpression of circ0001666 leads to low expression of E-cadherin and upregulation of Vimentin, and promotes EMT in pancreatic cancer cells. Mechanistically, circ0001666 acts as a sponge for miR-1251 to weaken the inhibition of miR-1251 on the downstream target SOX4, and the high expression of SOX4 in turn regulates the EMT of cancer cells by upregulating the expression of EZH2 and promoting the invasive properties of pancreatic cancer cells (94). Xu et al reported that HepG2 and Huh7 cells overexpressing miR-145 had increased expression of E-cadherin and reduced expression of N-cadherin, leading to reduced migration and invasion abilities.…”

Emerging roles of long noncoding and circular RNAs in pancreatic ductal adenocarcinoma

“…circ-0001666 (chr6:170,626,457-170,639,638) overexpression in PDAC increases transcription factor SOX4 expression, a direct downstream effector of miR-1251 , by binding to miR-1251 ( Zhang et al, 2021 ). Silencing circ-0001666 repressed EMT in PDAC cells by upregulating miR-1251 and downregulating SOX4 ( Zhang et al, 2021 ). This study indicated that circ-0001666 functions via a ceRNA mechanism.…”