Background:
Due to the limitations of strategies for its early diagnosis and treatment, pancreatic cancer (PC) remains a substantial human health threat. We previously discovered a methylation-mediated lncRNA, LINC00261, which is downregulated in PC tissues. However, the underlying role of LINC00261 in PC remains largely unknown.
Methods:
Quantitative real-time PCR and in situ hybridization were performed to evaluate the expression levels of LINC00261 in PC, adjacent nontumor and normal pancreas tissues. The clinical significance of LINC00261 was assessed in multicenter PC samples. The functions of LINC00261 in PC were investigated by gain- and loss-of-function assays
in vitro
and
in vivo
. Potential downstream pathways and mechanisms were explored via RNA sequencing and bioinformatic analyses. RNA immunoprecipitation and chromatin immunoprecipitation assays were used to validate the underlying mechanisms. Pyrosequencing and targeted demethylation of the LINC00261 promoter were performed to explore the upstream epigenetic mechanisms and therapeutic potential.
Results:
LINC00261 was significantly downregulated in PC tissues, and its expression was positively associated with the prognosis of PC patients. Phenotypic studies indicated that LINC00261 overexpression significantly suppressed PC cell proliferation, migration and metastasis
in vitro
and
in vivo
. c-Myc was identified as a downstream target of LINC00261. LINC00261 repressed c-Myc transcription by physically interacting and binding with the bromo domain of p300/CBP, preventing the recruitment of p300/CBP to the promoter region of c-Myc and decreasing the H3K27Ac level. Moreover, the methylation level of the LINC00261 promoter was high in PC tissues and was correlated with poor prognosis. Targeted demethylation of the LINC00261 promoter inhibited PC progression both
in vitro
and
in vivo
.
Conclusions:
Our findings indicate that methylation-mediated LINC00261 suppresses PC progression by epigenetically repressing c-Myc expression. These findings expand the therapeutic potential of LINC00261, possibly providing evidence to support the development of epigenetic drugs or therapeutic strategies. This research adds further insights into the etiology of PC and indicates that LINC00261 may be a prognostic and therapeutic target in PC.
Background
MicroRNAs (miRNAs), as an indispensable type of non-coding RNA (ncRNA), participate in diverse biological processes. However, the specific regulatory mechanism of certain miRNAs in pancreatic ductal adenocarcinoma (PDAC) remains unclear.
Methods
The expression of miR-194-5p in PDAC tissue microarray and cell lines were detected by RNA-scope and real-time quantitative PCR (RT-qPCR). The function of proliferation and migration carried by miR-194-5p in vitro and vivo was observed by several functional experiments. Informatics methods and RNA sequencing data were applied to explore the target of miR-194-5p and the upstream circular RNA (circRNA) of miR-194-5p. RNA-binding protein immunoprecipitation (RIP) assay and dual-luciferase reporter assay confirmed the relationships between miR-194-5p and SOCS2 or miR-194-5p and circPVRL3. The proliferation and migration abilities of SOCS2 and circPVRL3 were accessed by rescue experiments.
Results
In this study, we aimed to clarify the molecular mechanisms of miR-194-5p, which has critical roles during PDAC progression. We found that the expression of miR-194-5p was significantly upregulated in PDAC tissue compared to tumor-adjacent tissue and was highly related to age and nerve invasion according to RNAscope and RT‒qPCR. Overexpression of miR-194-5p accelerated the cell cycle and enhanced the proliferation and migration processes according to several functional experiments in vitro and in vivo. Specifically, circPVRL3, miR-194-5p, and SOCS2 were confirmed to work as competing endogenous RNAs (ceRNAs) according to informatics methods, RIP, and dual-luciferase reporter assays. Additionally, the rescue experiments confirmed the relationship among miR-194-5p, circPVRL3, and SOCS2 mRNA. Finally, the circPVRL3/miR-194-5p/SOCS2 axis activates the PI3K/AKT signaling pathway to regulate the proliferation and metastasis of PDAC.
Conclusion
Our findings indicated that an increase of miR-194-5p caused by circPVRL3 downregulation stimulates the PI3K/AKT signaling pathway to promote PDAC progression via the circPVRL3/miR-194-5p/SOCS2 axis, which suggests that the circPVRL3/miR-194-5p/SOCS2 axis may be a potential therapeutic target for PDAC patients.
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