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Mol Cancer. 2017 Feb 7;16(1):35. doi: 10.1186/s12943-017-0603-1.

Hypoxia-inducible microRNA-224 promotes the cell growth, migration and invasion by directly targeting RASSF8 in gastric cancer.

Author information

1
Department of Gastroenterology, First Hospital of Jilin University, No.71 Xinmin Street, Changchun, Jilin, 130021, People's Republic of China.
2
Department of Colorectal and anal surgery, First Hospital of Jilin University, Changchun, Jilin, 130021, People's Republic of China.
3
Department of Gastroenterology, First Hospital of Jilin University, No.71 Xinmin Street, Changchun, Jilin, 130021, People's Republic of China. xuhong_doctor@hotmail.com.

Abstract

BACKGROUND:

Hypoxia plays an important role in the development of various cancers. MicroRNAs (miRNAs) act as post-transcriptional regulators of gene expression and modulate the tumorigenesis, including gastric cancer. However, the roles and molecular mechanism of miR-224 in gastric cancer under hypoxia remain poorly understood.

METHOD:

Real-time PCR and Northern blot assay were used to examine the effects of hypoxia and HIF-1α on miR-224 expression. Luciferase and ChIP assays were performed to determine whether miR-224 was a transcriptional target of HIF-1α. Then MTT, colony formation, in vitro scratch and invasion assays were used to detect the effects of miR-224 on cell growth, migration and invasion under hypoxia, as well as the in vivo animal study. Luciferase assay and Western blot were performed to validate the targets of miR-224. Functional studies were performed to determine the roles of RASSF8 as that of miR-224 under hypoxia. The effects of RASSF8 knockdown on the transcriptional activity and translocation of NF-κB were investigated using Luciferase assay and Western blot, respectively. Finally, the expression levels of miR-224 and RASSF8 were detected using real-time PCR in gastric cancer tissues as well as lymph node metastasis tissues.

RESULTS:

We demonstrated that miR-224 was upregulated by hypoxia and HIF-1α. HIF-1α affected miR-224 expression at the transcriptional level. MiR-224 inhibition suppressed cell growth, migration and invasion induced by hypoxia, while miR-224 overexpression resulted in opposite effects. MiR-224 inhibition also suppressed tumor growth in vivo. We then validated that RASSF8 was a direct target of miR-224. RASSF8 overexpression inhibited cell growth and invasion, while RASSF8 knockdown ameliorated the inhibitory effects of miR-224 inhibition on cell growth and invasion. Furthermore, we found that RASSF8 knockdown enhanced the transcriptional activity of NF-κB and p65 translocation, while RASSF8 overexpression resulted in opposite effects. Inhibition of NF-κB activity by PDTC attenuated the effects of RASSF8 knockdown on cell proliferation and invasion. Finally, miR-224 was upregulated in both gastric cancer tissues and lymph node metastasis positive tissues, while RASSF8 expression was opposite to that of miR-224.

CONCLUSION:

These results indicate that hypoxia-inducible miR-224 promotes gastric cancer cell growth, migration and invasion by downregulating RASSF8 and acts as an oncogene, implying that inhibition of miR-224 may have potential as a therapeutic target for patients with hypoxic gastric tumors.

KEYWORDS:

Gastric cancer; Hypoxia-inducible factor-1α (HIF-1α); RASSF8; miR-224; microRNA (miRNA)

PMID:
28173803
PMCID:
PMC5297251
DOI:
10.1186/s12943-017-0603-1
[Indexed for MEDLINE]
Free PMC Article

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