Original ArticlesHypoxia-induced microRNA-590-5p promotes colorectal cancer progression by modulating matrix metalloproteinase activity
Introduction
Colorectal cancer (CRC) is one of the most common cancers and the second leading cause of cancer-related deaths worldwide [1]. Although diagnosis and treatment have improved over the years, approximately 50–60% of patients diagnosed with CRC develop distant metastasis, the major cause of serious morbidity and mortality in CRC patients. Several studies have shown that distant metastasis, particularly to the liver, is contributed to poor prognosis in patients with CRC [2,3]. However, comprehensive understanding of the mechanisms of CRC metastasis remains a challenge due to the intricate pathways underlying regulation of gene expression during disease progression. Therefore, it is important to find key molecules and molecular mechanisms that regulate tumor growth and metastasis to further clarify metastatic mechanisms and explore new promising therapeutic targets.
Hypoxia represents a condition of inadequate oxygen often encountered in solid tumors, including CRC. Hypoxia may cause cells to acquire more aggressive phenotypes by modulating genetic programs that can facilitate cellular adaptation to hypoxic conditions [4]. These common aggressive features include cell migration, invasion, growth, and metastasis. The cellular response to hypoxia is mainly mediated by hypoxia-inducible factors (HIFs), HIF-1α and HIF-2α, which are stabilized under hypoxia, facilitating coordinated regulation of multiple genes involved in processes that drive dissemination, invasion and angiogenesis, shifting cancer cells towards a metastatic phenotype [[5], [6], [7]].
MicroRNAs (miRNAs) are a new class of endogenous, small, 19–24 nucleotide noncoding RNAs that regulate target gene translation and stability [8]. Numerous studies suggest that miRNAs play an important role in regulating cell functions, including migration and invasion. Expression of miRNA is widely altered in cancer, and miRNA deregulation is implicated in tumor development and progression [9]. Many studies have shown that the amplification or overexpression of miRNAs can trigger downregulation of tumor suppressors or other genes involved in cell differentiation, thereby contributing to tumor formation as oncogenes by stimulating proliferation, angiogenesis, and/or invasion. Conversely, downregulated miRNAs are considered as tumor suppressors that actively participate in the cancer development [10,11]. Accumulating evidence has shown that miRNA expression patterns are influenced by the tumor microenvironment, including hypoxia, and these molecules play an important role in the response mechanism triggered by hypoxia [12]. Importantly, various hypoxia-related miRNAs are up- or downregulated in cancer, indicating that they also function in tumor development and progression [13]. However, the functional roles of hypoxia-responsive miRNAs in tumor growth and metastasis are unclear and require further investigation.
Here, we firstly identified miR-590-5p as a hypoxia-sensitive miRNA in colon cancer cells and further demonstrated the possibility that hypoxia-induced miR-590-5p may be involved in CRC growth and metastasis and elucidated the molecular mechanism underlying its effects. Our results suggest that hypoxia-induced miR-590-5p promotes cell migration and invasion through direct targeting of reversion-inducing cysteine-rich protein with kazal motifs (RECK). Consistently, inhibition of miR-590-5p repressed CRC growth and metastasis. The collective findings support targeting of miR-590-5p as a promising therapeutic strategy for CRC.
Section snippets
Cell lines and culture conditions
The human colorectal cancer cell lines RKO and HCT116 were obtained from American Type Culture Collection (ATCC) and cultured in Dulbecco's modified Eagle medium (DMEM; Invitrogen), as recommended by the supplier. The Balb/c-derived mouse colon carcinoma cell line CT26 was cultivated in DMEM supplemented with 10% fetal bovine serum (FBS) (Hyclone) and 1% penicillin/streptomycin (Pen/Strep, Mediatech, Manassas, VA) at 37 °C and 5% CO2 in a humidified atmosphere. Exposure of cell cultures to
Identification of miR-590-5p as hypoxia-sensitive miRNAs in colon cancer cells and RECK is a direct and functional target of miR-590-5p
To identify the miRNAs regulated by hypoxia in colon cancer cells in vitro, we performed miRNA microarray analysis (Affymetrix miRNA 4.0) after exposure of cells to hypoxic conditions for 24 h. As shown in the heat map analysis (Supplementary Fig. S1A), we found that the expression of 187 of 2578 miRNAs were significantly changed (86 upregulated and 101 downregulated) at 24 h by more than two-fold in hypoxia, compared with that in normoxia. The microarray results were validated at the 12 and
Discussion
Aberrant miRNA expression has been described in tumor development and progression, and a growing number of miRNAs have been validated as a candidate of oncogenes or tumor suppressors in many cancers, including CRC [10,23]. However, the mechanistic role of miRNAs in various cancers is not yet completely understood. In particular, we lack a clear understanding of how miRNAs contribute to and interact with conditions in the tumor microenvironment, such as hypoxia. A hypoxic microenvironment is a
Acknowledgements
The biospecimens and data used for this study were provided by the Biobank of Inha University Hospital.
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