RETRACTED ARTICLE: The hypoxia-inducible factor-1 regulates the microRNA185 expression through binding to hypoxia response elements sequence 2

The interplay between HIF-1α and noncoding RNAs in cancer

Hypoxia is a classic characteristic of the tumor microenvironment with a significant impact on cancer progression and therapeutic response. Hypoxia-inducible factor-1 alpha (HIF-1α), the most important transcriptional regulator in the response to hypoxia, has been demonstrated to significantly modulate hypoxic gene expression and signaling transduction networks. In past few decades, growing numbers of studies have revealed the importance of noncoding RNAs (ncRNAs) in hypoxic tumor regions. These hypoxia-responsive ncRNAs (HRNs) play pivotal roles in regulating hypoxic gene expression at the transcriptional, posttranscriptional, translational and posttranslational levels. In addition, as a significant gene expression regulator, ncRNAs exhibit promising roles in regulating HIF-1α expression at multiple levels. In this review, we briefly elucidate the reciprocal regulation between HIF-1α and ncRNAs, as well as their effect on cancer cell behaviors. We also try to summarize the complex feedback loop existing between these two components. Moreover, we evaluated the biomarker potential of HRNs for the diagnosis and prognosis of cancer, as well as the potential clinical utility of shared regulatory mechanisms between HIF-1α and ncRNAs in cancer treatment, providing novel insights into tumorigenicity, which may lead to innovative clinical applications.

MicroRNA-185 inhibits angiogenesis in human microvascular endothelial cells through targeting stromal interaction molecule 1

Angiogenesis is a vital biological mechanism representing the adaptive response to a variety of pathological stimuli such as hypoxia. It is regulated by several pro-angiogenic and anti-angiogenic microRNAs. Studies have demonstrated an altered microRNA-185 (miR-185) expression in endothelial cells under hypoxic conditions; however, its role in angiogenesis has not been elucidated. We investigated the role of miR-185 in angiogenesis and found that miR-185 had an inhibitory effect on cell proliferation, migration, and tube formation. Stromal interaction molecule 1 (STIM1) appeared to be a direct target of miR-185 by computational prediction; this was confirmed by luciferase reporter assay. Silencing of the STIM1 gene was found to mimic miR-185-mediated inhibition of angiogenesis. STIM1 overexpression eliminated the anti-angiogenic effect of miR-185. Our study results suggest a direct interaction between miR-185 and STIM1 mRNA in microvascular endothelial cells. MicroRNA-185 acted as a negative regulator of angiogenesis in microvascular endothelial cells through downregulation of the STIM1 protein.

Interactional role of microRNAs and bHLH-PAS proteins in cancer (Review)

MicroRNAs (miRNAs) are recognized as an emerging class of master regulators that regulate human gene expression at the post-transcriptional level and are involved in many normal and pathological cellular processes. Mammalian basic HLH (helix-loop-helix)-PER-ARNT-SIM (bHLH-PAS) proteins are heterodimeric transcriptional regulators that sense and respond to environmental signals (such as chemical pollutants) or to physiological signals (for instance hypoxia). In the normal state, bHLH-PAS proteins are responsible for multiple critical aspects of physiology to ensure the cell accurate homeostasis, but dysregulation of these proteins has been shown to contribute to carcinogenic events such as tumor initiation, promotion, and progression. Increasing epidemiological and experimental studies have shown that bHLH-PAS proteins regulate a panel of miRNAs, whereas some miRNAs also target bHLH-PAS proteins. The interaction between miRNAs and certain bHLH-PAS proteins [hypoxia-inducible factor (HIF) and aryl hydrocarbon receptor (AHR)] is relevant to many vital events associated with tumorigenesis. This review will summarize recent findings on the interesting and complicated underlying mechanisms that miRNAs interact with HIFs or AHR in tumors, hopefully to benefit the discovery of novel drug-interfering targets for cancer therapy.