Knockdown of hypoxia inducible factor-2α inhibits cell invasion via the downregulation of MMP-2 expression in breast cancer cells

Staufen1 controls mitochondrial metabolism via HIF2α in embryonal rhabdomyosarcoma and promotes tumorigenesis

Elevated mitochondrial metabolism promotes tumorigenesis of Embryonal Rhabdomyosarcomas (ERMS). Accordingly, targeting oxidative phosphorylation (OXPHOS) could represent a therapeutic strategy for ERMS. We previously demonstrated that genetic reduction of Staufen1 (STAU1) levels results in the inhibition of ERMS tumorigenicity. Here, we examined STAU1-mediated mechanisms in ERMS and focused on its potential involvement in regulating OXPHOS. We report the novel and differential role of STAU1 in mitochondrial metabolism in cancerous versus non-malignant skeletal muscle cells (NMSkMCs). Specifically, our data show that STAU1 depletion reduces OXPHOS and inhibits proliferation of ERMS cells. Our findings further reveal the binding of STAU1 to several OXPHOS mRNAs which affects their stability. Indeed, STAU1 depletion reduced the stability of OXPHOS mRNAs, causing inhibition of mitochondrial metabolism. In parallel, STAU1 depletion impacted negatively the HIF2α pathway which further modulates mitochondrial metabolism. Exogenous expression of HIF2α in STAU1-depleted cells reversed the mitochondrial inhibition and induced cell proliferation. However, opposite effects were observed in NMSkMCs. Altogether, these findings revealed the impact of STAU1 in the regulation of mitochondrial OXPHOS in cancer cells as well as its differential role in NMSkMCs. Overall, our results highlight the therapeutic potential of targeting STAU1 as a novel approach for inhibiting mitochondrial metabolism in ERMS.

The Role of Hypoxia-Inducible Factor Isoforms in Breast Cancer and Perspectives on Their Inhibition in Therapy

Simple Summary

In many types of cancers, the activity of the hypoxia-inducible factors enhances hallmarks such as suppression of the immune response, altered metabolism, angiogenesis, invasion, metastasis, and more. As a result of observing these features, HIFs became attractive targets in designing anticancer therapy. The lack of effective breast treatment based on HIFs inhibitors and the elusive role of those factors in this type of cancer raises the concern wheter targeting hypoxia-inducible factors is the right path. Results of the study on breast cancer cell lines suggest the need to consider aspects like HIF-1α versus HIF-2α isoforms inhibition, double versus singular isoform inhibition, different hormone receptors status, metastases, and perhaps different not yet investigated issues. In other words, targeting hypoxia-inducible factors in breast cancers should be preceded by a better understanding of their role in this type of cancer. The aim of this paper is to review the role, functions, and perspectives on hypoxia-inducible factors inhibition in breast cancer.

Abstract

Hypoxia is a common feature associated with many types of cancer. The activity of the hypoxia-inducible factors (HIFs), the critical element of response and adaptation to hypoxia, enhances cancer hallmarks such as suppression of the immune response, altered metabolism, angiogenesis, invasion, metastasis, and more. The HIF-1α and HIF-2α isoforms show similar regulation characteristics, although they are active in different types of hypoxia and can show different or even opposite effects. Breast cancers present several unique ways of non-canonical hypoxia-inducible factors activity induction, not limited to the hypoxia itself. This review summarizes different effects of HIFs activation in breast cancer, where areas such as metabolism, evasion of the immune response, cell survival and death, angiogenesis, invasion, metastasis, cancer stem cells, and hormone receptors status have been covered. The differences between HIF-1α and HIF-2α activity and their impacts are given special attention. The paper also discusses perspectives on using hypoxia-inducible factors as targets in anticancer therapy, given current knowledge acquired in molecular studies.

Hypoxia-Induced Scleral HIF-2α Upregulation Contributes to Rises in MMP-2 Expression and Myopia Development in Mice

Purpose

Scleral hypoxia is a key factor that induces hypoxia-inducible factor-1α (HIF-1α) upregulation, and this response contributes to myopia progression. Currently, we aim to determine if the different HIF subtypes, including HIF-1α and HIF-2α, mediate hypoxia-induced myopia development through promoting scleral MMP-2 expression and collagen degradation.

Methods

Our study included: (1) time-course of scleral HIF-2α, MMP-2, and COL1α1 expression during form-deprivation myopia (FDM) development was determined in C57BL/6J mice. (2) The effect of silencing either HIF-1Α or HIF-2A on hypoxia-induced alterations in MMP-2 expression was analyzed in cultured human scleral fibroblasts (HSFs) under a hypoxic condition (i.e. 1% oxygen). (3) To knock-down either HIF-1α or HIF-2α expression in the sclera, we performed Sub-Tenon's capsule injection of an adeno-associated virus (AAV)8-packaged Cre overexpression vector (AAV8-Cre) in HIF-1α^fl/fl or HIF-2α^fl/fl mice. HIF-1α, HIF-2α, MMP-2, and COL1α1 expression were analyzed by Western blot or quantitative real-time PCR (qRT-PCR). In addition, the effects of scleral HIF-2α knock-down on normal refractive development and FDM development were evaluated.

Results

The time-dependent increases in scleral HIF-2α mimicked the HIF-1α expression profiles as we previously described. Hypoxia significantly promoted MMP-2 expression in HSFs, and this upregulation was solely alleviated by HIF-2A rather than HIF-1A silencing. Scleral HIF-2α knockdown significantly inhibited form-deprivation (FD)-induced MMP-2 upregulation and declines in COL1α1 accumulation and myopia development. Although scleral HIF-1α knockdown also significantly suppressed FD-induced declines in COL1α1 accumulation, it did not abrogate scleral MMP-2 upregulation.

Conclusions

HIF-2α rather than HIF-1α induces myopia development through upregulating MMP-2 and promoting collagen degradation in the sclera.

Neuroprotective Effect of HIF Prolyl Hydroxylase Inhibition in an In Vitro Hypoxia Model

A novel potent analog of the branched tail oxyquinoline group of hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitors, neuradapt, has been studied in two treatment regimes in an in vitro hypoxia model on murine primary hippocampal cultures. Neuradapt activates the expression of HIF1 and HIF2 target genes and shows no toxicity up to 20 μM, which is more than an order of magnitude higher than its biologically active concentration. Cell viability, functional activity, and network connectivity between the elements of neuronal networks have been studied using a pairwise correlation analysis of the intracellular calcium fluctuations in the individual cells. An immediate treatment with 1 μМ and 15 μМ neuradapt right at the onset of hypoxia not only protects from the death, but also maintains the spontaneous calcium activity in nervous cells at the level of the intact cultures. A similar neuroprotective effect in the post-treatment scenario is observed for 15 μМ, but not for 1 μМ neuradapt. Network connectivity is better preserved with immediate treatment using 1 μМ neuradapt than with 15 μМ, which is still beneficial. Post-treatment with neuradapt did not restore the network connectivity despite the observation that neuradapt significantly increased cell viability at 1 μМ and functional activity at 15 μМ. The preservation of cell viability and functional activity makes neuradapt promising for further studies in a post-treatment scenario, since it can be combined with other drugs and treatments restoring the network connectivity of functionally competent cells.

Antitumor effects of baicalin on ovarian cancer cells through induction of cell apoptosis and inhibition of cell migration in vitro

Baicalin, an active flavone isolated from Scutellaria baicalensis Georgi, has been demonstrated to induce various beneficial biochemical effects such as anti‑inflammatory, anti‑viral, and antitumor effects. However, the antitumor mechanism of baicalin is not well understood. In the present study, baicalin was demonstrated to inhibit the viability and migration of a widely used ovarian cancer cell line, A2780, in a dose‑dependent manner. MTT assays revealed that cell viability significantly decreased in ovarian cancer cells treated with baicalin compared with untreated cells, without effect on normal ovarian cells. Flow cytometric analysis indicated that baicalin suppressed cell proliferation by inducing apoptosis. The underlying mechanisms involved were indicated to be downregulation of the anti‑apoptotic protein B‑cell lymphoma 2 apoptosis regulator and activation of caspase‑3 and ‑9. In addition, wound healing and transwell assays revealed that cell migratory potential and expression of matrix metallopeptidase (MMP)‑2 and MMP‑9 were significantly inhibited when cells were exposed to baicalin, compared with untreated cells. The present study therefore suggested that baicalin has the potential to be used in novel anti‑cancer therapeutic formulations for treatment of ovarian cancer.

Inhibition of pro-/active MMP-2 by green tea catechins and prediction of their interaction by molecular docking studies

Matrix metalloproteinases (MMPs) play a crucial role in developing different types of lung diseases, e.g., pulmonary arterial hypertension (PAH). Green tea polyphenolic catechins such as EGCG and ECG have been shown to ameliorate various types of diseases including PAH. Our present study revealed that among the four green tea catechins (EGCG, ECG, EC, and EGC), EGCG and ECG inhibit pro-/active MMP-2 activities in pulmonary artery smooth muscle cell (PASMC) culture supernatant. Based on the above, we investigated the interactions of pro-/active MMP-2 with the green tea catechins by computational methods. In silico analysis revealed a strong interaction of pro-/active MMP-2 with EGCG/ECG, and galloyl group has been observed to be responsible for this interaction. The in silico analysis corroborated our experimental observation that EGCG and ECG are active in preventing both the proMMP-2 and MMP-2 activities. Importantly, these two catechins appeared to be better inhibitors for proMMP-2 in comparison to MMP-2 as revealed by gelatin zymogram and also by molecular docking studies. In many type of cells, activation of proMMP-2 occurs via an increase in the level of MT1-MMP (MMP-14). We, therefore, determined the interactions of MT1-MMP with the green tea catechins by molecular docking analysis. The study revealed a strong interaction of MT1-MMP with EGCG/ECG, and galloyl group has been observed to be responsible for the interaction.