Conversion of stationary to invasive tumor initiating cells (TICs): role of hypoxia in membrane type 1-matrix metalloproteinase (MT1-MMP) trafficking

Proteases Regulate Cancer Stem Cell Properties and Remodel Their Microenvironment

Proteolytic activity is perturbed in tumors and their microenvironment, and proteases also affect cancer stem cells (CSCs). CSCs are the therapy-resistant subpopulation of cancer cells with tumor-initiating capacity that reside in specialized tumor microenvironment niches. In this review, we briefly summarize the significance of proteases in regulating CSC activities with a focus on brain tumor glioblastoma. A plethora of proteases and their inhibitors participate in CSC invasiveness and affect intercellular interactions, enhancing CSC immune, irradiation, and chemotherapy resilience. Apart from their role in degrading the extracellular matrix enabling CSC migration in and out of their niches, we review the ability of proteases to modulate CSC properties, which prevents their elimination. When designing protease-oriented therapies, the multifaceted roles of proteases should be thoroughly investigated.

Effects of CoCl2-simulated hypoxia on the expression levels of matrix metalloproteinases in renal adenocarcinoma cells and renal tubular epithelial cells

Renal cell carcinoma (RCC) and chronic kidney disease (CKD) are associated with hypoxia, but the effects of hypoxia on the process of angiogenesis in the two diseases are dramatically different. Some of matrix metalloproteinases (MMPs), such as MMP2 and MMP9, may have a role because they represent the most prominent family of proteinases associated with angiogenesis. In the present study, the differential response of human renal cell cancer cells (786-0), human renal tubular epithelial cells (HK-2) and human microvascular endothelial cells (HMEC-1) to hypoxia with regards to the expression of MMP2, MMP9, MMP14, TIMP2, RECK was investigated. Cobalt chloride (CoCl₂) treatment was used to simulate the hypoxia environment in RCC and CKD. The expression levels of HIF-1α, RECK, MMP2, MMP9, MMP14 and TIMP2 in HK2, 786-0 and HMEC-1 cells were determined by western blot analysis after incubation with varying concentrations of CoCl₂ for 24 h. It was indicated that the effects of hypoxia on the endogenous expression of RECK and MMP2 differed depending on the considered cell type. Notably, the RECK expression was significantly decreased in 786-0 cells under hypoxia, whereas this expression was slightly increased in HK2 and HMEC-1 cells. Furthermore, the MMP2 expression was significantly increased in HMEC-1 cells under hypoxia, whereas the expression was slightly decreased in HK2 and 786-0 cells. These results demonstrate that 786-0, HK2 and HMEC-1 cells respond differently under hypoxic conditions. Furthermore, MMP2 and RECK may serve divergent roles in HK2 and HMEC-1 cells under hypoxic conditions.

The interplay between microRNAs and Twist1 transcription factor: a systematic review

Twist1 (also known as Twist) is a transcription factor that belongs to the family of basic helix-loop-helix (bHLH) proteins. It functions as a negative regulator of epithelial gene expression and a positive regulator of mesenchymal gene expression, thereby leading to induction of the epithelial mesenchymal transition (EMT), a process in which epithelial cells acquire the motile and migratory characteristics of mesenchymal cells. In addition to regulating the expression of protein-coding genes, Twist1 regulates the expression of microRNAs (miRNAs), adding a regulatory layer to EMT induction. Interestingly, the mRNA of Twist1 represents a downstream target of miRNAs, indicating an intricate network between miRNAs and Twist1. This network was shown to play multiple roles in cancer cell migration, invasion, and metastasis. The network can induce angiogenesis, protect cells from oncogene-induced apoptosis and senescence, enhance cancer cell resistance to conventional therapies, and increase cancer stem cell (CSC) populations. Recently, miRNAs have attracted considerable attention as potential promising tools in cancer therapies. Thus, this systematic review was conducted to clarify the reciprocal link between Twist1 and miRNAs in order to provide potential candidate miRNAs for diagnostic and therapeutic approaches in cancer treatment.

miR-181a-5p Inhibits Cancer Cell Migration and Angiogenesis via Downregulation of Matrix Metalloproteinase-14

Upregulation of matrix metalloproteinase MMP-14 (MT1-MMP) is associated with poor prognosis in cancer patients, but it is unclear how MMP-14 becomes elevated in tumors. Here, we show that miR-181a-5p is downregulated in aggressive human breast and colon cancers where its levels correlate inversely with MMP-14 expression. In clinical specimens, enhanced expression of MMP-14 was observed in cancer cells located at the invasive front of tumors where miR-181a-5p was downregulated relative to adjacent normal cells. Bioinformatics analyses defined a potential miR-181a-5p response element within the 3'-untranslated region of MMP-14 that was validated in reporter gene experiments. Ectopic miR-181a-5p reduced MMP-14 expression, whereas miR-181a-5p attenuation elevated MMP-14 expression. In support of a critical relationship between these two genes, miR-181a-5p-mediated reduction of MMP-14 levels was sufficient to decrease cancer cell migration, invasion, and activation of pro-MMP-2. Furthermore, this reduction in MMP-14 levels was sufficient to reduce in vivo invasion and angiogenesis in chick chorioallantoic membrane assays. Taken together, our results establish the regulation of MMP-14 in cancers by miR-181a-5p through a posttranscriptional mechanism, and they further suggest strategies to elevate miR-181a-5p to prevent cancer metastasis.

Hypoxia promotes HO-8910PM ovarian cancer cell invasion via Snail-mediated MT1-MMP upregulation

The molecular mechanisms of ovarian cancer cell invasion under hypoxia remain unclear. Here we employed a 3D collagen model and chick chorioallantoic membrane (CAM) invasion assay to explore the influence of hypoxia on ovarian cancer cell invasion. Hypoxia (both 1% O2 and CoCl2 150 and 250 µM) induced HO-8910PM ovarian cancer cell invasion in 3D collagen and collagenolysis determined by hydroxyproline. Pretreatment with a hypoxia inducible factor-1α inhibitor, YC-1, or MMP inhibitor, GM6001, significantly inhibited 3D collagen invasion and degradation and cell proliferation. Hypoxia stimulated both mRNA and protein expressions of membrane-type 1 matrix metalloproteinase (MT1-MMP) and promoted MT1-MMP translocation to the cell surface in an YC-1 sensitive manner. MT1-siRNA transfection inhibited hypoxia-induced invasion, proliferation, and collagen degradation of cells in 3D collagen. Hypoxia stimulated Snail mRNA and protein expression as well as translocation to nucleus in an YC-1 sensitive manner. Overexpression of Snail with a recombinant plasmid in HO-8910PM cells resulted in an enhanced invasion in 3D collagen. Transfection with Snail-specific siRNA significantly decreased MT1-MMP expression and 3D collagen invasion. Hypoxia-treated cells significantly broke the upper CAM surface of 11-day-old chick embryos and infiltrated interstitial tissue, completely blocked in the presence of YC-1 or GM6001, or after MT1-MMP siRNA or Snail siRNA transfection. Together, these data suggest that hypoxia promotes HO-8910PM ovarian cancer cell traffic through 3D matrix via Snail-mediated MT1-MMP upregulation, a possible molecular mechanism of ovarian cancer cell invasion under hypoxia.

In vivo imaging of membrane type-1 matrix metalloproteinase with a novel activatable near-infrared fluorescence probe

Membrane type-1 matrix metalloproteinase (MT1-MMP) is a protease activating MMP-2 that mediates cleavage of extracellular matrix components and plays pivotal roles in tumor migration, invasion and metastasis. Because in vivo noninvasive imaging of MT1-MMP would be useful for tumor diagnosis, we developed a novel near-infrared (NIR) fluorescence probe that can be activated following interaction with MT1-MMP in vivo. MT1-hIC7L is an activatable fluorescence probe comprised of anti-MT1-MMP monoclonal antibodies conjugated to self-assembling polymer micelles that encapsulate NIR dyes (IC7-1, λ_em: 858 nm) at concentrations sufficient to cause fluorescence self-quenching. In aqueous buffer, MT1-hIC7L fluorescence was suppressed to background levels and increased approximately 35.5-fold in the presence of detergent. Cellular uptake experiments revealed that in MT1-MMP positive C6 glioma cells, MT1-hIC7L showed significantly higher fluorescence that increased with time as compared to hIC7L, a negative control probe lacking the anti-MT1-MMP monoclonal antibody. In MT1-MMP negative MCF-7 breast adenocarcinoma cells, both MT1-hIC7L and hIC7L showed no obvious fluorescence. In addition, the fluorescence intensity of C6 cells treated with MT1-hIC7L was suppressed by pre-treatment with an MT1-MMP endocytosis inhibitor (P < 0.05). In vivo optical imaging using probes intravenously administered to tumor-bearing mice showed that MT1-hIC7L specifically visualized C6 tumors (tumor-to-background ratios: 3.8 ± 0.3 [MT1-hIC7L] vs 3.1 ± 0.2 [hIC7L] 48 h after administration, P < 0.05), while the probes showed similarly low fluorescence in MCF-7 tumors. Together, these results show that MT1-hIC7L would be a potential activatable NIR probe for specifically detecting MT1-MMP-expressing tumors.

Overexpression of membrane-type 2 matrix metalloproteinase induced by hypoxia-inducible factor-1α in pancreatic cancer: Implications for tumor progression and prognosis

Membrane-type 2 matrix metalloproteinase (MT2-MMP) has been identified as a powerful modulator of the pericellular environment that promotes tumor invasion and metastasis. In this study, we investigated the association of MT2-MMP and hypoxia-inducible factor-1α (HIF-1α) expression in pancreatic cancer with regard to their clinical prognostic significance. Of the tissue specimens obtained from the 78 patients included in this study, 46 (59%) were found to be positive for MT2-MMP immunostaining and MT2-MMP expression was colocalized with HIF-1α in pancreatic cancer. Using the Spearman's rank analysis, the protein and mRNA expression level of MT2-MMP was found to be significantly correlated with HIF-1α and CD34-microvascular density in pancreatic cancer. Furthermore, the expression of MT2-MMP in response to hypoxia was increased in a time-dependent manner and the promoter luciferase reporter revealed upregulation of MT2-MMP expression induced by HIF-1α in pancreatic cancer cells. Moreover, the Cox regression model indicated that MT2-MMP was an independent prognostic factor in patients with pancreatic cancer. Our results demonstrated that the overexpression of MT2-MMP was induced by HIF-1α in response to hypoxia and was an independent prognostic factor for pancreatic cancer progression.

Timed deletion of Twist1 in the limb bud reveals age-specific impacts on autopod and zeugopod patterning

Twist1 encodes a transcription factor that plays a vital role in limb development. We have used a tamoxifen-inducible Cre transgene, Ubc-CreERT2, to generate time-specific deletions of Twist1 by inducing Cre activity in mouse embryos at different ages from embryonic (E) day 9.5 onwards. A novel forelimb phenotype of supernumerary pre-axial digits and enlargement or partial duplication of the distal radius was observed when Cre activity was induced at E9.5. Gene expression analysis revealed significant upregulation of Hoxd10, Hoxd11 and Grem1 in the anterior half of the forelimb bud at E11.5. There is also localized upregulation of Ptch1, Hand2 and Hoxd13 at the site of ectopic digit formation, indicating a posterior molecular identity for the supernumerary digits. The specific skeletal phenotypes, which include duplication of digits and distal zeugopods but no overt posteriorization, differ from those of other Twist1 conditional knockout mutants. This outcome may be attributed to the deferment of Twist1 ablation to a later time frame of limb morphogenesis, which leads to the ectopic activation of posterior genes in the anterior tissues after the establishment of anterior-posterior anatomical identities in the forelimb bud.

Hemoglobin level in cervical cancer: a surrogate for an infiltrative phenotype

OBJECTIVE

Hemoglobin (Hb) is a prognostic factor in cervical cancer, but the underlying mechanisms remain unknown. In this study, we hypothesized that low Hb level, either before or during radiotherapy (RT), is a surrogate for a more infiltrative and therefore aggressive disease, with uterine corpus invasion and nodal metastases.

METHODS AND MATERIALS

Prospectively collected data of patients with locally advanced cervical cancer treated with curative intent using chemoradiation at a tertiary academic center was reviewed. All eligible patients had a positron emission tomographic scan and pelvic magnetic resonance imaging. Hemoglobin levels before RT and Hb nadir during RT were collected from the medical record.

RESULTS

The median follow-up for 263 eligible patients was 38.7 months. Ninety-six patients (36.5%) had both uterine corpus invasion and positron emission tomography-positive nodal disease (C+N+). Patients with pretreatment Hb level of less than 120 g/L were more likely to have C+N+ disease (47%) compared with patients with a high pretreatment Hb level (32%; P = 0.034). The 3-year disease-free survival and overall survival (OS) were significantly lower in the C+N+ group compared with the remaining patients (40.1% vs 76.1%, P < 0.001, and 59.7% vs 83.1%, P < 0.001, respectively). Patients with low Hb nadir were more likely to have a C+N+ disease (P < 0.001), and low Hb nadir during RT was significantly an indicator of a higher recurrence rate (P = 0.002) and lower OS (P < 0.001). In multifactor analysis, statistically significant prognostic factors for OS included histology, high-echelon nodal involvement, tumor volume on magnetic resonance imaging, C+N+ status, and Hb nadir during treatment. Pretreatment Hb level was not an independent prognostic factor.

CONCLUSIONS

The combination of corpus invasion and nodal metastases is associated with lower Hb level and inferior prognosis. Because C+N+ state is related to tumor growth from early invasion to the time of presentation, it is unlikely that the correction of Hb level during treatment will have a major impact on outcome.

The quinoxaline di-N-oxide DCQ blocks breast cancer metastasis in vitro and in vivo by targeting the hypoxia inducible factor-1 pathway

Background

Although tumor hypoxia poses challenges against conventional cancer treatments, it provides a therapeutic target for hypoxia-activated drugs. Here, we studied the effect of the hypoxia-activated synthetic quinoxaline di-N-oxide DCQ against breast cancer metastasis and identified the underlying mechanisms.

Methods

The human breast cancer cell lines MCF-7 (p53 wildtype) and MDA-MB-231 (p53 mutant) were treated with DCQ under normoxia or hypoxia. Drug toxicity on non-cancerous MCF-10A breast cells was also determined. In vitro cellular responses were investigated by flow cytometry, transfection, western blotting, ELISA and migration assays. The anti-metastatic effect of DCQ was validated in the MDA-MB-231 xenograft mouse model.

Results

DCQ selectively induced apoptosis in both human breast cancer cells preferentially under hypoxia without affecting the viability of non-cancerous MCF-10A. Cancer cell death was associated with an increase in reactive oxygen species (ROS) independently of p53 and was inhibited by antioxidants. DCQ-induced ROS was associated with DNA damage, the downregulation of hypoxia inducible factor-1 alpha (HIF-1α), and inhibition of vascular endothelial growth factor (VEGF) secretion. In MCF-7, HIF-1α inhibition was partially via p53-activation and was accompanied by a decrease in p-mTOR protein, suggesting interference with HIF-1α translation. In MDA-MB-231, DCQ reduced HIF-1α through proteasomal-dependent degradation mechanisms. HIF-1α inhibition by DCQ blocked VEGF secretion and invasion in MCF-7 and led to the inhibition of TWIST in MDA-MB-231. Consistently, DCQ exhibited robust antitumor activity in MDA-MB-231 breast cancer mouse xenografts, enhanced animal survival, and reduced metastatic dissemination to lungs and liver.

Conclusion

DCQ is the first hypoxia-activated drug showing anti-metastatic effects against breast cancer, suggesting its potential use for breast cancer therapy.

The quinoxaline di-N-oxide DCQ blocks breast cancer metastasis in vitro and in vivo by targeting the hypoxia inducible factor-1 pathway

BACKGROUND

Although tumor hypoxia poses challenges against conventional cancer treatments, it provides a therapeutic target for hypoxia-activated drugs. Here, we studied the effect of the hypoxia-activated synthetic quinoxaline di-N-oxide DCQ against breast cancer metastasis and identified the underlying mechanisms.

METHODS

The human breast cancer cell lines MCF-7 (p53 wildtype) and MDA-MB-231 (p53 mutant) were treated with DCQ under normoxia or hypoxia. Drug toxicity on non-cancerous MCF-10A breast cells was also determined. In vitro cellular responses were investigated by flow cytometry, transfection, western blotting, ELISA and migration assays. The anti-metastatic effect of DCQ was validated in the MDA-MB-231 xenograft mouse model.

RESULTS

DCQ selectively induced apoptosis in both human breast cancer cells preferentially under hypoxia without affecting the viability of non-cancerous MCF-10A. Cancer cell death was associated with an increase in reactive oxygen species (ROS) independently of p53 and was inhibited by antioxidants. DCQ-induced ROS was associated with DNA damage, the downregulation of hypoxia inducible factor-1 alpha (HIF-1α), and inhibition of vascular endothelial growth factor (VEGF) secretion. In MCF-7, HIF-1α inhibition was partially via p53-activation and was accompanied by a decrease in p-mTOR protein, suggesting interference with HIF-1α translation. In MDA-MB-231, DCQ reduced HIF-1α through proteasomal-dependent degradation mechanisms. HIF-1α inhibition by DCQ blocked VEGF secretion and invasion in MCF-7 and led to the inhibition of TWIST in MDA-MB-231. Consistently, DCQ exhibited robust antitumor activity in MDA-MB-231 breast cancer mouse xenografts, enhanced animal survival, and reduced metastatic dissemination to lungs and liver.

CONCLUSION

DCQ is the first hypoxia-activated drug showing anti-metastatic effects against breast cancer, suggesting its potential use for breast cancer therapy.

Development of a high-throughput three-dimensional invasion assay for anti-cancer drug discovery

The lack of three-dimensional (3-D) high-throughput (HT) screening assays designed to identify anti-cancer invasion drugs is a major hurdle in reducing cancer-related mortality, with the key challenge being assay standardization. Presented is the development of a novel 3-D invasion assay with HT potential that involves surrounding cell-collagen spheres within collagen to create a 3-D environment through which cells can invade. Standardization was achieved by designing a tooled 96-well plate to create a precisely designated location for the cell-collagen spheres and by using dialdehyde dextran to inhibit collagen contraction, maintaining uniform size and shape. This permits automated readout for determination of the effect of inhibitory compounds on cancer cell invasion. Sensitivity was demonstrated by the ability to distinguish varying levels of invasiveness of cancer cell lines, and robustness was determined by calculating the Z-factor. A Z-factor of 0.65 was obtained by comparing the effects of DMSO and anti-β1-integrin antibody, an inhibitory reagent, on the invasion of Du145 cancer cells, suggesting this novel assay is suitable for large scale drug discovery. As proof of principle, the NCI Diversity Compound Library was screened against human invasive cancer cells. Nine compounds exhibiting high potency and low toxicity were identified, including DX-52-1, a compound previously reported to inhibit cell migration, a critical determinant of cancer invasion. The results indicate that this innovative HT platform is a simple, precise, and easy to replicate 3-D invasion assay for anti-cancer drug discovery.