Cancer is a multistep disease based on crucial interactions between tumor cells and the microenvironment (extracellular matrix and stroma/immune cells). In fact, during dissemination, tumor cells ...have to escape from the primary tumor mass, cross the basal membrane, interact with endothelial cells to enter blood vessels (intravasation), survive in the bloodstream, get in contact with endothelial cells again to exit the bloodstream (extravasation) and seed in distant organs. Interactions between tumor and stroma cells are strongly coordinated by microRNAs (miRNAs), small non-coding RNAs able to silence protein coding genes by binding to specific recognition sites, mostly located at the 3’ UTR of mature mRNAs. Relevantly, miRNA expression is often altered (overexpression or downregulation) in tumor cells and influenced by stroma cells. At the same time, miRNAs are abundant and essential in stroma cells during tumor cell dissemination and their expression is influenced by tumor cells. In fact, for instance, conditional ablation of Dicer in the endothelium of tumor bearing-mice leads to reduced tumor growth and microvessel density. In this review, we specifically focus on the role of miRNAs in endothelial cells regarding their positive or negative intervention on tumor angiogenesis or lymphoangiogenesis or when tumor cells detach from the tumor mass and intravasate or extravasate in/out of the blood vessels. Examples of pro-angiogenic miRNAs are miR-9 or miR-494, often overexpressed in tumors, which accumulate in tumor cell microvescicles and, therefore, get transferred to endothelial cells where they induce migration and angiogenesis. Differently, miR-200 and miR-128 are often downregulated in tumors and inhibit angiogenesis and lymphoangiogenesis. Instead, miR-126 controls intravasation while miR-146a, miR-214, miR-148b govern extravasation, in a positive or negative manner. Finally, at the end, we summarize opportunities for therapeutic interventions based on miRNAs acting on endothelial cells.
Melatonin, a hormone secreted by pineal gland, exerts antimetastatic effects by reducing tumor cell proliferation, migration and invasion. MicroRNAs (miRNAs) are small, non-coding RNAs that play a ...crucial role in regulation of gene expression and biological processes of the cells. Herein, we search for a link between the tumor/metastatic-suppressive actions of melatonin and miRNA expression in triple-negative breast cancer cells. We demonstrated that melatonin exerts its anti-tumor actions by reducing proliferation, migration and c-Myc expression of triple negative breast cancer cells. By using Taqman-based assays, we analyzed the expression levels of a set of miRNAs following melatonin treatment of triple negative breast cancer cells and we identified 17 differentially expressed miRNAs, 6 down-regulated and 11 up-regulated. We focused on the anti-metastatic miR-148b and the oncogenic miR-210 both up-regulated by melatonin treatment and studied the effect of their modulation on melatonin-mediated impairment of tumor progression. Surprisingly, when miR-148b or miR-210 were depleted in triple-negative breast cancer cells, using a specific miR-148b sponge or anti-miR-210, melatonin effects on migration inhibition and c-myc downregulation were still visible suggesting that the increase of miR-148b and miR-210 expression observed following melatonin treatment was not required for the efficacy of melatonin action. Nevertheless, ours results suggest that melatonin exhibit a compound for metastatic trait inhibition, especially in MDA-MB-231 breast cancer cells even if a direct link between modulation of expression of certain proteins or miRNAs and melatonin effects has still to be established.
Ten-eleven translocation (Tet) genes encode for a family of hydroxymethylase enzymes involved in regulating DNA methylation dynamics. Tet1 is highly expressed in mouse embryonic stem cells (ESCs) ...where it plays a critical role the pluripotency maintenance. Tet1 is also involved in cell reprogramming events and in cancer progression. Although the functional role of Tet1 has been largely studied, its regulation is poorly understood. Here we show that Tet1 gene is regulated, both in mouse and human ESCs, by the stemness specific factors Oct3/4, Nanog and by Myc. Thus Tet1 is integrated in the pluripotency transcriptional network of ESCs. We found that Tet1 is switched off by cell proliferation in adult cells and tissues with a consequent genome-wide reduction of 5hmC, which is more evident in hypermethylated regions and promoters. Tet1 downmodulation is mediated by the Polycomb repressive complex 2 (PRC2) through H3K27me3 histone mark deposition. This study expands the knowledge about Tet1 involvement in stemness circuits in ESCs and provides evidence for a transcriptional relationship between Tet1 and PRC2 in adult proliferating cells improving our understanding of the crosstalk between the epigenetic events mediated by these factors.
Tumor progression is based on a close interaction between cancer cells and Tumor MicroEnvironment (TME). Here, we focus on the role that Cancer Associated Fibroblasts (CAFs), Mesenchymal Stem Cells ...(MSCs) and microRNAs (miRs) play in breast cancer and melanoma malignancy.
We used public databases to investigate miR-214 expression in the stroma compartment of primary human samples and evaluated tumor formation and dissemination following tumor cell injections in miR-214 overexpressing (miR-214
) and knock out (miR-214
) mice. In addition, we dissected the impact of Conditioned Medium (CM) or Extracellular Vesicles (EVs) derived from miR-214-rich or depleted stroma cells on cell metastatic traits.
We evidence that the expression of miR-214 in human cancer or metastasis samples mostly correlates with stroma components and, in particular, with CAFs and MSCs. We present data revealing that the injection of tumor cells in miR-214
mice leads to increased extravasation and metastasis formation. In line, treatment of cancer cells with CM or EVs derived from miR-214-enriched stroma cells potentiate cancer cell migration/invasion in vitro. Conversely, dissemination from tumors grown in miR-214
mice is impaired and metastatic traits significantly decreased when CM or EVs from miR-214-depleted stroma cells are used to treat cells in culture. Instead, extravasation and metastasis formation are fully re-established when miR-214
mice are pretreated with miR-214-rich EVs of stroma origin. Mechanistically, we also show that tumor cells are able to induce miR-214 production in stroma cells, following the activation of IL-6/STAT3 signaling, which is then released via EVs subsequently up-taken by cancer cells. Here, a miR-214-dependent pro-metastatic program becomes activated.
Our findings highlight the relevance of stroma-derived miR-214 and its release in EVs for tumor dissemination, which paves the way for miR-214-based therapeutic interventions targeting not only tumor cells but also the TME.
Advanced ovarian cancers are initially responsive to combinatorial chemotherapy with platinum drugs and taxanes but, in most cases, develop drug resistance. We recently showed that, in vitro, ...hepatocyte growth factor (HGF) enhances death of human ovarian cancer cell lines treated with cisplatin (CDDP) and paclitaxel. The present study addresses whether in vivo HGF makes ovarian carcinoma cells more responsive to these chemotherapeutics.
Using Lentiviral vectors carrying the HGF transgene, we transduced SK-OV-3 and NIH:OVCAR-3 ovarian carcinoma cell lines to obtain stable autocrine and paracrine HGF receptor activation. In vitro, we assayed growth, motility, invasiveness, and the response to CDDP and paclitaxel of the HGF-secreting bulk unselected cell populations. In vivo, we tested the cytotoxic effects of the drugs versus s.c. tumors formed by the wild-type and HGF-secreting cells in immunocompromised mice. Tumor-bearing mice were treated with CDDP (i.p.) and paclitaxel (i.v.), combined in different schedules and doses.
In vitro, HGF-secreting cells did not show altered proliferation rates and survival but were strongly sensitized to the death triggered by CDDP and paclitaxel, alone or in combination. In vivo, we found a therapeutic window in which autocrine/paracrine HGF made tumors sensitive to low doses of the drugs, which were ineffective on their own.
These data provide the proof-of-concept that in vivo gene therapy with HGF might be competent in sensitizing ovarian cancer cells to conventional chemotherapy.
Phenotypic changes induced by extracellular vesicles have been implicated in mesenchymal stromal cell-promoted recovery of AKI. MicroRNAs are potential candidates for cell reprogramming toward a ...proregenerative phenotype. The aim of this study was to evaluate whether microRNA deregulation inhibits the regenerative potential of mesenchymal stromal cells and derived extracellular vesicles in a model of glycerol-induced AKI in severe combined immunodeficient mice. We generated mesenchymal stromal cells depleted of Drosha to alter microRNA expression. Drosha-knockdown cells produced extracellular vesicles that did not differ from those of wild-type cells in quantity, surface molecule expression, and internalization within renal tubular epithelial cells. However, these vesicles showed global downregulation of microRNAs. Whereas wild-type mesenchymal stromal cells and derived vesicles administered intravenously induced morphologic and functional recovery in AKI, the Drosha-knockdown counterparts were ineffective. RNA sequencing analysis showed that kidney genes deregulated after injury were restored by treatment with mesenchymal stromal cells and derived vesicles but not with Drosha-knockdown cells and vesicles. Gene ontology analysis showed in AKI an association of downregulated genes with fatty acid metabolism and upregulated genes with inflammation, matrix-receptor interaction, and cell adhesion molecules. These alterations reverted after treatment with wild-type mesenchymal stromal cells and extracellular vesicles but not after treatment with the Drosha-knockdown counterparts. In conclusion, microRNA depletion in mesenchymal stromal cells and extracellular vesicles significantly reduced their intrinsic regenerative potential in AKI, suggesting a critical role of microRNAs in recovery after AKI.
We previously demonstrated that miR-214 is upregulated in malignant melanomas and triple-negative breast tumors and promotes metastatic dissemination by affecting a complex pathway including the ...anti-metastatic miR-148b. Importantly, tumor dissemination could be reduced by blocking miR-214 function or increasing miR-148b expression or by simultaneous interventions. Based on this evidence, with the intent to explore the role of miR-214 as a target for therapy, we evaluated the capability of new chemically modified anti-miR-214, R97/R98, to inhibit miR-214 coordinated metastatic traits. Relevantly, when melanoma or breast cancer cells were transfected with R97/R98, anti-miR-214 reduced miR-214 expression and impaired transendothelial migration were observed. Noteworthy, when the same cells were injected in the tail vein of mice, cell extravasation and metastatic nodule formation in lungs were strongly reduced. Thus, suggesting that R97/R98 anti-miR-214 oligonucleotides were able to inhibit tumor cell escaping through the endothelium. More importantly, when R97/R98 anti-miR-214 compounds were systemically delivered to mice carrying melanomas or breast or neuroendocrine pancreatic cancers, a reduced number of circulating tumor cells and lung or lymph node metastasis formation were detected. Similar results were also obtained when AAV8-miR-214 sponges were used in neuroendocrine pancreatic tumors. Based on this evidence, we propose miR-214 as a promising target for anti-metastatic therapies.
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In this issue of Molecular Therapy, Dettori et al. (2018) propose a new anti-miR-214-based therapy to control tumor spread. They tested the efficacy of two anti-miR-214 compounds and an AAV8 expressing a miR-214 sponge in multiple mouse models of tumor progression and showed that miR-214 inhibition led to reduced tumor metastasis with no side effects.
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