Non-small cell lung cancer (NSCLC) accounts for ∼80% of all lung cancers. Although some advances in lung cancer therapy have been made, patient survival is still quite poor. Two microRNAs, miR-221 ...and miR-222, upregulated by the MET proto-oncogene, have been already described to enhance cell survival and to induce TNF-related apoptosis-inducing ligand (TRAIL) resistance in NSCLC cell lines, through the downregulation of p27(kip1), PTEN and TIMP3. Here, we further investigated this pathway and showed that miR-130a, expressed at low level in lung cancer cell lines, by targeting MET was able to reduce TRAIL resistance in NSCLC cells through the c-Jun-mediated downregulation of miR-221 and miR-222. Moreover, we found that miR-130a reduced migratory capacity of NSCLC. A better understanding of MET-miR-221 and 222 axis regulation in drug resistance is the key in developing new strategies in NSCLC therapy.
Thyroid carcinomas comprise a broad spectrum of tumors with different clinical behaviors. On the one side, there are occult papillary carcinomas (PTC), slow growing and clinically silent, and on the ...other side, rapidly growing anaplastic carcinomas (ATC), which are among the most lethal human neoplasms. We have analysed the microRNA (miR) profile of ATC in comparison to the normal thyroid using a microarray (miRNACHIP microarray). By this approach, we found an aberrant miR expression profile that clearly differentiates ATC from normal thyroid tissues and from PTC analysed in previous studies. In particular, a significant decrease in miR-30d, miR-125b, miR-26a and miR-30a-5p was detected in ATC in comparison to normal thyroid tissue. These results were further confirmed by northern blots, quantitative reverse transcription-PCR analyses and in situ hybridization. The overexpression of these four miRs in two human ATC-derived cell lines suggests a critical role of miR-125b and miR-26a downregulation in thyroid carcinogenesis, since a cell growth inhibition was achieved. Conversely, no effect on cell growth was observed after the overexpression of miR-30d and miR-30a-5p in the same cells. In conclusion, these data indicate a miR signature associated with ATC and suggest the miR deregulation as an important event in thyroid cell transformation.
MicroRNAs (miRNAs) are a class of small non-coding RNAs involved in a wide range of basic processes such as cell proliferation, development, apoptosis and stress response. It has recently been found ...that they are also abnormally expressed in many types of human cancer. We analyzed the genome-wide miRNA expression profile in human thyroid papillary carcinomas (PTCs) using a microarray (miRNACHIP microarray) containing hundreds of human precursor and mature miRNA oligonucleotide probes. Using this approach, we found an aberrant miRNA expression profile that clearly differentiates PTCs from normal thyroid tissues. In particular, a significant increase in miRNA (miR)-221, -222 and -181b was detected in PTCs in comparison with normal thyroid tissue. These results were further confirmed by northern blot and quantitative RT-PCR analyses. Moreover, RT-PCR revealed miR-221, -222 and -181b overexpression in fine needle aspiration biopsies corresponding to thyroid nodules, which were eventually diagnosed as papillary carcinomas after surgery. Finally, miR-221, -222 and -181b overexpression was also demonstrated in transformed rat thyroid cell lines and in mouse models of thyroid carcinogenesis. Functional studies, performed by blocking miR-221 function and by overexpressing miR-221 in human PTC-derived cell lines, suggest a critical role of miR-221 overexpression in thyroid carcinogenesis. In conclusion, these data, taken together, indicate an miRNA signature associated with PTCs, and suggest miRNA deregulation as an important event in thyroid cell transformation.
The miR-483-3p is upregulated in several tumors, including liver tumors, where it inhibits TP53-dependent apoptosis by targeting the pro-apoptotic gene BBC3/PUMA. The transcriptional regulation of ...the miR-483-3p could be driven by the β-catenin/USF1 complex, independently from its host gene IGF2, and we previously demonstrated that in HepG2 hepatoblastoma cells carrying wild-type TP53 the upregulation of the miR-483-3p overcomes the antitumoral effects of the tumor-suppressor miR-145-5p by a mechanism involving cellular glucose availability. Here we demonstrate that in HepG2 cells, the molecular link between glucose concentration and miR-483-3p expression entails the O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT), which stabilizes the transcriptional complex at the miR-483 promoter. HepG2 cells showed reduced miR-483-3p expression and increased susceptibility to 5-fluorouracil (5-FU)-induced apoptosis in presence of the inhibitor of glycolysis 2-deoxy-d-glucose (2-DG). However, in vivo experiments showed that HepG2 cells with higher miR-483-3p expression were selected during tumor progression regardless of 5-FU treatment. Furthermore, treatment with 2-DG alone did not significantly reduce HepG2 xenograft load in immunodeficient mice. In conclusion, we show that in HepG2 cells glucose uptake increases the expression of the oncogenic miR-483-3p through the OGT pathway. This suggests that depletion of the miR-483-3p may be a valuable therapeutic approach in liver cancer patients, but the use of inhibitors of glycolysis to achieve this purpose could accelerate the selection of resistant neoplastic cell clones.
Deregulation of the miR-15a/16-1 cluster has a key role in the pathogenesis of chronic lymphocytic leukemia (CLL), a clinically heterogeneous disease with indolent and aggressive forms. The ...miR-15a/16-1 locus is located at 13q14, the most frequently deleted region in CLL. Starting from functional investigations of a rare SNP upstream the miR cluster, we identified a novel allele-specific mechanism that exploits a cryptic activator region to recruit the RNA polymerase III for miR-15a/16-1 transcription. This regulation of the miR-15a/16- locus is independent of the DLEU2 host gene, which is often transcribed monoallellically by RPII. We found that normally one allele of miR-15a/16-1 is transcribed by RNAPII, the other one by RNAPIII. In our subset of CLL patients harboring 13q14 deletions, exclusive RNA polymerase III (RPIII)-driven transcription of the miR-15a/16-1 was the consequence of loss of the RPII-regulated allele and correlated with high expression of the poor prognostic marker ZAP70 (P=0.019). Thus, our findings point to a novel biological process, characterized by double allele-specific transcriptional regulation of the miR-15a/16-1 locus by alternative mechanisms. Differential usage of these mechanisms may distinguish at onset aggressive from indolent forms of CLL. This provides a basis for the clinical heterogeneity of the CLL patients carrying 13q14 deletions.
Molecular mechanisms protecting cardiomyocytes from stress-induced death, including tension stress, are essential for cardiac physiology and defects in these protective mechanisms can result in ...pathological alterations. Bcl2-associated athanogene 3 (BAG3) is expressed in cardiomyocytes and is a component of the chaperone-assisted autophagy pathway, essential for homeostasis of mechanically altered cells. BAG3 ablation in mice results in a lethal cardiomyopathy soon after birth and mutations of this gene have been associated with different cardiomyopathies including stress-induced Takotsubo cardiomyopathy (TTC). The pathogenic mechanism leading to TTC has not been defined, but it has been suggested that the heart can be damaged by excessive epinephrine (epi) spillover in the absence of a protective mechanism. The aim of this study was to provide more evidence for a role of BAG3 in the pathogenesis of TTC. Therefore, we sequenced BAG3 gene in 70 TTC patients and in 81 healthy donors with the absence of evaluable cardiovascular disease. Mutations and polymorphisms detected in the BAG3 gene included a frequent nucleotide change g2252c in the BAG3 3'-untranslated region (3'-UTR) of Takotsubo patients (P<0.05), resulting in loss of binding of microRNA-371a-5p (miR-371a-5p) as evidenced by dual-luciferase reporter assays and argonaute RNA-induced silencing complex catalytic component 2/pull-down assays. Moreover, we describe a novel signaling pathway in cardiomyocytes that leads to BAG3 upregulation on exposure to epi through an ERK-dependent upregulation of miR-371a-5p. In conclusion, the presence of a g2252c polymorphism in the BAG3 3'-UTR determines loss of miR-371a-5p binding and results in an altered response to epi, potentially representing a new molecular mechanism that contributes to TTC pathogenesis.
The High Mobility Group proteins HMGA1 are nuclear architectural factors that play a critical role in a wide range of biological processes. Since recent studies have identified the microRNAs (miRNAs) ...as important regulators of gene expression, modulating critical cellular functions such as proliferation, apoptosis and differentiation, the aim of our work was to identify the miRNAs that are physiologically regulated by HMGA1 proteins. To this purpose, we have analysed the miRNA expression profile of mouse embryonic fibroblasts (MEFs) carrying two, one or no Hmga1 functional alleles using a microarray (miRNA microarray). By this approach, we found a miRNA expression profile that differentiates Hmga1-null MEFs from the wild-type ones. In particular, a significant decrease in miR-196a-2, miR-101b, miR-331 and miR-29a was detected in homozygous Hmga1-knockout MEFs in comparison with wild-type cells. Consistently, these miRNAs are downregulated in most of the analysed tissues of Hmga1-null mice in comparison with the wild-type mice. ChIP assay shows that HMGA1 is able to bind regions upstream of these miRNAs. Moreover, we identified the HMGA2 gene product as a putative target of miR-196a-2, suggesting that HMGA1 proteins are able to downregulate the expression of the other member of the HMGA family through the regulation of the miR-196a-2 expression. Finally, ATXN1 and STC1 gene products have been identified as targets of miR-101b. Therefore, it is reasonable to hypothesize that HMGA1 proteins are involved in several functions by regulating miRNA expression.
MiRNAs and Cancer Visone, Rosa; Croce, Carlo M
The American journal of pathology,
04/2009, Letnik:
174, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Cancer is the result of a complex multistep process that involves the accumulation of sequential alterations of several genes, including those encoding microRNAs (miRNAs). miRNAs are a class of 17- ...to 27-nucleotide single-stranded RNA molecules that regulate gene expression posttranscriptionally. A large body of evidence implicates aberrant miRNA expression patterns in most, if not all, human malignancies. This article reviews our current knowledge about miRNAs, focusing on their involvement in cancer and their potential as diagnostic, prognostic, and therapeutic tools.
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