Constitutive activation of the ETS-1-miR-222 circuitry in metastatic melanoma.

MicroRNAs-221 and -222 are highly upregulated in several solid tumors, including melanomas. We demonstrate that the proto-oncogene ETS-1, involved in the pathogenesis of cancers of different origin, is a transcriptional regulator of miR-222 by direct binding to its promoter region. Differently from 293FT cells or early stage melanomas, where unphosphorylated ETS-1 represses miR-222 transcription, in metastatic melanoma the constitutively Thr-38 phosphorylated fraction of ETS-1 induces miR-222. Despite its stepwise decreased expression along with melanoma progression, the oncogenic activity of ETS-1 relies on its RAS/RAF/ERK-dependent phosphorylation status more than on its total amount. To close the loop, we demonstrate ETS-1 as a direct target of miR-222, but not miR-221, showing the novel option of their uncoupled functions. In addition, a spatial redistribution of ETS-1 protein from the nucleus to the cytoplasm is also evidenced in advanced melanoma cells. Finally, in vivo studies confirmed the contribution of miR-222 to the increased invasive potential obtained by ETS- silencing.

MicroRNA-221 and -222 pathway controls melanoma progression.

MicroRNAs (miRNAs) represent a new family of small noncoding RNAs that negatively regulate gene expression. Recent studies demonstrated miRNA involvement in all the main biological processes, including tumor development as a consequence of an aberrant deregulated expression. Growing evidence is showing the capability of miRNA expression profiles to unequivocally distinguish between normal and neoplastic tissues, leading to the identification of new diagnostic and/or prognostic molecular markers. In addition, miRNAs might eventually represent new targets to aim at as innovative therapeutic approaches, particularly relevant in those types of cancer, such as melanoma, which are still lacking effective traditional therapies. In particular, the inhibition of miRNA-221 and -222, which are abnormally expressed in melanoma and favor the induction of the malignant phenotype by downregulating c-KIT receptor and p27Kip, might in the future represent an efficient treatment for translation into the clinical setting.

The promyelocytic leukemia zinc finger-microRNA-221/-222 pathway controls melanoma progression through multiple oncogenic mechanisms.

The incidence of cutaneous melanoma is steadily increasing. Although several molecular abnormalities have been associated with melanoma progression, the mechanisms underlying the differential gene expression are still largely unknown and targeted therapies are not yet available. Noncoding small RNAs, termed microRNAs (miR), have been recently reported to play important roles in major cellular processes, including those involved in cancer development and progression. We have identified the promyelocytic leukemia zinc finger (PLZF) transcription factor as a repressor of miR-221 and miR-222 by direct binding to their putative regulatory region. Specifically, PLZF silencing in melanomas unblocks miR-221 and miR-222, which in turn controls the progression of the neoplasia through down-modulation of p27Kip1/CDKN1B and c-KIT receptor, leading to enhanced proliferation and differentiation blockade of the melanoma cells, respectively. In vitro and in vivo functional studies, including the use of antisense "antagomir" oligonucleotides, confirmed the key role of miR-221/-222 in regulating the progression of human melanoma; this suggests that targeted therapies suppressing miR-221/-222 may prove beneficial in advanced melanoma.

MicroRNA-133 controls cardiac hypertrophy.

Growing evidence indicates that microRNAs (miRNAs or miRs) are involved in basic cell functions and oncogenesis. Here we report that miR-133 has a critical role in determining cardiomyocyte hypertrophy. We observed decreased expression of both miR-133 and miR-1, which belong to the same transcriptional unit, in mouse and human models of cardiac hypertrophy. In vitro overexpression of miR-133 or miR-1 inhibited cardiac hypertrophy. In contrast, suppression of miR-133 by 'decoy' sequences induced hypertrophy, which was more pronounced than that after stimulation with conventional inducers of hypertrophy. In vivo inhibition of miR-133 by a single infusion of an antagomir caused marked and sustained cardiac hypertrophy. We identified specific targets of miR-133: RhoA, a GDP-GTP exchange protein regulating cardiac hypertrophy; Cdc42, a signal transduction kinase implicated in hypertrophy; and Nelf-A/WHSC2, a nuclear factor involved in cardiogenesis. Our data show that miR-133, and possibly miR-1, are key regulators of cardiac hypertrophy, suggesting their therapeutic application in heart disease.

Expression of alternative transcripts of ferroportin-1 during human erythroid differentiation.

BACKGROUND AND OBJECTIVES: Ferroportin-1 (FPN1) is expressed in various types of cells that play critical roles in mammalian iron metabolism and appears to act as an iron exporter in these tissues. The aim of this study was to investigate whether erythroid cells possess specific mechanisms for iron export. DESIGN AND METHODS: The expression of FPN1 during human erythroid differentiation, the characterization of alternative transcripts, the modulation by iron and the subcellular localization of this protein were studied. RESULTS: FPN1 mRNA and protein are highly expressed during human erythroid differentiation. The iron-responsive element (IRE) in the 5'- untranslated region (UTR) of FPN1 mRNA is functional but, in spite of that, FPN1 protein expression, as well as mRNA level and half-life, seem not to be affected by iron. To explain these apparenthy discordant results we searched for alternative transcripts of FPN1 and found at least three different types of transcripts, displaying alternative 5' ends. Most of the FPN1 transcripts code for the canonical protein, but only half of them contain an IRE in the 5'-UTR and have the potential to be translationally regulated by iron. Expression analysis shows that alternative FPN1 transcripts are differentially expressed during erythroid differentiation. Finally, sustained expression of alternative FPN1 transcripts is apparently observed only in erythroid cells. INTERPRETATION AND CONCLUSIONS: This is the first report describing the presence of FPN1 in erythroid cells at all stages of differentiation, providing evidence that erythroid cells possess specific mechanisms of iron export. The existence of multiple FPN1 transcripts indicates a complex regulation of the FPN1 gene in erythroid cells.