MicroRNA deregulation in thyroid cancer

In cancer microRNAs are often dysregulated with their expression patterns being correlated with clinically relevant tumor characteristics. Recently, microRNAs were shown to be directly involved in cancer initiation and progression. Despite the large amount of data showing strong correlations between cancer phenotype and microRNAs aberrant expression, very little is known about the molecular mechanisms inducing such deregulation. Thyroid carcinomas comprise a heterogeneous group of neoplasms with distinctive clinical and pathological characteristics. Activating mutations in Ras genes are frequently found in poorly differentiated and in anaplastic thyroid carcinomas. We have recently shown that oncogenic activation of Ras is able to change the expression of several microRNAs in thyroid epithelial cells. One of the top aberrantly expressed ones is miR-21, a microRNA prevoiusly reported overexpressed in a wide variety of cancers and causally linked to cellular proliferation, survival and migration. By using an inducible Ras oncogene we demonstrated that constitutively active Ras induce overexpression of miR-21 at very early times after its activation, and that such overexpression is maintained at later times as well as in chronically Ras-transformed cells. Analysis of a panel of thyroid tumors with different hystotypes revealed that miR-21 is overexpressed mainly in anaplastic carcinomas, thus correlating with the most aggressive phenotype. Interestingly, this induction seems to be cell-type specific, since the inducible Ras oncogene is unable to increase miR-21 levels in cultured fibroblasts. Moreover, our data show that at least two different Ras downstream pathways are necessary to induce miR-21 expression. We then asked if the ability of Ras in inducing miR-21 overexpression is verified in vivo. To answer this question we analyzed the expression of this microRNA in a mouse model of Ras-induced lung tumorigenesis, showing that Ras constitutive activation is able to increase miR-21 levels in normal lung and that the Ras-initiated lung cancer progression is accompained by a further increase in miR-21 expression. Taken together, our data strongly suggest that the oncogenic activation of Ras could be responsible for the increased expression of miR-21 frequently observed in human cancers

EMT and induction of miR-21 mediate metastasis development in Trp53-deficient tumours

Missense mutations in TP53 gene promote metastasis in human tumours. However, little is known about the complete loss of function of p53 in tumour metastasis. Here we show that squamous cell carcinomas generated by the specific ablation of Trp53 gene in mouse epidermis are highly metastatic. Biochemical and genome-wide mRNA and miRNA analyses demonstrated that metastases are associated with the early induction of epithelial-mesenchymal transition (EMT) and deregulated miRNA expression in primary tumours. Increased expression of miR-21 was observed in undifferentiated, prometastatic mouse tumours and in human tumours characterized by p53 mutations and distant metastasis. The augmented expression of miR-21, mediated by active mTOR and Stat3 signalling, conferred increased invasive properties to mouse keratinocytes in vitro and in vivo, whereas blockade of miR-21 in a metastatic spindle cell line inhibits metastasis development. Collectively these data identify novel molecular mechanisms leading to metastasis in vivo originated by p53 loss in epithelia

Selective dicer suppression in the kidney alters gsk3β/β-Catenin Pathways Promoting a Glomerulocystic Disease

Dicer is a crucial enzyme for the maturation of miRNAs. Mutations in the Dicer gene are highly associated with Pleuro Pulmonary Blastoma-Family Dysplasia Syndrome (PPB-FDS, OMIM 601200), recently proposed to be renamed Dicer syndrome. Aside from the pulmonary phenotype (blastoma), renal nephroma and thyroid goiter are frequently part of Dicer syndrome. To investigate the renal phenotype, conditional knockout (cKO) mice for Dicer in Pax8 expressing cells were generated. Dicer cKO mice progressively develop a glomerulocystic phenotype coupled with urinary concentration impairment, proteinuria and severe renal failure. Higher cellular turnover of the parietal cells of Bowman's capsule precedes the development of the cysts and the primary cilium progressively disappears with cyst-enlargement. Upregulation of GSK3β precedes the development of the glomerulocystic phenotype. Downregulation of β-catenin in the renal cortex and its cytosolic removal in the cells lining the cysts may be associated with observed accumulation of GSK3β. Alterations of β-catenin regulating pathways could promote cystic degeneration as in other models. Thus, miRNAs are fundamental in preserving renal morphology and function. Alteration of the GSK3β/β-catenin pathway could be a crucial mechanism linking miRNA dysregulation and the development of a glomerulocystic disease

Stopshock Project

Il Progetto si propone di indentificare e validare principi attivi salvavita di pronto impiego per uso civile (medicina delle catastrofi) e militare (missioni peace keeping) - Il Progetto \ue8 promosso dal Ministero della Difesa e prevede la partecipazione di esperti di altri paesi