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Anaplastic thyroid cancer (ATC) is an extremely aggressive tumor characterized by marked epithelial mesenchymal transition, which leads, almost invariably, to death. Peroxisomal proliferator-activated receptor (PPAR)-gamma agonists have recently emerged as potential antineoplastic drugs. To establish whether ATC could be a target of PPAR gamma agonists, we first examined PPAR gamma protein expression in a panel of six ATC cell lines and then studied the biologic effects of two PPAR gamma agonists, ciglitazone and rosiglitazone, that belong to the class of thiazolidonediones. PPAR gamma protein was present and functional in all ATC cell lines. Both ciglitazone and rosiglitazone showed complex biological effects in ATC cells, including inhibition of anchorage-dependent and -independent growth and migration, and increased apoptosis rate. Rosiglitazone-induced growth inhibition was associated with cell cycle arrest and changes in cell cycle regulators, such as an increase of cyclin-dependent kinases inhibitors p21(cip1) and p27(kip1), a decrease of cyclin D1, and inactivation of Rb protein. Rosiglitazone-induced apoptosis was associated with a decrease of Bcl-X(L) expression and caspase-3 and -7 activation. Moreover, rosiglitazone antagonized IGF-I biological effects by up-regulating phosphatase and tensin homolog deleted from chromosome 10 with subsequent inhibition of the phosphatidylinositol 3-kinase/Akt signaling pathway. Finally, rosiglitazone increased the expression of thyroid-specific differentiation markers. In conclusions, these data suggest that PPAR gamma agonists induce a partial reversion of the epithelial mesenchymal transition in ATC cells by multiple mechanisms. PPAR gamma agonists may, therefore, have a role in the multimodal therapy currently used to slow down ATC growth and dissemination.

Idiopathic pulmonary fibrosis (IPF) is a progressive fibroproliferative disease characterized by an accumulation of fibroblasts and myofibroblasts in the alveolar wall. Even though the pathogenesis of this fatal disorder remains unclear, transforming growth factor-β (TGF-β)-induced differentiation and proliferation of myofibroblasts is recognized as a primary event. The molecular pathways involved in TGF-β signalling are generally Smad-dependent yet Smad-independent pathways, including phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt), have been recently proposed. In this research we established ex-vivo cultures of human lung fibroblasts and we investigated the role of the PI3K/Akt pathway in two critical stages of the fibrotic process induced by TGF-β: fibroblast proliferation and differentiation into myofibroblasts. Here we show that the pan-inhibitor of PI3Ks LY294002 is able to abrogate the TGF-β-induced increase in cell proliferation, in α- smooth muscle actin expression and in collagen production besides inhibiting Akt phosphorylation, thus demonstrating the centrality of the PI3K/Akt pathway in lung fibroblast proliferation and differentiation. Moreover, for the first time we show that PI3K p110δ and p110γ are functionally expressed in human lung fibroblasts, in addition to the ubiquitously expressed p110α and β. Finally, results obtained with both selective inhibitors and gene knocking-down experiments demonstrate a major role of p110γ and p110α in both TGF-β-induced fibroblast proliferation and differentiation. This finding suggests that specific PI3K isoforms can be pharmacological targets in IPF.

No abstract

Idiopathic pulmonary fibrosis (IPF) is a progressive fibroproliferative disease whose molecular pathogenesis remains unclear. In a recent paper, we demonstrated a key role for the PI3K pathway in both proliferation and differentiation into myofibroblasts of normal human lung fibroblasts treated with TGF-β. In this research, we assessed the expression of class I PI3K p110 isoforms in IPF lung tissue as well as in tissue-derived fibroblast cell lines. Moreover, we investigated the in vitro effects of the selective inhibition of p110 isoforms on IPF fibroblast proliferation and fibrogenic activity. IHC was performed on normal and IPF lung tissue. Expression levels of PI3K p110 isoforms were evaluated by western blot and flow cytometry analysis. Fibroblast cell lines were established from both normal and IPF tissue and the effects of selective pharmacological inhibition as well as specific gene silencing by small interfering RNAs were studied in vitro. No significant differences between normal and IPF tissue/tissue-derived fibroblasts were observed for the expression of PI3K p110 α, β and δ isoforms whereas p110γ was more greatly expressed in both IPF lung homogenates and ex vivo fibroblast cell lines. Myofibroblasts and bronchiolar basal cells in IPF lungs exhibited strong immunoreactivity for p110γ. Positive staining for the markers of proliferation proliferating cell nuclear antigen and cyclin D1 was also shown in cells of fibrolastic foci. Furthermore, both p110γ pharmacological inhibition and gene silencing were able to significantly inhibit proliferation rate as well as α-SMA expression in IPF fibroblasts. Our data suggest that PI3K p110γ isoform may have an important role in the etio-pathology of IPF and can be a specific pharmacological target.