FOXO transcription factors in cancer development and therapy.

The forkhead box O (FOXO) transcription factors are considered as tumor suppressors that limit cell proliferation and induce apoptosis. FOXO gene alterations have been described in a limited number of human cancers, such as rhabdomyosarcoma, leukemia and lymphoma. In addition, FOXO proteins are inactivated by major oncogenic signals such as the phosphatidylinositol-3 kinase pathway and MAP kinases. Their expression is also repressed by micro-RNAs in multiple cancer types. FOXOs are mediators of the tumor response to various therapies. However, paradoxical roles of FOXOs in cancer progression were recently described. FOXOs contribute to the maintenance of leukemia-initiating cells in acute and chronic myeloid leukemia. These factors may also promote invasion and metastasis of subsets of colon and breast cancers. Resistance to treatment was also ascribed to FOXO activation in multiple cases, including targeted therapies. In this review, we discuss the complex role of FOXOs in cancer development and response to therapy

Interferon-α mediates human beta cell HLA class I overexpression, endoplasmic reticulum stress and apoptosis, three hallmarks of early human type 1 diabetes

Aims/hypothesis: Three hallmarks of the pancreatic islets in early human type 1 diabetes are overexpression of HLA class I, endoplasmic reticulum (ER) stress and beta cell apoptosis. The mediators of these phenomena remain to be defined. The type I interferon IFNα is expressed in human islets from type 1 diabetes patients and mediates HLA class I overexpression. We presently evaluated the mechanisms involved in IFNα-induced HLA class I expression in human beta cells and determined whether this cytokine contributes to ER stress and apoptosis. Methods: IFNα-induced inflammation, ER stress and apoptosis were evaluated by RT-PCR, western blot, immunofluorescence and nuclear dyes, and proteins involved in type I interferon signalling were inhibited by small interfering RNAs. All experiments were performed in human islets or human EndoC-βH1 cells. Results: IFNα upregulates HLA class I, inflammation and ER stress markers in human beta cells via activation of the candidate gene TYK2, and the transcription factors signal transducer and activator of transcription 2 and IFN regulatory factor 9. Furthermore, it acts synergistically with IL-1β to induce beta cell apoptosis. Conclusions/interpretation: The innate immune effects induced by IFNα may induce and amplify the adaptive immune response against human beta cells, indicating that IFNα has a central role in the early phases of diabetes

PDGF-D expression is down-regulated by TGFβ in fibroblasts

Transforming growth factor-β (TGFβ) is a key mediator of fibrogenesis. TGFβ is overexpressed and activated in fibrotic diseases, regulates fibroblast differentiation into myofibroblasts and induces extracellular matrix deposition. Platelet-derived growth factor (PDGF) is also a regulator of fibrogenesis. Some studies showed a link between TGFβ and PDGF in certain fibrotic diseases. TGFβ induces PDGF receptor alpha expression in scleroderma fibroblasts. PDGF-C and -D are the most recently discovered ligands and also play a role in fibrosis. In this study, we report the first link between TGFβ and PDGF-D and -C ligands. In normal fibroblasts, TGFβ down-regulated PDGF-D expression and up-regulated PDGF-C expression at the mRNA and protein levels. This phenomenon is not limited to TGFβ since other growth factors implicated in fibrosis, such as FGF, EGF and PDGF-B, also regulated PDGF-D and PDGF-C expression. Among different kinase inhibitors, only TGFβ receptor inhibitors and the IκB kinase (IKK) inhibitor BMS-345541 blocked the effect of TGFβ. However, activation of the classical NF-κB pathway was not involved. Interestingly, in a model of lung fibrosis induced by either bleomycin or silica, PDGF-D was down-regulated, which correlates with the production of TGFβ and other fibrotic growth factors. In conclusion, the down-regulation of PDGF-D by TGFβ and other growth factors may serve as a negative feedback in the network of cytokines that control fibrosis

Growth factors regulate PDGF-D and PDGF-C expression.

<p>MRC5 cells were treated with TGFβ 4 ng/ml, EGF 50 ng/ml, FGF-4 10 ng/ml (in the presence of heparin 10 µg/ml), PDGF-BB 20 ng/ml alone or all together for 24 h and PDGF-D (A) and PDGF-C (B) gene expression was measured by RT-qPCR. (C) AG01523 fibroblasts were treated with TGFβ 4 ng/ml, IL-1β 10 ng/ml or both for 24 h and PDGF-D gene expression was measured by q-PCR. The average of 3 experiments is shown with S.E.M, * p<0.05, ** p<0.005, *** p<0.0005.</p

PDGF-D and PDGF-C regulation by TGFβ at the mRNA and protein levels.

<p>(A) and (D), MRC5 human fibroblasts were pre-treated with TGFβ receptor inhibitor SB431542 (10 µM) 30 min before treatment with TGFβ (4 ng/ml) for 24 h. The control condition was treated with DMSO alone. PDGF-D and PDGF-C mRNA expression was measured by RT-qPCR and normalized with the housekeeping gene RPLP0. (B) and (E) MRC5 cells were treated with TGFβ (4 ng/ml) for the indicated period of time. PDGF-D and PDGF-C protein expression was analyzed by western blotting. Blots were re-hybridized with an anti-β-actin antibody as control. (C) Active PDGF-DD levels were measured by ELISA in the culture supernatant of MRC5 cells treated or untreated with TGFβ 4 ng/ml for 24 h. The average of 3 experiments is shown with S.E.M, ** p<0.005, *** p<0.0005.</p