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In the present study we investigate the role of c-FLIP in autophagosome biogenesis. c-FLIP is an apoptosis modulator [1] and plays a complex role in cellular homeostasis [2]. In the last few years a cross-talk between autophagy and apoptosis has been highlighted [3], but this complex mechanism still remains partially unknown. In c-FLIP-/- MEFs (mouse embryonic fibroblasts) compared to WT MEFs we analysed two well-known autophagy markers, LC3 and p62, under different autophagy-inducing stimuli (torin 1, starvation and tunicamycin). We found a strong reduction of the autophagic flux in c-FLIP-/- MEFs. We then studied the activation state of specific markers at each stage of the autophagic process and c-FLIP was found to participate in the nucleation stage and to bind key factors in the autophagosomes nucleation. Then we analysed the autophagic flux at increasing times and doses after treatment with autophagic inducers. A positive correlation was observed between death increase and autophagic flux induction in WT MEFs. Cell death was partially reversed by combining drug treatments with autophagy inhibitors. On the contrary, autophagy inhibition did not affect the basal low-level death of c-FLIP-/- MEFs. Further experiments are currently ongoing to better characterize the involved mechanisms and we can conclude that c-FLIP protein absence reduces autophagy-dependent cell death. [ABSTRACT FROM AUTHOR]

Toll-like receptors (TLRs) recognize microbial/viral--derived components that trigger innate immune response and conflicting data implicate TLR agonists in cancer, either as protumor or antitumor agents. We previously demonstrated that TLR3 activation mediated by its agonist poly(I:C) induces antitumor signaling, leading to apoptosis of prostate cancer cells LNCaP and PC3 with much more efficiency in the former than in the second more aggressive line. The transcription factor hypoxia-inducible factor 1 (HIF-1) regulates several cellular processes, including apoptosis, in response to hypoxia and to other stimuli also in normoxic conditions. Here we describe a novel protumormachinery triggered by TLR3 activation in PC3 cells consisting of increased expression of the specific I.3 isoform of HIF-1α and nuclear accumulation of HIF-1 complex in normoxia, resulting in reduced apoptosis and in secretion of functional vascular endothelial growth factor (VEGF). Moreover, we report that, in the less aggressive LNCaP cells, TLR3 activation fails to induce nuclear accumulation of HIF-1α. However, the transfection of I.3 isoformof hif-1α in LNCaP cells allows poly(I:C)--induced HIF-1 activation, resulting in apoptosis protection and VEGF secretion. Altogether, our findings demonstrate that differences in the basal level of HIF-1α expression in different prostate cancer cell lines underlie their differential response to TLR3 activation, suggesting a correlation between different stages of malignancy, hypoxic gene expression, and beneficial responsiveness to TLR agonists. [ABSTRACT FROM AUTHOR]