Plasticity of Fas receptor signalling in colorectal adenocarconoma – PLAF

We use different experimental approaches including trans activation experiments, overexpression and RNA interference. Functionnal studies include cell death and proliferation analysis.

We observed that Fas tyrosine phosphorylation correlates with survival of CRC cells. Site-directed mutagenesis studies strongly suggest that the dephosphorylation of Fas turns on the apoptosis signal while the phosphorylation of Fas turns off the cell death signal

Our project should help to better understand the already known therapeutic targets as fas, EGFR and Kras but also to identify new drugables targets in the context of colorectal cancer therapy.

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Fas (CD95/Apo-1) is a major apoptosis regulator that, in some cellular context, can also signal proliferation and survival pathways. Thus the control of Fas signalling plasticity is central to the balance of life and death decision of the cell, and understanding this issue is crucial for the development of cancer treatment strategies.

In colorectal cancer (CRC), the malignant cells frequently coexpress Fas and its ligand (FasL) but often have a markedly reduced susceptibility to FasL-induced, Fas-mediated apoptosis and Fas-induced signalling by FasL can activate proteins that promote survival and proliferative functions in CRC cells that are resistant to Fas-induced cell death. Thus far the mechanisms of the resistance to Fas-mediated apoptosis and the contribution of Fas-mediated survival pathway in CRC remain unclear.

Increasing evidence has suggested role of posttranslational modifications and membrane dynamics of Fas in the control of its signalling mode and cancer etiology. We hypothesize that the membrane dynamics and posttranslational modifications of Fas (Palmitoylation/nitrosylation and glycosylation/phosphorylation) are key factors in determining its life/death signalling balance in CRC, and thus the therapeutic responses. We will study the integrated mechanisms of Fas membrane dynamics and posttranslational modifications in the control of its signaling in CRC, with respect to the response to the neoadjuvant and/or first line radiotherapy (RT) -/+ chemotherapy (CT) regimen to ultimately identify potential targets, predictive factors, and physiopathologic markers that will aid the design of well-targeted therapeutic strategies. Specifically we will:
?Assessing the Fas non cell death pathways in CRC cells (Task 1)
?Dissecting the molecular events (constitutive and FasL-induced) involved in Fas early signalling with two mains axis: the regulation of membrane dynamics and the post translational modifications (Task 2), with a special interest to the intracellular proximal membrane region (Task3)

The studies will be carried out using CRC cell lines, primary cells, biopsy tissues. We will employ various approaches in cellular and molecular biology, biophysics, biochemistry, and genetics to elucidate the integrated mechanisms of Fas membrane dynamics and posttranslational modifications in the control of its signaling in CRC.

Studying the roles of Fas membrane dynamics, phosphorylation, glycosylation, palmitoylation/nitrosylation and the actors involved, we expect a clear picture of the relationship among Fas modifications that explains its behaviour, signalling events, and cellular responses. This will provide more targets in Fas signalling pathway for the design of therapeutic strategies. Studying the posttranslational modifications in biopsy tissues will allow the identification of modification sites and patterns. This may lead to the use of these modifications as predictive/physiopathologic markers for treatments and delineate the pathways involved that will allow the identification of targets for development of treatments with improved specificity. And by investigating genetic alterations in CRC tissues, we expect to identify genetic components of Fas membrane dynamics and posttranslational modifications and to obtain pharmacogenetics information of Fas as predictive and/or physiopathologic markers for the treatments of CRC