Pharmacological approach based on actin cytoskeleton remodeling for the treatment of cancer

Coordinators: C. Auclair (Partner 10) and R. Dodd (Partner 13)
Financial support from January 2012 until December 2014

Over 10 years ago, Partner 10 has initiated a new approach to understand cell cancer status by asking: how can a tumor cell escape from its malignant trajectory? Is there a specific signaling that will still allow a tumor cell to switch to at least a partial loss of its malignant potential with a subsequent suppression of its malignant phenotype?
Along this line, Partner 10 started in the past years a pharmacology program whose objective was to identify some specific molecular basis of malignant phenotype maintenance and ultimately the identification of key processes whose pharmacological manipulation would result in tumor phenotypic reversion. In agreement with previous observations, they hypothesized that the changes in the cytoskeletal architecture which is one of the main molecular mechanisms underlying tumor progression could be a pertinent target process and that pharmacological-induced actin network rearrangement may result in phenotypic reversion thanks to the rescue of adhesion and motility controls. This axis rests on the fundamental work developed earlier which has led Partner 10, thanks to a genomic approach, to the identification of a key gene (zyxin) for which the reduction in expression is directly responsible for the acquisition of the tumoral phenotype in the Ewing sarcoma model (see patent). The under-expression of this gene leads to a strong modification of the dynamics of actin polymerization resulting in a polarization of the cells, a loss of cell-cell membrane interactions, and an increase in the cellular motility. These observations have been the starting point of the development of a pharmacological project, whose objective is the identification of compounds able to reconstitute actin networks mainly in tumoral phenotypes which under-express zyxin (down regulation of zyxin is observed in various sarcomas, in melanoma and in leukemia such as AML and ALL). Actin cytoskeleton organization may as well modulate the anti-apoptotic status of tumor cells and one work package (WP) of the project will concern the study of the relations between the actin network architecture and sensitivity to ionizing radiation (Partner 8).

Based on the above considerations, we are in the process of identifying new antitumor drugs acting by a completely non-toxic process through the reversion of the tumoral phenotype. Along this line, molecular and functional screening procedures have allowed us to identify the β-carboline harmine as actin dynamics modulators resulting in the decrease of cell motility, the restoration of cell-cell adhesion and in fine the disappearance of the tumor phenotype. Through a pluridisciplinary endeavor involving five different partners (Partner 8, 10, 12, 13 & 15) and the technology platforms, this project aims at: 1) identifying the molecular target(s) of harmine and elucidating the mechanism of actin dynamics modulation (aim 1); 2) identifying organic molecules in the β-carboline series which restore actin cytoskeleton architecture in tumor cells leading to the decrease of cell motility and in the rescue of cell-cell adhesion properties (aim 2); 3) synthesizing new β-carboline derivatives and performing molecular optimization on the selected compounds (aim 3); 4) investigating the effect of actin dynamics modulators on the ionizing radiation efficiency (aim 4).


The secretion of Translationally Controlled Tumor Protein (TCTP): mechanisms, animal models and prognostic value in breast cancer patients.

Coordinator : A. Telerman (Partner 9)
Starting date: January 2013

Recent data from the partner laboratories (P.P. Di Fiore, J-C Marine and Telerman, partner 10) show a reciprocal repression between p53 and TCTP (Amson et al., 2012), in which p53 represses at the transcriptional level TCTP and TCTP promotes the MDM2-mediated proteasomal degradation of p53. Previous results (M. Vidal, J-C Marine and Telerman) indicate that p53 promotes the secretion of TCTP by the non-classical protein secretion pathway of which the exosomes (Amzallag et al., 2004; Lespagnol et al., 2008b; Passer et al., 2003). The secretion of p53 is mediated by a direct transcriptional target namely TSAP6. All together these results indicate that there is a strong antagonism between p53 and TCTP.
In this project we aim at investigating the mechanisms by which the p53-TSAP6 axis promotes the secretion of TCTP. Obviously "chasing out" of the cell TCTP is necessary for p53, otherwise TCTP promotes its degradation. For the purpose of this work we generated several animal models to investigate these processes properly:
1. TSAP6 knockout mice (TSAP6 KO)
2. TCTP heterozygous knockout mice (TCTP +/- KO)
3. TCTP conditional knockout mice (TCTP cKO)
In these animal models we suggest to investigate:
1. How the p53-TSAP6 pathway regulates protein and RNA secretion and more specifically the secretion of TCTP. This will provide with a comprehensive view of the secretome regulated by the p53-TSAP6-TCTP axis.
2. How p53-TSAP6 mechanistically are regulating this secretion process.
3. How the secretion of proteins by the p53-TSAP6-TCTP axis influences tumor formation and reversion
4. Finally we will investigate the clinical relevance of TCTP secretion by measuring its levels in the sera of a large cohort of breast cancer patients.
The long term goal of the present project is therefore to develop drugs targeting TCTP (Amson et al 2012) and to co-develop a bioassay assessing TCTP status in cancer patients.
The clinical perspective is to propose a TCTP inhibitor in patients defined by TCTP expression.


Therapeutic applications for TCTP in the frame of the tumor reversion program: Design and synthesis of new TCTP inhibitors

Coordinators: S. Messaoudi (Partner 15) and A. Telerman (Partner 9)
Starting date: January 2014

Tumor reversion is the biological process by which highly tumorigenic cells lose at great extent or entirely their malignant phenotype. In this context, partner 10 (A. Telerman and R. Amson) established biological models of reversion, which was done by deriving revertant cells from different tumors. Additionally, they showed that TPT1/TCTP is the most strongly downregulated protein in the revertant cells compared with the parental cancer cells. They demonstrated that decreasing the expression of TPT1/TCTP results in either apoptosis or reprogramming of cancer cells into revertants.

Through a pluridisciplinary programm (Medicinal Chemistry, Molecular Modeling and Biology)  involving partners 10 and 15, the purpose of our research is to understand the molecular program of tumor reversion and its clinical application.