Abstract 1915: The role of the E2F2 and ID3 transcription factors in colon tumour growth and cellular dissemination.
Authors: Guenot Dominique , Voegelin Manon , Guérin Eric , Nicolet Céline , Gaub Marie-Pierre 
Published: August 2014

In order to identify molecular markers prognostic of initiation and/or progression of human colon cancer (CC), a genome-wide analysis was performed and highlighted a micro-deletion at the 1p36.11-12 region in 23% (n = 115) and 47% (n = 59) of adenomas and carcinomas, respectively. This region contains the E2F2 and ID3 genes, which are known to regulate the cell cycle and cell differentiation, respectively. In addition, E2F2, is described as either oncogenic or tumour suppressor, depending on the tissue or cell type. The micro-deletion incidence depends on tumour stages (60% in early stages whereas only 34% in metastatic stages and further clinical analysis showed that patients with deleted E2F2 had a lower rate of recurrence and a better overall survival. Also, RT-QPCR evidenced that E2F2 and ID3 transcript expression levels decrease in human CC. Therefore, to assess the role of the deletion in tumour growth and metastatic activity, we evaluated the functional consequences of the loss of these genes both in vitro in human colon cancer cells that were transiently depleted of either E2F2 or ID3 and in vivo in immunodeficient mice.

Both gene transcript expressions were down-regulated by transient siRNA transfection in the human epithelial CC cell line Caco-2/TC7. Consequences were evaluated by immunocytochemistry for proteins involved in the cell architecture and in cell-cell and cell-matrix junctions, and at the expression level by RT-QPCR and Western Blot analyses. Functional analyses were assessed for the migratory potential with the wound healing assay, for proliferation with the MTS assay, and for adhesion on substrates such as laminin, collagen I and fibronectin. The in vivo metastastic potential was evaluated with E2F2- and ID3-silenced cells that were intra-splenically implanted.

E2F2 down-regulation and that of ID3 at a lesser extend, reduced proliferation and induced severe morphological modifications, associated with relocalization of structural members of adherens junctions (beta-catenin, APC), tight junctions (Claudin-1, ZO-1) and cytoskeleton (F-Actin, Cytokeratin-19). The integrins alpha5, alphaV, alpha2 and beta-1, were downregulated and the adhesion properties on laminin-111, but not on collagen I or fibronectin were lost. Moreover, inhibition of E2F2 and ID3 expression leads to a decreased migratory potential. The intra-spenic injection in immunodeficient mice of HT29 cells stably transduced to underexpress E2F2 and ID3, leads to lower / slower development of liver metastases.

In conclusion, for a clinical aspect, the micro-deletion of the 1p36.11-12 region is a good prognosis for the event-free survival, and from a more basic and functional aspect, the loss of E2F2 and ID3 expression regulates tumor growth and dissemination through functions involving migration and adhesion.

Citation Format: Dominique Guenot, Manon Voegelin, Eric Guérin, Céline Nicolet, Marie-Pierre Gaub. The role of the E2F2 and ID3 transcription factors in colon tumour growth and cellular dissemination. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1915. doi:10.1158/1538-7445.AM2013-1915