Identification by systematic in situ hybridization screen on medaka embryos of new genes as targets for anti-cancer therapy

Authors: Guillaume Serin, Violette Thermes, Frédéric Vincent, Jochen Wittbrodt, Jean-Stéphane Joly, Philippe Genne

Abstract: cell proliferation and apoptosis. A lost of balance between cell proliferation and apoptosis results in cancer. Aims of the 5th PCRD European Project EAC –
Embryos Against Cancer – were i) to identify new unknown medaka (orizias lapizes) proteins implicated in these two cellular mechanisms during embryo morphogenesis and ii) to estimate the interest of their human homolog as targets for anti-cancer therapy. High throughput analysis of an hybridization pattern collection, constructed with Medaka (Oryzia latipes) cDNA library, enabled characterization of several new genes highly expressed in dedicated domains of intense cell proliferation, localized in the optic tectum or the retina under development. The human
homologues of these genes were analyzed through a validation process for their role in proliferation of cancer cells. First, their mRNA expression was evaluated from a panel of primary tumors and tumor cell lines. Also, we have tested if the reduction of their expression by RNA interference changed the cell proliferation rate or induced apoptosis. If positive, we isolated human cDNA, observed over-expression effects on proliferation and characterized protein partners.
One of these genes, Simplet, is directly involved into cell proliferation mechanisms: injection of morpholino antisens into medaka egg provoked a delay in cell division, gastrulation defects, and apoptotic phenotype, finally conducing to embryonic death. hSimplet (FAB53) is expressed in tumoral cells.
Y2H screening and co-immuno-precipitation assays showed that hSimplet interacts with 14-3-3 protein, an important tumor suppressor gene (Development, 2006, 133: 1881-90).

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