[The retinoblastoma gene: will therapeutic use of its tumor suppressive properties be possible?]

The retinoblastoma is a rare childhood tumor which occurs in children, 40% of them being diagnosed in an hereditary context. The gene involved in the hereditary predisposition and in the tumoral development was isolated (RB-1) and is of the antioncogene-type. RB-1 mutations were found in many other tumors. The absence of the antioncogene protein expression is responsible for the tumor development and a contrario its presence in normal cells has tumor suppressive properties. This property was demonstrated by phenotype reversion of retinoblastoma or other cell lines (with no RB-1 protein), induced by reintroduction of the gene coding for the normal RB-1 protein. The normal RB-1 protein undergoes multiple phosphorylations during the cell cycle, regulating its activity, the active form being hypophosphorylated. RB-1 is involved in the transcription regulation of many cell cycle genes, and in cell differentiation. Experimental animal models are under investigation, in order to established whether RB-1 overexpression in normal cells will protect them from tumor development, and to plan tumor gene therapy by injection of recombinant viruses allowing RB-1 expression in tumor cells.