INTRODUCTION OF A NORMAL RETINOBLASTOMA (RB) GENE INTO RB-DEFICIENT LYMPHOBLASTOID-CELLS DELAYS TUMORIGENICITY IMMUNODEFECTIVE MICE

Inactivation of the Rb susceptibility gene occurs in various human can cers and has been associated with tumorigenicity. Rb ene is inactivate d in 30% of acute leukaemias. The effect of Rb protein expression was assessed in the lymphoblastoid cell line IM-9 defective for Rb protein , after stable transfection with a wild-type Rb gene. The Rb transgene was under the control of the MoMuLv-LTR. Protein expression by the tr ansduced cells was confirmed by Western blot and flow cytometry analys es. Compared to the parental cell line, growth rate remained unchanged in the Rb transfected clones. In SCID mice however, tumor formation o riginating from these clones was delayed. The current data suggest the refore that, in this Rb-defective haematopoietic cell line, Rb express ion correlates with reduced tumorigenicity but not with reduced growth rate. (C) 1998 Elsevier Science Ltd. All rights reserved.