THE RB GENE SUPPRESSES THE GROWTH OF NORMAL-CELLS

The suppression of tumor formation, first demonstrated by somatic cell hybrid and microcell fusion experiments, suggests the existence of a class of genes that selectively suppress the growth of tumor cells but not normal cells. The reintroduction of these genes into tumor cells presumably renders the cells responsive to in vivo growth inhibitory e nvironment. As the inheritance of a defective retinoblastoma gene (Rb- 1) allele results in a predisposition to the development of various ca ncers, and since inactivation of both alleles are observed in tumor ce lls, the Rb gene has been suspected to have the ability to suppress tu mor growth. Data presented here demonstrated that different types of n ormal cells, which have a limited life span, were also growth arrested by a transfected Rb gene. Cell lines which are resistant to the growt h suppression effect of the Rb gene in vitro, retain the ability to fo rm tumors in nude mice even in the presence of a stable and highly exp ressed wild type Rb protein. We conclude that while the Rb gene can su ppress the growth of many tumor cell lines, its growth suppression eff ect is not tumor specific.