The human wild-type Rb cDNA has been inserted into a retrovirus vector DOL and introduced into the human breast cancer cell MDAMB468,which has a large deletion of exons 3-27 of Rb genes,by electroporation transfection techniques.The exogenous Rb gene expresses the 110kd Rb protein.The morphology of the transfected cells is similar to that of the parent MDAMB468 cells.With the expression of Rb protein,the growth rate of MDAMB468 cells decreases by about 50%,and the colony formation ability in soft agaris repressed completely.After injection of 3times;106Rb+ cells and Rb-MDAMB468 cells into nude mice,the tumors formed from 106Rb+ cells are smaller than those from Rb-cells.The cell population of G1 and S phase of Rb+ MDAMB468 cells increases and the proliferation quotient decreases by about 50%.This result supports the former report the Rb protein. （Chin J Ocul Fundus Dis,1993,9:135-140）