Disclosed are methods of controlling cell cycle progression by introducing into a cell to be controlled a composition selected from the group consisting of p56.sup.RB protein, a fragment of the p56.sup.RB protein, and the gene encoding p56.sup.RB protein to alter the cell cycle progression while maintaining the viability of the cell. The p56.sup.RB protein has been found to have the unexpected and surprising characteristic of being soluble in low concentrations of glycerol, thereby enhancing its value in pharmaceutical applications and the gene encoding p56.sup.RB when delivered to the hyperproliferating cell inhibits cellular proliferation.