This invention provides a transgenic mouse with a p16INK4a promoter sequence that controls expression of a protein such that it is expressed preferentially in senescent cells. The protein either directly induces apoptosis, or converts a prodrug to a cytotoxic compound. In addition, the mouse is injected with syngeneic tumor cells, or has second transgene that causes tumors to form. Removing senescent cells from the mouse may result in the formation of fewer tumors.