【阅读理解】In 2006, Blackburn, of the University of California, San Francisco, and Greider, of Johns Hopkins University in Baltimore, shared the Lasker prize for basic medical research with Jack Szostak of Harvard Medical School. Their work set the stage for research suggesting that cancer cells use telomerase to sustain their uncontrolled growth. The research by Blackburn and Greider helps suggest the role of______.