To develop agents that will block telomerase in the human body, investigators must also have a sharper picture of exactly how the enzyme functions. How does it attach to DNA? How does it "decide" on the number of telomeric subunits to add? DNA in the nucleus is studded with all manner of proteins, including some that specifically bind to the telomere. What part do telomerebinding proteins play in controlling the activity of telomerase? Would altering their activity disrupt telomere elongation? Within the next 10 years we expect to learn a great deal about the interactions among the various molecules that influence telomere length.
Research into the regulation of telomere size could also yield benefits beyond new therapies for cancer. A popular approach to gene therapy for various diseases involves extracting cells from a patient, inserting the desired gene and then returning the genetically corrected cells to the patient. Frequently, though, the extracted cells proliferate poorly in the laboratory. Perhaps insertion of telomerase alone or in combination with other factors would temporarily enhance replication capacity, so that larger numbers of therapeutic cells could be delivered to the patient.
Modern research into telomeres has come a long way from the initial identification of repetitive DNA on the ends of chromosomes in a unicellular pond dweller. Elongation of telomeres by telomerase, initially considered to be merely a "cute" mechanism by which some single-cell creatures maintain their chromosomes, has proved, as ever, to be other than it seemed. Telomerase is, in fact, the predominant means by which nucleated cells of most animals protect their chromosomal end segments. And, now, study of this once obscure process may lead to innovative strategies for fighting a range of cancers.
In the early 1980s scientists would not have set out to identify potential anticancer therapies by studying chromosome maintenance in Tetrahymena. The research on telomerase reminds us that in studies of nature one can never predict when and where fundamental processes will be uncovered. You never know when a rock you find will turn out to be a gem.