Telomere-based cancer treatment: emerging targeted therapies.

Chemotherapy and radiation therapy are standard care in cancer treatment; however, both have numerous adverse side effects because they affect healthy as well as cancerous cells. The side effects, including decreased white blood cell count, nausea, hair loss, and fatigue, can be severe enough that patients may decide to forgo treatment. Targeted therapies are treatments that focus on specific molecules in cancerous cells and avoid disruption of healthy cells. Telomeres, the ends of chromosomes, are possible targets. In healthy cells, telomeres become shorter with each cell division, limiting the number of divisions that a normal cell can undergo. Many cancer cells have telomerase activity, which rebuilds telomeres after each cell division and confers immortality to cancer cells. Telomerase is an enzyme normally present to a significant degree only in the cells of developing fetuses. Treatments that target the telomerase enzyme itself or the chromosomal telomeres are being developed and tested in early clinical trials. This article focuses on several approaches to telomere-targeted therapy.