[Telomeres, telomerase and development of cancer].

The chromosome ends, telomeres, shorten during each cell division due to the inability of DNA polymerase to replicate the ends of linear chromosomes. The telomere length serves as a clock determining the remaining replicative capacity of the cell. After 50-100 doublings, the cell becomes senescent. Rarely, a cell overcomes the senescence blockade, and eventually becomes immortal. Cellular immortalisation is almost always accompanied by the expression of the enzyme telomerase, which synthesises telomeric DNA. Telomerase is present in approximately 85% of malignancies. The detection of telomerase activity in cancer cells represents a possible cancer diagnostic and prognostic tool, and telomerase inhibition may become a novel therapeutic strategy in cancer patients.