Alternative Lengthening of Telomeres

Alternative Lengthening of Telomeres (also known as "ALT") is a telomerase-independent mechanism by which cancer cells avoid the degradation of telomeres.

At each end of the chromosomes of most eukaryotic cells, there is a telomere: a region of repetitive nucleotide sequences which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes. At each cell division, the telomeres get shorter, eventually preventing further cell division. Healthy adult somatic cells in mammals do not have active telomerase enzymes, so that cancer cells stop proliferating unless they have a mutation which restores the telomeres. Often, this is due to a telomerase enzyme being reactivated, but alternative mechanisms also occur.