Does Telomerase Expression Cause Cancer?
The evidence suggests that telomerase expression by itself does not cause cancer. In a January 1999 paper, Carol Morales and colleagues showed that when telomerase is expressed in human fibroblast cells, the cells continued to divide past their Hayflick limit, but they did not exhibit the other changes typical of cancer, such as accelerated growth rate, loss of contact inhibition and acquisition of serum-independent growth. However, it may well be that telomere shortening acts as one of the cell’s “last-ditch” defenses against cancer, and that telomerase expression, by re-lengthening the telomeres, removes that last line of defense. The cell has other mechanisms to prevent uncontrolled division, such as the “checkpoint” between the G1 and S phases of the cell cycle and the regulatory effect of the p53 protein. Cancer arises when genetic mutations cause the cell to escape these mechanisms, and ultimately to escape the effect of telomere shortening by expressing telomerase. Could a Telom
