Since some cancers do not express telomerase, how are they maintaining their telomeres?
There have been over 1000 published studies on telomerase activity and human cancers. Approximately 85-90% have been reported to have detectable telomerase activity. This includes all stages of cancer and in some instances early cancers may not have yet immortalized and these would be “mortal tumors”. In addition there is the possibility that some cancers may have an alternative pathway for maintaining telomeres. The telomeres in these types of cancers should be heterogeneous in length, varying from very big to very small in size as previously described in yeast and in human fibroblasts treated with viral oncoproteins such as SV40 T-antigen. Several thousand primary human tumors have been examined for telomeres and almost none have these types of telomeres. In addition to “mortal tumors” and alternative telomere maintenance mechanisms, perhaps most telomerase negative human tumors that have been reported can be explained by some of the following: 1) experimental human error during the
