5 replies to this topic

[olaf.larsson]

Why do cancers always activate telomerase or ALT? It seems to me that cancers always have telomere elongation mechanism activated it is strange to me if cells have 60 to 80 celldivisions before telomeres are to short the cancers should be able to at least in some cases grow to 2^60 cells. Why are there no tumors without telomere elongation?

[rahein]

Because the tumor would not be able to grow to a substantial size without having the telomerase protein activated. Cells have ~60 divisions after they are differentiated in an adult there are many fewer divisions left (don’t know the exact number though). Assuming there are 30 left the maximum number of divisions is 2^29th. This assumes that no cells die and we know that the body will try to kill of caner cells. This limits that number dramatically.

Mutated/ cancerous cells form regularly and only have the possibility of becoming a tumor if one of the mutations is the activation of telomerase. I assume there are exceptions to this rule though as I am not a micro biologist.

[olaf.larsson]

How about this: Before angiogenesis is aquired the tumor doesn´t get nutrient to expand so the cells are dividing and dieing all the time without the person notice it. The tumor has thus made many more divisions than one could expect from the size of it.

[kevin]

From what I understand, telomerase is necessary because the RNA primers which initiate synthesis are removed and leave the chromosome a little shorter with each replication. Is there a way to use DNA primers and to prevent their excision?

[olaf.larsson]

"From what I understand, telomerase is necessary because the RNA primers which initiate synthesis are removed and leave the chromosome a little shorter with each replication. Is there a way to use DNA primers and to prevent their excision? "

Yes man but cells divide untill telomeres, are gone and there should be about 50-60 cellreplications before that, so you could at least in some cases expect to find tumors consitsting of 2^40 cells without telomere elongating ability. The weight of a such tumor would be about 0.1 kg so it could cause health problems.