Final answer:
Cancerous tumors require stem cells in addition to telomerase for their growth and maintenance.
Step-by-step explanation:
Cancerous tumors have the ability to generate their own telomerase, which can extend the length of their telomeres. However, this is not sufficient for tumor growth because they also require stem cells. Stem cells have the ability to self-renew and differentiate into different cell types, which is crucial for the growth and maintenance of the tumor.
Stem cells provide a continuous supply of new cells to the tumor, replenishing the population of cancer cells that undergo apoptosis or are eliminated by the immune system. Additionally, stem cells have a higher proliferative capacity compared to differentiated cells, allowing for rapid tumor growth.