The ability for cancer cells to divide indefinitely is made possible because:

The ability for cancer cells to divide indefinitely is made possible because Cancer cells rebuild their telomeres after every cell division.

At each end of the chromosome, there is a region of repetitive nucleotide sequences, this is called telomere and when a cell begins to become cancerous, it divides more often. Telomeres are crucial for the survival of cancer cells and they are maintained by an enzyme called telomerase.