PML and acute promyelocytic leukemia: Factors that regulate transcription of telomere repeats and the activity of telomerase are also relevant [18, 19] as well as features of the ALT pathway like PML (promyelocytic leukemia) nuclear bodies at telomere repeats that are associated with a variety of proteins and referred to as APBs (ALT-associated PML nuclear bodies) [20–23].