GPT and neoplasm: Telomere extension in ALT-positive tumor cells can be efficiently induced by DSB formation and appears to occur as a conservative DNA replication process similar to Break-Induced replication (BIR), requiring Pol δ, PCNA, RFC as well as the accessory subunits of Pol δ, the POLD3 the homolog of yeast Pol32, and POLD4 [223,224,225,226] (see Figure 2B).