PML and cancer: ALT has been found to occur in about 10%–15% cancers and is often characterized by co-localization of telomeres with the promyelocytic leukemia (PML) bodies (known as ALT-associated PML bodies (APBs)), exceedingly heterogeneous telomere length, extra-chromosomal DNA circles, and high frequencies of telomere sister chromatid exchange (T-SCE) (Cesare and Reddel, 2010; Chung et al., 2012).