Whole-genome sequencing of 644 elephant tissue samples using the HiSeq 2500 System identified multiple copies of TP53. Compared to human cells, elephant cells demonstrated increased apoptotic response following DNA damage, which could account for the low incidence of cancer (4.81%) in elephant populations.
What elephants can teach scientists about fighting cancer in humans http://www.latimes.com/science/sciencenow/la-sci-sn-elephant-cancer-story-20151007-story.html
How elephants avoid cancer http://www.nature.com/news/how-elephants-avoid-cancer-1.18534
Journal of the American Medical Association, DOI: 10.1001/jama.2015.13134