This is the first I've heard that some large mammals are much less susceptible to cancer.
TP53 is the gene that makes P53 - the 53rd protein registered in a big protein database that biochemists started because they simply couldn't name things fast enough. It suppresses tumors and mutations by detecting broken stretches of DNA.
In some serious types of CLL and other cancers, the TP53 is deleted or is itself mutated.
P53 was named "molecule of the year" in 1993 (How did we miss that announcement?)
It may hold hope for gene therapy. If another TP53 gene could be inserted in a different chromosome, the outcome could shift. Usually one of the concerns in gene therapy is whether they work too well or in unexpected ways. But the existence of stable, multiple copies in animals that live a long time shows that it doesn't have many drawbacks. I'm sure it's more complicated than it sounds to my uneducated ear, but I'll bet a bunch of scientists dropped their coffee or tea cups and said "lets start writing a proposal."