Well, supposing a human could tolerate a transfusion of shark blood, and supposing sharks were immune to cancer, I suppose a person who got that treatment would be immune to shark cancer. I don’t see a whole lot of advantage in that, though. I’ve never known anyone who got shark cancer anyway.
But seriously, sharks are not immune to disease and they do get cancer. Shark cancer has been reported since 1908 and has been documented in 23 species of sharks.
William Lane made a lot of money from gullible people, though, selling shark cartilage and his fraudulent book, Sharks Don’t Get Cancer.
Moral of the story: Don’t believe everything you read, no matter how popular it seems. Don’t blindly follow the mentally crippled masses; check out the facts for yourself.