Let's hope this works in humans: cancer-curing mouse blood.

If it does work for humans, the consequences might make a good science fiction (?) plot as the immunes get herded up and used as donors. Bloodlegging becomes the new bootlegging.

I'd rather imagine a situation where the donors aren't forbidden to sell their special blood. For a short time, the donors make a bundle of cash, and over time the lure of profits brings more money into the effort to discover the mechanism behind the effect and synthesize and improve on it.

Another SF-useable twist on this is the beneficial effects it would have on space travel. Given a magic-bullet treatment for any and all cancers, even those in an advanced state, spacecraft bound for Mars might require only enough radiation shielding (from environmental sources and from things like NTR engines and nuclear power systems) to keep from killing the crew outright -- less payload mass spent on radiation shielding means more mass available for equipment, supplies, and improved safety and reliability elsewhere in the spacecraft. It could similarly make O'Neill-type colonies and asteroid settlements easier to construct, since less deadweight mass would be needed for radiation shielding.

On the other hand, this has already been examined (particularly with regards to the potential downsides) in science fiction...Michael Flynn wrote a story in the late 1980s, "The Washer at the Ford", featuring a nanotechnology-based generic cancer cure/preventative. Naturally, being the late 1980s, this technology was portrayed as a mixed blessing, the clear benefits of its medical application being potentially outweighed by the risk that the bloodthirsty Reaganesque warmongers in the military would see its availability as license to indulge their lust to use nuclear weapons "just because".