How do cancers have sophisticated mechanisms for evading immune responses when they don’t have any adaptive pressure? The cancer dies with the victim. It seems like the equivalent of mashing on the keyboard and getting a valid program.
The only problem is that these individually minded (cancer) cells have every ability of your healthy cells and have basically stopped caring about the greater whole and care about themselves. Then they evolve at a micro level for their survival to fend off chemo, immune system, radiation etc. All it takes is one adapted/surviving cell to come back strong.
The sophisticated mechanisms for evasion exist because they have all the methods of evading your immune system that healthy multicellular organisms need to function and they multiply and increase their mutation rate to try new methods to survive and thrive.
I view cancer cells as single cells to understand their behavior with the adaptations of all the healthy cells returning to their “baser instincts”.
Source: Caretaker of a cancer patient and former cell bio major
PS: Take all the above with a grain of salt
Fuck Cancer
A human cell can never survive on its own. But there might have been a time when cells could have benefited from "pulling the escape hatch" and taking their chances instead of continuing cooperation within a damaged early multicellular organism.
The adaptive pressure is your body constantly detecting and killing pre-cancerous cells. Eventually some will get a lucky mutation and slip through.