The heterogeneity of cancer, with many different underlying genetic changes and immune responses, explains why gene therapy has not been successful for most cancers.

“and so the way I try to think about it myself is if um you see a hundred kids with autism and let's just pick a number that's somewhat conservative we would say that that's 85 90% uh heritable it simply means that the underlying genes for each of them were inherited but they might have nothing to do with each other across all of those children just as we would say all of the women who have breast cancer have acquired mutations that gave them breast cancer but they could all be very different”