What is the significance of interclonal cooperation in tumorigenesis?

I have been reading about tumorigenesis in Drosophila Melanogaster lately, there are 3 questions which I have in mind:

1. How does interclonal cooperation differ from the canonical tumor evolution model?
2. How do fly tumours differ from human tumours?
3. If interclonal cooperation is important for the evolution of a certain tumour, what testable consequences can be predicted?