A Power-Point-like presentation (with audio) by Jerry McLaughlin, documenting his long-term research on paw paw while working at Purdue University, can be found at:
The presentation is quite illuminating, as it compares the use of paw paw extract (which includes a number of anti-cancer metabolism agents), against a number of commonly used, more toxic, chemotherapy chemicals. Paw paw extract seems to be more specific, more effective, and to also have few side effects... The presentation also describes his difficulties getting scientific/public attention to the benefits of the plant....
Additional information on paw paw can be found in Wikipedia, at: