Graviola, a plant found in Mexico said to cure cancer. Anyone heard of it or used it?

i have a friend who took this, he had prostate cancer, and is doing well.  That is not ovarian cancer.  Another friend has just heard about this and another is looking into it on mainstream Cancer sites.  Of course they can't recommend it and give possible big side effects.  I'm wondering if any of you have heard of this or had any experience with it.  Thanks so much.  Carrot358