“Yes, some parts of the cannabis plant have been shown to kill cancer cells in certain cases.” 

“Even if you don’t believe in any of that “hippie medicine” stuff, there’s been some actual scientific research done on cannabis and cancer, and a lot of it is promising. Spend a half-hour browsing around the National Center for Biotechnology Information website (ncbi.nlm.nih.gov) and you’ll find numerous studies on how various cannabinoids have been shown to slow or even kill tumor growth in everything from breast cancer to prostate cancer to skin cancer, thanks to our body’s natural endocannabinoids system.”

More: http://www.westword.com/2013-08-22/news/can-marijuana-cure-cancer/full/