“…THC and other cannabinoids are actively being investigated for various useful clinical purposes, including the treatment of cancer through the inhibition of tumor growth.
A new study by Salazar et al. in The Journal of Clinical Investigation demonstrates that THC causes tumor cells to begin to degrade themselves from the inside (a process called autophagy, i.e. “self-eating”). Although autophagy has been shown to promote cell survival in some cases and cell death in others, the authors show that in this case it causes cancer cells to undergo programmed cell death (apoptosis). Thus, THC activates a series of events within cancer cells, inhibiting tumor growth.”
More: http://scienceblogs.com/scientificactivist/2009/04/02/thc-gives-cancer-cells-the-mun/