The rationale of synthetic lethality applied to the design of novel anti-cancer therapies. Two linked nodes (blue circles) represent a SL interaction. (A) In cancer disease, one of the SL partners would appear mutated (red triangle) contrasting to healthy cells where no mutation is accounted for. (B) The attack by drugs to the SL partner of the cancer-related mutated gene might cause a selective damage to tumor cells. In this case, the inactivation of both SL partners only happens in tumor cells.