Minimal hitting sets for incomplete drug-response graphs. When information about the response of some strains to some drugs is unavailable the strain-drug response graph is incomplete. This could result in an overestimate of the size of the minimal hitting set. a) For example, if the response of strain 3 to drug 1 has not been tested, and the corresponding edge is missing (dashed line), we will be force to cover drug 2. This will increase the minimal hitting set size from 2 to 3 drugs. b) Estimated minimal hitting set size of the NCI60 strain-drug response graph, after assuming that only a certain fraction of the interactions were tested. Note that data for 10% of the strain-drug pairs was already missing from the original dataset and, therefore, we cannot go beyond 90%. The dashed-dotted, solid and dashed line represent the minimum, average and maximum minimal hitting set sizes over 100 incomplete strain-drug response graphs. For each graph the minimal hitting set was estimated using 100 runs of the highest-degree-first algorithm.