DiscussionMany new anti-cancer drugs target kinase activity. Unfortunately, methods to monitor the drug effects at the enzymatic level in patient derived tumor tissue are limited. Here, a novel molecular profiling method for application in biomarker discovery is presented that is based on measuring kinase activities in tumor tissue extracts. An ex vivo activity-based approach which involves assessment of inhibition by a drug of interest, is illustrated for leukemia, locally advances rectal cancer, lung cancer and melanoma tumors. The discovery of prognostic and predictive biomarkers is illustrated with case studies of LARC and breast and lung cancer. Here we present the applicability of this approach for biomarker discovery in multiple tumors of different origin.