Cancer research is at a crossroads. Traditionally, cancer has been thought of as a disease of gene mutation, where the stepwise accumulation of cancer gene mutations is the key, and the identification of common gene mutations has been considered to be essential for diagnosis and treatment. Despite extensive research efforts and accumulated knowledge on cancer genes and pathways, the clinical benefits of this traditional approach have been limited. Recently, cancer genome sequencing has revealed an extensive amount of genetic heterogeneity where the long-expected common mutation drivers have...