Tumor has been well recognized as a highly complex disease. A number of regulating mechanisms of tumorigenesis have been uncovered in great details. In the previous issues of JMCB, we published several papers on different aspects of tumorigenesis. For example, Lieberman et al. (2011) reviewed the role of a DNA-repair protein RAD9 during tumorigenesis. Dr Wu's laboratory uncovered that the cellular context-dependent molecular networks rather than an individual gene/protein make the decision to be or not to be a tumor (Song et al., 2012). In addition, Jia et al. (2011) showed that a key regulator in embryonic stem cells, SOX2, might promote tumorigenesis by increasing the apoptosis-resistant properties of prostate cancer cells.