DDB2 and Familial prostate cancer: We then investigated DDB2 protein expression in human prostate cancer tissues and found that the DDB2 protein was expressed predominately in the nuclei of basal cells and rarely in luminal cells in normal prostate tissues (Figure 3A), a result consistent with previous reports that DDB2 is a nuclear protein, and the nuclear signal of DDB2 expression is exclusively used for immunohistochemistry evaluation in human colon cancer tissues [18, 32].