Overexpression of hPer1 inhibits cell proliferation (Gery et al., 2006, 2007) and reduces the expression of Cyclin B1 and WEE1 proteins, promotes apoptosis, and inhibits cell proliferation in HCT116 human colonic cancer cells and in human prostate cancer cells (Gery et al., 2006; Cao et al., 2009). Here, PER1 is linked to Familial prostate cancer.