Steroid hormones are reported to have a function in controlling KLK expression, but they, however, cannot be the sole factor controlling KLK expression in cancer (Yousef and Diamandis, 2002), as there are relatively short distances between adjacent kallikrein genes [as short as 1.5 kb between KLK1 and KLK15 (Yousef et al, 2000)], with no classic promoter elements or hormone response elements. The gene discussed is KLK4; the disease is cancer.