The uptake of PSA testing has led to a two-fold increase in the age-standardized incidence of prostate cancer, first in the US from 55 to 107 new cases per 100,000 men between 1980–1995 and later in Sweden, from 52 to 111 new cases per 100,000 men between 1990–2005 [26]. Here, KLK3 is linked to prostate cancer.