The human kallikrein (KLK) gene family, localized on chromosome 19q13.4, is composed of 15 genes encoding low molecular mass serine proteases (30 KD) of known or predicted trypsin-like or chymotrypsin-like activity, which dysregulate different types of cancer including ovarian, giving either a favorable or unfavorable prognosis [55–57]. The gene discussed is KLK4; the disease is cancer.