The kallikrein-related peptidases (KLKs) and their encoding genes have increasingly attracted attention among scientists and clinicians worldwide as they represent interesting and functionally distinct biomarkers both under physiological and pathophysiological conditions. The first volume of this book set on kallikrein-related peptidases is concerned with the characterization, regulation, and interactions of these proteases within the protease web. The second volume reviews the role of these proteases as biomarkers in a wide range of malignancies including cancers of the lung, prostate, breast, ovary, kidney, stomach, and colon. It provides clinicians, physician scientists, and cancer researchers with in-depth overviews on the emerging clinical relevance of KLK protein or gene expression in these malignancies. ese malignancies.