Tumor markers kallikreins

Prostate-specific antigen (PSA, hK3) and, more recently, human glandular kallikrein 2 (hK2) are used as tumor markers for prostate cancer. Several... 

Luo L, Bunting P, Scorilas A, Diamandis EP. Human kallikrein 10 A novel tumor marker for ovarian carcinoma Clin Chim Acta 2001 306 111-118. 

With few exceptions, an increase in the activity or mass of an enzyme or isoenzyme is not specific or sensitive enough to be used for identifying the type of cancer or the specific organ involvement. An exception is PSA. PSA has mild protease activity and amino acid sequence homology with serine protease of the kallikrein family.It is expressed by normal, benign, hyperplastic, and cancerous prostate glands and minimally by other tissue. Until the application of PSA as a marker for prostate cancer, tumor enzymes had lost most of their popularity for use as cancer markers. Enzymes were used historically as tumor markers before the discovery of oncofetal antigens and the advent of monoclonal antibodies. The abnormalities of enzymes as a marker for cancer are either the expression of the fetal form of the enzyme (isozyme) or the ectopic production of enzymes. 

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